Cast Plate
Aluminum is almost never just aluminum. While it is possible to buy pure and high-purity aluminum, they are almost never used as-is. This nearly pure aluminum is used as a feedstock for deposition chambers to coat other structural materials with a thin layer of aluminum, or as a chemical, thermal, or electrical control material in testing. Aluminum is almost never used in its pure state, and it is certainly never used as a structural material.
The aluminum that most people encounter in daily life are in fact aluminum alloys—carefully blended with other metals and materials like silicon, and heat treated to create desirable properties. The following are the properties of these aluminum alloys:
- greater strength
- enhanced corrosion resistance
- increased electrical and thermal conductivity
While these alloys share commonalities, such as in terms of thermal conductivity, each heat treatable alloy has its own unique physical properties.
Common Aluminum Alloy Properties
Aluminum is famously a lightweight material. This property has made certain aluminum alloys a go-to choice for aircraft, spacecraft, and ground vehicles where weight savings result in significant improvements in performance. This isn’t wrong, but it would be more accurate to say that one of the most valuable aluminum alloy properties is its high strength-to-weight ratio. This is a near-universal advantage of aluminum alloys, some other advantages are:
- Conductivity: Aluminum conducts both heat and electricity very well. It is second only to copper in this ability, and this has made it desirable for heat sinks, radiators, and electrical wiring.
- Cold Stable: Many metals become brittle as temperatures drop. Aluminum is not one of these metals. Aluminum in fact grows stronger while remaining flexible. This makes it useful for a range of cryogenic applications.
- Corrosion Resistance: Aluminum, when exposed to air, develops a thin layer of oxide that protects the surface and increases its corrosion resistance. This makes structural aluminum very long-lasting with low maintenance needs compared to metals like steel.
- Non-magnetic: In spite of its electrical conductivity, aluminum is non-magnetic. This makes it useful for busbars and other high electrical load components where magnetic interactions would be an issue. It also makes excellent housing and casings for magnetic materials like compasses and hard drives.
- Non-sparking: Aluminum is non-sparking against itself and ferrous metals. This property is useful in environments where flammable fumes or combustibles are a potential hazard.
These aluminum alloy properties will hold true no matter what the formulation of any particular aluminum alloy is. The main difference in aluminum alloy properties between alloys is their mechanical properties, or how they act under tension and strain. Another potential concern is their workability—whether or not an aluminum alloy can undergo the machining or welding process easily without compromising its mechanical or structural properties.
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Mechanical and Structural Aluminum Alloy Properties
An aluminum alloy can take on a range of different properties depending on the other elements added to the alloy alongside the aluminum. Common elements include metals like magnesium, copper, and zinc. They can also include nonmetallic elements like silicon. These additional elements can add strength, or they can also add characteristics to the aluminum when it is worked. The addition of silicon and zinc can make aluminum flow better when it is molten—allowing for better casting at the cost of interfering with the anodizing response and making anodizing cast aluminum a challenge.
In addition to these alloying elements, there are also different treatments that substantially affect the strength of the alloy. Artificially aged T6 aluminum is effectively heat treated for extra strength, while T4 aluminum is naturally aged or allowed to sit until it becomes stabilized and stronger. Then there are hardening treatments where the aluminum is deliberately strained beyond its yield point making it more difficult to deform in the future. Afterward, they may then be annealed, or heated and allowed to naturally cool to further enhance their strength.
The Most Important Aluminum Alloy Property: Strength
When it comes to aluminum alloy properties, strength is probably of the most immediate concern. It’s the property that will most often make the difference between success and critical failure of anything built with aluminum.
Strength can have a variety of definitions but the most common is material tensile strength—strength when being pulled or bent. Other definitions include:
- Yield Strength: the force where it finally gives way
- Elastic Modulus: the force it can resist before deforming
- Shear Modulus: the parallel force it can resist before deforming
A chart of aluminum alloy properties for these different definitions of the most common aluminum alloys can be seen below.
| Aluminum Alloy Properties | |||||
| Alloy | Temper | Elastic Modulus | Shear Modulus | Yield Strength | Tensile Strength |
| 1100 | – | 10, 000,000 psi | 3,750,000 psi | 3,500 psi | 11,000 psi |
| 1100 | H12 | 10, 000,000 psi | 3,750,000 psi | 11,000 psi | 14,000 psi |
| 2014 | – | 10, 800,000 psi | 4,000,000 psi | 8,000 psi | 22,000 psi |
| 2014 | T6 | 10, 600,000 psi | 4,000,000 psi | 58,000 psi | 66,000 psi |
| 2014 | T62 | 10, 800,000 psi | 4,000,000 psi | 59,000 psi | 67,000 psi |
| 2017 | T4 | 10, 500,000 psi | 3,950,000 psi | 32,000 psi | 55,000 psi |
| 2024 | T3 | 10, 600,000 psi | 4,000,000 psi | 42,000 psi | 64,000 psi |
| 2024 | T4 | 10, 600,000 psi | 4,000,000 psi | 40,000 psi | 62,000 psi |
| 2025 | T6 | 10, 400,000 psi | 3,900,000 psi | 33,000 psi | 52,000 psi |
| 2124 | T851 | 10, 400,000 psi | 4,000,000 psi | 57,000 psi | 66,000 psi |
| 2219 | T62 | 10, 500,000 psi | 4,000,000 psi | 33,000 psi | 54,000 psi |
| 2618 | T61 | 10, 700,000 psi | 4,100,000 psi | 42,000 psi | 55,000 psi |
| 3003 | – | 10, 000,000 psi | 3,750,000 psi | 5,000 psi | 14,000 psi |
| 3003 | H18 | 10, 000,000 psi | 3,750,000 psi | 25,000 psi | 27,000 psi |
| 3003 | H112 | 10, 000,000 psi | 3,750,000 psi | 10,000 psi | 17,000 psi |
| 354 | T61 | 10, 600,000 psi | 4,000,000 psi | 36,000 psi | 47,000 psi |
| 355 | T51 | 10, 200,000 psi | 3,800,000 psi | 22,000 psi | 27,000 psi |
| 355 | T6 | 10, 300,000 psi | 3,800,000 psi | 23,000 psi | 37,000 psi |
| 356 | T7 | 10, 300,000 psi | 3,850,000 psi | 21,000 psi | 29,000 psi |
| 356 | T6 | 10, 300,000 psi | 3,850,000 psi | 20,000 psi | 30,000 psi |
| 5052 | – | 10, 200,000 psi | 3,800,000 psi | 9,500 psi | 25,000 psi |
| 5052 | H32 | 10, 200,000 psi | 3,800,000 psi | 23,000 psi | 31,000 psi |
| 5056 | H38 | 10, 300,000 psi | 3,750,000 psi | 50,000 psi | 60,000 psi |
| 5056 | ANL | 10, 300,000 psi | 4,000,000 psi | 22,000 psi | 42,000 psi |
| 6061 | T4 | 10, 000,000 psi | 3,800,000 psi | 16,000 psi | 30,000 psi |
| 6061 | T6 | 10, 000,000 psi | 3,800,000 psi | 35,000 psi | 42,000 psi |
| 6062 | – | 10, 000,000 psi | 3,750,000 psi | 5,000 psi | 14,000 psi |
| 6062 | T4 | 10, 000,000 psi | 3,750,000 psi | 16,000 psi | 26,000 psi |
| 6062 | T6 | 10, 000,000 psi | 3,750,000 psi | 35,000 psi | 38,000 psi |
| 6063 | T42 | 10, 000,000 psi | 3,750,000 psi | 10,000 psi | 17,000 psi |
| 6063 | T5 | 10, 000,000 psi | 3,750,000 psi | 16,000 psi | 22,000 psi |
| 6063 | T6 | 10, 000,000 psi | 3,750,000 psi | 25,000 psi | 30,000 psi |
| 6151 | T6 | 10,100,000 psi | 3,850,000 psi | 37,000 psi | 44,000 psi |
| 7050 | T7452 | 10,100,000 psi-11,600,000 | – | 60,000 psi | 68,000 psi |
| 7050 | T74 | – | – | 58,000 psi | 70,000 psi |
| 7075 | T6 | 10, 400,000 psi | 3,900,000 psi | 70,000 psi | 78,000 psi |
| 7075 | T6 | – | – | 63,000 psi | 73,000 psi |
| A356 | T651 | 10, 400,000 psi | 3,900,000 psi | 28,000 psi | 38,000 psi |
| D712 | T5 | 10, 300,000 psi | 3,800,000 psi | 20,000 psi | 32,000 psi |
These are only the most common aluminum alloys, there are others in widespread use, including proprietary aluminum alloys like Mic 6 and alternatives like Alimex and Alca 5. The most important aluminum alloy properties in those cases aren’t necessarily their overall strength. Instead, it is their dimensional stability while being machined, closely followed by their ability to remain dimensionally stable under changing temperatures.
Other proprietary blends like Duramold and Aluminum Max 5 by PCP are made specifically for use in vacuum and injection-forming molds. If there is an industrial use for aluminum alloys then there is a formulation and treated alloy with aluminum alloy properties that are specially made with that use in mind.
It can be difficult to know what the most important aluminum alloy properties actually are, even if you are an expert metalworker or machinist.
A Supplier Who Can Find the Aluminum Alloy With Properties You Need
If your head is spinning trying to figure out what aluminum alloy and properties you need, then turn to an expert. Industrial Metal Service has been a leading aluminum provider for silicon valley businesses for decades. We are now bringing our expertise in aluminum and metals nationwide.