Thermal Conductivity of Aluminium

Pure aluminium conducts about 59 % as well as copper but at a third of the density, so per unit of mass it is the better conductor — the reason heat sinks, radiators and overhead transmission conductors are aluminium. The alloying penalty is severe and routinely overlooked: 6061-T6, the structural workhorse, manages only 167 W/(m·K), and 7075-T6 about 130. Extruded heat sinks are usually 6063, chosen partly because it retains around 200 W/(m·K).

Temper matters too, because it changes how much solute is in solution versus precipitated: 6061 in the T4 temper conducts less than in T6. Take 237 as pure metal at room temperature and use the alloy datasheet for anything real. In fin design the conductivity mostly sets the fin efficiency — beyond a certain thickness-to-length ratio, extra conductivity buys almost nothing, and the convective film coefficient is what limits the heat sink.