(1. 中车长春轨道客车股份有限公司，长春 130062；
2. 中国科学院 长春应用化学研究所，长春 130022)
摘 要: 本文研究了热处理对砂型铸造Mg-4Sm-0.6Zn-0.4Zr合金显微组织和力学性能的影响，并运用光学显微镜、X射线衍射、扫描电子显微镜、透射电子显微镜以及力学实验设备对该合金进行了表征与分析。结果表明：铸态合金主要有α-Mg和Mg3Sm组成；固溶处理之后，Mg3Sm相完全溶入到基体且晶粒并未发生明显长大。250 ℃峰时效合金中主要的析出相为基面γ″沉淀相。峰时效态合金展示了最好的力学性能，其抗拉强度、屈服强度和断后伸长率分别为210 MPa、153 MPa和4.0%。根据峰时效态合金的强化机制的定量分析结果，发现峰时效态合金主要的强化效果来自于弥散分布的细小的γ″的沉淀强化，其对屈服强度的贡献为120 MPa，约占总屈服强度的80%。
关键字: Mg-Sm；稀土镁合金；力学性能；砂型铸造
（1. CRRC Changchun Railway Vehicles Co., Ltd., Changchun 130062, China;
2. Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China）
Abstract:In this work, the effects of heat treatment on microstructure and mechanical properties of sand-cast Mg-4Sm-0.6Zn-0.4Zr alloy were investigated through the microstructure analysis by optical microscopy(OM), X-ray diffractometry(XRD), scanning electron microscopy(SEM) and transmission electron microscopy(TEM) and mechanical properties testing. The results indicate that the as-cast alloy is mainly comprised of α-Mg matrix and eutectic Mg3Sm phase. After solution treatment, the coarse second phases are almost dissolved into Mg matrix and the grains do not grow significantly. The dominant precipitates of the alloy peak-aged at 250 ℃ are identified as basal γ″ phase. Also, the peak-aged alloy displays the best mechanical properties with ultimate tensile strength of 210 MPa, yield strength of 153 MPa, and elongation to failure of 4.0%. In addition, the dominant strengthening effect in peak-aged alloy is considered as precipitation strengthening induced by the dispersed fine γ″ precipitate based on the quantitative analysis results of the strengthening mechanism. The contribution of precipitation strengthening to yield strength is 120 MPa, accounting for about 80% of the total yield strength.
Key words: Mg-Sm; rare-earth Mg alloy; mechanical properties; sand casting
