Mg-4.3Li-1.08Y-5.83Zn合金的微观组织与塑性不稳定性研究

Microstructure and Plastic Instability of Mg-4.3Li-1.08Y-5.83Zn Alloy

采用常压铸造及热挤压方法制备Mg-4.3Li-1.08Y-5.83Zn变形合金,通过光学显微镜、扫面电子显微镜、能谱和X射线衍射分析以及拉伸实验,研究合金的微观组织和变形行为及其力学性能变化。研究结果表明:Mg-4.3Li-1.08Y-5.83Zn合金的微观组织中形成了I-Mg_3YZn_6准晶相和W-Mg_3Y_2Zn_3及Mg_(0.97)Zn_(0.03)第2相,从而使合金的屈服强度和抗拉强度大幅度提高;在1×10^(-5)~1×10^(-2)s^(-1)应变率范围内,该合金产生了明显的塑性不稳定行为,随着应变率提高,动态应变时效机制主导的塑性不稳定性是使合金的屈服强度和抗拉强度表现为负的应变率敏感性的根本原因。

Mg-4. 3Li-1.08Y-5.83Zn deforming alloy is prepared using conventional casting and hot extru- sion processing. The mierostructure, deformation behavior and mechanical properties of the alloy are in- vestigated by optical microscope, scanning electron microscope, energy density spectrum and X-ray dif- fraction analyses, and tensile tests. The results show that the quasi-crystalline phase I-Mg3YZn6 , and the secondary phase W-Mg3Y2Zn3 and Mg0.97Zn0.03 are generated in the microstructure of Mg-4. 3Li-1.08Y- 5.83Zn alloy, thus enhancing the yield strength and ultimate tensile strength significantly. The tensile tests at different strain rates show that the plastic instability occurs in the strain rate range from 1 × 10-5 s-1 to 1 ×10-2 s-1 and the yield and ultimate strengths of the alloy exhibit negative strain rate sensitivity with the increase in strain rate. A reasonable mechanism for this is attributed to the dynamic strain aging （DSA） occurring during tensile deformation.