Research On Microstructure Evolution And Corrosion Behavior Of Biological Magnesium Alloy Based On Plastic Deformation

Magnesium alloy is known as a revolutionary biomedical metal material because of its good specific strength,bone induction,biocompatibility and biodegradability.However,the poor mechanical properties of magnesium alloy at room temperature and the rapid degradation rate in human body limit its clinical application.The results show that reasonable plastic deformation can significantly refine the grain size of magnesium alloy,improve its mechanical properties and biological corrosion resistance.Taking ZK60 magnesium alloy as the research object,the effects of plastic deformation mode（tensile deformation,compression deformation,cyclic rotating bending deformation）and deformation parameters（deformation temperature,strain rate,equivalent strain）on its microstructure and biological corrosion resistance were studied.By optimizing the plastic deformation parameters,the grain size of ZK60 magnesium alloy after plastic deformation is obviously refined,and the biological corrosion resistance is improved to a certain extent.The main contents of this paper are as follows:（1）In order to obtain the effect of different deformation parameters on Microstructure of ZK60 Magnesium Alloy during tensile deformation,tensile tests were carried out at different temperatures,different strain rates and different equivalent strains.The results show that with the increase of temperature,the decrease of strain rate and the increase of equivalent strain,the average grain size of ZK60 magnesium alloy first decreases and then increases.When the temperature is 250℃,the strain rate is 6×10^-4 s^-1,the equivalent strain is 0.14,the grains of ZK60 magnesium alloy after deformation are relatively fine.The average grain size is 8.41 μm.Compared with the original tissue,it decreased by 11.94%.（2）In order to obtain the effect of different deformation parameters on the microstructure of ZK60 Magnesium Alloy during compression deformation,compression experiments were carried out at different temperatures,different strain rates and different equivalent strains.The results show that with the increase of temperature,the decrease of strain rate and the increase of equivalent strain,the average grain size of ZK60 magnesium alloy first decreases and then increases.When the temperature is 250℃,the strain rate is 1.2×10^-3 s^-1,the equivalent strain is 0.14,the grain size of ZK60 magnesium alloy after compression is obviously refined.The average grain size is 7.62 μm.Compared with the original grain,it is reduced by 20.21%.（3）In order to obtain the influence of different deformation parameters on the microstructure and properties of ZK60 Magnesium Alloy during cyclic rotating bending deformation,the cyclic rotating bending experiments of different temperature,different strain rate and different equivalent strain were carried out.The results show that with the increase of temperature and the decrease of strain rate,the average grain size of ZK60 magnesium alloy is decreasing first and then increasing.With the increase of the cumulative equivalent strain,the average grain size of ZK60 magnesium alloy decreases gradually.When the deformation temperature is 250℃,the strain rate is 1.2×10^-3 s^-1,the cumulative equivalent strain is 0.14,the grain refinement effect of ZK60 magnesium alloy is the best.The average grain size is 6.82 μm.Compared with the original tissue,it decreased by 28.59%.At this time,the mechanical properties of the deformed samples were obviously improved,and the tensile strength was increased by 5.82%,and the elongation after fracture increased by 12.16%.（4）In order to obtain the effect of different plastic deformation methods on the microstructure of ZK60 magnesium alloy,the microstructure of ZK60 magnesium alloy after tensile deformation,compression deformation and CRB deformation was analyzed under certain temperature,strain rate and equivalent strain.The results show that the grain refinement effect of ZK60 magnesium alloy after CRB deformation is the most obvious,and the average grain size decreases by 28.59%compared with the original structure.（5）In order to obtain the effect of plastic deformation on the biological corrosion resistance of ZK60 magnesium alloy,the biological corrosion experiments of ZK60 magnesium alloy after tensile deformation,compression deformation and CRB deformation were carried out under certain temperature,strain rate and equivalent strain.The results show that the biological corrosion resistance of ZK60 magnesium alloy after deformation is improved to a certain extent.The order of biological corrosion resistance from good to bad is as follows:CRB deformation sample,tensile deformation sample,compression deformation sample,original sample.