铸态GWK镁合金的腐蚀行为及其与组织的关联性

Corrosion behavior of as-cast GWK magnesium alloy and its relationship with microstructure

分析了Gd、Y元素含量对Mg-Gd-Y-Zr(GWK)合金铸态微观组织和腐蚀性能的影响,并研究了合金的腐蚀行为及其与组织的关联性。结果表明:合金的组织主要由α-Mg固溶体和位于晶界的Mg5(Gd,Y)化合物组成,α-Mg包括晶内初生α-Mg和晶界附近的共晶α-Mg两部分,共晶α-Mg中含有更高含量的Gd、Y元素。Mg5(Gd,Y)与共晶α-Mg构成主要的腐蚀微电偶,Mg5(Gd,Y)作为阳极被优先腐蚀并沿晶界向内部发展,合金由此发生腐蚀并在腐蚀初期形成晶间腐蚀的形貌特征。随着Gd、Y元素含量的增加,Mg5(Gd,Y)化合物的数量增多,共晶α-Mg的腐蚀电位正移,导致腐蚀微电偶的电极面积和电动势相应增大,合金的电偶腐蚀程度加剧,耐腐蚀性降低。

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 ofα-Mg solid solution and Mg5(Gd,Y)compound located at grain boundaries,theα-Mg includes the primaryα-Mg in the grain and the eutecticα-Mg near the grain boundary,and the eutecticα-Mg contains higher contents of Gd and Y elements.The Mg5(Gd,Y)forms the main corrosion galvanic couple with eutecticα-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 eutecticα-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.