Finite element analysis of multidirectional forging dies for severe plastic deformation of magnesium alloy

Abstract

Ultrafine grain of metals can be obtained through severe plastic deformation techniques. One of the severe plastic deformation techniques is multidirectional forging, in which multiple forging is applied on a workpiece in three orthogonal directions. In this study, the multidirectional forging, with varying die dimensions, each with a single press on one plane of a magnesium alloy workpiece was analysed using finite element method. The material of workpiece was AZ91 magnesium alloy while the material of the die is AISI A2 tool steel. The workpiece has dimension of 21.2 mm x 22.2 mm x 20 mm There were three models of the die with the plunger movement is in y-direction. In Model 1, the die dimension was 21.2 mm x 20 mm x 21.2 mm. The deformation constraints were applied on sample in z-direction while the clearance for deformation was 0.6 mm for each side of x-direction. For Model 2, the die dimension was 21.2 mm x 18 mm x 22.2 mm. The deformation constraint was along z-axis and a clearance of 1.1 mm for each side of x-axis. For Model 3, the dimension was 22.2 mm x 20 mm x 21.2 mm. Each side of the die has clearance of 0.6 mm and 0.5 mm in x-axis and z-axis, respectively. Analysis was done on the magnitude and distribution of strain on the magnesium alloy workpiece. The results showed that the highest equivalent plastic strain occurred in Model 2 with 1.27. The most uniform strain distribution was shown by Model 3 die.