Effect Of Heat Treatment On Microstructure And Properties Of Extruded 2195 Al-li Alloy Profiles

The 21 st century the vigorous development of the aerospace field on the material of the lightweight design is put forward very high requirements,and the traditional Al-Cu and Al-zinc-Mg-alloy(Cu),compared to lithium aluminium alloy due to have relatively low density and high elastic modulus,specific strength and specific stiffness,since 21 century is considered to be the most competitive one of aerospace materials.2195 Al-Li alloy is a kind of aging strengthening alloy.Different aging systems will lead to differences in the types,density,size and distribution of precipitated phase in al-Li alloy,which will affect the mechanical properties and corrosion resistance of the alloy.At present,the research on the effect of heat treatment system on mechanical properties and corrosion resistance of 2195 Al-Li alloy extruded profiles is mainly focused on single-stage aging and artificial aging after pre-deformation,while the research on multistage aging,especially the regression re-aging,is less.In order to obtain high mechanical properties and corrosion resistance at the same time,the influence of different solution regimes on the second phase and recrystallization of extruded 2195 Al-Li alloy profiles was investigated.The influence mechanism of single stage aging,double stage aging and regression re-aging on microstructure,mechanical properties and corrosion properties was studied,which provided theoretical guidance for heat treatment process of extruded 2195 al-li alloy profiles.The main research work and conclusions are as follows:(1)The effect of solution treatment parameters on microstructure and properties of extruded 2195 Al-Li alloy profiles was studied.After solution treatment in the range of 495℃～540℃,0.5h～5h,with the increase of temperature and time,the degree of recrystallization of the alloy increases,and the proportion of the second phase in the matrix decreases gradually,but the phenomenon of "curing" appears.The recrystallization degree of the alloy is 12.9% and the proportion of the second phase is 0.63% when the solution temperature is 525℃-60 min.(2)The effect of different aging regimes on mechanical properties of2195 Al-Li alloy after solution treatment at 525℃-60 min was studied.After single stage,double stage and regression reaging,the tensile strength and elongation of the alloy reach 579 MPa,578MPa,609 MPa and 5.5%,7.28%,7.72%,respectively.Compared with peak aging,the tensile strength and elongation after regression re-aging increased by 5.1% and2.2% respectively.(3)The effect of different aging regimes on the corrosion resistance of extruded 2195 Al-Li alloy profiles was studied.The intergranular corrosion resistance and spalling corrosion resistance are in the order of regression reaging > under-aging > two-stage aging > peak aging.The order of stress corrosion resistance is regression reaging > two-stage aging > peak aging >under-aging.The results show that the resistance of 2195 al-Li alloy to intergranular,spalling and stress corrosion is the best under the condition of regression reaging.