镁合金新型复合挤压的有限元和实验研究

Studies on finite element simulation and experiments of a new compound extrusion for magnesium alloy

针对镁合金的棒材的工业化制备和加工,提出了一种新型的镁合金复合挤压方法,将正挤压(Extrusion)和剪切(Shear)结合(简称ES),建立了ES挤压的三维有限元热力耦合模型及条件,模拟了ES挤压的流动网格、累积应变演化,设计并制造了适合于卧式挤压机上的ES挤压模具,进行了ES工艺实验。数值模拟结果表明,ES挤压可以显著提高镁合金变形过程的累积应变;试验结果表明,ES挤压可以得到尺寸很小的动态再结晶晶粒,并改善了组织均匀性;理论分析表明,ES挤压过程镁合金具有多级动态再结晶的特性,可以逐步有效的细化微观组织。ES挤压在模具结构、工艺参数合理的条件下可以大大细化镁合金微观组织,并具有工业生产的实用性。

Deformation capacity and strength for the traditional extruded rods of magnesium alloy are rather poor. A new type of magnesium alloy composite extrusion is presented which combines the extrusion and ECAP （ equal channel angular pressing） , that is to say extrusion and shear are combined （shorten ES）. Three-dimensional （3D） thermal-mechanical coupled finite element models （FEM） are established by DEFORMTM-3D. Deformation behavior including flow modes and accumulated strain was studied. The same extrusion experiments were done with identical conditions as simulation. 1-2 μm grain size of recrystallization grains can be obtained at extrusion ratio of 32 and extrusion temperature 420 ℃. The theoretical analysis and finite element simulation results shows that ES process could refine grains of magnesium alloys effectively. The research results could provide a fundamental and practical guidelines to produce high performance magnesium rod with fine microstructure.