Aluminum Castings – Properties
Aluminum castings combine low weight with good strength, corrosion resistance and ease of machining. Their properties, however, depend on the alloy, the casting process and heat treatment – the same shape cast from different alloys or by different methods can perform quite differently.
Key Properties of Aluminum Castings
| Property | What it means in practice |
|---|---|
| low density (approx. 2.7 g/cm³) | a casting is almost three times lighter than a steel one of the same shape |
| corrosion resistance | a natural oxide layer protects the surface; best in copper-free alloys |
| thermal conductivity | efficient heat dissipation – motor housings, heat sinks |
| machinability | fast CNC machining at high cutting speeds |
| strength | depends on the alloy and temper; the highest strength comes from heat-treatable alloys, e.g. in the T6 temper |
| recycling | aluminum can be remelted repeatedly, and remelting uses only a small fraction of the energy needed to produce primary aluminum |
Limitations to keep in mind
- Lower stiffness – the modulus of elasticity of aluminum is about one third that of steel, so a casting often needs ribs.
- Lower hardness – surfaces exposed to wear must be protected, e.g. with a sleeve or a coating.
- High-temperature strength – drops faster than in steel; for elevated-temperature service, a suitable alloy and temper are selected.
- Thermal expansion – higher than steel, which must be taken into account in joints with steel parts.
What determines the properties of a specific casting
- Alloy – silicon improves castability, magnesium enables heat treatment hardening, and copper increases strength but lowers corrosion resistance.
- Technology – rapid solidification in a permanent mold or die produces a finer structure than a sand mold.
- Heat treatment – solution treatment and aging (T6) significantly increase strength and hardness.
- Metal and mold quality – porosity and inclusions reduce strength, which is why the metal is refined, and the mold and gating system are designed to ensure proper feeding of the casting.
The minimum mechanical properties of castings for each alloy, process and temper are specified in PN-EN 1706 – this is the basis for acceptance.
In short: aluminum castings are lightweight, corrosion-resistant, good heat conductors and easy to machine. They have lower stiffness and hardness than steel. Their properties depend on the alloy, casting process, heat treatment and metal quality.
See also: aluminum casting alloys, alloys we cast, heat treatment of castings i standards and parameters of aluminum castings.
Need aluminum castings? Send a drawing or 3D model to odlewnia@adjatech.pl or call: +48 61 662 43 37 (Mon–Fri 8:30 a.m.–4:30 p.m.).
Scope of services: foundry production capabilities.