Effect Of Solution Treatment And Cold Rolling Deformation On Microstructure And Properties Of Al-Cu-Mg Alloy

Al-Cu-Mg alloys are widely used in aviation and aerospace fields.Although deformation strengthening of Al-Cu-Mg alloy after solution and peak aging can significantly improve the strength,it also causes a significant decrease in plasticity.To make the alloy have high strength and high plasticity at the same time,2324 aluminum alloy was taken as the specific research object in this study.By combining hot rolling deformation with cold rolling deformation,the influence of cold rolling deformation after solution treatment and preaging on the microstructure and mechanical properties of hot rolled Al-Cu-Mg alloy was studied by using optical microscopy,scanning electron microscopy,EBSD technology,transmission electron microscopy and universal tensile testing machine.In this paper,the microstructure and mechanical properties of as-cast,annealed and hot-rolled alloys were first observed.The microstructure observation results show that the average grain size of the as-cast alloy is 145.3μm.After annealing,the average grain size increased to 197.7μm.When the alloy is deformed by hot rolling,equiaxed grains change into strip grains.The mechanical properties test results show that the hot rolled alloy has the best comprehensive mechanical properties,the tensile strength is295.2 MPa,the yield strength is 236.5 MPa,and the elongation is 9.2%.Second,the effect of solution treatment on the microstructure and mechanical properties of hot rolled Al-Cu-Mg alloy was studied.The results show that increasing solution time,the second phase in the alloy decreases.When the solution time exceeds50 min,the number of insoluble phases in the alloy is basically unchanged,and these insoluble phases are mainly the Al₂Cu Mg phase and Al₂Cu phase containing trace Fe and Mn elements.The mechanical properties test results show that with the increasing solution time,the rolling direction and transverse strength of the alloy increase,and the elongation decreases.After solution treatment for 50 min and natural aging for 72h,the comprehensive mechanical properties of the alloy in the rolling direction were the best,with tensile strength of 428.4 MPa,yield strength of 277.0 MPa and elongation of 19.7%.The best transverse mechanical properties are also achieved in50 min solution treatment and natural aging for 72 h,with tensile strength of 429.0MPa,yield strength of 265.4 MPa and elongation of 20.6%.Fracture morphology analysis shows that the fracture mode of the alloy is microporous aggregation fracture.Finally,the effect of cold rolling deformation after preaging on the microstructure and mechanical properties of the alloy was studied.The microstructure observation results show that the undissolved Al₂Cu Mg phase and Al₂Cu phase in the alloy are broken by cold rolling deformation.TEM observation showed that there were many rod-like Al₂₀Cu₂Mn₃ phases in the matrix,and there were a large number of tangled dislocations near the phase,which had a significant strengthening effect on the alloy.In the alloy with cold rolling deformation of 19%,the dislocation density reaches the maximum.EBSD analysis results show that with increasing cold rolling deformation,S,R,Cube,Goss,Brass texture content increases,and<111>、<110>texture content decreases.The mechanical property test results show that with the increase of cold rolling deformation,the strength of the alloy increases,and the elongation remains at a high level.When the cold rolling deformation is 11%,the comprehensive mechanical properties of the alloy in rolling direction are the best,with tensile strength of 465.0MPa,yield strength of 291.6 MPa and elongation of 19.0%.At this time,the transverse tensile strength of the alloy is 469.9 MPa,the yield strength is 318.0 MPa,and the elongation is 16.9%.In this study,the optimum parameters of solution and thermomechanical treatment of Al-Cu-Mg（2324）alloy are as follows:solution treatment 495^oC/50 min,preaging 4 h,cold rolling deformation 11%,natural aging 72 h:solution treatment495℃/50 min,preaging 4 h,cold rolling deformation 11%,natural aging 72 h.Under the optimum process conditions,the comprehensive mechanical properties of Al-Cu-Mg alloy are the best,the rolling tensile strength is 465.0 MPa,the yield strength is291.0 MPa,and the elongation is 19%.Horizontal:469.9 MPa,318.0 MPa,16.9%.