(1. 福州大学 机械工程及自动化学院，福州 350116；
2. 中冶瑞木新能源科技有限公司，唐山 063299)
摘 要: 通过超声振动辅助热拉伸实验，研究温度和超声振动对AZ31B镁合金板材力学行为的影响。结果表明：热振联合作用下材料的屈服强度和抗拉强度下降，伸长率和塑性提高，动态再结晶延迟发生。随着振幅的增加，屈服强度和抗拉强度降低的幅度增加，伸长率先增大后减小。与无振动时的伸长率对比，当振幅为9.1 μm时，伸长率增大的幅度最大，分别为32.3%(150 ℃)和23.2%(200 ℃)。基于热激活机制和位错密度演化理论构建超声振动下镁合金热拉伸的本构关系模型，并结合实验验证模型的准确性。该本构模型能有效地预测不同温度和振幅下材料的应力-应变关系，预测曲线与实验曲线吻合较好。该模型的建立为超声振动下金属热塑性成形的有限元模拟提供了理论基础。
关键字: 镁合金；本构建模；超声辅助；拉伸实验；力学行为
（1. School of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350116, China;
2. MCC Ramu New Energy Technology Co., Ltd., Tangshan 063299, China）
Abstract:The effects of temperature and ultrasonic vibration on the mechanical behavior of AZ31B magnesium alloy sheet were studied by ultrasonic vibration assisted hot tensile tests. The results show that with the applying of the ultrasonic vibration, the yield strength and tensile strength are decreased, the elongation and plasticity are improved, and the onset of the dynamic recrystallization is delayed. With the increase of the amplitude, the yield strength and tensile strength further decrease, while the elongation first increases and then decreases. Comparing with that without ultrasonic vibration, the elongation under the vibration of 9.1 μm increases by 32.3% (150 ℃) and 23.2% (200 ℃), respectively, to the maximum extent among the experimental results. Based on the thermal activation mechanism and dislocation density evolution theory, the constitutive model used to describe the hot tensile behavior of Mg alloy sheet under ultrasonic vibration is established. The performance of this model is evaluated by the experiment. The model can effectively predict the stress-strain responses of materials under different temperatures and amplitudes, and the predictive curves are in good agreement with the experimental curves. It provides a theoretical basis for the finite element simulation of metal sheet in hot plastic forming under ultrasonic vibration.
Key words: magnesium alloy; constitutive model; ultrasonic vibration; tensile test; mechanical behavior
