Research On Heat Treatment Of 7050 Aluminum Alloy

Al-Zn-Mg-Cu(7000series)A1 alloy are heat-treatable aluminium alloys,heat treatment system optimization is an important means to improve the performance of ultra high strength aluminum alloy,the mechanical properties and stress corrosion resistance can be improved by heat treatment.7050 aluminum alloy are widely used in the aeronautical and aerospace industries because of their low quenching sensitivity,high strength,excellent stress corrosion resistance properties and good process performance.By optimizing the parameters of 7050 aluminum alloy heat treatment,obtain suitable heat treatment process,provide a useful reference for the promotion of its production and application.In this paper,based on 7050 aluminum alloy hot rolled plate,solution and aging treatments have been investigated.The effect of heat-treatment on microstructure and propertis of 7050 aluminum alloy had been investigated by vickers hardness,tension,electrical conductivity measurement and DSC analysis combined with metallographic microscope,scanning electron microscope and X-ray diffraction.The heat treatment process parameters of of 7050 aluminum alloy were optimized.The main conclusions of the thesis were as follows:(1)There are ? phase,S phase,T phase and Al7Cu2Fe phase in 7050 aluminum alloy.With the increase of the solution temperature,prolonging the holding time of solution,the remaining second phase significantly reduced,to a certain extent tends to be stable.the A17Cu2Fe phase is insoluble phase,there are still remained in 484 ?.(2)With the increase of the solution temperatureand the extension of solution time,the recrystallization percentage of alloy is increasing.After solution at 477?for 1h,the recrystallization percentage of alloy is 37.6%;With the solution time extended to 6h,the recrystallization percentage of alloy reached 54.2%.(3)After solution at 477? for 1h,quenched at 40? water,the microhardness of the alloy reaches the maximum value of 194.62HV,the electric conductivity is 31.6%IACS,and the degree of solid solution is better.Therefore,the optimum solution process of 7050 aluminum alloy is solution at 477? for lh,and the quenching temperature is 40 ?.(4)The hardness and electrical conductivity of 7050 aluminum alloy increased rapidly at the initial stage of aging at 121 ? of aging at a single stage,the electrical conductivity of the alloy has been increasing.After aging for 24h,the hardness reached the peak value of 194.62HV.(5)The analysis results of double stage aging test showed that the aging time of the second step aging has a great influence on the hardness and conductivity of the alloy.Comprehensive consideration of the strength,the conductivity,the hardness and other properties,the optimum aging process of 7050 alloy is 121 ?x6h+177?×12h.Under the above conditions,the microhardness is 168.75HV,the electrical conductivity is 36.9%IACS,the tensile strength is 540MPa,the elongation is 14.5%.