热处理对Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr(wt%)合金组织和性能的影响

Effect of Heat Treatment on the Microstructure and Mechanical Properties of Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr (wt%) Alloy

摘要:

采用差热分析(DSC)、光学显微镜(OM)、X射线衍射(XRD)、扫描电子显微镜(SEM)、能量色散谱(EDS)及拉伸测试等手段研究了Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr合金经过不同热处理方式后的组织演变及力学性能。提出了500°C固溶处理15h、225°C时效处理40h的最佳热处理制度。500°C固溶15h后,层状长周期堆积有序(LPSO)结构消失,晶界处的(Mg,Zn)3(Y,Sm)从网状相溶解成颗粒状,同时形成大量的长条状相Mg12(Y,Sm)Zn。时效处理后,大量弥散的β′相析出到α-Mg晶粒中,有利于提高合金的屈服强度。试验合金的屈服强度(YS)、抗拉强度(UTS)和延伸率(EL)分别为170.0 MPa、260.8 MPa和14.1%。热处理后断口由沿晶断裂向穿晶断裂转变。

Abstract:

The microstructure evolution and mechanical properties of Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr alloy after different heat treatment experiments were investigated by differential thermal analysis (DSC), optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and tensile test, and the optimum heat treatment systems composing of solid-solution treatment at 500°C for 15 hours and aging treatment at 225°C for 40 hours were proposed. After the solution treatment at 500°C for 15 hours, the layer long period stacking ordered (LPSO) structure disappears, whereas (Mg,Zn)3(Y,Sm) at the grain boundary dissolves into a granular state from the reticular phase, and a large number of long strip phases Mg12(Y,Sm)Zn are formed at the same time. After the aging treatment, a large number of dispersed β′ phases precipitate into the α-Mg grains and it is beneficial to improve the yield strength of the experimental alloy. The yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of the experimental alloy are 170.0 MPa, 260.8 MPa and 14.1%, respectively. The fracture mode changes from intergranular to transgranular fracture after the heat treatment process.