Microstructure Control and Performance Evolution of Hypereutectic Al–20Mg₂Si Alloy by Novel Al–Ca–Sb Masteralloy

Abstract

Herein, the microstructure control and performance evolution of hypereutectic Al–20Mg2Si alloy with the addition of novel Al–3.3Ca–10Sb master alloy are investigated. It is found that AlCa11Sb9 and CaSb2 compounds are successfully synthesized through in situ melt reaction of masteralloy. With 0.45 wt% Al–3.3Ca–10Sb master alloy addition, primary Mg2Si particles in hypereutectic Al–20Mg2Si alloy are significantly refined from more than 150 μm to 10.7 μm, which are accompanied with the 3D morphologies changing from dendrites to octahedrons. After heat treatment, Brinell hardnesses of Al–20Mg2Si alloys are remarkably improved to 112 HB. Furthermore, it is also found that the cooling rate of Al–3.3Ca–10Sb master alloys has certain influence on the refinement effect of Al–Mg2Si alloys. The excellent complex modification of this master alloy on Al–20Mg2Si alloy can be attributed to the existence of CaSb2 particles as the heterogeneous nucleation sites of Mg2Si particles and the inhibiting growth effect of residual Ca atoms adsorbed on the surface of Mg2Si phase.