Effective strains caused by different process conditions of extrusion-shear and its influences on the microstructures of AZ31 magnesium alloy

摘要

To improve strengths and microstructures evolution for magnesium alloy, extrusion-shear (ES) has been widely investigated because of its potentiality to produce ultra-fine grained microstructures of magnesium alloys. It is crucial to explore the effects of process parameters especially extrusion speeds and extrusion ratios on the deformation behaviors of magnesium alloy during ES process. Three-dimensional (3D) geometric models of ES processes with different extrusion speeds and extrusion ratios have been applied. Different extrusion speeds have been regarded as the initial conditions used in DEFORMTM-3D software, and different extrusion ratios have been taken. The microstructures evolvements have been analyzed by the simulation and experimental results. The strains in the extruded rods have been predicted during ES process. ES process with different extrusion speeds and extrusion ratios have been applied to fabricate AZ31 magnesium alloy rod with preheated temperature 400°C. The strains of ES process slightly increase with the rise of extrusion speeds. Average grain sizes prepared by lower extrusion speeds are bigger than those prepared by higher speeds with the same die structures. The strains slightly decrease with the rise of extrusion ratios. The average sizes of microstructures for magnesium alloy prepared by ES extrusion decrease with the rise of extrusion ratios.