(1. 有研科技集团有限公司国家有色金属及电子材料分析测试中心，北京 100088；
2. 国合通用测试评价认证股份公司，北京 101407；
3. 北京有色金属研究总院，北京 100088；
4. 国标(北京)检验认证有限公司，北京 101407；
5. 有研工程技术研究院有限公司 有色金属材料制备加工国家重点实验室，北京 101407)
摘 要: 采用扫描电子显微镜、电子背散射衍射、透射电子显微镜、高角度环形暗场-扫描透射，分析了Mg-7Gd-5Y-1Nd-xZn-0.5Zr(x=0, 1, 2, 质量分数，%)挤压态合金微观组织结构和力学性能，旨在探索Zn对于合金性能影响的微观机制。结果表明：在Mg-7Gd-5Y-1Nd-0.5Zr合金中添加Zn元素，不仅形成LPSO结构，也促进了Mg5(RE, Zn)颗粒的析出，并与Zr形成Zn-Zr相。LPSO结构不仅能阻碍晶粒长大，细化晶粒；也能够阻碍动态再结晶，从而形成动态再结晶晶粒和变形晶粒共存的双模结构，动态再结晶晶粒为 //ED织构，变形晶粒为 //ED织构。微米级大尺寸Mg5(RE, Zn)颗粒会导致应力集中，引起裂纹的萌生，降低合金的塑性；均匀分布的亚微米级Mg5(RE, Zn)颗粒起第二相强化作用，并能钉扎晶界，阻碍晶粒长大。对比3种挤压态合金，Mg-7Gd-5Y-1Nd-2Zn-0.5Zr合金获得了最优的力学性能，其抗拉强度、屈服强度和伸长率分别为365 MPa、276 MPa和17.5%。
关键字: 镁合金；挤压；长程堆垛有序(LPSO)结构；HAADF-STEM；力学性能
（1. National Center of Analysis and Testing for Nonferrous Metals and Electronic Materials, GRINM Group Co., Ltd., Beijing 100088, China;
2. China United Test and Certification Co., Ltd., Beijing 101407, China;
3. Beijing General Research Institute for Nonferrous Metals, Beijing 100088, China;
4. Guobiao (Beijing) Testing and Certification Co., Ltd., Beijing 101407, China;
5. State Key Laboratory of Nonferrous Metals and Processes, GRIMAT Engineering Institute Co., Ltd., Beijing 101407）
Abstract:The microstructure and mechanical properties of extruded Mg-7Gd-5Y-1Nd-xZn-0.5Zr (x=0, 1, 2, mass fraction, %) alloys were investigated by scanning electron microscope(SEM), transmission electron backscattered diffraction(EBSD) and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM). The addition of Zn element can form long period stacking ordered (LPSO) structures, promote the precipitation of Mg5(RE, Zn) phases and form Zn-Zr compounds with Zr element. LPSO structures can not only restrict grain growth, refines grain, but also prevent dynamic recrystallization, resulting in dynamic recrystallization grains and deformable grains coexisted, the DRX grains with a //ED texture, and the deformed grains with //ED texture. The large size micron-scale Mg5(RE, Zn) particles can reduce the toughness and plasticity of the alloy, the uniformly distributed submicron-scale Mg5(RE, Zn) particles play the role of second phase strengthening and can nail grain boundaries, and hinder grain growth. For three extruded alloys, the Mg-7Gd-5Y-1Nd-2Zn-0.5Zr alloy obtains the optimal mechanical properties, the tensile strength, yield strength and elongation are 365 MPa, 276 MPa and 17.5%, respectively.
Key words: magnesium alloys; extrusion; long-period stacking ordered (LPSO) structures; HAADF-STEM; mechanical properties
