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研究了微量添加Zn和Nd元素对于砂型铸造Mg-5Gd-4Y-Zr(mass%)镁合金显微组织,时效硬化行为和力学性能的影响规律。结果表明:Zn或者Nd元素的微量添加可以明显改变铸态Mg-5Gd-4Y-Zr合金的晶粒尺寸和第二相的种类、形貌、数量,进而提升其室温拉伸力学性能。对3种合金的固溶处理工艺进行优化,发现Mg-5Gd-4Y-0.8Nd-Zr合金在二级固溶处理条件时会发生铸造表皮附近晶粒异常长大的现象,该现象可以通过改为单级固溶消除;此外,该微合金化还可以显著提升Mg-5Gd-4Y-Zr合金的时效硬化响应能力以及合金峰值时效态的室温和高温强度,而且Nd元素的强化效果更好,其中Mg-5Gd-4Y-0.8Nd-Zr合金的室温和250℃下的抗拉强度、屈服强度、断裂伸长率分别可以达到303 MPa、215 MPa、1.2%和283 MPa、200 MPa、7.2%。
The effects of Zn and Nd additions on the microstructure, age hardening behavior and mechanical properties of sand-cast Mg-5Gd-4Y-Zr (mass%) magnesium alloy were investigated. The results show that the addition of Zn or Nd can obviously change the grain size of the as-cast Mg-5Gd-4Y-Zr alloy and the type, morphology and amount of the second phase, thereby enhancing its tensile mechanical properties at room temperature. The solution treatment process of the three alloys was optimized and it was found that the phenomenon of abnormal grain growth near the casting skin occurs in the Mg-5Gd-4Y-0.8Nd-Zr alloy during secondary solution treatment. In addition, the micro-alloying can also significantly improve the age-hardening response of Mg-5Gd-4Y-Zr alloy and the room temperature and high temperature strength of the alloy peak aging state, and the strengthening effect of Nd element is better, The tensile strength, yield strength and elongation at break of Mg-5Gd-4Y-0.8Nd-Zr alloy at room temperature and 250 ℃ can reach 303 MPa, 215 MPa, 1.2% and 283 MPa, 200 MPa and 7.2% .