Study On High Temperature Deformation And Rolling Forming Of As-cast ZK60 Magnesium Alloys

As a representative lightweight material,magnesium alloy has a very good development prospect in the era of pursuing lightweight.To study the thermoplastic deformation behavior of magnesium alloy,improve its microstructure and mechanical properties,and broaden its application field,this paper took as-cast ZK60 magnesium alloy as the research object and carried out the hot compression experiment on the homogenized magnesium alloy using the MMS-200 thermal simulation testing machine.The influence of thermal deformation parameters on the flow stress and microstructure of ZK60 magnesium alloy was analyzed.Meanwhile,the constitutive model and hot processing map of ZK60 magnesium alloy were constructed to provide theoretical guidance for hot-working of ZK60 magnesium alloy.Finally,the numerical simulation and microstructure simulation of the rolling process of magnesium alloy were carried out.The rolling process parameters were optimized by combining them with the hot working diagram,and the rolling experiment was carried out with the optimal rolling process to observe the microstructure and test the mechanical properties.The following research results were obtained:(1)The hyperbolic sinusoidal constitutive model of ZK60 magnesium alloy was established through the analysis of the experimental data of hot compression,and the thermal activation energy Q=142.051KJ/mol and the stress index n=4.27692 were obtained.(2)The hot working diagram of ZK60 magnesium alloy was drawn when the strain variable was 0.2,0.5,and 0.8.According to the hot working diagram,it was found that the deformation condition of low deformation temperature and high strain rate should be avoided when the strain variable was 0.2.When the stress variable is 0.5,there is no instability zone.When the strain variable is 0.8,the material has a small amount of instability zone.When the strain is 0.8,the material should avoid plastic deformation at temperatures above 660 K.(3)Through the numerical simulation and microstructure simulation of the rolling process of ZK60 magnesium alloy,combined with the hot working diagram,the optimal rolling scheme was selected(single pass reduction of 15%,rolling temperature of 623K),and the rolling experiment of the optimal scheme was carried out,the tensile strength of the rolled sheet increased by 30% and the elongation increased by 45%.