纯镁粉末坯往复挤-镦的数值模拟及实验研究

采用DEFORM-2D有限元软件对纯镁粉末多道次往复挤-镦块体机械冶金过程进行有限元模拟,分析了往复挤-镦过程中的流场、应力场及应变场等相关场量变化规律.模拟结果表明：挤压段材料纵向流动,镦粗段材料横向流动,流速和流向的不一致形成强烈的交替剪切效应,且试样的主变形区域处于三向压应力状态.试样的等效应变呈不均匀分布,但应变的均匀性随着往复挤-镦道次的增加而有所改善.3道次往复挤-镦实验结果表明：试样产生显著的条带状组织,主变形区强烈的剪切力将原镁粉表面的氧化物和其内部的孔隙破碎,形成强烈的致密效应,相对密度接近0.98,组织上达到了良好的冶金结合.

Numerical Simulation and Experiment Study of the Pure Magnesium Powder in Cyclic Extrusion-upsetting

A two-dimensional finite element model was used to analyze the deformation behavior of the magnesium powder in the multi-pass cyclic extrusion-upsetting (CEU) bulk mechanical alloying process, and the distributions of velocity field, effective stress field and equivalent strain field of the sample during CEU process were obtained. The simulation results indicate that powder particles flow vertically during extrusion and flow transversely during upsetting. The intense alternate shearing deformation was attributed to the inconformity of the flow rate and the flow direction during the cyclic extrusion-upsetting process; and the lord deformation region of the sample was located three according compressive stress state. Inhomogeneous deformations exist in the sample and the uniform region of equivalent strain increases with the increse of the CEU processing numbers. In addition, The experimental results of cyclic extrusion-upsetting process for three times showed that the banded structure was generated in the sample, and the intense shearing force broke the initial oxide and the inner hole of the sample, so the intense densification effect was formed during the CEU process. The relative density was measured to about 0.98 and the favourable metallurgical combination was obtained.