| 7150 aluminum alloy has become a major structural material in the aerospace industry because of its excellent properties such as light weight,excellent overall performance,and low manufacturing cost.At present,fracture toughness,fatigue strength,conventional strength,and corrosion resistance are listed as the four main assessment indicators for high-strength aluminum alloys.As the main bearing member material for aircrafts,7150 aluminum alloy is required to take both tensile strength and corrosion resistance into consideration.To improve fracture toughness and fatigue strength.Aluminum alloy processed by Retrogression and re-aging(RRA)process has excellent comprehensive performance.This research mainly focuses on the effects of regression temperature and regression time on the mechanical properties,microstructure,fracture toughness,and fatigue properties of 7150 aluminum alloy.By changing the regression process parameters in regression and re-aging treatment,hardness,electrical conductivity and tensile properties of the alloy after heat treatment were tested.The regression temperature and regression aging were studied on7150 alloy hardness,electrical conductivity,yield strength and elongation.The effect of intensity change showed that the regression temperature was 170°C,and the regression time was within 200-600 min.The hardness and strength of 7150 aluminum alloy decreased with the extension of regression time,and the change of conductivity was opposite.The hardness,yield strength and tensile strength of the alloy are the highest at200 min after the regression time,which are 203.7 HB,585 MPa,and 613 MPa,respectively.The lowest conductivity is still higher than that of the T6 alloy.The regression and re-aging treatment with a regression temperature of 170°C and a regression time of 200 min enables the alloy to obtain the best combination of strength and ductility and electrical conductivity.The transmission microstructure of the alloy under different aging conditions was observed to investigate the microstructure characteristics of the alloy in the under-aging,peak-aging,and RRA states,as well as the deformation characteristics of the alloy.The fracture toughness test and fatigue performance test were selected,and the microstructure,fracture morphology and fracture behavior of 7150 alloy were studied by scanning electron microscope(SEM),transmission electron microscope(TEM)and energy spectrum(EDS).The results showed that the results were 170?.The fracture toughness KQ of RRA aging alloy treated by 500 min regression is the highest,reaching61.4 MPa·m1/2.The fracture toughness KQ value of RRA aging alloy at 180?/100 min regression was the lowest,and the fracture toughness KQ value of the RRA aging alloy treated at 170?was between the both,and the fracture toughness of the alloy was at the middle level.The fatigue strength of RRA aging alloy at 170?/200 min regression is the highest,and the fatigue strength of RRA aging alloy is the lowest at 180?/240 min regression.Under the action of high stress cycle,the fatigue life of T6 state alloy is the longest,which is one order of magnitude higher than that of RRA state alloy treated with 170?/200 min regression,and the phenomenon of cyclic softening occurs during the low cycle fatigue.The fatigue crack of 7150 Aluminum alloy usually sprouts on the surface of the specimen,but the oxidation and impurity formed in the process of casting influence the fatigue property of the alloy,which makes the alloy easy to crack in the mixture of the oxide clip and cause the alloy fatigue fracture.The best aging process is120?/24 h+170?/200 min+120?/ 24h. |
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