Review on Hot Working Behavior and Strength of Calcium-Containing Magnesium Alloys

In recent years, calcium has been a chosen alloying element as an alternative to rare-earth elements for developing creep-resistant magnesium alloys, which find promising applications for components in automobile and aerospace industries, and as bio-implants. In this paper, the research covering the influence of Ca additions to several magnesium alloy systems on their strength, microstructure, and hot workability is reviewed. During mechanical processing, the formation of basal texture is considerably weakened by Ca addition. Ca-containing alloys have limited workability and can be processed only by choosing the right combination of temperature and strain rate that corresponds to the occurrence of dynamic recrystallization (DRX). This can be done without trial-and-error through the use of processing maps. The processing maps for hot working of low-Ca containing alloys typically exhibit three DRX domains while the maps for high-Ca alloys typically exhibit only two DRX domains. In particular, the high-Ca alloys have to be processed at lower strain rates and higher temperatures since the high volume content of intermetallic particles prevents DRX at high strain rates. Flow instabilities occur rampantly in Ca-containing alloys, particularly in high-Ca alloys, at lower temperatures and higher strain rates that have to be avoided during their thermo-mechanical processing.