锻压技术

大塑性锻压道次对车用Mg-13Gd-4Y-2Zn-0.5Zr合金组织演变的影响

英文标题：Influence of large plastic forging passes on microstructure evolution of automotive Mg-13Gd-4Y-2Zn-0.5Zr alloy

作者：高飞1 张永2 王强3

单位：1. 河南交通职业技术学院汽车学院 2. 长沙汽车电器研究所有限责任公司 3. 河南理工大学机械工程学院

分类号：TG146.2

出版年,卷(期):页码：2022,47(4):62-67

摘要：

采用热处理方法制得由LPSO相组成的Mg-13Gd-4Y-2Zn-0.5Zr合金，对合金在锻压阶段出现的扭折、孪生、动态再结晶转变机制进行了分析，再根据显微组织的变化特征优化力学特性。研究结果表明：变形铸态合金组织中包括α-Mg基体及网型共晶化合物，在515 ℃下均匀化热处理40 h后网型共晶相在铸态合金中达到了回溶程度，在420 ℃下退火处理12 h后网型共晶相转变为尺寸不均匀分布的合金晶粒。1道次变形后在某些晶粒中由多个变体激发而引起孪生；2、3道次变形后，合金中形成了更多由动态再结晶晶粒构成的孪生晶粒；4道次变形后晶粒中原有的条状孪晶全部消失。通过提高锻压道次，试样获得了更高的抗拉强度与伸长率。研究发现断口发生了准解理断裂，表现为塑性特征，提高锻压道次后，形成了大量尺寸更小的韧窝，使合金的力学强度获得了明显提升。

Mg-13Gd-4Y-2Zn-0.5Zr alloy composed of LPSO phase was prepared by heat treatment method. Then, the transformation mechanism of torsion, twinning and dynamic recrystallization for the alloy during the forging process were analyzed, and the mechanical properties were optimized according to the change characteristics of microstructure. The results show that the microstructure of as-cast alloy consists of α-Mg matrix and reticulated eutectic compounds. The reticulated eutectic phase in as-cast alloy reaches the degree of remelting after homogenization treatment at 515 ℃ for 40 h, and the reticuleted eutectic phase transforms into alloy grains with uneven size distribution after annealing at 420 ℃ for 12 h. After one pass deformation, multiple variants are excited in some grains to cause twins, after two and three passes deformation, the alloy forms more twins composed of dynamic recrystallization grains, and after four passes deformation, the original strip twins in the grains all disappear. Therefore, by increasing the forging passes, the specimen obtains higher tensile strength and elongation. The research shows that quasi cleavage fracture occurs at the fracture, which is characterized by plasticity. In addition, after increasing the forging pass, a large number of dimples with smaller size are formed, and the mechanical strength of the alloy is obviously improved.

基金项目：

河南省高等学校青年骨干教师培养计划项目（2017GGJS241）

作者简介：高飞（1983-），男，硕士，讲师 E-mail：gaofei122983@163.com

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