均匀化处理和挤压对Mg-Y-RE-Zr合金组织性能的影响

Effects of Homogenization and Extrusion on Microstructure and Mechanical Properties of Mg-5Gd-3Nd-xY-0.5Zr Alloy

通过调整元素Y的含量,制备了多种Mg-Y-RE-Zr镁合金,对合金不同状态下微观组织和力学性能进行了分析和测试。结果表明,不同合金晶界上的化合物以Mg24Y5,Mg41Nd5,Mg5Gd等为主,随着元素Y含量的增加,晶界上的化合物数量和尺寸增加,晶粒平均尺寸变化较小,保持在50～60μm;经过均匀化处理(535℃×24h)后,合金中化合物的分布由铸态时连续的岛状分布变为弥散细小的颗粒状分布,Mg5Gd相基本上全部分解并溶入基体中,合金中弥散分布的点状颗粒相主要为Mg24Y5和Mg41Nd5相;经过挤压变形后,合金的组织得到细化,平均晶粒尺寸在20μm左右,合金的抗拉强度、屈服强度和伸长率都有大幅度的提高,其中Mg-5Gd-5Y-3Nd-0.5Zr合金表现出了较好的综合力学性能;在设计的合金中,元素Y的含量(质量分数)应控制在5%以下。

Microstructure and mechanical properties of Mg-5Gd-3Nd-0.5Zr alloys containing different Y contents were investigated under different conditions. The results reveal that compounds at grain boundary in the alloys are mainly composed of Mg24Y5,Mg41Nd5 and Mg5Gd,furthermore,with increasing in Y content,the numbers and grain size of the compounds at the grain boundary are increased,however,average grain size still keeps approximately 50~60 μm,showing slightly change. After homogenization treatment at 535℃ for 24 hours,compounds in the alloys are converted from continuous island structure at as-cast state into dispersively fine particles,where dispersively distributed particles in the alloys are mainly composed of Mg24Y5 and Mg41Nd5 phase while Mg5Gd phase is mostly decomposed and dissolved into the matrix. After extrusion,the microstructure with approximately 20 μm in average grain size can be observed in the alloy,and tensile strength,yield strength and elongation of the alloys can be greatly improved,in which desirable comprehensive mechanical properties can be observed in Mg-5Gd-5Y-3Nd-0.5Zr. The Y content should be controlled less than 5% in weight in designed alloys.