(大连交通大学 材料科学与工程学院 连续挤压教育部工程研究中心，大连 116028)
摘 要: 通过热压缩实验研究AZ31镁合金挤压杆料在变形温度300、400和500 ℃，应变速率0.1、0.01和0.001 s-1条件下的流变行为，基于Arrhenius方程建立流变应力的本构模型，其中激活能Q为132.45 kJ/mol，应变硬化系数n为4.67。依据AZ31镁合金高温变形中的动态再结晶(Dynamic recrystallization，DRX)机理和位错密度演化规律，建立宏观变形-微观组织多尺度耦合的位错密度模型，该模型能够反映热加工过程中的加工硬化、动态回复(Dynamic recovery，DRV)、低角晶界(Low angle grain boundaries，LAGB)和高角晶界(High angle grain boundaries，HAGB)等机制的交互作用。利用ABAQUS的VUSDFLD子程序进行热压缩过程的有限元模拟，获得DRX分数、LAGB和HAGB位错密度的数值模拟结果以及压缩载荷。结果表明：实验载荷与模拟结果基本吻合，本文提出的AZ31镁合金位错密度模型是合理的。
关键字: AZ31镁合金；本构模型；位错密度模型；有限元模拟
（Continuous Extrusion Engineering Research Center, Ministry of Education, School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028）
Abstract:Thermal-mechanical behavior of AZ31 magnesium alloy extruded rod was investigated by thermal compression experiment at the deformation temperatures of 300, 400, 500 ℃ and the strain rates of 0.1, 0.01, 0.001 s-1. A flow stress constitutive model of the alloy was established based on the regression analysis by the Arrhenius type equation. The activation energy Q is 132.45 kJ/mol and the strain hardening coefficient n is 4.67. According to the dynamic recrystallization (DRX) mechanism of AZ31 magnesium alloy at high temperature deformation, a multi-scale coupled dislocation density model of macroscopic deformation-microstructure of magnesium alloy during high temperature deformation was proposed. The model could reflect the interactions among work hardening, dynamic recovery (DRV), transformation from low angle grain boundaries (LAGB) into high angle grain boundaries (HAGB) and mechanisms during the hot working process. Furthermore, the finite element simulation of the compression process was performed by VUSDFLD subroutines in ABAQUS software. As a result, DRX volume fraction, compression force, and the dislocation density of HAGB and LAGB are obtained. It is obvious that the simulated results are similar to the experimental force. The new proposed dislocation density model of AZ31 magnesium alloy is reasonable.
Key words: AZ31 magnesium alloy; constitutive model; dislocation density model; finite element simulation
