Microstructure And Properties Effect Of Initial Deformation Energy Storage, Heating Rate And Solution Time On Ultra High Strength Aluminum Alloy Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025Sr

Al-Zn-Mg-Cu ultra high strength aluminum alloy is a key structural material in aerospace and automotive manufacturing. To improve the strength, toughness and corrosion resistance of the alloy is the research direction of ultra high strength aluminum alloy. In this paper, Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025 Sr super high strength aluminum alloy was used as the test material, and the microstructure evolution of the alloy during the annealing process was tested by annealing at different heating rates to the gradient temperature. The effects of different initial energy storage on the properties of the alloy at different heating rates and solid solution time were explored.Metallographic observation, EBSD and XRD analysis, hardness, electrical conductivity,tensile property test, intergranular corrosion and spalling corrosion test were carried out to test the properties and microstructure of the alloy. The main research work and conclusions are as follows:The effects of annealing temperature that was heat treated as rapid heating and slow heating on the Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025 Sr ultra high strength aluminum alloy extruded materials and hot-pressed materials were investigated. The results show that the conductivity increases and then decreases with the increase of temperature, the hardness decreases and then increases with the increase of temperature.The dislocation density of the alloy is reduced to 0 when the annealing temperature is between 300 ℃ and 450 ℃, and the dislocation is re produced when the annealing temperature reaches 470 ℃. The average size of alloy decreases slightly during heating annealing to 300 ℃ grain, grain size of the alloy annealed to 470 ℃increased significantly. Compared with the extruded materials the average grain size and low angle grain boundaries of hot-pressed materials has been significantly reduced,dislocation and grain boundary strengthening has improved.The extruded materials’ microstructure and mechanical properties effect of Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025 Sr ultra high strength aluminum alloy heat-treated by rapid heating, slow heating annealing and 2 h, 24 h solution time for T6 aging were investigated. The results show that the slow heating annealing can reducethe grain size of the alloy, compared to 2 h solution, 24 h solution is alloy insoluble second phase reduction. The hardness of the alloy is above 215 HV, and the conductivity is about 25%IACS. The yield strength of the extruded material samples were 647.9 MPa, 697.1 MPa, after 2 h, 24 h solid solution and aging. The enhancement of strength mainly comes from the strengthening of solution strengthening and precipitation strengthening, and then is the low angle grain boundary strengthening. The corrosion resistance of the alloy is 3, the corrosion resistance of the solid solution 24 h alloy is better than that of the solid solution 2 h.The effects of initial deformation energy storage, annealing temperature rising rate and solution time by T6 aging on mechanical properties and microstructure of high strength aluminum alloy Al-11.54Zn-3.51Mg-2.26Cu-0.24Zr-0.0025 Sr high strength aluminum alloy hot-pressed materials were studied. Results showed that the hot-pressed materials average grain size is increased significantly than extruded materials,comparing with average grain size of alloy by rapid warming is reduced by slow heating,alloy average grain size is decreased by 24 h solution than 2 h solution. The hardness,conductivity of hot-pressed materials changed little than extruded material, tensile strength is above 700 MPa, the yield strength is over 670 MPa, the elongation was above 5%. Slow heating can improve the strength of the alloy and elongation, in 2 h solid solution system, the yield strength of the alloy was increased from 676.3 MPa to687.1 MPa, the elongation increased from 5.6% to 7.2%. The enhancement of strength mainly comes from the strengthening of solid solution strengthening and precipitation strengthening. The elongation rate of the alloy was significantly increased heat-treated by plastic deformation processing, the intergranular corrosion resistance and corrosion resistance of 24 h solid solution alloy were significantly improved compared with the 2h solution.