(1. 湖南科技大学 机电工程学院，湘潭 411201；
2. 湖南科技大学 材料科学与工程学院，湘潭 411201；
3. 湖南科技大学 湖南省新能源汽车产学研海智创新中心，湘潭 411201；
4. 重庆大学 材料科学与工程学院，重庆 400044)
摘 要: 为了改善传统热轧AZ31镁合金板材的微观组织，提升其综合力学性能，本文采用二道次变路径轧制与深冷处理相结合的方法，研究了深冷处理对二道次不同路径轧制下AZ31镁合金微观组织和力学性能的影响。结果表明：经深冷处理后，AZ31镁合金轧制板材晶粒平均尺寸显著细化至7.8 μm，织构强度能够由16弱化至9.5，合金组织中有孪晶生成，少量的第二相在晶界处析出。此外，二道次同一路径轧制下的板材经过20 min深冷处理，塑性得到极大改善，断裂伸长率高达23.2%；与传统轧制工艺相比，二道次交叉路径轧制板材经20 min的深冷处理，其硬度、抗拉强度分别由68 HV和246 MPa提升至75.8 HV、268 MPa。
关键字: 镁合金；二道次变路径轧制；深冷处理；微观组织；力学性能
（1. College of Mechanical and Electrical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China;
2. College of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China;
3. Hunan Provincial Overseas-wisdom Innovation Center of New Energy Vehicle in Industrial-academic-research Cooperation, Hunan University of Science and Technology, Xiangtan 411201, China;
4. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China）
Abstract:In order to improve the microstructure and mechanical properties of traditional hot-rolled AZ31 magnesium alloy sheets, the effects of cryogenic treatment on microstructure and mechanical properties of AZ31 magnesium alloy sheets were studied by using the method of two-pass variable paths rolling combined with cryogenic treatment. The results show that, after cryogenic treatment, the grain size of rolled AZ31 magnesium alloy sheet is refined to 7.8 μm dramatically and the texture is also weakened from 16 to 9.5, meanwhile, the second phase precipitates along the grain boundary and produces small portions of twins after cryogenic treatment. In addition, after 20 min cryogenic treatment, the ductility of AZ31 magnesium alloy sheet is greatly intensified, and the fracture elongation is as high as 23.2%. Compared with the traditional rolling process, the strength and hardness of two-pass cross-path rolling combined with 20-min cryogenic treatment are significantly strengthened, and the hardness and tensile strength increases from 68 HV and 246 MPa to 75.8 HV and 268 MPa, respectively.
Key words: magnesium alloy; two-pass variable paths rolling; cryogenic treatment; microstructure; mechanical properties
