Effects of Ce on Microstructure of As-Cast Mg-6Zn Alloy

Abstract

Phase constitution and phase transition temperature are important factors to influence deformation parameters, recrystallization behavior and density of precipitates of wrought Mg-Zn-Ce alloys. In this work the microstructures and phase constitution of as-cast Mg-6Zn-xCe (x = 0.6, 1, 2) alloys were characterized by XRD, SEM, TEM and DTA. The results show that the major compounds in Mg-6Zn-0.6Ce are blocky Mg4Zn7 phase, laminar Mg7Zn3 phase and cellular T phase. All compounds are almost blocky and cellular T phase in Mg-6Zn-1Ce alloy, and all T phase transformed to block in Mg-6Zn-2Ce alloy. The onset temperatures of phase transformation of T phase are increased with increasing Ce contents due to the decrease of solid solubility of Zn in T phase. The corresponding endothermic peaks of T phase in Mg-6Zn-0.6Ce, Mg-6Zn-1Ce and Mg-6Zn-2Ce are 358 °C, 494 °C and 514 °C, respectively. The increase of content of Ce result in the decrease of the concentrations of Zn in matrix, which leads to the decrease of β1′ precipitate density and the increase of onset temperatures of melting of matrix.