Microstructure evolution,mechanical properties and diffusion behaviour of Mg-6Zn-2Gd-0.5Zr alloy during homogenization

Lei Xiao，Guangyu Yang，Yang Liu，Shifeng Luo，Wanqi Jie

State Key Laboratory of Solidification Processing,Northwestern Polytechnical University

摘 要：The microstructure evolution and mechanical properties of Mg-6 Zn-2 Gd-0.5 Zr alloy during homogenization treatment were investigated. The as-cast alloy was found to be composed of dendritic primaryα-Mg matrix, α-Mg +W（Mg₃Zn₃Gd₂） eutectic along grain boundaries, and icosahedral quasicrystalline I（Mg₃Zn₆Gd） phase within α-Mg matrix. During homogenization process, α-Mg +W（Mg₃Zn₃Gd₂） eutectic and I phase gradually dissolved into a-Mg matrix, while some rod-like rare earth hydrides（GdH2）formed within α-Mg matrix. Both the tensile yield strength and the elongation showed a similar tendency as a function of homogenization temperature and holding time. The optimized homogenization parameter was determined to be 505℃ for 16 h according to the microstructure evolution. Furthermore,the diffusion kinetics equation of the solute elements derived from the Gauss model was established to predict the segregation ratio of Gd element as a function of holding time, which was proved to be effective to evaluate the homogenization effect of the experimental alloy.

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