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利用光学显微镜、SEM及EDS分别观察了不同Nd含量的Mg-6Zn-0.9Zr合金,讨论了微量稀土元素Nd在Mg-6Zn-0.9Zr合金中的存在形式、对组织及性能的作用影响机理;同时采用等温热处理法研究了Nd含量对Mg-Zn-Zr合金非枝晶组织的影响。结果表明:稀土元素Nd能够细化Mg-6Zn-0.9Zr合金的铸态组织,在加入Nd元素的合金中出现Mg41Nd5相;随着Nd含量的增加,合金的固相颗粒尺寸逐渐减小,圆整度显著提高,同时固相率明显降低,非枝晶组织主要包括球状及类似球状的初生固相颗粒,以及晶界处和包裹在初生颗粒间的共晶组织。
The microstructure of Mg-6Zn-0.9Zr alloy with different Nd content was observed by optical microscope, SEM and EDS respectively. The effect of rare earth element Nd in Mg-6Zn-0.9Zr alloy on the microstructure and properties was discussed. The effect of Nd content on the non-dendritic structure of Mg-Zn-Zr alloy was also investigated by isothermal heat treatment. The results show that the rare earth element Nd can refine the as-cast microstructure of Mg-6Zn-0.9Zr alloy, and Mg41Nd5 phase appears in the alloy containing Nd element. With the increase of Nd content, the solid particle size of the alloy gradually decreases, The degree of solidity increased significantly, while the solid fraction decreased significantly. The nondendritic microstructure mainly consisted of spheroidal and globular primary solid particles, and the eutectic structure at the grain boundaries and between the primary particles.