Rolling And Heat Treatment To Manufacture High Performance 7055 And 7075 Alloys

7xxx alloy is the aluminum alloy with high strength and hardness at this stage.By adjusting the process,the strength of 7xxx alloy can be further improved,and the production energy consumption can be reduced,which is conducive to saving costs and expanding its engineering applications.In this study,commercial 7055 and 7075 alloys were selected as raw materials and processed by different rolling and heat treatment processes,such as solution-warm rolling-aging treatment,quenching after hot rollingaging treatment and quenching after hot rolling-warm rolling-aging treatment.The microstructure of the samples after processing was characterized and analyzed by optical microscope,scanning electron microscope and transmission electron microscope,and the mechanical properties of the above samples were tested by microhardness tester and universal testing machine.This paper studied the effect of rolling and heat treatment on the microstructure and mechanical properties of 7055 and7075 alloys,and explored the feasibility of producing high-performance 7055 and 7075 alloys by rolling and heat treatment.For the 7055 alloy,due to the Zr element,the Al3 Zr phase can be formed to suppress the grain coarsening in the process of heat treatment and plastic deformation processing.Therefore,7055 alloy exhibited fine elongated grain structure,and this structure was not changed by the subsequent heat treatment and deformation process.The warm rolling before aging and the hot rolling before quenching led to the formation of high density dislocations inside the samples,which promoted the precipitation of theη′ phase during the subsequent aging treatment and shortened the time required for artificial aging treatment.The process of solution-warm rolling-artificial aging treatment significantly strengthened the 7055 alloy.The yield strength and tensile strength of the samples were 687 MPa and 725 MPa,respectively.The main strengthening effects of the above sample were precipitation strengthening and dislocation strengthening.The 7055 alloy processed by rapid quenching after hot rolling had a low cooling rate.The low cooling rate led to the formation of large size ηsteady-state phase with a high volume fraction in the grain,which consumed a lot of Zn and Mg solute atoms and was not conducive to subsequent aging precipitation strengthening.The comprehensive mechanical properties of 7055 alloy were slightly worse than those of 7055 alloy treated with traditional solid solution-aging treatment.For the 7075 alloy,both warm rolling before aging and hot rolling before quenching could refine the grains.In addition,rolling led to the formation of dislocations in the alloys,which promoted the precipitation of the η′ phase in the subsequent aging treatment,improved the strength and hardness of the alloy,and shortened the time required for artificial aging.Due to the fine Cr-rich phase and low Zn and Mg contents of the 7075 alloy,Different form 7055 aluminum alloys,hot rolling before quenching did not cause severe coarsening of the precipitation phase.The water quenching after hot rolling-warm rolling-natural aging treatment process can significantly optimize the mechanical properties of 7075 alloy.The 7075 alloy sample manufactured by this process can obtain the highest strength,and the yield strength and tensile strength of the sample were 566 MPa and 608 MPa,respectively.The main strengthening effects were dislocation strengthening,precipitation strengthening and fine grain strengthening.