(中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用透射电镜、扫描电镜、能谱分析、X射线衍射及力学性能等测试手段，研究热处理工艺对水冷铸造的Mg-8Gd-3Y-1Nd-0.5Zr(质量分数)合金显微组织、力学性能和耐腐蚀性能的影响。合金铸态显微组织由α-Mg、Mg(Gd,Y)相、富Zr小颗粒相和β-Mg24Y5网状共晶组成。在520 ℃固溶24 h后，合金中共晶相固溶进基体，固溶演变过程为α-Mg+β-Mg24Y5相+ Mg(Gd,Y)→过饱和α-Mg固溶体+Mg(Gd,Y)相。225 ℃时效，合金的析出序列为 Mg(S.S.S.S)→β″(DO19)→β′(CBCO)→β1(FCC)→β(FCC)，时效24 h达到峰时效态，合金的室温抗拉强度达到 231 MPa，伸长率为 3.4%。时效处理能提高合金耐腐蚀性能，225 ℃时效72 h时合金析出稳定β(FCC)相，平均析氢速率最小，为0.22 mL/(cm2·h)，合金的耐腐蚀性能最强。
关键字: Mg-8Gd-3Y-1Nd-0.5Zr合金；固溶处理；显微组织；力学性能；析出序列
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of heat treatments on the microstructures and properties of the Mg-8Gd-3Y-1Nd-0.5Zr alloy were studied. The cast Mg-8Gd-3Y-1Nd-0.5Zr alloy consists α-Mg, Mg(Gd,Y) second phases and eutectic phases of Zr-rich particle phase and β-Mg24Y5 reticular. After solid solution treatment at 520 ℃ for 24 h, the microstructure evolution of the alloy follows this sequence, α-Mg+β-Mg24Y5 phase + Mg(Gd,Y)→oversaturated α-Mg solid solution +Mg(Gd,Y) phase. After aged at 225 ℃, the second phases in the Mg-8Gd-3Y-1Nd-0.5Zr alloy precipitate following this sequence, Mg(S.S.S.S)→β″(DO19)→β′(CBCO)→β1(FCC)→β(FCC). The peak aging state occurs when the alloy is aged at 225 ℃ for 24 h. The room temperature tensile strength gets 231 MPa and the elongation rate gets 3.4%, respectively. Moreover, aging treatment improves the corrosion resistance of the alloy. After aged at 225 ℃ for 72 h, stable β(FCC) phase precipitates in the Mg-8Gd-3Y-1Nd-0.5Zr alloy, which express the best corrosion resistance. The lowest average hydrogen precipitation rate is 0.22 mL/(cm2·h).
Key words: Mg-8Gd-3Y-1Nd-0.5Zr alloy; solid solution treatment; microstructure; mechanical property; precipitation sequence
