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Aluminum is the most commonly used non-ferrous metal today.

 It is also number 3 in terms of its abundance, following only silicon and oxygen.

Aluminum Production Process

Introduction to Aluminum

To understand what the aluminum casting process is we must first look at the properties of aluminum. Aluminum is the most abundant metallic element in the earth's crust, of which it forms nearly 8%. It always occurs as a compound, some of its minerals being bauxite, cryolite, corundum, alunite, diaspore, turquoise, spinel, and such silicates as kaolin, feldspar, and mica. Bauxite a ferruginous aluminum hydroxide, is the basic raw material from which the metal aluminum is produced.
Impurities are removed from the bauxite by chemical processing to make alumina (aluminum oxide). The bauxite is crushed, mixed in a caustic soda (sodium hydroxide) solution, and then heated by steam under pressure to dissolve the alumina. Settling and filtration remove impurities. After cooling, the solution is agitated, and crystals of hydrated alumina are formed. These crystals are washed and then dried in long rotating kilns. The final product, alumina or aluminum oxide is a very hard crystalline substance having the appearance of refined sugar. Four pounds of bauxite yields approximately two pounds of alumina.
Electrolyzing a solution of alumina in molten fluorides makes aluminum; this electrolysis takes place in reduction pots or cells at a reduction plant. Aluminum reduction plants produce pure, high quality primary aluminum. The reduction process removes the oxygen from the alumina, which consists of almost equal parts of aluminum and oxygen and leaves pure aluminum. Two kg of alumina yields one kg of aluminum.

Characteristics of Aluminum

Aluminum is lightweight, has excellent strength, high thermal and electrical conductivity, high reflectivity, good corrosion resistance, excellent workability, and attractive appearance. It can be given almost any finish. It is nonmagnetic, nontoxic, and non- sparking.
Aluminum weighs 32.523887897 kg/dm3 (kilogram / cubic decimeter), approximately 1/3 the density of steel, copper, and brass. Some of the stronger aluminum alloys exceed the strength of mild steel. The melting point of aluminum is 758 degrees Celcius.
The high thermal conductivity of aluminum is a marked advantage in any application where it is desirable to conduct or dissipate heat quickly and uniformly. On a weight basis, aluminum is the most efficient heat conductor of the common metals.

ALUMINIUM Knowledge and news Specific for Die casting industry

To understand what the aluminum casting process is we must first look at the properties of aluminum. Aluminum is the most abundant metallic element in the earth's crust, of which it forms nearly 8%. It always occurs as a compound, some of its minerals being bauxite, cryolite, corundum, alunite, diaspore, turquoise, spinel, and such silicates as kaolin, feldspar, and mica. Bauxite a ferruginous aluminum hydroxide, is the basic raw material from which the metal aluminum is produced.
Impurities are removed from the bauxite by chemical processing to make alumina (aluminum oxide). The bauxite is crushed, mixed in a caustic soda (sodium hydroxide) solution, and then heated by steam under pressure to dissolve the alumina. Settling and filtration remove impurities. After cooling, the solution is agitated, and crystals of hydrated alumina are formed. These crystals are washed and then dried in long rotating kilns. The final product, alumina or aluminum oxide is a very hard crystalline substance having the appearance of refined sugar. Four pounds of bauxite yields approximately two pounds of alumina.
Electrolyzing a solution of alumina in molten fluorides makes aluminum; this electrolysis takes place in reduction pots or cells at a reduction plant. Aluminum reduction plants produce pure, high quality primary aluminum. The reduction process removes the oxygen from the alumina, which consists of almost equal parts of aluminum and oxygen and leaves pure aluminum. Two kg of alumina yields one kg of aluminum.

Characteristics of Aluminum

Aluminum is lightweight, has excellent strength, high thermal and electrical conductivity, high reflectivity, good corrosion resistance, excellent workability, and attractive appearance. It can be given almost any finish. It is nonmagnetic, nontoxic, and non- sparking.
Aluminum weighs 32.523887897 kg/dm3 (kilogram / cubic decimeter), approximately 1/3 the density of steel, copper, and brass. Some of the stronger aluminum alloys exceed the strength of mild steel. The melting point of aluminum is 758 degrees Celcius.
The high thermal conductivity of aluminum is a marked advantage in any application where it is desirable to conduct or dissipate heat quickly and uniformly. On a weight basis, aluminum is the most efficient heat conductor of the common metals.

Two international studies confirm the benefits of the light metal

Two studies that relate to the beneficial use of aluminium in the automotive industry for cars, trucks and trailers, were recently published. The studies were based on the same premises: The use of aluminium results in a lower vehicle weight with a corresponding decrease in fuel con-sumption and CO2 emissions. 

Greater weight reduction potential than steel 
Using aluminium in key automotive components can safely reduce vehicle weight by as much as 40%, compared to only 11% for high-strength steel, according to a study conducted by the University of Aachen. The report, conducted by the Institut für Kraftfahrzeuge at the University of Aachen for the European Aluminium Association, analyzed 26 automotive components to assess the further potential or limits of weight reduction for both steel and aluminium. 
«Aluminium use in the automotive sector has increased steadily for the past four decades; how-ever this new study makes clear the environmental and safety advantages of the high-strength, low-weight material have yet to be fully realized. This study combined with other data on the benefits of aluminium suggest a total of about 238 kilos of additional weight savings, which could result a nearly 10% further improvement in fuel economy over a typical auto today. This can be done while maintaining - if not further improving – vehicle safety» said Randall Scheps, Chairman of the Aluminium Association’s Aluminium Transportation Group and Alcoa’s Director of Ground Transportation. 
The study found that using aluminium could result in significant weights savings for the analyzed components, ranging from 14 to 49%. Using a state-of-the art steel reference car, the maxi-mum weight reduction potential of aluminium in car bodies is approximately 40%. 
«Aluminium is more crash absorbent than steel and can safely cut vehicle weight without reducing vehicle size. This offers great potential, since lighter vehicles can produce fewer emissions and need less fuel or battery power to operate» Scheps said. 
Weight reduction potential using high strength steel was limited to only an additional 11%. The reason the potential weight reduction using high strength steel is so small, is that nearly 40% of the parts analyzed simply cannot be made thinner regardless of the grade of steel used. 
Potential for automotive aluminium lightweighting varies and options include maintaining a steel body with aluminium closures, hang-on and mounting parts, hybrid or multi-material designs for the body and full aluminium body. 
«The study confirms that the lightweighting potential is still considerable. Debates in Europe usually focus on improving powertrain technologies to improve the well-to-wheel energy con-version efficiency, but this only addresses the ‘supply’ side of the story and ideally should be complemented by vehicle mass reduction, in order to reduce the ‘demand’ for energy at the wheel» added Bernard Gilmont, Transportation & Building Director for the European Aluminium Association. Scheps concluded that «lightweighting the world’s overall transportation fleet through the use of aluminium has the potential to reduce greenhouse gas emissions by nearly 660 million tons annually, or 9% of global, transportation-related greenhouse gas emissions». 

Fuel and payload savings improve in trucks and trailers 
Substituting high strength, low weight aluminium for more traditional materials in Class 8 truck and trailers can eliminate 1500 kilos from the vehicle weight, according to a new report released by Ricardo Inc. The study was commissioned by the Aluminum Association Inc.’s Aluminum Transportation Group to analyze the fuel efficiency impact of lightweighting Class 8 trucks and trailers. The study simulated different configurations of vehicles and payload conditions (i.e. unloaded, gross vehicle weight [GVW] and half-GVW load) for the major drive cycles that represent commercial transportation in the United States. Based on these findings, aluminium could yield annual savings of fuel and emissions in Class 8 trucks and trailers as high as 6,000 litres and 17.9 tons of CO2. When considering these results for the total United States fleet, approximately two million vehicles, the overall economic and environmental impact of weight savings may be 4 billion litres of diesel and 10 million tons of CO2 per year. Driven largely by payload considerations, aluminium has experienced more than 30 years of continual growth in commercial applications. Today, the average Class 8 vehicle uses over 450 kilos of aluminium; however, this new study confirms that by further reducing overall vehicle weight with aluminium, transporters can load their vehicles with an additional 6.5% of payload at gross vehicle weight (GVW). This equates to fewer trips and an “effective” fuel and emissions savings of 6.5% for equivalent average ton-mile freight efficiency

Die casting is a precision process that involves injecting molten metal under high pressure into a die, or mold, of a desired shape. Dies are usually constructed with long-lasting, quality steel. Upon solidification and cooling of the material, the design, which can support a range of complex geometries and intricate details, is ejected for quenching, machining or finishing.

From the creation of scale replica cars and airplanes to the durable mechanical parts housed in their real-life counterparts, die casting is one of the most cost-effective and versatile manufacturing processes in the world.

This process can be repeated again and again with incredible dimensional accuracy, making it one of the best ways for manufacturing a high volume of castings.

In addition, some castings are completely finished when they are ejected from the die, which can eliminate the need for machining and additional finishing work. By offering a high-speed production process, precision and high-quality castings, die casting has become a valuable manufacturing method since its invention in 1838.

One of the most important choices to make when setting out to die cast a design is determining the type of alloy best suited to its specific application. Aluminum, magnesium, zinc, and zinc-aluminum (ZA) are the most common types of metallic alloys used in the die casting process. Each alloy has its own physical and mechanical properties, which are important factors in determining the longevity, strength, and overall functionality of the finished product. Unlike copper or ferrous alloys, the most commonly used alloys have lower melting temperatures, which influences cast ability. The complexity of the part, the minimum wall thickness and the required precision of the part will also influence how castable it is.

Depending on the application of your design and the metal alloy used, there are several different methods of die casting which offer more flexibility in manufacturing. These include the hot chambercold chamber and squeeze casting processes.

Hot chamber die casting is ideal for metals with lower melting temperatures like zinc and magnesium, and cold chamber processes are used for metallic alloys like aluminum that have higher melting temperatures. Squeeze casting is a process that requires no gas entrapment and produces high-quality components.

Aluminum, magnesium, zinc and zinc-aluminum are the four most commonly used alloys in die casting processes worldwide. The design’s application, material density, tensile strength, yield strength, melting temperature and modulus of elasticity are all important factors in selecting the alloy best suited to your design needs.

Aluminum Alloys

While it is not considered as castable as zinc due to a higher melting temperature, aluminum is the most commonly used alloy in the die casting industry, and it remains one of the most economical materials used in high-volume casting projects. Die cast aluminum parts can be found in everything from the components used to run your car to the electronics and power tools millions of people utilize every day.

With a specific gravity of 2.7, aluminum is considered to be a lightweight, structural material, but it is rarely cast in its purest form.

Because of the risk of hot cracking and shrinkage, aluminum is often alloyed with other materials including silicon, magnesium and copper.

  • Silicon increases fluidity, pressure tightness and modulus of elasticity in the alloy. In addition, silicon also reduces the metal’s specific gravity, thermal expansion and shrinkage. It also improves corrosion resistance.
  • Copper is used to increase corrosion resistance, tensile strength and the hardness of the alloy, providing it with superior mechanical properties.

There are now several aluminum alloys available to designers which are practical for a wide range of applications because of their varying physical and mechanical properties.

In addition to being lightweight, aluminum alloys are also resistant to corrosion, maintain strength at high temperatures provide high dimensional stability when casting intricate geometries and areas with thin wall thickness. They also possess high thermal and electrical conductivity. Machining aluminum is easier as well when compared to other materials including iron, steel and titanium.


Commonly Used Aluminum Alloys and Their Benefits

Seven of the eight most commonly used aluminum alloys are based on a system of eutectic composition, where 11.7 percent silicon is used as a reference point in grouping them.

Alloy 380 is used in a variety of products including home appliances, furniture, power tools, automotive parts, electronics and lawnmower housings because it offers the best range of properties for both the finished product and casting. With a combination of 8.5 percent silicon, and 3.5 percent copper, alloy 380 also offers a tensile strength of 324 megapascal, or 3304.43 kgf/cm².

Alternatives to alloy 380 include alloys 383 and 384, which are more resistant to hot cracking, and they offer improved die filling characteristics during the casting of complex components.

When compared to other aluminum alloys, alloy 360 offers greater strength during exposure to higher temperatures. It also offers better resistance to corrosion.

Alloy 443 offers the highest ductility, or the ability to stretch under tensile strength, of all aluminum alloys.

While zinc is ideal for casting components with thin walls, aluminum alloy 413 is useful for casting a variety of intricate parts. When manufacturing hydraulic cylinders, or other pressure machinery, it also offers better pressure tightness compared to its counterparts.

Alloy 390 provides better resistance to abrasion and wear, and it was originally developed for automotive engine blocks. However, alloy 390 offers the lowest ductility of aluminum alloys with elongation less than 1 percent.

Higher ductility comes from Alloy 518, which also possesses excellent resistance to corrosion when compared to other alloys used in casting.

Magnesium Alloys

Magnesium is another lightweight structural material commonly used in die casting, but like aluminum, it is alloyed with other metals to provide greater stability and better mechanical properties. In combination with metals like silicon, manganese, aluminum and zinc, magnesium alloys have become a great asset to the die casting industry. With a specific gravity of 1.7, magnesium is the lightest of the commonly used alloys available.

Alloy AZ91D is about 9 percent aluminum and 1 percent zinc, and it is the most widely used available magnesium alloy. AZ91D offers excellent strength, corrosion resistance and better castability compared to other magnesium alloys. By putting limits on impurities such as iron, copper and nickel, better corrosion resistance is obtained, making AZ91D one of the best choices when casting components that need to withstand wear.

Alloys AM60B, AM50A and AM20 are also commonly used in die casting, but they offer better ductility, while still maintaining corrosion resistance and strength. For applications that require enhanced strength when exposed to higher temperatures, alloys AS41B and AE42 are often the best option.

Magnesium is lightweight, and it has a durable structure for certain die cast components. Substituting magnesium components in place of heavier aluminum ones may contribute to lower fuel costs in vehicles, which has car manufacturers developing new technology to utilize magnesium’s unique properties.

For engine components that are susceptible to higher temperatures and corrosion, alloys AS41B and AE42 are an excellent choice. All magnesium alloys exhibit a high tensile yield strength and modulus of elasticity.

Zinc and Zinc-Aluminum Alloys

When it comes to casting components with tight tolerances and areas with thinner wall sections, no other alloys compare to the zinc and zinc-aluminum alloys. The element has a specific gravity of 7.0, making it one of the heaviest materials commonly used in die casting. Zinc is perfect for miniature die casting parts in high volume through a special hot-chamber injection process.

Like magnesium and aluminum, zinc is alloyed with other metals to provide better corrosion resistance, stability, dimensional strength and impact strength. Several of the available zinc alloys are referred to as ZAMAK, an acronym for zinc, aluminum, magnesium and copper.

Zinc 3 is the most commonly used zinc alloy, and it is sometimes exclusively used by die casters because of its tendency to be priced lower. In addition, the alloy provides a better surface finish during higher production rates, and it’s still capable of casting stable, intricate designs and complex components.

Another alternative to Zinc 3 is Zinc 5, which is used for its increased tensile strength, hardness and lower ductility. When it comes to producing a higher volume of components with thin walls, Zinc 7 can be used as it has a higher fluidity than other zinc alloys, which could increase production rates.

When looking for the highest strength and creep resistance, or deformation under mechanical stress, the Zinc-Aluminum alloy, ZA-8, is the best choice. With 8.4 percent aluminum and 1 percent copper content, ZA-8 provides lower densities with higher resistance to wear. Zinc alloys also provide better impact strength when compared to other commonly cast alloys.


Aluminum vs. Zinc Alloys

Just like with magnesium, one of the main differences between aluminum and zinc alloys is that zinc has a lower melting temperature and requires lower pressures for casting. Zinc is considered to be the most castable of all of the commonly used alloys.

By having a lower melting temperature, this enables a zinc die to last much longer than an aluminum die. Dies are expensive, and keeping them in service longer will provide a more cost-effective approach to large volume casting projects.

In addition, zinc’s lower melting temperature allows for hot chamber casting, which is less expensive than cold chamber processes. By using the hot chamber die casting method, production speed will also be increased. Zinc is one of the toughest alloys around, and it surpasses even aluminum in its ability withstand impact.

Another advantage to using a zinc alloy over an aluminum one is that zinc is great for castings with very intricate details and thin walls. When utilizing zinc, very little machining, trimming or finishing work is needed as the lower pressure and melting point reduce the thermal shock it experiences during casting. When casting in zinc, it maintains a smoother surface when a component is ejected from a die.


Aluminum vs. Magnesium Alloys

Like aluminum, magnesium alloys are utilized in the casting of automotive parts and provide their own unique mechanical and physical properties. While there have been experiments conducted to substitute magnesium for aluminum, it is still softer, less stable, more expensive and tends to bend easier when under stress.

While aluminum alloys take longer to solidify compared to magnesium alloys, its alloys provide a longer die life. In addition, aluminum does not require as much finishing work as magnesium. Special treatments and coatings are needed when determining a magnesium casting’s application.

When compared to the cost of melting aluminum, new technology has lowered the expenses required to melt magnesium alloys, but casting requires a higher injection speed. Conversely, magnesium has a quicker ejection time over aluminum castings. Magnesium is also better at casting components with thinner walls and tighter tolerances than aluminum.

However, even with the many advantages of magnesium, aluminum remains a less expensive alternative for die casting.


Zinc vs. Magnesium alloys

One of the main differences between magnesium and zinc alloys is that zinc and zinc-aluminum alloys require lower pressure and temperatures for casting. Because of a lower casting temperature, zinc provides a much longer die life than magnesium, which can help reduce production costs.

Unlike magnesium, which requires special treatments and coatings for corrosion resistance and finishing, zinc alloys also offer excellent corrosion resistance and a better surface finish when they are ejected from the die.


Determining Alloy and Casting Costs

Aluminum remains the most inexpensive alloy per cubic cm of all the commonly used alloys in die casting, but market value still fluctuates. Depending on the application and size of your design, costs may be lower based on the amount of material needed and the weight of the material.

Magnesium and aluminum are lightweight materials that offer excellent stability, but they have higher melting temperatures than zinc, which can contribute to higher casting costs. Hot chamber casting, which can be utilized with zinc and magnesium alloys, is less expensive than cold chamber processes, and it can run at a faster rate.

Die manufacturing is also an expensive process, and while the costs remain steady for the actual production of the die, determining the overall expected life a die is a good way to reduce expenses. For alloys like zinc, die life lasts much longer. Magnesium’s melting temperature is lower than aluminum and will allow for a longer die life as well.

When considering what alloy best suits your design needs, machining and finishing operations should also be considered. Zinc and zinc-aluminum alloys offer superior results over aluminum and magnesium when it comes to finishing, and they can drastically reduce the workload needed to produce a final product.

The most important thing to consider when selecting an alloy is the unique mechanical and physical properties they provide and how those will impact the performance and longevity of your design’s application.

For projects involving exposure to higher temperatures, aluminum offers better strength than other alloys. For designs that require a high yield strength and modulus of elasticity, zinc alloys are the best choice. Magnesium also offers many benefits due to its lighter weight, and it can be substituted for aluminum for specific components.


Aluminum is produced in two phases: refining the bauxite ore into aluminum oxide, and then smelting the aluminum oxide to release pure aluminum.

The manufacturing processes of aluminum include:


The broad term used to describe removal of material from a workpiece in the form of chips by covering several different processes such as; cutting, grinding, milling, drilling, tuning, etc. The same lathes, drill presses, milling machines and other metal-removal equipment commonly found in metalworking shops are routinely used to shape aluminum alloys. The metal may be turned, bored, milled or machined at the maximum speeds of which most machines are capable.


The process of fusing aluminum to itself or to other metal mediums through welding bending a mechanical fastening. Automotive aluminum can be joined by most of the same processes used to join steel. Improved materials, equipment and processes have made aluminum joining effective and reliable. Weld bonding, in particular, is especially well suited to aluminum, providing enhanced structural stiffness and excellent durability.


The process of cutting up a large aluminum sheet into workable pieces. Aluminum sheets are blanked and formed by stamping using the same equipment as is used today for steel. Clean-cut edges from a correct punch/die clearance are essential for developed blank production. Stamping die clearances, die radii and blank hold-down force must all be set-up for the forming characteristics of automotive aluminum.


Auto aluminum's manufacturability and workability have been proven in many ways, including bending and hydroforming processes that offer ease of tooling, cost-effectiveness, and a high degree of flexibility.


The process of coating aluminum to protect its surface. The cost of finishing to today's standards of corrosion and paint performance is high. A more efficient finishing system can be used with aluminum than with mild or galvanized steel due to its greatly enhanced corrosion resistance.

How is Aluminum Formed?

Aluminum can be formed in a number of ways.

Rolled – plate, sheet or foil. Plate is used in applications such as airplanes and building envelopes. Sheet is used in products such as car bodies, cans and trailers. Foil is used in food and beverage packaging as well as heat exchanges.

Forged – one of the oldest metalworking methods. Forging involves the shaping of aluminum using compression or hammering. Used to create high-strength parts.

Cast – the most common aluminum forming method casting involves pouring molten aluminum into a mold to duplicate a pattern. Used for production of high-volume parts requiring minimal machining. The Automotive industry is the largest market for castings.

Extruded – this process that yields almost unlimited design latitude to create shapes. Extrusions can be cut, machined, drilled, punched, hydroformed, notched, painted, anodized, brushed, or polished. Widely used in automotive, aerospace, marine, industrial and building applications.

Aluminum is Easily Alloyed with Other Elements:

  • Aluminum can be alloyed with magnesium, silicon, copper, zinc, and other elements.
  • Alloying aluminum improves traits such as formability, strength, or corrosion resistance.
  • Chemical composition limits for alloys are reviewed and registered by The Aluminum Association, Inc.
    • 5000-series alloys are used in structural and architectural products.
    • 6000-series alloys are easily formed, machined and are used in auto structural and non-structural components.
    • 7000-series alloys can be hardened to the degree that they are useful in aerospace.

In simple terms, the strength of the chemical bond between aluminium and oxygen is significantly stronger than the same bond between iron and oxygen. As a result, much more energy is required to split the bond and form the metal.

Energy-intensive to make, aluminium can save energy when it’s used to make lightweight, fuel-reducing transport. 

There is another complication that makes the situation worse: the relative chemical stability of the two oxides (alumina and iron oxide) and carbon monoxide. Above around 700°C, oxygen prefers to be bonded with carbon than with iron. This means that if you put coal or charcoal with iron ore above 700°C, you can make metallic iron. This discovery was one of the greatest breakthroughs in the history of the human race and underpins a large proportion of the Australian economy, as Australia is blessed with plentiful and rich sources of iron oxide and carbon (coal).

Unfortunately, this is not the case for aluminium oxide. The same reaction needs around 2000°C before metal is made. And, in fact, at that temperature a lot of aluminium carbide and vapour - waste products - is also made. As you can imagine, operating a furnace at 2000°C with poor yield is not attractive and this route for making aluminium has never taken off. Alcoa is currently trying to develop this route but it is unclear whether the “carbothermic route” to aluminium will ever be economically feasible.

Aluminium is made by dissolving the oxide into molten salts, at around a more modest 960°C, and applying a current to help break down the oxide. This is the Hall-Heroult process, which dominates world aluminium production at the moment. The process typically loses around 50% of the incoming energy as low grade heat, which is due in part to the fact that the salts required to dissolve the oxide are so corrosive that there no practical way to keep the heat in. There are also great challenges in the anode and cathode technology in the Hall-Heroult process that result in large resistance losses.

In general, high temperature electrolytic routes for making metals are the last resort for a metal producer. They suffer from low productivity and relatively high energy losses compared to standard pyrometallurgical processes. The aluminium industry would love to have the equivalent of the modern ironmaking blast furnace, which can produce around 3 million tonnes of metal per year in a small fraction of the volume, compared to the many acres of Hall-Heroult cells required to produce that much metal.

Building and Construction

Approximately one-fifth of the world's total consumption of aluminum is used by the construction industry. Bridges, domes, and roofs of several big structures, like markets, sports complexes, and stadiums make use of aluminum. It suits the cladding, stairways, railings, etc. Its malleable nature and stylish, shiny appearance makes it suitable for home décor items, like window frames, door knobs, railings, grills, curtain bars, as well as artifacts, indoor and outdoor furniture, doors, and interior panels. Aluminum can be cut, welded, bonded, tapered, and joined with other material. It is also used as a cladding to provide insulation for buildings along with stones and bricks. Aluminum scrap, casting, fabricating, pipes, sheets, tubing, tanks, bars, wire, stampings, windows, pins, doors, rods, railings, ladders, shutters, building bridges, skylights, etc., used in commercial buildings are also made up of this metal.


Around one-fifth of the extracted aluminum is used in the packaging of foods, beverages, pharmaceuticals, etc. Cans, trays, foils, bottles, thermos, utensils, kettles, refrigerators, toasters, and saucepans are made of this element. Aluminum is used as it keeps the food safe, prevents pathogens from entering the food, and does not affect the taste or smell of the food packed in it. It resists corrosion, repels water, and is non-toxic, which reduces spoilage of food items. In fact, aluminum helps protect the food items stored in it from other harmful elements, and hence, it serves as an excellent packaging material.


About a quarter of aluminum is used in transportation. Aircraft carriers, trains, ships, boats, buses, and other motor vehicles make use of aluminum because of its strength and weightlessness. Frames, exteriors, wiring, and electrical systems in airplanes make use of aluminum. Its resistance to corrosion and ability to form alloys with other metals makes it highly efficient to be extensively used in the transportation and automobile industry.

Automobile Industry

The metal is widely used in cars. Aluminum car parts have good thermal and aesthetic properties. These car parts are quite cheap. Few car parts, such as wheels, engine blocks, suspension components, hoods, transmission housings, and wheel spacer bars are made of aluminum. Other parts, such as carburetors housings, handles, few ornaments and logos, brackets, mirrors, air filler adapters, alternator housings, impellers, and fan clutch parts also involve its use. Valve covers are also made of this metal.


Electrical equipment, power lines, and electricity make use of about 10% aluminum. Its low density and high ductility is what makes it suitable for the transmission of high voltage electricity over long distances. Power lines of copper are expensive and need extra support structures to support its high electrical conductivity. Aluminum does not require all these, which saves on costs and being resistant to corrosion, it increases its durability. Hence, aluminum is replacing copper in transformers and wiring systems. It can also be used in casings, mountings, fuse boxes, satellite dishes, television sets, household appliances, sound systems, and other communication and electronic equipment.

Some Other Uses

  • Many consumer products make use of aluminum, which include household fittings, gas cylinders, containers, bicycles, etc.
  • The highly reflective nature of aluminum is useful in making mirrors and heat reflectors.
  • Marine equipment, like ship bodies, helipads, handrails, etc., make use of aluminum.
  • Baseball bats, tennis racquets, golf clubs, watches, etc., are also made up of this metallic element.
  • Super purity aluminum, which is 99.980 to 99.999% pure, is used in CDs and other electronic equipment.
  • Many salts and compounds of aluminum are used in manufacturing glass, ceramics, paper, paints, and artificial gemstones.
  • Some countries manufacture coins that are made of aluminum, or its alloy with copper.


Hardening caused by the precipitation of a constituent from a super-saturated solid solution.

All-over marking

A method of identifying sheet, plate and strip by printing at close intervals over the surface the name or symbol of the manufacturer, the relevant specification number and, in some cases, the temper and thickness of the material.

Alloying element

An element intentionally introduced in controlled quantity into a base metal or an alloy.

Aluminium alloy

A metallic substance, consisting of an intentional admixture of elements, the predominant element being aluminium.


The relative orientation of two adjacent faces of a section generally measured over the full Length of both.


Thermal treatment intended to soften a metal or alloy hardened by cold work or artificial ageing.


An electrochemical method of producing an integral oxide film on aluminium surfaces. The thickness and other film characteristics can be controlled to meet varied requirements for improved corrosion resistance, improved abrasion resistance, electrical insulation or as a pre-treatment for subsequently applied coatings.

Anodizing quality material

Material with characteristics that make it suitable for decorative anodizing after suitable preliminary treatment. As a general rule the purer the aluminium alloy the better it will anodize.

Anodizing test

A non-destructive test for detecting certain defects in material that is anodized and rinsed. If cracks or other superficial flaws are present in the material, they retain some of the chromic acid solution which subsequently seeps out and stains the anodic film.

Architectural anodizing

Anodizing to be used in permanent, interior, exterior and static situations where both attractive appearance and long life are essential.

Arrested mandrel

A mandrel attached to an auxiliary extrusion ram. As the main ram moves forward the mandrel is held stationary in the die, resulting in a product of uniform wall thickness along the length.

Artificial ageing

Thermal treatment of an alloy that increases precipitation treatment the hardness and strength by precipitation of constituents from the super-saturated solid solution at above room temperature.

As-quenched condition

The condition of an alloy during the time immediately following the quench and before the mechanical properties have been significantly raised by precipitation hardening.

Back end defect

A longitudinal discontinuity in the extreme extrusion defect rear portion of an extruded product that is normally discarded.

Back extrusion

A process in which a heated ingot in an enclosed container is extruded backwards over the mandrel and supporting stem.


A round, rectangular or regular polygonal solid section supplied in straight lengths. The term is applied to materials of not less than 6mm diameter or minor dimension.


The treatment of articles in a rotating tumbling container in the presence of abrasives and water for deburring or to produce a variety of surface textures.


Consignment, or a part thereof, comprising products of the same grade or alloy, temper and thickness or cross section, processed in the same manner.

Bend radius

The radius of curvature of the former around which a specimen is bent.

Bend test

The bending of a specimen to conform with a predetermined radius and angle, to assess bending characteristics and ductility.

Billet (Also often called a bloom)

A semi-finished product of square, rectangular, or round section, hot rolled, or forged. Producing billets or blooms from ingots by forging is called cogging, while by rolling is called blooming.

Bite mark

A mark on the roll coating caused by the initial feeding of the ingot, which is subsequently transferred to the hot rolled slab.


A piece of metal prepared for subsequent fabrication by forming, bending, cupping, drawing, impact extrusion, pressing, etc.


The production of circles and other shapes by shearing on a blanking press.

Blanking die

A die used for shearing circles and other blanks.

Blanking press

A press used for shearing blanks from plate, sheet or strip.

Blast cleaning

The projection of abrasive grit, sand, small grit blasting particles of steel, glass or other materials, sand blasting or a mixture of abrasive grit, water and air, shot blasting to strike the surface of an article in order vapor blasting to clean it. A matt or satin finish is produced, depending upon the particle size used.


A raised area on the surface of the metal caused by the expansion of a gas enclosed in a sub-surface void.

Bolt stock

Round bar or wire suitable for the manufacture of bolts.

Bond blister

A blister at the interface between the coating and the core of clad products.

Bore test

A test on tube to verify freedom from constriction by passing a metallic bob or wire of specified dimensions through the tube.


The deviation, in the form of an arc, of the longitudinal axis of a product.

Bored extrusion ingot

An extrusion ingot with a central bored extrusion billet longitudinal hole produced by machining.

Brazing rod

Rod of an alloy with a low melting range for use as filler metal in brazing.

Brazing sheet

Sheet of a low melting range alloy or clad with a low melting range alloy, used for brazing.

Brazing strip

Strip of a low melting range alloy or clad with a low melting range alloy, used for brazing.

Brazing wire

Wire of an alloy with a low melting range for use as filler metal in brazing.

Breaking down

The initial hot-working operation whereby a heavy reduction is given to rolling ingot or cast forging stock.

Bright anodizing

Anodizing with brightness as a primary objective.


Departure from flatness represented by alternate bulges and hollows along the length of a rolled product, the edges of which remain reasonably flat.

Bull block

A machine for drawing rod, bar and tube in coil form through one die.


A thin ridge of roughness on an edge left by a cutting operation such as slitting, trimming, shearing, blanking, sawing etc.


Bar or section for use as a common junction between electrical circuits.


Metal taken from the same melt in a furnace or crucible, or of several melts mixed in the same furnace or crucible before pouring, or metal taken from a furnace without subsequent addition (when a continuous melting process is used). In the case of continuous or semi continuous casting procedures this is also regarded as the product of a cycle up to 24 h where the same alloy and shape is cast.

Chatter marks

Regularly spaced superficial transverse markings produced by vibration between the metal and the working surface during fabrication.

Chemical brightening

Chemical treatment to improve the specular reflectivity of a surface.

Chemical conversion coating

Treatment of material with chemical solutions dipping or spraying to increase the thickness of the natural oxide film on the surface or to build up an oxide film bearing chromates or phosphates.

Chill casting

A process in which molten metal is poured into a permanent mould and solidified.


A circular blank fabricated from plate, sheet or foil.

Circumscribing circle

A circle that will just contain the cross section of an extrusion, usually designated by its diameter.

Clad material

Material that has a thin layer of aluminium or aluminium alloy metallurgically bonded to itusually by rolling, extruding or drawing.

Clipper die

A die used for removing the flash from stampings trimmer die and forgings.


The removal of the flash from drop stampings and pressings.

Close-to-form forging

A die forging of such dimensional accuracy that subsequent machining is eliminated or reduced to a minimum.

Closed die

Forging dies, usually in pairs, into which impressions have been cut to impart the required shape.

Coating blister

A blister in the coating of a clad product.


A final cold forging operation applied to obtain close tolerances.

Cold compression

Working of forged material at room temperature under compression through the thickness in the solution treated condition immediately after quenching to relieve internal stresses caused by quenching, and to minimize distortion during machining.

Cold working

Modification of a metal structure by working work hardening at room temperature or moderate temperatures, strain hardening resulting in an increase in strength and hardness with a general loss of ductility.

Colour anodizing

Incorporation of colouring matter either during anodizing or by subsequent processing into the film of anodized aluminium.


An inward curvature across the width of a surface of a rolled or extruded product.


Uniformity of wall thickness throughout the cross section of a tube. The tolerance on concentricity is established by the wall thickness tolerance.

Conductor wire

Wire possessing the requisite electrical and mechanical properties for use as an electrical conductor.


A hollow cylinder in an extrusion press from which the ingot is extruded.

Container stock sheet

Thin sheet used for the fabrication of packing can stock sheet containers and closures by pressing or forming operations.

Continuous casting

A process in which liquid metal is solidified rapidly in a water-cooled mould or die and continuously withdrawn and cut while the mould is being simultaneously replenished with liquid metal.

Control bar

A forged test bar in a given alloy, of known response to heat treatment, that is included in a furnace load to check the effectiveness of the heat treatment operation.

Controlled atmosphere

An atmosphere in which the concentration, temperature and pressure of constituents are maintained within controlled limits so as to minimize (or more rarely induce) certain reactions between the atmosphere and the material treated, e.g. oxidation.

Controlled stretching

Stretching to effect a specified extension (percentage permanent set) in order to relieve internal stress and to minimize distortion during machining.


An outward curvature across the width of a surface of a rolled or extruded product.

Cooling curve

A curve showing the relationship between time and temperature during the cooling of a metal.

Core blister

A blister in the core of clad material.

Corner radius

The radius of an arc to which adjacent sides of a product are tangential.


The deterioration of a metal by chemical or electrochemical reaction with its environment.

Critical quenching rate

The minimum mean cooling rate from solution treatment temperature necessary to enable an alloy to meet specified mechanical property requirements in the precipitation hardened condition.


The removal, by shearing or sawing, of the ends of cast or semifabricated products at an intermediate stage of processing.


The difference in thickness between one edge and the centre of a rolled product.

Cut-up test

A destructive test carried out on forgings to verify details of the grain flow and mechanical properties in various positions in the forgings.

Decking corrugated sheet

Formed sheet, usually of asymmetrical profile, having narrow, steep-sided troughs interspaced with wide flats.

Deep drawing

The forming of deeply recessed parts by means of plastic deformation of the material.

Deep drawing sheet

Specially produced sheet with characteristics that make it suitable for deep drawing.

Deep drawing strip

Specially produced strip with characteristics that make it suitable for deep drawing.


The removal of oil or grease, usually by a suitable organic solvent or an aqueous detergent.

Delayed ageing

Natural ageing delayed by keeping an alloy at a delayed age hardening temperature below room temperature. After returning to room temperature the natural ageing process continues normally.


Heating for a relatively long period at a temperature generally above 200 C, applied to certain non-heat treatable alloys in order to reduce their susceptibility to stress corrosion.


An operation designed to remove torsional deviations from the transverse axis along the length of an extrusion.

Die forging

A forging shaped by working in closed dies.

Die lines

Continuous longitudinal lines formed on extruded or drawn products by minor irregularities on the bearing surfaces of the die.

Die scores

Relatively deep continuous longitudinal lines on extruded or drawn products caused by the build-up of aluminium on the bearing surface of the die.

Differential annealing

The heating of blanks so that the peripheral annulus or other specified parts only are annealed.

Diffusion in clad material

Diffusion of the alloying constituents from the core to the cladding during thermal treatment.

Diffusion staining

Patchy discoloration that may arise from diffusion in clad material.

Dimensional tolerance

An allowable amount of deviation from a specified geometrical characteristic.

Direct chill (DC) casting

A casting technique in which the metal is solidified in a water-cooled open-ended mould from the bottom of which water is directly applied to the emerging ingot.

Direct extrusion

A process in which an ingot in the container is forced under pressure through an aperture in a stationary die.

Directional properties

The mechanical properties of a product in various directions with respect to the grain flow.

Dished edges

Departure from flatness associated with edge distortion during shearing, slitting or blanking.

Double skin

A thin surface layer separated from the parent material by a film of oxide or other foreign matter and originating during extrusion, sometimes described as a sub-surface defect.

Draft angle

Taper on the sides of die impressions and forgings to facilitate removal of the forgings from he die.

Draw bench

A machine for drawing bar, rod, sections and tubing in straight lengths.

Draw plug

A plug used in drawing tube to control the draw bulb internal dimensions.


The process of pulling material through a die to reduce the size, change the cross section or shape, or work harden the material.

Drawing die

A block of steel, or block containing a hard insert, with a hole of the required contour through which the product is pulled.

Drawing out

Increasing the length and reducing the cross-sectional area of forging stock by working under a hammer or press.

Drawn tube

A hollow product of uniform wall thickness, produced by cold drawing from tube bloom.

Drift expanding test / Drift Test

The diametrical expansion of the end of a tube sample to a predetermined amount by the insertion of a cone, to assess the quality of the tube. For ‘welded’ aluminium scaffolding tube this test is carried out to BS1139.

Drop forging

A die forging produced between a stationary bottom die and a free-falling weighted top die.

Drop hammer

A forging machine in which the force of the blow is derived from a free-falling weighted top die.

Drop stamping

A drop forging produced between closed dies.

Duplex ageing

Artificial ageing carried out in two successive stages at different temperatures.

Dye penetrant test

A non-destructive test in which clean and degreased material is immersed in or covered by a dye penetrant for a specified period. After the residual superfluous penetrant has been removed and a developer applied, the dye seeps out from any flaws and cracks, thereby making them easily visible.


Wavy projections spaced symmetrically around the rim of a deep drawn article due to variation in directional properties.

Eddy current test

A non-destructive test in which the impedance of a coil carrying an alternating current, which surrounds an article will vary with the characteristics of that article and thus can sometimes be used for the assessment of specific characteristics, e.g. internal soundness and thickness of anodic film.

Electrical conductivity

The reciprocal of electrical volume resistivity. Electrical conductivity is often expressed in terms of percentage of the International Annealed Copper Standard.

Electrical volume resistivity

The resistance of a specimen of unit length electrical resistivity and unit cross-sectional area of a given volume resistivity material.


Electrochemical treatment to improve the brightening specular reflectivity of a surface.

Embossed finish

A pattern mechanically impressed on a surface by rolling or pressure.

Embossed sheet

Sheet with embossed finish.

Equiaxed grains

Grains or crystals that have approximately the same dimensions in three axial directions.

Equivalent round

The diameter of a circle whose area is equal to the cross-sectional area of an extruded or drawn section.


The production of a uniform matt finish by controlled chemical (acid or alkali) or electrochemical attack.

Etching test

The treatment of a sample using a chemical reagent to reveal the macro-structure of the material.

Extruded round tube

A circular hollow extrusion of uniform wall thickness not subjected to cold drawing.

Extruded section

An extruded solid or hollow shape excluding bar, round tube and wire.

Extrusion die

A block of tool steel having one or more holes of the required contour through which an extrusion ingot is forced.

Extrusion effect

A characteristic non-recrystallized core in certain alloys that have been extruded. This results in higher tensile properties in the longitudinal direction than are obtained with the same alloys when in other wrought forms.

Extrusion ingot

A cylindrical or rectangular casting used Extrusion billet for extrusion. NOTE: See also hollow extrusion Ingot.

Extrusion press

A machine consisting essentially of a container, a ram or other pressure-applying device, and a die, used for the production of extrusions.

Extrusion ratio

The ratio of the cross-sectional area of the extrusion container to that of the extruded product.


The removal of unwanted metal from a forging at any stage of production.


A thin flange of excess metal squeezed out between the rolls in the production of hot rolled rod.

Finishing die

A die used during the final forging operation.

First-off forging

An initial sample made from new dies and used for checking dimensional and metallurgical quality.

Fixed mandrel

A tapered mandrel attached to the main extrusion ram. As the latter moves forward the mandrel passes through the hollow ingot and die giving a product slightly tapering in wall thickness along the length.

Flanging test

A test in which a disc-shaped rim of predetermined size is formed at the end of a tube sample to assess its suitability for the manufacture of tubular rivets.


A thin flange of excess metal squeezed out between the die faces in the production of a die forging.

Flash annealing

Annealing carried out by heating quickly and holding for a short time at an appropriate temperature.

Flash line

The line on a stamping or pressing corresponding parting line to the plane of contact between the dies used in the process of manufacture.

Flashless forging

A forging produced within totally enclosed dies that preclude the exudation of excess metal between the parting faces of the dies. NOTE: See also flash and flash line.

Flattened wire

Material produced by flattening round wire between rolls.


The removal of deformation in plate, sheet or strip in order to produce a flat product. The operation is carried out by stretching, local reverse bending, etc.

Flattening test

A test in which a tube sample is flattened in a direction perpendicular to the longitudinal axis until the diameter or major axis is reduced to a predetermined value.


The extent to which the surface of a product approaches a true plane.

Floating mandrel

A tapered mandrel, that is not attached to, but moves forward with, the main extrusion ram and that is left free to centre itself in a hollow extrusion ingot. The resulting product tapers slightly in wall thickness along the length.

Fluorescent penetrant test

A dye penetrant test for detecting flaws and cracks using a fluorescent dye with subsequent examination of the dried material under ultraviolet radiation.


A cold-rolled product of rectangular section thickness not greater than 0.2mm.


Semi-finished coiled strip for further rolling to foil.

Forged ring

A ring of regular cross section produced by either trunnioning or rolling, which results in the principal direction of grain flow being circumferential, i.e. concentric with the ring.


A shape produced by hammering or pressing, usually when hot, between open or closed dies.

Forging ingot

A solid circular or rectangular casting used for subsequent forging.

Forging mandrel

A cylindrical bar on which a forged ring is expanded by the process of trunnioning.

Forging stock

A rod, bar or other wrought section suitable for forging.

Formed section

Section produced from strip by roll-forming or drawing, or both, or from sheet by the use of a press brake.

Fracture test

A test in which a piece of metal is notched and broken, and the fractured surface examined in order to assess grain structure and freedom from defects.

Free machining alloy

An alloy that, by virtue of its chemical composition and condition, is designed to give, on machining, small broken chips, lower power consumption, better surface finish and/or longer tool life.

Frosted finish

A white, slightly specular finish produced by etching.

Full heat treatment

Solution treatment followed by artificial ageing.

Gauge length

The prescribed part of the cylindrical or prismatic portion of the testpiece on which elongation is measured at any moment during the test. In particular, a distinction should be made between the following:

(a)  the original gauge length ( ), gauge length before the test piece is strained; and

(b)  the final gauge length ( ), gauge length after the test piece has been fractured and the fractured parts have been carefully fitted together so that they lie in a straight line.

General purpose

Formed sheet with symmetrical, near-sinusoidal corrugated sheet profile 19mm deep at 76.2mm pitch.

Grain flow

Elongation of the grain structure in the direction of working.

Grain growth

The coarsening of the grain structure occurring under certain conditions of heating.

Grain size

The mean size of metal grains usually expressed in terms of the number of grains per unit area or as the mean grain diameter.

Grey plate finish

A matt finish produced by a special rolling technique.

Hammer forging

A forging produced by repeated blows in a forging hammer.

Hand forging

A forging produced by manipulating metal between open dies.

Hard anodizing

Anodizing under special conditions to produce a hard film offering extremely high resistance to abrasion.


The resistance of a metal to plastic deformation usually by indentation.

Hardness test

A test by which the resistance to deformation is determined, usually by relating the load applied to an indenter of prescribed form to the depth or surface area of the impression produced.

Heat treatable alloy

An alloy capable of being strengthened by suitable heat treatment.

Heat treatment

The heating and cooling of a solid metal or alloy in such a way as to obtain desired conditions or properties. Heating for the sole purpose of hot working is excluded from the meaning of this term.

Heat-treatment batch

A quantity of material of one alloy of the same dimensions and produced in the same way, solution treated in one furnace load, or such material so solution treated and subsequently artificially aged in one furnace load. More than one heat-treatment batch may comprise a furnace load. In the aircraft sphere the material is normally from one cast.

Herring bone mark

Superficial markings taking the form of alternate light and dark bands forming a V or W pattern across the width of strip-mill rolled material.

Holding time at temperature

The duration of holding at the prescribed temperature, including the specified tolerance from the time when the coolest part of the metal attains the minimum specified temperature.

Hollow extrusion ingot

An extrusion ingot with a central longitudinal hollow extrusion billet hole produced either at the casting stage or by machining a solid ingot.

Hollow section

An extruded shape, other than round, the cross section of which completely encloses a void or voids and which is not subject to cold drawing.


A process in which metal is heated at high temperature during a specified time generally in order to facilitate working and to confer certain desirable properties on the semi-fabricated product.

Hot line quenching / Hot mill quenching

Cooling of a rolled product leaving the hot line or hot mill with the primary object of retaining soluble constituents in solid solution after quenching.

Hot rolled rod

An approximately round section, normally of 9.5mm nominal diameter, produced by a hot rolling process.

Hot shortness

Brittleness in metal in the hot forming range and also the characteristic of a metal that results in a loss of plasticity at or near the melting point.

Hot working

Plastic deformation of a metal or alloy within a temperature range and at a rate such that significant strain hardening does not occur.

Immersion coating

Chemical surface treatment in which other metals (zinc, tin, copper, lead, silver, Nickel) are deposited on aluminium by chemical displacement and serve as a substrate for subsequent electroplating or electroless plating.

Impact extrusion

A process in which an unheated slug is extruded through a die by a single blow in the direction of the blow, or in the space between the punch and the closed die in the direction counter to the blow.


Metallic or non-metallic substances in a metal or alloy that were not intentionally added.


Extraneous material accidentally entrapped within the metal during casting.

Incubation period

The interval between the quenching operation and the start of a significant change in properties produced by precipitation hardening.

Indirect extrusion

A process whereby a moving die located at the end of a hollow ram is forced against a stationary ingot.


A cast form suitable for remelting or billet fabricating.

Integral colour anodizing

Production of colour anodized finishes by the use of special alloys of aluminium and/or special organic electrolytes that produce a colour during anodizing.

Integral test piece

A tensile test sample produced integrally with the work-piece usually on forgings.

Intercrystalline corrosion

Corrosion occurring preferentially at grain intergranular corrosion boundaries.


The practice of protecting the surface of plate, sheet and strip by separating adjacent surfaces by suitable paper or plastics film.

Internal stress

Stresses set up within the material as a result of previous operations, e.g. casting, thermal treatment or fabrication.

Irregular section

A solid drawn or extruded section the profile of which cannot be divided readily into approximate rectangles of measurable dimensions.

Isothermal quenching

Quenching carried out in a medium at a temperature intermediate between the solution treatment temperature and room temperature, and at which the metal is held for a prescribed time to induce precipitation hardening.


An abrupt bend or departure from flatness.

Laminated product

Composite product consisting of two or more sheets or films joined together, e.g. paper to foil, plastics film to foil, etc.


Internal crack aligned parallel to the principal surfaces of a sheet or plate.


An open-ended surface discontinuity formed as a result of metal folding over during mechanical working.

Lateral curvature

The lateral departure, in the form of an arc, edge curvature of an edge from straightness.

Layer wound coil

Wire wound layer on layer across the width of a spool, where the width of the coil is greater than the width of the material.


The dimension that lies in the direction of maximum working.


Grinding with a coarse abrasive to remove scurfing superficial defects either to produce a decorative finish or preparatory to further processing.


Fusion of the lower-melting point constituents of an alloy during hot working or thermal treatment.

Lock-seamed tube

Tube formed from strip, the seam being mechanically locked.

Long transverse direction

The direction along the major axis at right angles to the longitudinal direction.

Longitudinal direction

The direction parallel to the principal elongation during working.

Longitudinal properties

The properties in the direction parallel to the principal elongation during working.

Lower critical strain

The minimum amount of cold work or cold deformation necessary to initiate recrystallization during subsequent annealing or solution heat treatment and which usually causes the growth of coarse grains.

Luders lines

Surface markings resulting from localized flow that appear on some alloys after light straining. They lie approximately parallel to the direction of maximum shear stress (about 45 to the direction of applied stress).

Machining stock

Bar or wire usually supplied to close tolerances and suitable for repetition machining operations.


A steel insert within the die orifice controlling the internal form of hollow products during extrusion, forging or drawing.

Mass effect

The effect of the size and shape of an article on the rate of heat transfer during quenching, resulting in variations in mechanical properties from the outside to the centre.

Matching draft angle

A draft angle greater than the natural draft angle necessitated on forgings unequally disposed about the flash line to provide coincident edges on that line.

Matt finish

A diffuse finish usually produced by etching, scratch brushing or blast cleaning.

Mean diameter

The sum of any two diameters at right angles divided by two.

Mean wall thickness

The sum of the wall thickness of tube measured at the ends of any two diameters at right angles, divided by four.

Mechanical polishing

Polishing with an abrasive belt or flexible rotating mop carrying an abrasive buffing compound.


A machining process in which metal is removed by a revolving multi-edged cutter to provide flat or profile surfaces.

Mirror finish

A rolled or polished finish with high specular reflectivity.


The maximum lateral displacement of any point in that part of a forging formed by one die from its correct position relative to the part of the forging formed in the other die of the pair.


Preliminary die-shaping prior to forging between closed dies.

Moulding die

A die that shapes the stock prior to forging preforming die between closed dies.

Multi-hole die

An extrusion die having more than one hole.

Multi-hole die effect

Non-concentric configuration of grain structure resulting from the use of multi-hole dies.

Nail wire

Alloy wire of high corrosion resistance suitable for the manufacture of nails.

Natural ageing

Increasing the hardness and strength of an alloy by spontaneous precipitation of constituents from a super-saturated solid solution at room temperature.

Natural draft angle

The minimum draft angle compatible with consistent freeing of the top die from the product during forging.

Natural oxide film

The film of aluminium oxide that forms naturally on aluminium and is relatively impervious to atmospheric attack. The thickness of this film and the protection it offers can be increased by Anodising.

Non-heat treatable material

An alloy incapable of being strengthened by thermal treatment.

Oil staining

Staining associated with the partial decomposition of residual lubricant during thermal treatment.

Oilcan effect

In sheet or strip, a localized departure from flatness that behaves in a similar manner to the diaphragm of an oilcan under alternating pressure.

Orange peel effect

Surface roughening on formed products resulting from the use of coarse grained material.

Open die

A forging die with a flat face, i.e. a die into which no impression has been cut.


The departure of the cross section of a round tube, bar or wire from a true circle.


Artificial ageing treatment at too high a temperature or for too long a period, resulting in slight softening of the metal after the maximum hardening effect has been achieved. In some cases this may be done deliberately,

e.g. to improve resistance to stress corrosion.


Modification of the structure of an alloy made evident by the fusion of certain constituents and by a reduction in mechanical properties.Overheated material cannot be reclaimed by thermal or mechanical treatment.


Stretching to such a degree that stretcher markings develop or the grain structure of the metal is revealed.

Pack marks

Small superficial marks associated with differential metal flow in pack rolling.

Pack rolling

The simultaneous rolling of two or more thicknesses of sheet, strip or foil.

Pancake coil

Narrow strip and flattened wire wound layer on layer where the width of the coil is equal to the width of the material.

Partial annealing

Thermal treatment of a cold worked metal or alloy to reduce the strength to a controlled, but not fully softened, level.

Patterned sheet

Sheet on which a raised or indented pattern has been impressed on either one or both faces.

Patterned strip

Strip on which a raised or indented pattern has been impressed on either one or both faces.

Percentage elongation

The elongation of the gauge length after after fracture (A) fracture, expressed as a percentage of the original gauge length

Percentage reduction area

The maximum change in cross-sectional area that has occurred divided by the original cross-sectional area, expressed as a percentage. In the tensile test the percentage reduction of area, Z, is the maximum change in cross-sectional area that has occurred during the test, S - S , divided by the original cross-sectional area, S , expressed as a percentage.  S is the minimum cross-sectional area afterfracture).

In extrusion the percentage reduction of area is the change of cross-sectional area that has occurred during the extrusion, S - s, divided by cross-sectional area before extrusion, S, expressed as a percentage. Here S relates to the cross section of the container.

Peripheral coarse grain

An area of recrystallized grains at the peripheral grain band periphery of an extruded product (or forged product if made from extruded stock), which has lower properties than the non-recrystallized core.

Peripheral grain band

See peripheral coarse grain.


Irregular surface roughness caused by intermittent adhesion between the forming tools and the metal.

Piercing mandrel

A mandrel attached to an auxiliary ram that pierces solid extrusion ingots and thereafter serves as an arrested mandrel.


Metal in a form suitable for remelting, cast directly from the extraction process without being subjected to any intermediate metallurgical processing.

Pitting corrosion

Localized corrosion resulting in small pits or craters in the metal surface.


A product of rectangular section over 6mm thick, supplied flat and with less control of surface finish than applies to sheet.


Reducing one end of a rod, bar, tube or wire to tagging a size capable of passing through a drawing die.

Porthole die

An extrusion die that incorporates a mandrel as an integral part of the die assembly. Bridge, spider, duo and self-stripping dies are special forms of porthole die. These are used to produce extruded hollow products from solid extrusion ingots.


A short thermal treatment applied after quenching and before the end of the incubation period.

Precipitation annealing

Heating quenched and precipitation hardened metal for a sufficient length of time at a temperature between the artificial ageing temperature and the solution treatment temperature in order to produce a relatively high degree of softening by means of coalescing the hardening precipitates.

Precision forging

A die forging made to special tolerances.


A process in which the workpiece is raised to the temperature required for entry to the first hot working operation. In some cases this may be combined with homogenization.


A general term for a machine employing pressure to deform or shear metal.

Press discard

That portion of an extrusion ingot that is left unextruded.

Press forging

A die forging made on a mechanical or hydraulic press by one or more applications of sustained pressure.

Press quenching

Cooling of an extruded product leaving the die with the primary object of retaining soluble constituents in solid solution after quenching.


The shaping of sheet or forging stock between closed dies on a mechanical or hydraulic press.

Pressure test

A hydraulic or pneumatic test applied to tube to ensure that the material will withstand a specified pressure for a specified time without unacceptable leakage or distortion.

Pretreatment priming

The application of a solution containing a resin, a chromate and an acid, which is allowed to dry on and provide the key for subsequent painting.

Primary aluminium

Metal extracted by reduction from, or by decomposition of, an aluminium compound, which has not been subjected to any fabricating other than casting into pigs or ingots. Scrap from the ingot producer's own operations, which arises directly from the casting or working of primary melts, may be incorporated in primary melts without modifying the character of primary melts, provided that the identity of the scrap metal is fully established and maintained, and that no metallic impurities foreign to the producer's primary unalloyed aluminium operation are a possible cause of contamination.


The application of a priming paint, often pigmented with a corrosion inhibitor such as zinc chromate, after suitable pretreatment.

Printed foil

Foil printed with a design or all-over colour.

Profile wire

A solid section, other than round, square or regular polygonal, of 10mm maximum dimension, produced by a wire-drawing process. Typical sections are pinion, serrated, half-round and triangular.

Proof stress (Rp)

The stress at which a non-proportional elongation equal to a specified percentage of the original gauge length occurs. When a proof stress is specified, the non-proportional elongation should be stated (e.g. 0.2% or 1%) and the symbol used for the stress should be supplemented by an index giving this prescribed percentage of the original gauge length, e.g. Rp0.2.

Protective anodizing

Anodizing where protection against corrosion or wear is the primary object and appearance is of secondary or no importance.

Protective oiling

The application of oil to products to provide temporary protection against atmospheric attack during transit and during storage.


The removal of metal from rolled or extruded products by perforating or shearing on a press with a punching die.


A process of cooling a metal or alloy from an elevated temperature by contact with a solid, a liquid or a gas, at a rate rapid enough to retain some or all of the hardening constituents in solid solution. NOTE: See also as-quenched condition, critical quenching rate, isothermal quenching, quenching stress, self-quenching alloy.

Quenching stress

Non-uniform stress retained within the metal after quenching.

Random lengths

Cut pieces usually specified between wide limits of length.


Formation of a new grain structure by the heating of cold worked material.

Recrystallization annealing

Thermal treatment to soften a cold worked metal or alloy by complete recrystallization.


The correction of dimensional irregularities.


The straightening of round bar, rod or tube by a rotary and flexing action by passing it through offset driven rollers.

Reeling marks

Superficial spiral markings present on round extruded or drawn products that have been straightened by reeling.

Refined aluminium

Metal of very high purity (conventional aluminium content 99.95% and more) that is obtained by special metallurgical treatments.

Reflector sheet

Rolled material with characteristics that make

it especially suitable for the manufacture of anodized reflectors.

Regular section

A solid drawn or extruded section, not otherwise covered by the definition of a bar, that can be conveniently divided into approximate rectangles with measurable dimensions, e.g. angles, channels, tees, etc. The ratio of maximum thickness to minimum thickness of such regular sections does not exceed 4:1.


Heating metal to hot working temperature. In general no structural changes are intended.

Residual stress

Such internal stress as may be left in the finished product after fabricating operations, including stress relieving (where applicable), have been carried out.


A surface effect in the form of a very slight repeated transverse wave or shadow mark, sometimes encountered with rolled or drawn products.

Rivet stock

Round bar or wire suitable for the manufacture of rivets.

Roll mark

A defect on plate, sheet, strip or flattened wire, repeated at regular intervals and caused by an imperfection in the roll surface.

Roll-bonded sheet

A composite of two sheets pressure welded together during rolling except at predetermined areas that are subsequently inflated to form a labyrinth or passageway.

Roller levelling

The flattening of plate or sheet by passing it between a series of staggered rolls of small diameter.

Roller straightening

The straightening of an extrusion, other than round, by passing it through a series of staggered rolls of small diameter.

Rolling ingot

A solid rectangular casting used for rolling rolling block into plate, sheet, strip and foil. rolling slab

Ruling thickness

The dimension of a bar, forging or component across which the time of transfer is the longest in heat treatment operations.

Satin finish

A fine-textured matt finish.

Satin-finish sheet

Sheet having a fine-textured matt finish on one or both surfaces.

Satin-finish strip

Strip having a fine-textured matt finish on one or both surfaces.

Scaffold tube

Extruded tube of dimensions and strength suitable for scaffolding.


The surface machining of extrusion ingot, forging stock, rolling ingot and wire bars (or of semi-finished wrought products) preparatory to their fabrication.

Scratch-brushed finish

A matt or satin finish produced by abrasion with rotating wire brushes.

Screw stock

Round bar or wire suitable for the manufacture of screws.

Sealing of anodic coatings

A treatment applied after anodizing to reduce porosity and/or absorptivity of the coating.

Seamless tube

Tube in which there is no split or deliberate longitudinal bonding of two or more edges by pressure, fusion or mechanical interlocking.

Secondary aluminium

Metal obtained by the recovery and treatment of metal that has been submitted to at least one fabricating process by casting or working and does not conform to the definition of primary or refined aluminium.

Secondary aluminium alloy

Alloy obtained by the recovery and treatment of metal that has been submitted to at least one fabricating process by casting or working.


Non-uniform distribution or concentration of impurities or alloying constituents that arises during the solidification of an ingot.

Self-quenching alloy

An alloy that is relatively insensitive to cooling rate from solution heat treatment temperature, i.e. in which the critical quenching rate is normally less than the rate of cooling in still air.

Semicontinuous casting

A process in which the liquid metal is, solidified rapidly in a water-cooled mould or die and continuously withdrawn until the required length has been produced, when casting is discontinued.

Shaped tube

Drawn tube of a shape other than round.


The drawing of hot rolled rod, tube or wire through a die with a cutting edge in order to remove a thin layer from its surface.

Shear strength

The maximum stress that the material is capable of sustaining in shear.

Shear test

A test in which the test piece is stressed in shear until fracture to determine its shear strength.


The cutting of metal by the use of a press or guillotine.


A rolled product of rectangular section over 0.2mm but not exceeding 6mm thick, supplied flat.

Sheet mill

A mill used for cold rolling either plate or sheet.

Short transverse direction

The direction along the minor axis at right angles to the longitudinal direction.

Single-hole die

An extrusion die having only one hole.


The reduction of the outside diameter of tube sinking pass by pulling it through a die without using a draw plug or mandrel.

Sintered aluminium powder

A wrought product made from fine oxidized product aluminium powder by compacting, sintering, hot pressing and subsequent working.

Skin pass

A light cold rolling of sheet or strip to improve surface finish and to minimize stretcher strain on further manipulation. This operation may increase the elastic limit and to a lesser extent the tensile strength.

Sliding fit

The ability of two pieces of metal, one having internal and the other external bearing surfaces of complementary shape, to fit and move easily one within the other.


The cutting of strip into two or more widths by the use of rotary shears.


A thin elongated piece of the parent metal adhering imperfectly to the surface of a product.


A blank prepared for impact extrusion.

Solution treatment

A thermal treatment in which an alloy is heated to a suitable temperature, and is held at this temperature long enough to allow constituents to enter into solid solution and is then quenched.

Speed cracking

Transverse surface cracks produced by excessive speed cross hatching extrusion speed and/or extrusion emergence temperature.

Spectrochemical  Analysis

Test performed to verify material chemistry

Spinner straightening

The automatic straightening and cutting to and cutting length of coiled wire by feeding it through a machine consisting of rotating offset dies in tandem with a pair of cropping dies.

Split tube

Tube formed from strip with an open seam.

Spring back

The partial elastic recovery of materials after cold deformation.

Stabilization treatment

Thermal treatment used to accelerate constitutional or structural changes in order to promote stability in dimensions, mechanical properties, structure or internal stress under service conditions.


The shaping of sheet or forging stock between closed dies on a drop hammer.

Step ageing

Artificial ageing treatment carried out in successive stages at different temperatures.

Stepped extrusion

An extrusion having one or more abrupt changes in cross section along its length.

Stop mark

A transverse peripheral ridge on a product arising from a stoppage during rolling, extrusion or drawing.


The removal of longitudinal distortion in a drawn or extruded product.


The extent to which the axis or the edge of a product approaches to a straight line.

Strain hardening

Modification of a metal structure by working cold working at room temperature or moderate temperature work hardening resulting in an increase in strength and hardness with a general loss of ductility.

Stress corrosion

Failure by cracking resulting from selective directional attack caused by simultaneous interaction of sustained tensile stress at an exposed surface with the chemical or electrochemical effects of a service environment.

Stress relieving

The reduction of residual internal stresses by thermal or mechanical means.

Stretcher grip marks

Transverse indentation at the ends of a product impressed by the grips of the stretching machine.

Stretcher strain markings

Permanent surface distortion in the form of either flamboyant patterns or Luders lines that appear when materials are stretched. The onset of these markings varies according to the type of material and the degree of stretching.


The levelling of rolled materials or the straightening of extruded and drawn materials by imparting sufficient permanent extension to remove distortion.  NOTE: See also overstretching.


A cold rolled product of rectangular section supplied in coil, over 0.2mm but not exceeding 3mm thick.

Strip mill

A mill with coiling equipment, employed for the cold rolling of strip.

Super annealing

The annealing of heat treatable alloys followed by a slow, controlled rate of cooling to produce a condition of maximum ductility with a minimum tendency to natural ageing.

Surface bloom

Surface discoloration that may develop on aluminium during exposure to moist atmospheres or during thermal treatment.

Surface texture

Those irregularities with regular or irregular spacing that tend to form a pattern or texture on the surface.


The reduction of the circular cross section of stock by a hammering or squeezing action.

Swageing die

Forging dies used in pairs, through which stock is worked by a hammering action, the circular cross section of the material thereby being reduced.

Tapered extrusion

An extrusion tapering continuously along its length.


Characteristic structural and mechanical properties produced in a metal or alloy by transformation processes,

e.g. mechanical and/or thermal treatments.

Temper drawing

Controlled reduction by drawing to develop the required mechanical properties.

Temper rolling

Controlled reduction by cold rolling to develop the required mechanical properties.

Tensile strength (R )

The maximum force divided by the original cross-sectional area of the test piece, i.e. nominal stress corresponding to the maximum force.

Tensile test

A test in which the test piece is stressed in tension, generally until fracture, to determine one or more of its tensile properties.

Tension levelling

A method of flattening strip continuously on a series of staggered rolls with applied tension, thus stretching the strip while bending it.


An allowable amount of deviation from a specified characteristic.


A projection of metal on a forging to facilitate manipulation during processing.

Tonghold test piece

A tensile test sample taken from the tongholdof a forging.

Torsion test

A test in which a sample is twisted axially for a given number of revolutions.

Traffic marks

Abrasions, usually dark in colour, resulting from relative movement between contacting metal surfaces during transit.

Transfer period

The time between removing the material from the solution treatment furnace and immersion in the quenching medium.

Tread plate / Treadplate

Plate upon which a raised or indented non-slip pattern has been impressed by rolling.


The removal of excess metal from the edges of dressing a semifabricated product.

Troughed type A corrugated

Formed sheet of asymmetrical profile with wide sheet truncated-vee troughs.


The expansion by rotary forging of a hollow round blank over a mandrel to increase the internal diameter with or without an increase in the external diameter.


A hollow wrought product that is long in relation to its cross section with a uniform wall thickness (except where corner radii are involved in shaped tube).

Tube bloom

A circular hollow extrusion of uniform wall be shell thickness used for the production of drawn tube.

Tube reducing

The production of tube from tube bloom by rolling on a mandrel.


The heavy moving portion of the drop stamp carrying the top die.

Turks head die

Four adjustable undriven rollers arranged mutually at right angles to serve as a die for the final shaping of solid and hollow sections, e.g. squares and rectangles.


Torsional deviation of the transverse axis along the length of a product.

Ultrasonic Testing

A method of non-destructive testing of solid metal For internal flaws utilizing high frequency sound waves.


Artificial ageing treatment at too low a temperature and/or for too short a period resulting in a failure to attain the maximum hardening effect.

Upper critical strain

The minimum amount of cold work necessary to eliminate the cold work structure of elongated grain and produce a fine recrystallized grain during annealing or solution heat treatment.


A method of working forging stock in order to increase its cross-sectional area.

Venetian blind strip

Thin gauge strip specially produced with characteristics that make it suitable for the manufacture of venetian blind slats.

Wavy edges

Departure from flatness represented by a corrugated or wave-like formation of the edges of a rolled product in which the centre area remains flat.

Welded tube

Tube formed from plate, sheet or strip with the abutting edges automatically welded.


The dimension that lies transverse to the direction of maximum working.


A round, square or regular polygonal solid section of not more than 10mm diameter or width across flats produced by drawing, usually supplied in coil.


A cast or extruded square or circular section used for the production of hot rolled rod and ultimately wire.

Work hardening

Modification of a metal structure by working cold working at room temperature or moderate temperatures strain hardening resulting in an increase in strength and hardness with a general loss of ductility.


Deformation of a metal with general elongation but not necessarily in a preferred direction. Working may be carried out hot or cold by such processes as rolling, extruding, forging etc.

Wrapping test

The test consists of winding the wire a specified number of turns around the mandrel of the diameter stated in the material specification. It may also include a specified programme of unwinding or of unwinding and rewinding.

Wrought product

Product made by hot, or hot and cold, plastic deformation of