The influences of shear deformation on the evolutions of the extrusion shear for magnesium alloy

Abstract

A new type of magnesium alloy extrusion-shear (short for ES) composite extrusion technology which combines the characteristics of direct extrusion and two pass equal channel extrusion has been put forward. The experiments of ES process and direct extrusion have been performed, and direct extrusion and ES dies suitable for industrial horizontal extruder have been designed and manufactured. Three-dimensional thermomechanical finite element models and conditions of the ES process and direct extrusion have been established. Extrusion forces and accumulated strains and stresses and temperatures evolution of the ES process have been obtained. The loads of the ES process increase obviously compared with those of direct extrusion. Maximum temperatures during the ES process are higher than those of direct extrusion. The computer simulation analyses of stress state for the billets reveal that part of the billet is exerted in four directions of compressive stress. The ES process could cause cumulative strains and shear stress in magnesium alloy billets than direct extrusion. Therefore, more grain refinements could be achieved. Based on the microstructure observations of center positions for the ES process and direct extrusion rods, grains have been effectively refined with extrusion temperature. It is found that there are many similarities between finite element simulation results and experimental results.