Research On The Microstructure And Corrosion Resistance Of WE43 Magnesium Alloy By Micro-arc Oxidation

As the lightweight material,Magnesium alloys have been widely used in all trades and professions due to their advantages such as high specific strength,low density,strong electromagnetic shielding,good damping and shock absorption.However,the poor corrosion resistance of magnesium alloys has severely limited its application.In order to improve the corrosion resistance of magnesium alloy,one of the most simple and effective method is to carry out the surface treatment for the magnesium alloy.This study used the method of laser surface melting(LSM)and micro-arc oxidation(MAO)to prepare ceramic coating on the surface of WE43 rare earth magnesium alloy.The numerical model for analyzing the temperature field in laser surface melting process was established by ANSYS,and the effects of different process parameters on the temperature were studied,analyzing the microstructure and corrosion resistance of the ceramic coating.Micro-arc oxidation process parameters and coating thickness prediction model was established based on the genetic algorithm optimization error back-propagation neural network.The major completed tasks were as follows:1.Numerical model was established for analysis of laser surface melting temperature field,using the APDL language with commercial software ANSYS.And this model was used in computing and analyzing the distribution law of temperature field with time in laser surface remelting process.2.The microstructures of the LSM-MAO and MAO coatings have been characterized by SEM and XRD.Results showed that the micro cracks and holes of LSM-MAO coating were less than MAO coating,and the porosity of LSM-MAO coating decreased by about 1/2.Therefore,the densification of the coating was improved.3.The corrosion resistance of the LSM-MAO and MAO coatings were analyzed by the electrochemical workstation and immersion test.Results showed that the corrosion current density of LSM-MAO coating decreased by an order of magnitude compared with MAO coating,the capacitive arc radius of electrochemical impedance spectrum of LSM-MAO coating was significantly larger than MAO coating,the period for the appearance of visible corrosion products of LSM-MAO coating was much longer than MAO coating,which indicated that LSM-MAO method in improving the corrosion resistance of magnesium alloy was better than MAO process.4.The genetic algorithm(GA)optimization error back-propagation(BP)neural netw-ork was proposed to predict the coating thickness of WE43 magnesium alloys under different MAO processing parameters including current size,pulse width and oxidation time.Results showed that the better function approximation ability and the stronger generalization ability achieved by GA-BP was more accurate than that of BP for identical training and test samples,the forecasting average error is 8.62% and 1.65% of BP and GA-BP,respectively.