Corrosion Properties And Mechanisms Of Ultrahigh Pressure Magnesium Alloys

From the perspectives of environmental protection and sustainable development,magnesium alloys have attracted much attention in recent years,and people consider it as one of the metals with great potential to replace traditional structural materials because of advantages such as high specific strength,low density and good casting properties.However,at the same time,it can not be overlooked that such metals have two extremely obvious disadvantages:low strength and poor corrosion performance,which has led to slow progress in practical applications.The surface coating method is complicated and the holding time is not long,and thus the corrosion resistance gradually weakens.Therefore,fundamentally speaking,improving the corrosion performance of magnesium matrix has become an urgent problem to be solved.In this experiment,supersaturated solid solution of Mg-Al alloy and Mg-Zn alloy was prepared by using ultra-high pressure equipment,and then the residual stress in the saturated solid solution was released by aging treatment.The main research methods used in this experiment include optical microscopy analysis,X-ray diffraction analysis,and electron microscopy analysis.The results show that there are two reasons for the superior corrosion resistance of this Mg-Al alloy compared to conventional Mg alloys.On the one hand,the alloy contains an ultra-high percentage of aluminum.Since the solid solubility of aluminum in the matrix increases,the precipitation of the second phase decreases,and the negative difference effect?NDE?and pitting corrosion are weakened,thereby increasing its corrosion performance.Secondly,the Mg₁₇Al₁₂2 nanophase with high index surface precipitated in the supersaturated solid solution of Mg-Al alloy after aging treatment.After being exposing to a corrosive environment,an aluminum-rich oxide film?Al₂O₃:95%?forms immediately on the metal surface.This oxide film can effectively resist corrosive ion invasion.Moreover,when the aluminum-rich layer is broken down by the polarization current or destroyed by the etching solution,it can be rapidly repaired to form a reliable and long-lasting protection.This kind of magnesium-aluminum alloy has great potential for development,which greatly broadens its application in biodegradable stents,automobile,aerospace,and electronic devices.