A fine microstructure of AZ31 magnesium alloy developed by composite extrusion in solid-liquid two-phase region

Abstract

A novel semi-solid extrusion shear process was proposed based on the idea of "process coupling and shortening process", which can improve the comprehensive mechanical properties by grain refinement. The casting process and solidification process of AZ31 semi-solid forming process were simulated via Anycasting software. The appropriate extrusion parameters were selected by comparing the results of simulation and experiment. The results show that in the deformation zone, the nucleation of AZ31 is promoted by dendrite fragmentation and pressure, leading to the achievement of a fine and uniform structure. The presence of the liquid phase is beneficial to coordinating the deformation during extrusion, reducing the effect of slip and twining on the texture, and thus the extrusion texture is weakened. The maximum basal texture strength is only 5.3 when the shear angle is 180°. Shear angle can further refine grains and improve comprehensive mechanical properties.The best mechanical properties are obtained at the shear angle of 150° with yield strength of 222 MPa, tensile strength of 309 MPa and elongation of 8%.

Keywords

• az31 magnesium alloy
• semi-solid forming
• anycasting
• simulation
• grain refinement