Tensile Behavior of Mg–Zn–Ca–Zr Alloy Forged in Semi-Solid State

Abstract

The Mg-6.0%Zn-2.0%Ca-1.5%Zr (mass%) alloy is suitable for a prematerial alloy in semi-solid forging because of its fine spherical structure and ignition-proof property. The tensile behavior dependent on the microstructural factors, such as size and form factor of primary α phase and the distance of crack propagation in the semi-solid forged alloys with solid fractions of 65 and 70% is clarified. The tensile properties are compared to those of the squeeze cast alloy as well. The size of primary α phase increases with an increase in holding time. In contrast, the size of remelted and resolidified α phase remains unchanged. The tensile strength and 0.2% proof stress of the semi-solid forged alloys decrease as the size of the ripened primary α phase increases, indicating the dependence of strength on the size of the ripened primary α phase. The elongation increases with an increase in holding time. The result is interpreted by the facts that the distance of crack propagation increases due to the increasing size of the ripened primary α phase and that the form factor of the ripened primary α phase is lowered by tensile deformation with an increasing holding time. The remelted and resolidified α phase has no effect on the tensile properties with an increase in holding time. The elongation of semi-solid forged alloy is approximately two times larger than that of the squeeze cast alloy.