Influence of Ca and Mn on Microstructure, Mechanical Properties, and Electrical Conductivity of As-Cast and Heat-Treated Al-Mg-Si Alloys

Abstract:

The Al-0.59Mg-0.54Si-X (X=0, 0.253Ca, 0.253Mn) alloys were prepared to investigate the effect of minor addition of Ca and Mn on the microstructure, mechanical properties, and electrical conductivity of the Al-0.59Mg-0.54Si-X alloys after casting, solid-solution, and aging treatments. Results show that the Ca and Mn addition can significantly refine the grains of α-Al matrix. Moreover, Ca can induce the precipitation of Mg₂Si and Al₂Ca particles with high contents in the as-cast α-Al grains, which contributes to the optimum mechanical properties of alloys. The solid-solution and aging treatments cause the coarsening of particles and the particle segregation at the grain boundaries, leading to the rapid decline in mechanical properties but an extraordinary increase in electrical conductivity (52.44%IACS) for the alloys. Mn addition can transform the coarse β-Al₅FeSi impurity phase at the grain boundaries into the α-Al(FeMn)Si particles and also induce the precipitation of Mg₂Si and AlMn particles in the as-cast alloys. Consequently, the Al-0.59Mg-0.54Si-0.253Mn alloy after solid-solution and aging treatment exhibits the optimal mechanical properties and acceptable electrical conductivity.