Upper bound analysis of thixotropic extrusion processes of semi-solid magnesium alloys
(1.School of Mechanical and Electrical Engineering, Nanchang University, Nanchang 330031, China2.State Key Laboratory of Die Technology, Huazhong University of Science and Technology, Wuhan 430074, China3.State Key Laboratory of Material Process and Die & Mould Technology,Huazhong University of Science and Technology, Wuhan 430074, China)
Abstract: The methodology was used to conduct the upper bound analysis of thixotropic extrusion process of semi-solid metal. The calculated formulas of deformed power were derived. The relationship among relative stress, frictional factor and die semi-angle were obtained. The relative stress increases with increasing frictional factor, whose value increases with increasing area reduction ratio of a certain die semi-angle. The relative stress firstly decreases and then increases with increasing die semi-angle at a certain area reduction ratio. So, the optimal die semi-angle exists with the corresponding minimum relative stress. The calculated results are in agreement with the experimental ones, which are applied to directing technological practice of axis-symmetry forward extrusion of semi-solid magnesium alloys.
Key words: semi-solid magnesium alloys； thixotropic extrusion； upper bound method