首页|Effect of heat treatment on corrosion behaviors of Mg-6Gd-3Y0.5Zr alloy
Effect of heat treatment on corrosion behaviors of Mg-6Gd-3Y0.5Zr alloy
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The microstructures and corrosion behaviors of as-cast,T4-treated,and T6-treated Mg-6Gd-3Y-0.5Zr alloys were systematically investigated by SEM,TEM,immersion test,and electrochemical corrosion test.The results show that the microstructure of the as-cast alloy is composed of α-Mg and Mg24(Gd,Y)5 eutectic phase,and in T4-treated alloy,Mg24(Gd,Y)5 phase dissolves into the α-Mg matrix,leading to an increase in the(Y,Gd)H2 phase.After T6 treatment,nanoscale Mg24(Gd,Y)5 phase dispersedly precipitates from the α-Mg matrix,and exhibits a specific orientation relationship with the α-Mg:(332)Mg24(Gd,Y)5//(10(1)1)α-Mg,[(13)6]Mg24(Gd,Y)5//[(1)2(1)0]α-Mg.The corrosion resistance of the Mg-6Gd-3Y-0.5Zr alloys can be ranked in the following order:T6-treated alloy exhibits the highest corrosion resistance,followed by the T4-treated alloy,and finally,the as-cast alloy.The corrosion products of the alloys are all composed of MgO,Mg(OH)2,Gd2O3,Y2O3,and MgCl2.The corrosion behavior of Mg-6Gd-3Y-0.5Zr alloy is closely related to the precipitated phase.By establishing the relationship between corrosion rate,hydrogen evolution rate,and corrosion potential,it is further demonstrated that during the micro galvanic corrosion process,the coarse Mg24(Gd,Y)5 phase in the as-cast alloy undergoes extensive dissolution,and(Y,Gd)H2 phase promotes the dissolution of the α-Mg matrix in the T4-treated alloy,intensifying the hydrogen evolution reaction.The T6-treated alloy,with dispersive precipitation of nanoscale Mg24(Gd,Y)5 phase,exhibits better corrosion resistance performance.
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