Effect Of Plasma Discharge On Fatigue Properties Of Magnesium Alloy During Micro Arc Oxidation

The stress effect of plasma discharge on the metal substrate during micro-arc oxidation process is the essential reason to reduce the fatigue performance of the metal substrate,but the cumulative energy of the plasma discharge and the maximum arc micro-area energy are controlled by the power load characteristics.Therefore,the cumulative thermal effect of arc discharge and the maximum arc micro area energy during the growth of ceramic layer under different power load characteristics are studied.The fatigue properties of the samples were studied by up-down method.Combined with the change and distribution of the average residual tensile stress of the magnesium substrate after the micro-arc oxidation treatment.The mechanism of plasma discharge on the fatigue performance of magnesium alloy micro-arc oxidation specimens under different power load characteristics is discussed,and the basis and realization method for the selection of the process to improve the fatigue performance of the metal substrate by micro-arc oxidation are proposed.Research indicates:When the 20?m ceramic layer was prepared under different power load characteristics,the plasma discharge energy,the increase in residual tensile stress of the metal substrate,the roughness of the film-substrate interface,and the fatigue properties of the corresponding samples were significantly different on the two sets of samples.The difference between the accumulated energy and the maximum micro-area energy of the first group is 21.5%and 91.4%,respectively.The increment of the residual tensile stress and the stress dispersion of the metal substrate differ by 14.4%and 52.2%,respectively,and the corresponding fatigue limit of the sample is 9.9%.The difference between the accumulated energy of plasma discharge and the maximum micro-area energy of the second group of samples is 44.3%and 14.4%,the difference between the increment and dispersion of residual tensile stress on the metal substrate is 44.6%and 44.2%,respectively,and the corresponding fatigue limit of the samples is 8.5%.The load characteristics of the power supply affect the plasma discharge energy,and the cumulative energy and the maximum micro-area arc energy respectively affect the increase of residual tensile stress on the magnesium substrate and the roughness of the film-substrate interface.The greater the accumulated energy of plasma discharge in the micro-arc oxidation process,the greater the increase in residual tensile stress on the metal substrate,and the lower the fatigue limit.The greater the discharge energy of the micro-area,the greater the roughness and stress dispersion of the film-substrate interface,and the lower the fatigue limit.When the load characteristics are the same,the roughness of the metal substrate surface will amplify the fluctuation degree of the film substrate interface caused by plasma discharge,and the fatigue limit of the sample is also different.When the roughness of the metal substrate increases from 1.5 ?m to 10 ?m,the fatigue limit of the sample decreases from 81.699 MPa to 72.033 MPa,a difference of 11.83%.