Effect Of Zn On Tensile Mechanical Property And Corrosion Resistance Of Mg-XZn-2.8Nd-0.6Zr-0.6Cd Alloy

The effects of different Zn content on mechanical property was investigated in Mg-(1.90～6.54)Zn-2.80Nd-0.60Zr-0.60Cd(wt.%) alloy system.The alloys were extruded at390℃,at a extrusion ratio of λ=16.The extruded samples were carry through two-step ageing at90℃/10h and150℃/6h at last by comparing with different aging curves. The microstructure, tensile mechanical property and corrosion resistance were investigated by using mechanical property testing, optic microscopy (OM), scaning electron microscopy (SEM), X-ray diffraction (XRD), transmitsion electron microscopy (TEM). Results of experiment can be concluded as follows:1. Compared single aging in150℃/16h with two-steps aging in90℃/10h+150℃/6h, the number of precipitate in alloy Mg-3.85Zn-2.8Nd-0.6Zr-0.6Cd (wt.%) became more, the size of precipitate became smaller in two-steps aging, so that effect of strengthen was more obvious.The yield strength and the ultimate tensile strength reached362MPa and392MPa respectively in Mg-6.54Zn-2.80Nd-0.60Zr-0.60Cd (wt.%) alloy,and the elongation reached7.5%.2. The yield strength increased in general with increasing of Zn content in alloy Mg-XZn-2.8Nd-0.6Zr-0.6Cd (wt.%), but it changed when the contents of Zn increased from3.85wt.%to5.20wt.%. It related to the ratio of Zn/Nd. The measured ratio of Zn/Nd was1.2when the content of Zn reached3.85, but it was3.10in theory. It was3.03when the content of Zn reached5.20, but4.11in theory. So the solution of Zn was higher in alloy Mg-3.85Zn-2.8Nd-0.6Zr-0.6Cd(wt.%) than that of Mg-5.20Zn-2.8Nd-0.6Zr-0.6Cd(wt.%). Coherency strengthen caused by β1’is more obvious in the alloy during artificial aging.3. It showed that the corrosion resistance was the best in Mg-3.85Zn-2.8Nd-0.6Zr-0.6Cd (wt.%) alloy no matter what alloy as-extruded or as-aging in the weightless rates graph. The corrosion resistance became lower after aging treatment because of growing of second phase and grain size.