Study On Microstructure And Properties Of Mg-Y-Ni-Zr Alloy

Magnesium alloys have high specific strength and specific stiffness,and they have great prospects as structural materials in the fields of electronics,automobiles and aviation.In this paper;OM and HAADF-STEM were used to characterize the long-period stacking ordered phase(LPSO)of Mg-5Y-2.5Ni-0.5Zr(at%)alloy in as-cast and solid solution states,and the aging precipitation phase was explored at the atomic scale.Study on the effect of heat treatment on corrosion performance by weight loss method and electrochemical method.(1)The as-cast alloy is mainly composed of the Mg matrix and the long-period stacking ordered phase.After the solution treatment,a part of the second phase is dissolved at the grain boundary,the crystal grains become large,and the LPSO phases having the network structure are formed around the grain boundary.Coexistence of 14H and 18R phases in as-cast and solid solution alloys.(2)A small amount of ?'phase occurs in the underage phase,and the zigzag distribution of the ?' phase and the hexagonal rare earth atom structure appear in the peak state.The lattice constant of the ?' phase is a=2a0=0.6418nm,b=4(?)a0=2.2232nm,where a0 represents the lattice constant of Mg.At peak aging,?" and ?'phases coexist,the increase of hardness is attributed to ?'phase and the hardness reaches 138 HV.The interaction between the LPSO phase and the ?' phase at the atomic scale under the aging and peak aging stages is explored along the[11(?)0]Mg direc tion.The distance between the two phases at the peak is about 0.84nm..(3)After the solution treatment(T4)of the alloy,the corrosion resistance of the alloy is lowered,and the corrosion resistance of the as-cast alloy is superior to that of the solid solution alloy.Electrochemical analysis is the instantaneous corrosion rate,and the alloy has the best corr,osion resistance after aging treatment for 8h.The weight loss experiment analyzed the average corrosion rate,the corrosion resistance of alloy was best after aging treatment for 90h,and the corrosion resistance was the worst after aging treatment for 8h.