Corrosion behavior of as-cast GWK magnesium alloy and its relationship with microstructure
The influence of Gd and Y element content on microstructure and corrosion performance of as-cast Mg-Gd-Y-Zr(GWK)alloys was analyzed,and the corrosion behavior of the alloy and its relationship with the microstructure were studied.The results show that the microstructure of the alloy is mainly composed of α-Mg solid solution and Mg5(Gd,Y)compound located at grain boundaries,the α-Mg includes the primary α-Mg in the grain and the eutectic α-Mg near the grain boundary,and the eutectic α-Mg contains higher contents of Gd and Y elements.The Mg5(Gd,Y)forms the main corrosion galvanic couple with eutectic α-Mg,and the Mg5(Gd,Y)is preferentially corroded as the anode and develops inward along the grain boundaries,causing the alloy to corrode and form intergranular corrosion morphology characteristics in the early stage of corrosion.As the content of Gd and Y elements increases,the number of the Mg5(Gd,Y)compounds increases,and the corrosion potential of eutectic α-Mg shifts positively,which leads to the increase of the electrode area and electromotive force of the corrosion micro-galvanic couple,the aggravation of the micro-galvanic corrosion and the decrease of the corrosion resistance of the alloy.
GWK magnesium alloycontent of Gd and Ymicrostructuremicro-galvanic corrosion
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