Az31 Magnesium Alloy Flexible Angle Extrusion Numerical Simulation

Magnesium alloy has been widely recognized as one of the lighteststructural material. But low yield strength and deformation ability at roomtemperature such as weaknesses has become important factors in restricted itsapplication. In order to design the high yield strength, better deformationability magnesium alloy, it is necessary to designed and developed a new typeof variable channel angular pressing (CCAE) mold model. In this article, thechange channel angular extrusion process of AZ31magnesium alloy has beensimulated by using the finite element analysis software DEFORM-3D. CCAEdeformation behavior, stress and strain are analyzed at different temperatures,different extrusion ratios. The experimental model was designed. The AZ31magnesium alloy CCAE experiment was done under the experimentalconditions from160℃-350℃, by extrusion ratio of2.25.Mechanicalproperties and microstructure were analyzed. The following conclusions wereobtained:(1) The grid firstly became bigger and then smaller when the temperaturerises while the extrusion ratio do not change. When the temperature remainsconstant, the squeezing ratio decreases, and the strain reduces. If the degree ofgrid refinement is lowered, the CCAE simulation runs more smoothly. Thehigher the temperature is, the smaller the extrusion pressure is. The larger theextrusion ratio is, the greater extrusion pressure it is needed, the greaterdecrease of extrusion pressure at the latter stage of the extrusion process andthe higher dynamic re-crystallization of the profile.(2) In the change channel angular extrusion process the specimen corneris the most vulnerable to fracture. With temperature increasing, channelconvergence stress concentration becomes relative dispersed, equivalent stressreduced. As the temperature increases, the equivalent stress is reducing. Themaximum compressive stress increases with the extrusion ratio increases, it isabout2to3times of equal channel angular pressing. The equivalent strain is unevenly distributed on the width of the sample. The influence of extrusionrate on the equivalent strain is greater than the temperature.(3) Mechanical properties of material are improved with the CCAE.Extrusion temperature of200℃, the tensile strength of magnesium alloys is ashigh as351MPa; at250℃,the yield strength is291MPa. At the Temperature of160℃and200℃, the material behaves as the ductile fracture. As Temperatureincreased, reflecting the mixed fracture characteristics is obvious.(4) Grain was refined after the CCAE deformation. At the extrusiontemperature of200℃, the grain size is about5μm. At the same time, there is amuch smaller grain size of fine grain. Deformation organization is uneven at250℃and300℃. Numerous small recrystallization grains surround the largegrain, showing a "necklace"-like organizational characteristics. The grain sizeis more uniform at350℃. As the deformation temperature increases, thematerial grain size initially increases and then decreases; the grain sizebecomes more monotonous. Material yield strength increased with theincreasing of degree of grain refinement, which meets typical Hall-Petchrelations.Metal flow trend and the grain change rule of the extrusion experimentaland numerical result are in good agreement. At250℃,experimental productcomprehensive mechanical properties of experimental product is best.