On the influence of quenching rate on the microstructural and mechanical properties of aluminium cast alloys A356 and A354

The impact of quench rate on the microstructural and mechanical behaviour is assessed in this paper. Two common commercial aluminium foundry alloys, A356 and A354, are investigated. Samples were produced by employing gradient solidification technology which generates uniformly and directionally solidified specimens with different microstructural coarsenesses. Generally, heat treatment is widely applied to strengthen the Al-Si-Cu-Mg cast alloys through precipitation hardening. Measurements of electrical conductivity have been conducted in order to indicate the sequences of precipitation formations. To optimise the precipitation hardening effect, it is essential to understand the quench sensitivity. It can be concluded that the quench rate significantly influences the mechanical properties; the tensile strength and strength coefficient are enhanced with an increase in quench rate. The ductility instead increases with a reduced quench rate, which might be due to the more ductile α-Al matrix with corresponding coarsening and reduced level of hardening precipitates.