Effect Of Nd Alloying And Heat Treatment On Corrosion Resistance Of Mg-6Zn-Mn Alloys

As the lightest metal structure material, magnesium alloys are widely applied in the fields such asautomobile, communication, aeronautic and astronautic industries and so on. The corrosion resistantmagnesium alloy with high strength is one of the interested researches recently. This paper focus onthe Mg-6Zn-Mn alloys with the purpose of improving the corrosion properties. The modificationeffect and mechanisms of the Nd rare-earth, heat-treatment on the microstructure, mechanicalproperties and corrosion resistance of Mg-6Zn-Mn alloys were investigated by means of OM, XRD,SEM, EDS, electrochemical workstation, tensile test machine and other modern analysis methods.The element alloying modification results show that Nd rare element could refined the grain size,modified the microstructure. The best average size of grain in Mg-6Zn-Mn alloy was30μm when Ndaddition was1.5%. As the Nd content increased, the morphology of the reinforced phase chang fromdiscontinuous distribution into network distribution. The refining mechanism of Nd alloying was Ndcould chang the solidification condition, increased the constitutional supercooling degree and reducednucleation of interfacial tension.Nd addition could remarkably improve the tensile strength and corrosion resistance. With1.5%Nd addition, the tensile strength of alloy was195MPa,16%higher than the base alloy, the hardnesswas increased to67.5HV. The results of Nd element alloying on corrosion resistance show that thecorrosion resistance of alloy with1.5%Nd addition significantly improved. The average corrosion ratewas0.63g·m-2·h-1, reduced by50%. The corrosion current density was reduced by one order ofmagnitudes.T4solution treatment and T6aging treatment both could effectively improve the tensile strengthand corrosion resistance. The alloy with1.5%Nd addition has best integrated performance. The tensilestrength of alloy under T4solution treatment increased to205MPa, the average corrosion rate was0.63g·m-2·h-1, the corrosion potential was-1.440V. The tensile strength of alloy under T6agingtreatment increased to215MPa, the average corrosion rate was0.48g·m-2·h-1, the corrosion potentialwas-1.224V. The results of the corrosion residual strength research show that the alloy under T6aging treatment had the slowest deterioration rate.