Investigation On Magnesium Alloy Bending Products Processed By Staggered Extrusion(SE)

Compared with cast magnesium alloy,the magnesium alloy obtained by plastic processing has more advantages in strength,properties and reliability,among which extrusion process is the most representative.During the extrusion process,the billet is subjected to strong three-dimensional compressive stress,which can significantly refine the grains and improve the mechanical properties.It is one of the ideal choices for the forming of high-performance magnesium alloy products.In addition to the inherent properties of the material,the loading mode is one of the key conditions to determine the plastic yield,stress state and deformation uniformity of the billet during the extrusion process of magnesium alloy.By adjusting the loading mode and designing the action mode reasonably,additional shear stress can be produced to refine the microstructure and improve the properties of the extrusion products.In view of the above problems,a new process of bending forming integration-staggered extrusion(SE)was proposed in this paper.The bending products with curvature characteristics can be obtained by using the stem whose end was designed as step-like structure in the SE process.According to the experimental results of the SE process,with the increase of staggered distance(h)at the end of the stem,the bending height of the extrusion products increases significantly,but the bending radius decreases.The value of h is directly proportional to the maximum bending height of bending products and inversely proportional to the bending radius.From the comparison of velocity field distribution,it can be seen that the increase of h is one of the important factors affecting the velocity distribution difference along the transverse direction(TD)of the extrusion products at the die hole,and also one of the inducements for the bending characteristics of the extrusion products.The h of the stem and the ? are the key factors to determine the curvature and quality of extruded products.The results show that with the increase of h and ?,the more obvious the bending characteristics of the extruded products,and the extrusion load peak appears delay and decreases obviously.After the SE process,the AZ31 magnesium alloy grains were refined obviously and dynamic recrystallized structures were evenly distributed in bending products.The AZ31 Mg bending products were produced strong extrusion fiber texture by SE process,and texture intensity was higher at {0001} <11-20> and {10-11} <11-23>.The appearance of twins in AZ31 magnesium alloy bending products had a remarkable impact on the occurrence of dynamic recrystallization(DRX)and texture evolution.