基于位错演化理论的等径角挤压纳米微晶材料数值分析

Numerical Analysis of Nano-or Micro-Crystalline Materials during ECAP by Dislocation Evolution Method

研究材料微观组织的演化对应力、应变以及应变硬化等问题的影响,是实现等径角挤压成形技术的关键.以纯铝为例,基于位错演化模型,利用有限元分析方法对纯铝的等径角挤压变形行为进行了数值仿真,分析了挤压过程中材料应力、应变以及应变硬化的演化趋势及分布规律.结果表明:随着挤压道次增加,纯铝中等效应力逐渐增加,这导致材料中位错密度的增加;随着位错密度的增加,主应变最大值随后续挤压道次的增加呈增大趋势.因此,考虑等径角挤压过程中的位错演化等材料微观组织演化规律,对材料的实际挤压成形有指导作用.

The influence of the microstructure evolution of materials on the strain hardening, the stress and the strain is the key to make metal materials forming by equal channel angular pressing （ECAP）. On the basis of a dislocation evolution model, the finite element method was introduced to the deformation behavior of pure aluminum during the ECAP. And the simulated stress, strain and strain distribution and strain hardening were analyzed. The results show that the equivalent stress of the pure aluminum augments gradually with the pass increasing, which results in the increase of the dislocation density. With the dislocation density increasing, the maximum of the principal strain augments with the pass increasing. Therefore, the extrusion forming can be guided by the microstructure evolution law of the materials, such as the dislocation evolution of the ECAP.