Aluminium vs Copper
Aluminium and Copper are genuine alternatives to one another — a choice somebody actually makes — and differ on 7 measured properties, density most clearly.
Aluminium vs Copper
Aluminium
Al
The most abundant metal in the Earth's crust, and until the 1880s more valuable than gold because nobody could extract it cheaply.
Copper
Cu
A soft, ductile metal with exceptional electrical conductivity, and one of the first metals humans worked.
| Property | Aluminium | Copper |
|---|---|---|
| Atomic number | 13 | 29 higher |
| Density | 2.7 g/cm³ | 8.96 g/cm³ higher |
| Electrical conductivity | 37.7 MS/m | 59.6 MS/m higher |
| Melting point | 660.32 °C | 1084.62 °C higher |
| Mohs hardness Mohs hardness is an ordinal scale: values can be ranked, but differences and ratios between them are not meaningful. | about 2.75 | about 3 higher |
| Molar mass | 26.982 g/mol | 63.546 g/mol higher |
| Tensile strength Only one of the two has a figure we can stand behind, so there is nothing to compare. | 70–130 MPa | Not known |
| Thermal conductivity | 237 W/(m·K) | 401 W/(m·K) higher |
Choosing between them
Aluminium is recorded as a substitute for Copper — cheaper, lighter.
What it gives up: About two thirds the conductivity, so a bigger conductor for the same current — and it creeps under a terminal screw, which is why aluminium building wire needed different fittings.
In this application, on the evidence cited above.