Physically, chemically and mechanically, aluminum is a metal similar to steel, brass, copper, zinc, lead or titanium. It can be melted, cast, formed and machined in a similar way to these metals and conducts electric currents. In fact, often the same equipment and fabrication methods are used as for steel.
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Aluminum is a very light metal with a specific weight of 2.7 g/cm3, about a third of that of steel. This cuts the costs of manufacturing with aluminum. Again, its use in vehicles reduces dead-weight and energy consumption while increasing load capacity. This also reduces noise and improves comfort levels.
Its strength can be adapted to the application required by modifying the composition of its alloys. Aluminum-magnesium-manganese alloys are an optimum mix of formability with strength, while aluminum-magnesium-silicon alloys are ideal for automobile body sheets, which show good age-hardening when subjected to the bake-on painting process.
Aluminum naturally generates a protective thin oxide coating which keeps the metal from making further contact with the environment. It is particularly useful for applications where it is exposed to corroding agents, as in kitchen cabinets and in vehicles. In general, aluminum alloys are less corrosion-resistant than pure aluminum, except for marine magnesium-aluminum alloys. Different types of surface treatment such as anodising, painting or lacquering can further improve this property.
Aluminum is an excellent heat and electricity conductor and in relation to its weight is almost twice as good a conductor as copper. This has made aluminum the first choice for major power transmission lines. It is also a superb heat sink for many applications that require heat to be drained away rapidly, such as in computer motherboards and LED lights.
Aluminum is a good reflector of visible light as well as heat, and that together with its low weight, makes it an ideal material for reflectors in, for example, light fittings or rescue blankets. Cool roofs made of coated aluminum are invaluable in reducing internal solar heat within a house, by reflecting up to 95% of sunlight.
Aluminum is ductile and has a low melting point and density. It can be processed in several ways in a molten condition. Its ductility allows aluminum products to be formed close to the end of the product’s design. Whether sheets, foil, geometrical configurations, tubes, rods or wires, aluminum is up to them all.
In contrast to steel, which rapidly becomes brittle at low temperatures, aluminum shows increased tensile strength as temperatures drop.
Aluminum foil is only 0.007 mm in thickness, but is still durable and completely impermeable, keeping any food wrapped in it free of external tastes or smells. It keeps out ultraviolet rays as well.
Moreover, the metal itself is non-toxic and odorless, which makes it ideal for packaging sensitive products such as food or pharmaceuticals. The fact that recycled aluminum can be used reduces the carbon footprint for this stage of food and beverage manufacturers as well.
Aluminum is non-magnetic, making it useful for electrical shieldings as in computer disks, dish antennas, busbars or magnet housings.
Aluminum is non-toxic and is used to make woks, pressure cookers and many other cooking utensils without fear. It is easily cleaned and does not contaminate the food at any stage.
Aluminum is an excellent sound absorber and is used for constructing ceilings. It is also used in auto bumpers due to its shock-absorbing properties.
Aluminum produces no sparks when it comes into contact with itself or non-ferrous metals.
Aluminum is 100% recyclable and recycled aluminum is identical to the virgin product. This makes it a much more cost-effective source material for production runs. The re-melting of aluminum requires little energy: only about 5% of the energy required to produce the primary metal initially is needed in the recycling process.
This article was updated on 25th June, 2019
How to choose proper types of aluminum for different casting applications? Here we specify aluminum classifications, their properties, and a guide to select aluminum for a range of casting uses.
Aluminum is one of the most abundant elements on the Earth and widely used in many different industrial and non-industrial applications because of its good properties and versatility. From shipbuilding, automotive, aviation, decorative parts, outdoor furniture to kitchen accessories, we all see aluminum applications.
Aluminum varies in many types. Depending on the specific uses, there will be suitable types of aluminum with their particular properties. With different properties and chemical composition, each type of aluminum will behave differently in the process.
Therefore, it is very important to classify aluminum to understand the properties of each type to help the manufacturer choose the proper material for casting that meets the desired quality and customer’s requirement.
Grab this demand of knowledge, we open an article to discuss how to classify basic and common different types of aluminum and aluminum alloys go along with their characteristic properties and main applications.
Stay with us to dig out the answer!
Aluminum is considered as one of three most common elements on Earth, just place behind Oxygen and Sillic.
The chemical symbol of Aluminum is Al; Mass atom is 27 with atomic number of 13.
Although aluminum is quite common in nature, it is rarely found in its pure form. Instead, aluminum is often found in substances such as clay, bauxite, etc. Statistically, aluminum is found in about 270 different types of minerals.
Aluminum has low mechanical properties (σb = 6Kg / mm2, HB = 25, δ = 40%) so it is easy to deform, low cutting machinability.
The yield strength of pure aluminum is about 7–11 MPa, while aluminum alloy has a yield strength ranging from 200 MPa to 600 MPa.
When fabricating aluminum, it is common for manufacturers to add alloys (such as Cu, Mn, Mg, Si, Sn, Zn) to improve the properties of aluminum.
Depending on each purpose of the application, they are combined in different to produce an aluminum alloy with the desired properties.
To sum up, aluminum alloy is the combination of the aluminum element with alloying elements to increase workability, corrosion resistance, electrical conductivity, density, strength, etc. comparing with the pure aluminum element.
The basic alloying elements used to improve the properties of aluminum alloys include: Cu, Si, Mn, Mg and Zn.
Here are the properties of each alloy element when adding to the aluminum:
Alloy elementPropertiesCopper (Cu)Improves durability and formabilitySilicon (Si)Reduces melting temperature, increases flow dilution, and improves casting properties Manganese (Mn)Increases strength and toughnessMagnesium (Mg)Improved durability, and resistance to corrosionMg / SiIncreases strength, formability and tensile propertiesZinc (Zn)When combined with Mg and Cu, it improves durabilitySeparately, based on the method of fabrication and usage, we divide aluminum alloy into two main groups is Wrought aluminum alloy and cast aluminum alloy.
As mention above, the alloy elements are added to aluminum in a certain proportion. With wrought aluminum alloys, the amount of alloy elements is less than 4% of the total mass.
Wrought aluminum alloy is made by melting aluminum ingots with alloy elements, then cast into large plates before rolling, forging, or pulling into different object shapes. Based on the fabrication, wrought aluminum alloy comes in a variety of shapes, including sheet, plate, foil, wire or rod, etc.
Wrough aluminum alloysDepending on the alloying element composition, wrought aluminum alloy can be grouped into 7 main groups and 1 special group (group 8) as shown below.
In which, groups 2, 6, 7, 8 are heat-treatable groups to improve some mechanical properties, while groups 1, 3, 4, 5 belong to non-heat-treatable group.
Classification of Wrought Aluminum AlloyFor Example:
Aluminum alloy 5083 means belonging to group 5, Aluminum-Magnesium (Al / Mg) alloy; the original version (0); and the 83 identifies it in the 5xxx series. Aluminum 5183 is the first variant version of aluminum 5083.
All wrought aluminum alloy series follow this explanation. There is only one exception is 1XXX series of aluminum alloys (pure aluminum). In which, the last third and fourth digits indicate the minimum aluminum percentage above 99%.
For example, aluminum alloy 1350 has 99.50% minimize pure aluminum.
Table of Properties of Wrought aluminum alloy series
Alloy seriesCorrosion Resistance Strength Machining WeldabilityFormability/Having a larger amount compared to wrought aluminum alloys, cast aluminum alloys contain more than 22% of alloy elements.
Cast aluminum alloys are made by smelting bauxite (bauxite) ores in a furnace. Then the pure aluminum is separated and poured into the mold with alloying elements to create the desired casting shapes. The aluminum casting process can be done in many methods such as sand casting, die casting, or investment casting.
Comparison of Aluminum casting methods: https://vietnamcastiron.com/aluminum-casting-process/
Cast alluminum alloy used in sand casting processCast aluminum alloys include 9 groups. According to the Aluminum Association (AA) designation, it is divided into two groups, similar to wrought aluminum alloys.
(Please note that British Standard and German Standard DIN have different designations).
Groups are classified according to specific alloying element composition as shown below.
Classification of Cast Alluminum AlloyFor example:
Aluminum alloy 356.0: The first digit (3) indicates that it is of Si plus Cu and/or Mg series; 56 corresponds to a minimum of 99.56% aluminum, and the .0 indicates that it is a final shape casting and not an ingot.
Table of Properties of Cast aluminum alloy series
Alloy seriesCorrosion ResistanceWrought aluminum alloy and cast aluminum alloy use the same Designation System for the non-heat-treatable aluminum alloy group and the heat-treatable aluminum alloy group. As follows:
With aluminum alloy groups belonging to the Non-heat-treatable group, their strength is initially determined by the alloying element. The strength can then be increased (but decreased ductility) due to cold-working and strain-hardening processes such as rolling, forging, or pulling, etc.
After this state, the aluminum will have the final symbol “F” (as-fabricated). However, these alloys are eventually tempered to a constant temperature to ensure the mechanical does not change over time called temper stabilizing). These alloys have the following symbol with the letter “O” (annealed).
Non-heat-treated aluminum is commonly symbolized as: XXXX-Hxx
In which:
The letter “H” follows with the meaning that the aluminum has been “strain hardening” during the fabrication process.
The first digit after the H indicates a basic operation:
The second digit after the H indicates the degree of strain hardening:
For the heat-treatable aluminum alloy group, durability is created by the alloying of the alloy elements with pure aluminum. The alloying elements can dissolve independently or combine together in a solid solution with aluminum as the temperature increases.
However, this aluminum alloy group is very sensitive to temperature, which if kept at high temperatures for a long time, will result in a significant decrease in strength.
Heat-treated aluminum is commonly symbolized as: XXXX-Txxx
In which:
The letter “T” follows with the meaning of Thermally Treated
The first digit after the letter “T” has the following meaning:
The second and third digits, after the letter “T”, if any, have the meaning of clarifying the specific thermomechanical treatment method.
You will find above that aluminum comes in a range of types and classifications. It may make you get lost and confused about how to choose the proper types of aluminum for your casting uses.
Don’t worry, here we help you specify which things you need to consider as the priorities while choosing aluminum material for the castings.
There are 4 factors mostly effect on which types of aluminum should use including:
Each of these above concerns involve special requirements on the types of aluminum used.
Let break it down!
You got the tips to choose aluminum types on hand.
Here we go with some suggestions for specific casting applications.
Most aluminum rotor castings are fabricated from a pure aluminum alloy that belongs to the 1XX.X cast aluminum alloy series, particularly 100.0 (99.0% Al); 150.0 (99.5% Al), and 170.0 (99.7% Al).
The reason for this strict requirement is to minimize variations of electric performance relating to conductivity and reduce casting defects such as micro shrinkage or crack on after the casting process.
100.0 Aluminum alloy has a higher amount of iron and other impurities, hence it improves the casting performance. As the result, the higher the iron content is, the less shrinkage and cracks are likely to be created. Therefore, Alloy 100.0 is recommended to cast rotor parts that have dimensions larger than125 mm (5 in.).
Same answer to explain that why Alloy 150.0 is preferable than Alloy 170.0.
Regarding rotor casting parts that require high resistivity, the higher alloys are used to process by die casting. Commonly types include Alloys 443.2 and A380.2. These types of aluminum alloys can increase rotor conductivities from 25 to 35% IACS.
Aluminum automotive pistons are mostly manufactured by permanent mold casting process due to its flexible and economic advantage.
Alloy 332.0-T5 is widely applied to cast pistons for passenger cars thanks to its good mechanical and physical properties (involve low thermal expansion).
Pistons for heavy-duty engines require high thermal conductivity and superior properties at elevated temperatures. Hence, common alloys used are 336.0-T551 (A132-T551), 332.0-T5 (F132-T5), 242-T571 (142-T571).
The premium quality casting parts have super high casting requirements on dimension accuracy and finish, mechanical properties, soundness, grain structure.
Alloys use for these premium quality casting uses can name A201.0, A206.0, 224.0, 249.0, 354.0, A356.0 (D356.0), A357.0 (D357.0) and 358.0.
The criteria to specify these alloys are:
(1) controlled impurities tightly and;
(2) optimum concentrations of hardening elements.
All of these alloys have excellent yield strength, tensile strength, and especially elongation that hence they can be choose to produce premium casting parts.
Generally, aluminum alloyed with Silicon series are mostly used to cast commercial aluminum casting parts because of excellent casting performance.
Specifically, Alloys 443.0, 444.0, 413.0, and A413.0 additional provide superior corrosion resistance, excellent weld-ability, and low specific gravity. The detailed applications are listed below:
Silicon plus Copper alloy series including 213.0, 308.0, 319.0, and 333.0 offer good casting performance, moderately high strength, and good machinability.
T5 temper can be added to some of these alloys to improve hardness and machinability.
Alloy 356.0 (7 Si, 0.3 Mg) offers great casting ability and resistance to corrosion, hence widely applied in sand casting and permanent mold casting.
Additionally, 356.0 has good endurance makes it an affordable choice for complex castings that require materials with lightweight, excellent pressure, and good mechanical properties.
Typically, these aluminum alloys are used to manufacture: Furniture; Aircraft parts; Pump housings: Propellers: High-speed blowers: Automotive transmission cases: Water-cooled cylinder blocks; Engine controls; Nuclear energy installations, etc.
Aluminum ornamental castingAlluminum alloy 380.0 by far is the most widely applied material used in die casting process.
This alloy features very good casting-ability, good mechanical properties, less impurities and fair corrosion resistance.
Aluminum alloy 380.0 and A380.0 is commonly used for application of these flowing sections:
To sum up, we have discussed a detailed classification of different types of aluminum, their properties, and guide to choose an aluminum type for casting applications through the above content.
Please keep in mind that, selecting the proper types of aluminum for the casting parts is a very crucial process at the beginning that determines the casting part quality.
Hence, it is important to discuss with your customer toward the casting requirement for the material selection process.
Self-introduced, VIC is one of the leading aluminum casting foundries located in Vietnam and supplier of aluminum casting applications to the world need. As the OEM custom aluminum supplier, we manufacture cast aluminum products according to customer’s drawings and requirements.
Our casting products diversify, ranging from outdoor furniture, kitchen accessories, automotive parts, piston, bearing, to super high precise casting pieces.
If you are in need, don’t hesitate to contact us to place a discussion. Also, check our casting blog to get more updates relating to aluminum casting, foundry manufacturing weekly.
Reference
ASM Handbook. Volume 2B. Properties and Selection of Aluminum Alloys. Kevin Anderson, John Weritz, and J. Gilbert Kaufman, editors,DOI 10.31399/asm.hb.v02b.a0006575 .
ASM Handbook. Volume 2. Properties and Selection: Nonferrous Alloys and Special-Purpose Materials ASM Handbook Committee. p 123-151. DOI: 10.1361/asmhba0001061.