Zhang Ling, Wu Xiaoyu, Zhang Xiaofeng, Yang Xindong, Li Yinglong
School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China.
School of Mechanical and Engineering, Ningxia Institute of Technology, Shizuishan 753000, China.
Materials (Basel). 2022 May 31;15(11):3914. doi: 10.3390/ma15113914.
The hot deformation behavior of Mg-8.7Gd-4.18Y-0.42Zr alloy was investigated by uniaxial hot compression tests at 300-475 °C with strain rates of 0.002-10 s. The average activation energy was calculated as 227.67 KJ/mol and a constitutive relation based on the Arrhenius equation was established in this study. The results show that Mg-8.7Gd-4.18Y-0.42Zr magnesium alloy is a strain rate and temperature-sensitive material. When the temperature is constant, the flow stress increases with the increase of strain rate, while when the strain rate is stable, the flow stress decreases with the increase of temperature. DRX is the main softening mechanism of the alloy, including continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). Meanwhile, the DRX grains nucleate preferentially at the twin intersections in the parent grains under the deformation condition below 300 °C and gradually expand outward with the increase of strain. When the compression temperature is above 400 °C, DRX grains nucleate preferentially at the original grain boundary and then gradually expand inward with the increase of strain. The optimum deformation conditions of the studied alloy are performed at 400-450 °C and 0.002-0.02 s by a comprehensive comparison of the hot processing map, microstructure refinement, and formability.
通过在300 - 475°C下单轴热压缩试验，应变速率为0.002 - 10 s⁻¹，研究了Mg-8.7Gd-4.18Y-0.42Zr合金的热变形行为。计算得到平均激活能为227.67 KJ/mol，并基于阿伦尼乌斯方程建立了本构关系。结果表明，Mg-8.7Gd-4.18Y-0.42Zr镁合金是一种应变速率和温度敏感材料。当温度恒定时，流变应力随应变速率的增加而增加，而当应变速率稳定时，流变应力随温度的升高而降低。动态再结晶（DRX）是该合金的主要软化机制，包括连续动态再结晶（CDRX）和不连续动态再结晶（DDRX）。同时，在300°C以下的变形条件下，DRX晶粒优先在母晶粒的孪晶界处形核，并随着应变的增加逐渐向外扩展。当压缩温度高于400°C时，DRX晶粒优先在原始晶界处形核，然后随着应变的增加逐渐向内扩展。通过对热加工图、微观组织细化和成形性的综合比较，确定了所研究合金的最佳变形条件为400 - 450°C和0.002 - 0.02 s⁻¹。
