(大連交通大學 材料科學與工程學院 連續(xù)擠壓教育部工程研究中心，大連 116028)
摘 要: 通過熱壓縮實驗研究AZ31鎂合金擠壓桿料在變形溫度300、400和500 ℃，應變速率0.1、0.01和0.001 s-1條件下的流變行為，基于Arrhenius方程建立流變應力的本構(gòu)模型，其中激活能Q為132.45 kJ/mol，應變硬化系數(shù)n為4.67。依據(jù)AZ31鎂合金高溫變形中的動態(tài)再結(jié)晶(Dynamic recrystallization，DRX)機理和位錯密度演化規(guī)律，建立宏觀變形-微觀組織多尺度耦合的位錯密度模型，該模型能夠反映熱加工過程中的加工硬化、動態(tài)回復(Dynamic recovery，DRV)、低角晶界(Low angle grain boundaries，LAGB)和高角晶界(High angle grain boundaries，HAGB)等機制的交互作用。利用ABAQUS的VUSDFLD子程序進行熱壓縮過程的有限元模擬，獲得DRX分數(shù)、LAGB和HAGB位錯密度的數(shù)值模擬結(jié)果以及壓縮載荷。結(jié)果表明：實驗載荷與模擬結(jié)果基本吻合，本文提出的AZ31鎂合金位錯密度模型是合理的。
關(guān)鍵字: AZ31鎂合金；本構(gòu)模型；位錯密度模型；有限元模擬
（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
