Study On The Mechanism Of Strengthening And Toughening Of AZ80 Magnesium Alloy By Deformation Heat Treatment

Because of its light weight,high specific strength and excellent electromagnetic shielding ability,magnesium alloys are widely used in aerospace,national defense and military industries where there is a strong demand for lightweight components.However,the hexagonal closepacked crystal structure and limited slip system of magnesium alloys lead to poor room temperature strength and toughness.Improving the degree of plastic deformation of magnesium alloys,supplemented by a reasonable heat treatment process,can achieve a synergistic improvement in the strength and toughness of magnesium alloy components.Based on this,this paper takes AZ80 magnesium alloy as the research object.In view of the problems of insufficient deformation,uneven microstructure and low mechanical properties of magnesium alloy cup-shaped parts manufactured by traditional channel extrusion,it is proposed to realize shear deformation strengthening of magnesium alloy cup-shaped parts.A new process of Wchannel extrusion(WCE)for parts;in view of the problem of low radial deformation of metal in the manufacturing of magnesium alloy rims by the current extrusion process,which leads to the problem of poor strength and toughness of the spokes,a research on strengthening the performance of the matrix through pre-deformation and aging is proposed.ideas.The effects of heat treatment process on the microstructure,texture and properties of WCE magnesium alloy cups were mainly studied,and the effects of conventional heat treatment and pre-deformation aging heat treatment on the radial microstructure,texture and properties of magnesium alloy rims were co MPared.Through the above research,combined with WCE and pre-deformation aging process,the mechanism of strengthening and toughening of magnesium alloy components was systematically expounded.The main research conclusions formed are as follows:1)After the AZ80 cup is deformed by WCE,the average equivalent strain reaches 4.7,the grain size is refined from 120 ?m(homogenized state)to 4.7 ?m,and the mechanical properties are UTS=310.86 MPa,TYS=200MPa,EL=13.6% The best heat treatment process obtained is415?/60min+175?/24 h,and the mechanical properties are UTS=344MPa,TYS=218MPa,EL=14.5%.2)After conventional heat treatment of AZ80+0.4%Ce magnesium alloy rim(415?/1.5h+120?/18h-175?/30h),the average grain size is 57.89?m,the mechanical properties are UTS=350.50 MPa,TYS =196MPa,EL=11.1%;after pre-deformation and aging treatment(415?/1.5h+7%-120?/9h-175?/24h),the average grain size is 17.21?m,and the mechanical properties are UTS=364.0MPa,TYS=295.36 MPa,EL=10.0%3)For the cup-shaped parts prepared by WCE,after heat treatment,fine needle-shaped continuous precipitation phases are mainly precipitated inside the grains.The special factor decreases,and the Schmidt factor for non-basal plane slip increases to 0.431342,resulting in slip.Therefore,the combined effect of precipitation strengthening and texture strengthening enhances the strength and toughness of magnesium alloy cups.4)For the AZ80+0.4%Ce magnesium alloy rim,the addition of Ce consumes part of the Al element,reduces the proportion of bulk Mg17Al12 in the grain boundary,and purifies the grain boundary.Using the pre-deformation aging process,7% pre-deformation introduces deformation twins and dislocations into the matrix,which increases the volume fraction of the dispersed continuous precipitation phase,increases the precipitation spacing of the lamellar precipitation,and promotes the interaction between the continuous precipitation and the lamellar precipitation.formation;pre-deformation-induced twinning provides nucleation sites for the elongated precipitates and increases the volume fraction of the elongated precipitates.In addition,the grain size of the pre-deformed matrix was significantly refined from 57.89 ?m to 17.21 ?m co MPared with the conventional heat treatment process.Therefore,precipitation strengthening and grain refinement strengthening are the main reasons for the improvement of the strength and toughness of AZ80--0.4%Ce magnesium alloy rims.