Effect of Ca and Rare Earths on Compressive Creep Behavior of Mg-4Al Alloy

Abstract

The effect of Ca and rare earths on compressive creep behavior of Mg-4Al alloy was investigated with a special apparatus. The microstructures were analyzed by OM, XRD, SEM and EDS before and after compressive creep test. The results reveal that a small amount of Ca was added into AE41 alloy in order to refine the crystalline structure and improve the creep resistance. Comparing with NdPr rare earths alloy, the creep resistance of LPC rare earths alloy decreases, but is still better than AE41 alloy. The as-cast microstructure of AE41 alloy is mainly composed of α-Mg matrix and Al11Nd3 phase. The acicular Al11Nd3 phase is prone to decompose at high temperature, which leads to the poor creep resistance of AE41 alloy. The acicular Al11RE3 phase is gradually replaced by Al2Ca and Al2RE with Ca addition into AE41. LPC rare-earth mixture is in cluster at grain boundaries so that the creep resistance is worse than that of alloy containing NdPr rare-earth mixture.