Effects of Cu addition on microstructure and mechanical properties of as-cast magnesium alloy ZK60

The effects of Cu addition on the microstructure and mechanical properties of the as-cast magnesium alloy ZK60 were investigated with optical microscope, SEM, TEM, XRD, EPMA and tensile tester. The mechanism by which the mechanical properties are affected by Cu addition was discussed. The results show that Cu can effectively eliminate the intragranular solute segregations in the alloy, and the grain size of the alloy is decreased considerably with increasing the Cu amount. A ternary eutectic phase MgZnCu with a face-centered cubic structure is identified in the Cu-bearing alloys, which predominantly distributes at the grain boundary and acts as the nucleation sites of microcracks during the plastic deformation process. It is also found that the tensile properties of the alloy firstly increase by the trace addition of 0.5%-1%Cu and then decrease by a further addition up to 2.0%.

Effects of Cu on Microstructure and Corrosion Behaviour of Hot-Rolled Mg-3Zn-1Y Alloys

The microstructure and corrosion behaviour of hot-rolled Mg-3Zn-1Y-xCu alloys(x=0,1,3,5,wt%)were investigated.Results show that all Mg-3Zn-1Y-xCu alloys mainly consist ofα-Mg matrix and Mg_(3)Zn_(6)Y phases.The addition of Cu element promotes the formation of MgZnCu phase,and the amount of MgZnCu phase is increased with the increase in Cu content.Electrochemical and immersion test results show that the corrosion resistance of Mg-3Zn-1Y-xCu alloys is deteriorated after Cu addition,which can be attributed to the influence of the microstructure of alloys and the properties of the formed corrosion product film.The MgZnCu phase with high electrochemical potential accelerates the micro-galvanic corrosion as strong cathodic sites,and the decreased protection effect of the corrosion product film results from the variation in PBR value of the related compounds.