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采用OM、SEM、XRD、EBSD、TEM和电子材料试验机等手段研究了超细晶反挤压Mg-8%Sn-1Al-1Zn(质量分数)合金的组织和力学性能。结果表明:在250℃下,通过反挤压可以制备出具有超细晶组织的高强度Mg-8Sn-1Al-1Zn合金。在反挤压过程中,大部分粗大晶粒均通过动态再结晶转变为细小的等轴晶,其平均晶粒尺寸为1.92μm。另外,合金中存在大量的微米和纳米级Mg2Sn颗粒相。反挤压合金表现出典型的基面纤维织构。上述组织特征是动态再结晶、孪晶和第二相共同作用的结果。合金的室温抗拉屈服强度和压缩屈服强度分别为285和260MPa,合金的拉伸/压缩屈服点比率R高达0.91。合金的高强度和高R值主要归因于合金的细晶组织以及弥散分布的微纳米级第二相。
The microstructure and mechanical properties of the ultrafine-grained anti-extrusion Mg-8% Sn-1Al-1Zn (mass fraction) alloy were investigated by OM, SEM, XRD, EBSD, TEM and electronic material testing machine. The results show that high strength Mg-8Sn-1Al-1Zn alloy with ultra-fine grain structure can be prepared by reverse extrusion at 250 ℃. During the anti-extrusion process, most coarse grains were transformed into fine equiaxed grains by dynamic recrystallization with an average grain size of 1.92 μm. In addition, there are a large number of Mg2Sn particles in the alloy. The anti-extrusion alloy exhibits a typical basal fiber texture. The above tissue features are the result of dynamic recrystallization, twins and second phase interaction. Tensile yield strength and compressive yield strength of the alloy at room temperature were 285 and 260MPa, respectively, and tensile / compressive yield point ratio R of the alloy was as high as 0.91. The high strength and high R value of the alloy are mainly attributed to the fine grain structure of the alloy and the dispersed micro-nano second phase.