Thermal Expansion Coefficient of Aluminium
| Value | 0.0000234 1/K |
| Status | Measured: ± 5.00e-07 1/K (0.021 relative) |
| Source | ASM Handbook, Vol. 2: Properties of Nonferrous Alloys |
| Categories | Material PropertiesEngineering & Trademechanics |
| per kelvin | 0.0000234 1/K |
| per Celsius degree | 0.0000234 1/°C |
| per Fahrenheit degree | 0.000013 1/°F |
Learning zone
Aluminium moves twice as much as steel per degree, and it is soft enough that restraining it usually deforms something. A 6 m aluminium curtain-wall mullion swinging 80 °C between a winter night and a summer afternoon in direct sun changes length by 11 mm, which is why glazing systems are built around slip joints and gaskets rather than rigid connections, and why oversized clearance holes are specified where aluminium is bolted to steel.
The same coefficient explains automotive practice: an aluminium engine block with steel cylinder liners or steel head bolts needs the differential movement designed in, and aluminium pistons are machined undersize (or cam-ground oval) because they grow more than the bore around them. Alloy composition shifts it a little — 6061 is 23.6, 7075 is 23.4, casting alloys with high silicon are lower — but the factor of two against steel is the number to carry.