Study On Orientation Correlation Of Corrosion Behavior Of Mg-Al-Ca-Mn Alloys

Magnesium alloy has the advantages of low density,high strength-to-weight ratio,good damping resistance,recyclable and so on.As a light structural material,magnesium allouys have great application potential in automobile,aerospace,electronic information and other fields.However,the poor corrosion resistance of magnesium alloy has limited its wide use.In this paper,Mg-Al-Ca-Mn alloys were solution treated and and aged treated respectively.We tested the macro corrosion behavior of Mg-Al-Ca-Mn alloy by hydrogen evolution experiment and electrochemical impedance spectroscopy measurements.Based on electron backscatter diffraction(EBSD),computed X-ray tomography(CT)and diffraction contrast tomography(DCT),we studied the effect of alloying elements and G.P.zones on the corrosion behavior of Mg-Al-Ca-Mn alloys,and the correlation between the corrosion behavior and the crystal orientation of magnesium alloys,which provides a theoretical basis for improving the corrosion resistance of Magnesium alloys.After solution treated,all elements in Mg-Al-Ca-Mn alloys were dissolved almostly,no second phase was precipitated treated,and no obvious texture was observed.The strength of Mg-Al-Ca-Mn alloy is significantly improved after alloying.After solution treated and short-term aging treated,the high-density G.P.zones precipitated in Mg-AlCa-Mn alloy,which significantly improved the strength of the alloy.The effects of alloying elements and G.P.zones on the corrosion behavior and orientation correlation of Mg-Al-Ca-Mn alloys can be studied.Firstly,electrochemical impedance spectroscopy measurements and hydrogen evolution experiment were used to measure the macro corrosion performance of the Mg-Al-Ca-Mn alloys.Then,based on computed X-ray tomography(CT)and diffraction contrast tomography(DCT),the evolution of corrosion behavior and the relationship between corrosion behavior and grain orientation were observed in situ by four dimensional.After adding Al,Ca and Mn,the corrosion potential of the Mg-Al-Ca-Mn alloy increased and the corrosion current density decreased.Moreover,the corrosion resistance of the alloy was improved due to the combination of Mn with impurity elements such as iron and silicon.However,the corrosion potential became more negative and the corrosion current density increased further after G.P.zones were formed in the alloy.The formation of G.P.zones formed the micro galvanic corrosion between the nano precipitate and the matrix,which accelerated the corrosion of the alloy.In Mg-Al-Ca-Mn alloy,the corrosion rate of non-basal oriented grains is higher than that of basal oriented grains,and the corrosion propagated along the non-basal oriented grains.This is due to the higher surface energy of non-basal oriented grains.