(1. 重庆大学 材料科学与工程学院，重庆 400030；
2. 成都理工大学 工程技术学院，乐山 614007；
3. 美国汽车通用公司, 美国，48090)
摘 要: 在温度为320~440 ℃、应变率为0.001~1 s−1的变形条件下，采用Gleeble−1500热模拟机对挤压态AZ81镁合金的热压缩变形行为进行研究。结果表明：挤压态AZ81镁合金的流变应力随变形温度的升高而降低，随应变率的升高而升高，且随应变的增加，流动应力很快达到峰值，然后逐渐降低并趋于稳定。为评价挤压态AZ81镁合金在热模压成形过程中流动应力，结合Arrhenius方程并引入Zener-Hollomon参数，对流动应力做出相应的修正，根据修正后的流动应力构建挤压态AZ81镁合金流变应力高温变形本构模型。模拟结果表明：该模型的应力预测值与试验值吻合较好，计算精度较高，为后续的模压近/净终成形工艺参数的制定提供一定的理论参考。
关键字: 挤压态AZ81镁合金；热压缩模拟；流变应力；本构模型
as-extruded AZ81 magnesium alloy at elevated temperature
（1. College of Material Science and Engineering, Chongqing University, Chongqing 400030, China;
2. College of Engineering and Technical, Chengdu University of Technology, Leshan 614007, China;
3. General Motors Corporation, USA, 48090）
Abstract:The hot compression tests of AZ81 magnesium alloy were performed on Gleeble−1500 at deformation temperature of 320−440 ℃ and strain rate of 0.01−10 s−1. The results show that the relationship between stress and strain is affected obviously by the strain rate and deformation temperature. The flow stress becomes higher with increasing strain rate at constant temperature and lower with increasing deformation temperature at constant strain rate. In order to evaluate the hot-pressing process, a flow stress model was constituted based on Arrhenius equation and temperature-compensated strain rate factor, the Zener-Hollomon parameter, and modified further by considering the effect of strain on stress. The results show that the modified model agrees well with the experimental stress value under the experimental condition what offer a experimental theoretical basis for close-pressing net-shape.
Key words: as-extruded AZ81 alloy; hot compression simulation; flow stress; constitutive model
