Precipitation behaviour of micro-alloyed Mg-AL-CA alloys during heat treatment and hot compression

Abstract

Based on thermodynamic calculations, two micro-alloyed Mg-Al-Ca alloys, Mg-0.3Al-0.2Ca and Mg-0.1Al-0.5Ca, were selected in terms of the equilibrium precipitation temperatures of Al2Ca and Mg2Ca, respectively. The basic idea is to form precipitates during hot compression to examine their effect on hot deformation. Both alloys, cast by copper mould, were solution treated at 500°C for 8 hours to dissolve eutectic precipitates which formed in the as-cast microstructure, and then isothermally heat treated at 350°C for different times. SEM analysis of the heat treated alloys generally agreed with thermodynamic calculations. Hot compression tests were also conducted on solution treated alloys at 350°C with a strain rate of 0.01s-1 and different strains (10%, 30%, 60%, and 90%). The precipitation behaviour and microstructural evolution which was characterized by optical microscopy and SEM with BSE and EDS detectors during isothermal heat treatment and hot compression were compared.Key wordsMg-Al-Caprecipitationheat treatment and hot compression