A new approach to the design of a low Si-added Al–Si casting alloy for optimising thermal conductivity and fluidity

The effect of Ni on the thermal conductivity and fluidity of a low Si-added Al–Si casting alloy was investigated. The room temperature thermal conductivity of an Al–2 wt%Si alloy instantly dropped when adding 0.5 wt%Ni, whereas further additions of Ni up to 3 wt% had little influence on the thermal conductivity, which was in the range of 180–185 W/mK. The thermal conductivity was also estimated for the alloys cast at various cooling rates by measuring the electrical conductivity using the Wiedemann–Franz law and increased nearly linearly with an increase in the cooling rates. At such a low level of 2 wt%Si, the castability of the Al–Si alloys, which was evaluated by a fluidity spiral test, was enhanced by the Ni additions, exhibiting the maximum fluidity length at 0.5 wt%Ni.