| 7055 aluminum alloy is an ultra-high-strength aluminum alloy that can be strengthened by heat treatment.With high specific strength,good hot workability and excellent welding performance,it is widely used in the aerospace field.In this paper,the effects of homogenization treatment on the microstructure and mechanical properties of 7055 aluminum alloy were studied.After homogenization treatment,the effects of different deformation amounts of rolling deformation and multi-directional forging deformation on the microstructure and mechanical properties of 7055 aluminum alloy were analyzed,and its strengthening mechanism was discussed.The main conclusions are as follows:(1)The microstructure of as-extruded 7055 aluminum alloys are mainly composed of a-Al matrix and other second phases.The phases mainly include:MgZn2 phase,Al2CuMg phase and a small amount of acicular Al7Cu2Mg phase.The distribution of Cu,Mg and Zn in the alloy is uneven,and there are many coarse Al2CuMg phases gathered in the microstructure.(2)The optimum process of single-stage homogenization is 460 ?×24 h.By this process,the distribution of various alloy elements tends to be uniform,and the hardness reaches 140.4 HV5.When the temperature rises above 480?,aluminum alloys will occur obvious overburning.The two-stage homogenization process of 460 ?×24 h+480 ?×10 h further makes the residual phases dissolve into the matrix,and the volume fraction of the second phases is reduced to the lowest 8.5%,and the hardness reaches 153.3 HV5.In addition,the coarse Al2CuMg phases gradually spheroidizes during the homogenization.(3)During the rolling process,the grains are elongated and produce recrystallized grains.When the sample is rolled by 60%,the microstructure of the as-extruded completely disappears,and a large number of recrystallized grains are produced.The second phase distribution is more uniform and fine.When sample is rolled by 80%,the structure grains have grown up.During the rolling process,the second phases are still composed of MgZn2 phase and Al2CuMg phase.The texture of the as-extruded material is Cube texture and S texture.After rolling deformation,the texture orientation changes to {111}<110>and Brass texture,but the texture strength does not increase significantly.After the rolling deformation and solution aging treatment,the hardness and strength of the material show a trend of first increasing and then decreasing,but the elongation generally decreases.The mechanical properties of the 60%rolling deformation sample are the best.The hardness along the rolling direction(RD)is 210.2 HV5,and the tensile strength,yield strength and elongation are 650.1 MPa,628.5 MPa and 6.9%,respectively.The strengthening mechanisms of material performance improvement are mainly dislocation strengthening,fine grain strengthening and solid solution aging strengthening.(4)With the cumulative deformation of multi-directional forging increases,the microstructure alloys are refined,and a large number of recrystallized grains are produced at the boundaries between the original grains.When the cumulative deformation is ????=5.4,the average grains size is 5.3 ?m.The distribution of the second phase particles become more uniform,which is still composed of MgZn2 phase and Al2CuMg phase.After multi-directional forging,the texture orientation of the material changes to {110}<110>texture and a small amount of Gaussian texture,and the texture strength decreases.As the cumulative deformation increases,the mechanical properties of the material gradually improved.The hardness and tensile strength of the ???=5.4 cumulative deformation sample are the highest,which are 200.1 HV5 and 569.1 MPa,respectively,and the elongation is 14.2%.The fracture mode of the alloy is still ductile fracture.The strengthening mechanisms of alloy materials during the multi-directional forging process include dislocation strengthening,fine-grain strengthening and solution aging strengthening. |
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