Microstructure And Mechanical Properties Of Mg-9Gd-4Y-1Zn-0.8mn Alloy

Light magnesium alloy with high strength and high toughness is urgently needed in the development of aerospace,national defense and modern industry,which can effectively alleviate the problems of resources and environment in China.Mg-RE-TM with long period stacking ordered phase(LPSO phase)is the best high-strength magnesium alloy system at present,and its strength is over 500 MPa,which basically reaches the strength of commercial aluminum alloy.It has become an urgent problem to solve that how to solve the instability of high strength magnesium alloys and the difficulty of bulk forming by using effective toughening methods.In order to solve the above problems,it is necessary to clarify the mechanism of strengthening and toughening of the alloy,master the change law of strength and plasticity,and provide theoretical guidance for the application of the alloy.In view of this situation,the author adopts different means(heat treatment,extrusion deformation,micro-alloying)to regulate and control the LPSO phase which plays a major role in strengthening the alloy,and finally reveals the strengthening and toughening mechanism of the alloy.This paper through the heat treatment process for Mg-9Gd-4Y-1Zn-0.8Mn alloy LPSO phase in the controls,the results show that different heat treatment temperature and time affect the content,shape and distribution of LPSO,and then the alloy by squeezing 10 h in 520? has the best mechanical properties after heat treatment,the mechanical properties of tensile strength of 383 MPa,yield strength of 331 MPa,elongation of 12.1%.Then,the effect of extrusion deformation process on the LPSO phase in Mg-9Gd-4Y-1Zn-0.8Mn alloy was studied.The increase of extrusion temperature was conducive to the precipitation of LPSO,and the precipitation of LPSO would promote dynamic recrystallization and make the alloy grain fine.Increasing the extrusion ratio can effectively break the bulk LPSO at the grain boundary,hinder the growth of dynamic recrystallization grains,and achieve the purpose of refining grains.Finally,on the basis of the above research,we in the Mg-9Gd-4Y-1Zn-0.8Mn alloy elements added Ca,LPSO phase in heat treatment was studied and the effect of extrusion process of LPSO phase mechanism,found to block the Ca element to add promotes grain boundary phase precipitation,restrain the dynamic recrystallization grain size in the extrusion process,thereby damage strength and the plastic alloy.