Researches Of Mg Alloy Numerical Simulation And Experiment In Equal-Channel Angular Pressing Process

Mg alloy has many virtues, like high specific strength and high specific rigidity, excellent thermal conductivity, easy machining process and convenience of reclaim, which make it been applied widely in many industry fields, such as aviation, automobile industry and electron industry. Therefore, it has very important academic and applied significance to know how to get ultra-fine grain. As one kinds of getting ultra-fine grain methods, equal channel angular pressing (ECAP) has been extensively investigated.The billet material was Mg alloy with the geometry of 24 (diameter) mm×80 (length) mm in this paper. Experiments of ECAP were carried out; after which finite element models of Mg alloy had been founded based on the elastic-plastic finite element method. And ECAP process was simulated by finite element. Non-linear finite element software, MSC.Marc, was utilized to simulate the process of Mg alloy undergoing one pass ECAP, and analyze distribution of equivalent effective stress and equivalent effective stain, variation of pressing force versus time and influence of friction to the ECAP deformation process. The ECAP processing under different outer corner angleΨhas been simulated. The influences of outer corner angleΨon extrusion force and deformation homogeneity during the ECAP processing have been analyzed. Model of multiple passes in route A of Mg alloy was designed, which was simulated and observed in optical microstructure.The results indicated that curve of extrusion force versus time was divided into three stages: rapid increased stage, slow increased stage and steady stage in one pass ECAP process. Steady stage was main deformation stage, in which extrusion force was invariable and steady. The distribution of equivalent effective stress was inhomogeneous, which was biggest in the corner of die. The equivalent effective stain value was bigger in middle of billet than that in top and bottom. On the basis of equivalent effective stain distributing, equivalent effective stain was maximal in steady deformation region that looked like parallelogram. In order to get enough big steady deformation region, billet should be enough long. As friction coefficient increase, it not only resulted in increase of extrusion force but also heterogeneity of deformation. So friction should be reduced.Extrusion force was reduced with increase of outer corner angleΨand the time was long when extrusion force got steady stage. Considering extrusion force and homogeneity, best outer corner angleΨwas in scale of 16°～37°.Finite element simulation indicated shearing deformation extent and heterogeneity of billet was increased with increase of extrusion passes. Observation of microscopic structures indicated microstructures of billet was fine and heterogeneity of billet was increased, too.