热处理对Mg-12Y-1Al合金组织及性能的影响

Effect of heat treatment on microstructure and properties of Mg-12Y-1Al alloy

采用光学显微镜、X射线衍射仪及扫描电镜等研究固溶处理、时效处理后Mg-12Y-1Al合金的显微组织,利用拉伸实验分析热处理前后合金在室温及高温200℃下的力学性能,使用电化学方法测试热处理前后合金的耐腐蚀性能。结果表明:Mg-12Y-1Al合金的铸态组织由α-Mg基体、Mg_(24)Y_(5)相和Al_(2)Y相组成。Mg-12Y-1Al具有优异的高温热稳定性,在520℃×16 h(T4)固溶处理后,晶粒没有长大,产生新的长周期有序堆垛相(LPSO);225℃×30 h(T6)时效处理对组织的影响不大。与室温下的性能相比,T4态合金在200℃下的极限抗拉强度没有降低,而伸长率由室温的1.3%提高至12.5%。此外,Mg-12Y-1Al合金经固溶及时效处理后耐腐蚀性能得到提升,腐蚀电流密度由铸态的2.799×10^(-5)A/cm^(2)降低至1.551×10^(-5)A/cm^(2)。

The microstructure of Mg-12Y-1Al alloy with solution treatment and aging treatment was studied by optical microscope,X-ray diffraction and scanning electron microscope.The mechanical properties of the alloy before and after heat treatment at room temperature and 200℃were analyzed by tensile test,and the corrosion resistance of the alloy before and after heat treatment was tested by electrochemical methods.The results show that the as-cast microstructure of Mg-12Y-1Al alloy is composed ofα-Mg matrix,Mg_(24)Y_(5)phase and Al_(2)Y phase.Mg-12Y-1Al alloy has excellent high-temperature thermal stability.After solution treatment at 520℃for 16 h(T4),the grain size does not increase,and new long period stacking ordered(LPSO)phase forms;the subsequent aging treatment at 225℃for 30 h(T6)has little effect on the microstructure.Compared with the properties at room temperature,the ultimate tensile strength of T4 alloy at 200℃does not decrease,but the elongation increases from 1.3%to 12.5%.Moreover,the corrosion resistance of Mg-12Y-1Al alloy is improved after solution and aging treatment,and the corrosion current density decreases from 2.799×10^(-5)A/cm^(2)to 1.551×10^(-5)A/cm^(2).