The Effect Of Homogenization Treatments On Microstructures And Properties Of Al-Cu-Li-Sc-Zr Alloys

Al-Cu-Li alloy had been widely used in the aerospace field,but the macro/micro segregation and low melting point non-equilibrium eutectic in its ingot not only adversely affected the subsequent processing,but even caused the alloy ingot cracking.In this paper,combined with the development project of new Al-Li alloy,Al-Cu-Li-Sc-Zr alloy was taken as the research object,DSC analysis,microstructure characterization and mechanical properties testing were used to study the effect of multistage ingot homogenization on T6 and T8 microstructures after the hot rolled,texture and properties of the alloy,and the following conclusions were obtained:（1）At 350℃/4 h-410～460℃/（4～16 h）-520℃/48 h triple-stage homogenization treatments,dendrite segregation was eliminated and dispersed Al₃（Sc,Zr）dispersion phase particles are precipitated.The temperature in the second step of homogenization is 460℃,compared with the second step homogenization temperature of 410℃,more Al₃（Sc,Zr）dispersion phase particles are formed,but coarse Zr-rich phase particles are formed with the extension of homogenization time.（2）The Al₃（Sc,Zr）dispersion phase particles formed in the homogenization process not only have the strengthening effect,but also can promote Cu atoms to replace Al atoms at the interface between Al matrix and Al₃（Sc,Zr）particles during the aging treatment stage,and reduce the stacking fault energy of the alloy,and then cooperate with Li atoms to promote the precipitation of main strengthening phase Al₂Cu Li（T1）.（3）Under the effect of Al₃（Sc,Zr）dispersion phase particles,a large number of sub-grains with orientations less than 10°are formed in the grain of the solid solution sample of the rolled sheet,and these sub-grains are concentrated in the{111}orientation（{111}//rolling surface）,and the texture configuration is dominated by the S texture.After the T8（pre-stretching）treatment,the{011}orientation sub-grains is added to the{111}orientation sub-grains to strengthen the deformation texture components.（4）Under the test conditions in this paper,the combination of tensile strength and elongation after fracture of samples homogenized at 350℃/4h-460℃/4 h-520℃/48 h is the best:T6 state peak aging hardness is 166.23HV,tensile strength is 505Mpa,elongation after fracture is 11.48%;The peak aging hardness of T8 is 181.03 HV,tensile strength is 551 Mpa,elongation after fracture is 9.76%.