Stucture Evolution,Mechanical Properties And Refinement Mechanism Of ZK60 Magnesium Alloy Under Pulse Current Proceseing

With the growing energy crisis and the rising of environmental degradation,lightweight,green manufacturing is increasingly emphasized.As a kind of new environmental material,magnesium alloy,was widely used in aerospace,automobile,3c products,and many other fields because of its advantages such as low density,high specific strength,good shock absorption,good machining performance and easy recovery,etc..But due to the limitations of material preparation,processing technology,corrosion resistance and other factors,there is a huge gap between the potential development of magnesium alloy and its current practical application.Therefore,the research of magnesium alloy has important significance to widen the application of magnesium and alleviate the energy crisis.In this paper high energy pulse current was utilized to process hot rolled and cold rolled ZK60 magnesium alloy sheet.In order to obtain recrystallization microstructures at lower temperatures,effect of different experimental parameters such as electric pulse frequency,pulse width,and processing time on the static recrystallization of ZK60 alloys with different deformations was investigated.Moreover,thermal effect and athermal effect,nucleation and growth,the recrystallization mechanism during electropulsing treatment(EPT)were studied through experimental results and theoretical calculation.The results indicate that EPT can refine the microstructure and improve the comprehensive mechanical properties of magnesium alloy.After EPT,the average grain size of ZK60 alloy was refined from 150 ?m to 4 ?m,tensile strength and elongation were increased by 52.3% and 105%,respectively,and the texture intensity was also decreased.In addition,EPT will not only provide additional Gibbs free energy besides of Joule heat,but also reduce the recrystallization nucleation energy barrier,therefore improve the recrystallization nucleation rate at lower temperature and significantly refine recrystallization microstructure of magnesium alloy compared with the traditional heat treatment method.The mechanism of the recrystallization nucleation of ZK60 magnesim alloy with different deformations during EPT was explored.The nucleation mode of ZK60 magnesium alloy,which with different deformation amount,was very different in the process of EPT.The small deformation amount sample mainly nucleated in the grain boundary,while almost no new nucleation appear but recovery mainly occurred and more coarse inhomogeneous organization formed in the original grain interior;then,due to uniform deformation in the sample with large deformation amount,high angle grain boundaries were formed at the major areas in the early stage of EPT,resulting in nucleation and growth,and a fine uniform recrystallization structure formed finally.