Research On Mechanical Property And Preparation Of MB15-Y Magnesium Alloy

Magnesium alloy has a bright future for industrial application because of its manyunique advantages. However,the close-packed hexagonal lattice results in poor stressand plasticity, which astrict its application. This research aims to improve themechanical property of MB15magnesium alloy by adding Y, extrusion process andheating treatment.MB15-Y billets with different mass fraction of Y (wt%(Y)=0.2%、0.5%、1.0%、1.5%、2.0%was prepared by permanent mold casting.The influence of temperature anddeformation on the microstructure and mechanical property of MB15-Y wasinvestigated. The alloy was extruded under different temperature(T=300℃、350℃、400℃、450℃) and different extrusion ratios(λ=8、12、25).Then,the heat treatment processwas optimized by studying the as-aged,solution-teated and T6-teated alloy.The results indicated that the microstructure of MB15get refined with theaddition Y. The phase in as-cast alloy, distribute along the crystal boundary,changedfrom I-phase to W-phase along with the increasing of Y. It’s confirmed that themicrostructure and mechanical property of the alloy with1.0%Y was optimal. Thegrain was finest, the ultimate tensile strength(UTS) and the elongation(EL) reached231MPa and12.73%respectively at room temperature.The phase become W-phase totally during extrusion process in fish-bone,slenderrod and particle morphology. It effected the microstructure and mechanical propertygreatly. In general,the plasticity increase and stress decrease with the extrusiontemperature elevation.While the mechanical property din’t vary obviously when theextrusion ratios elevate. Therefore,300℃was the optimal extrusion temperature. Underthis temperature,the UTS of as-extruded alloy reached319MPa when λ=8,and theUTS,EL were311MPa,16.89%when λ=25. Thus,the ideal extrusion process was300℃and λ=25. Compared to T4and T5treatment, almost all the W-phase getdecomposed during T6treatment (500℃×2h+200℃×48h),and new precipitated phaseMg-Zn phase,Mg-Y phase appeared. The mechanical property was improvedevidently,for UTS and EL reached388MPa and21.37%.