变形温度对镁合金等通道转角挤压晶粒尺寸演变影响的有限元模拟

Deformation Temperature Dependence of Grain Size Evolution in Magnesium Alloys Processed by Equal Channel Angular Pressing in Finite Element Method

目的研究变形温度对AZ31B镁合金等通道转角挤压(ECAP)过程中晶粒尺寸演变的影响。方法建立AZ31B镁合金动态再结晶和晶粒长大数学模型,采用Fortran语言编写晶粒演变子程序,并通过商用有限元软件MARC的二次开发接口,建立耦合微观组织演变的AZ31B镁合金等通道转角挤压有限元模型,研究变形温度对等通道转角挤压过程应变场、再结晶百分数和晶粒尺寸的影响规律,并与实验结果进行比较。结果随变形温度从200℃增至400℃,原子热激活效应增强,再结晶百分数从75.37%增加至99%,平均晶粒尺寸从6.67μm增加至25.7μm,且晶粒尺寸分布均匀性增大,但是200℃变形的ECAP试样出现开裂。结论在250~300℃温度区间内进行ECAP变形,有助于获得细小均匀的微观组织,同时避免出现变形开裂。

The paper aims to study effects of deformation temperature on grain size evolution in AZ31B magnesium alloys processed by equal channel angular pressing （ECAP）. Mathematical models were established for dynamic recrystallization （DRX） and grain growth （GG） of AZ31B magnesium alloy, and grain evolution subprogram was written in FORTRAN lan- guage. ECAP finite element model was developed for AZ31B magnesium alloys subject to coupled microstructure evolution via second development interface of commercial finite element software MARC. Influence law of deformation temperature on strain field, recrystallization fraction and grain size during ECAP was studied and compared with experimental results. As the defor- mation temperature increased from 200 ~C to 400 ~C, atomic thermal activation effect was enhanced, the recrystallization frac- tion increased from 75.37% to 99%, the average grain size increased from 6.67 pm to 25.7 ~tm, and its distribution was more uniform at higher temperature. However, the ECAP sample was subject to cracking at 200 ~C deformation. ECAP deformation of AZ31B at 250-300 ~C can not only provide fine and uniform microstructure, but also preveent it from cracking.