Numerical and experimental study on extrusion of ZK60 Mg alloy using billet with temperature gradient

摘要

The adoption of high ram velocity is beneficial to enhance the production efficiency of the extrusion process, while it can cause an obvious temperature rise, resulting in rapid grain growth and even over-burning. In order to solve the conflicts between efficiency and quality, the temperature gradient was introduced on the billet, and the extrusion process of ZK60 Mg was studied based on numerical and experimental works. The results showed that a high ram velocity caused a high exit temperature and deteriorated the temperature uniformity, since large amount of heat was generated because of the severe deformation. The temperature gradient on billet strongly reduced the temperature rise and improved its uniformity. The partial dynamic recrystallization (DRX) took place in extruded ZK60 Mg profile, and the grain size was reduced by slowing down the ram velocity or introducing temperature gradient. The evidences of both continuous DRX (CDRX) and discontinuous DRX (DDRX) were found, and CDRX preferred to take place at low temperature. 10-10//ED fiber texture with (0001) basal planes parallel to ED existed, and the texture intensity with high ram velocity and without temperature gradient was much stronger. The tensile strength was enhanced by temperature gradient on billet due to the fine grain size and the strengthened residual strain.