Forging of Mg-3Al-1Zn-1Ca alloy prepared by high-frequency electromagnetic casting

Abstract

The 1 wt.%Ca-AZ31 alloy produced by electromagnetic casting (EMC) in presence of electromagnetic stirring (EMS) was extruded and then subjected to the closed-die forging to make a pulley for automobile application. Effective dynamic recrystallization (DRX) took place during the forging process, leading to formation of fully recrystallized grains with the average size of 3-4 mu m. High-forging ability and high degree of grain refinement achieved during the forging were attributed to the novel microstructure of the cast composed of small and equiaxed grains with the average size of similar to 50 mu m and thin layer (Al, Mg)(2) Ca phase at grain boundaries, which would provide more nucleation sites and a faster rate of recrystallization during deformation by forging as compared to that of the conventionally processed cast composed of large size grains and thick layer (Al, Mg)(2) Ca phase. The forged pulley exhibited the ultimate tensile strength of 273-286 MPa with tensile elongations of similar to 30%. The present result demonstrates a possibility that EMC + EMS techniques can be used in producing magnesium feed stocks with high-forging ability. (C) 2009 Elsevier Ltd. All rights reserved.