Effect Of Combined Deformation Heat Treatment On Microstructure And Mechanical Properties Of 2195 Al-Li Alloy

Compared with the conventional aluminum alloy,Al-Li alloy has lower density,better strength,plasticity and corrosion resistance,and has higher specific strength and specific modulus,so Al-Li alloy is gradually replacing the traditional aluminum alloy widely used in the new aerospace industry.Although Al-Li alloys have many excellent properties,their room temperature strength and plasticity are poor.The tensile strength and elongation of annealed 2195 Al-Li alloy at room temperature are 211MPa and 13.1%,respectively,which cannot meet the performance standards of space launch vehicle parts,and to some extent limit the application of Al-Li alloy.Therefore,how to improve the strength and plasticity of Al-Li alloy is the focus of this paper.Based on the 2195 Al-Li alloy as the research object,the introduction of compound deformation-a variety of heat treatment process,systematic study the complex deformation-many kinds of heat treatment process,microstructure and mechanical properties of 2195 Al-Li alloy evolution law,expounds the compound deformation-under a variety of heat treatment process,the second phase evolution law of precipitation,The corresponding relationship between them and mechanical properties was determined.The main contents and conclusions of this paper are as follows:（1）Cryogenic rolling 2195 alloy was treated by solution-aging process.The experimental results show that the mechanical properties of the alloy are greatly improved by precipitation strengthening phase during heat treatment,and the yield and tensile strength of the alloy are increased to 320 MPa and 378 MPa,respectively.The yield,tensile strength and quantitative density of T₁ phase all reach their peak values at 12 h of aging time.Therefore,the flow behavior of 2195 alloy strength mainly changes with the quantitative density of T₁ strengthened phase in the alloy（2）On the basis of the cryogenic deformation and aging heat treatment process,the cold-rolling and annealing process is introduced to form the cold-rolling and annealing process before aging.The results show that the strength of the alloy can be improved obviously by cold rolling and annealing before aging,and the yield strength and tensile strength of the alloy can increase to 500 MPa and 451 MPa,respectively.The strength of the alloy is mainly due to the increase of the quantity density of T₁ phase in the alloy,the size of the alloy is larger,and the effect of the dislocation pinning in the alloy is enhanced.（3）On the basis of exploring the cryogenic deformation aging heat treatment process,the warm rolling process is introduced to form the warm rolling process before aging.The yield strength and tensile strength of 2195 alloy can reach 513 MPa and 489 MPa,respectively,after hot rolling before aging.The strength of the alloy is mainly due to the presence of compact small size T₁ phase in the alloy,and the quantity density of T₁phase increases greatly.The reason why the strength of warm rolling alloy before aging is higher than that of cold rolling and annealing alloy before aging is that the positions of T₁ phase nucleation point in warm rolling alloy before aging increase...