Effect Of Heat Treatment On High Temperature Properties Of Spray Formed 2D70 Alloy

With the rapid development of aviation industry in recent years,the application of aluminum alloy in aerospace field has become more extensive.At present,the methods of improve the properties of aluminum alloy are mainly divided into adjusting the composition of alloy and heat treatment in the later stage,and adjusting the preparation process.The spray forming process is a kind of alloy preparation process which has gradually matured in recent years,through the way which properties of the alloy are improved and the best heat treatment scheme is sought.The 2D70 aluminum alloy is a typical representative of the 2XXX aluminum alloy.The main alloy composition elements are Al,Cu and Mg.On this basis,Fe and Ni elements are added to form a new alloy with certain heat resistance.The alloys were prepared by traditional casting and spray forming respectively.The microstructure and properties of the two alloys were compared and analyzed by the same hot extrusion process.Look for the best heat treatment for 2D70 alloy.Regarding the determination of the alloy solution treatment process,the selected solution treatment temperature is 520?,530?and540?,and the solution treatment time is 2 h,2.5 h,3 h,4 h,5 h,6 h,9h and 12h,respectively.The 530?solution treatment 2.5 h is determined the best solution treatment scheme for 2D70alloys.By aging treatment at 180?,190?,200?and 210?of four different temperatures.The 190?aging treatment 16 h was determined as the best single-stage aging treatment process.The results show that the properties of as-cast 2D70 alloy are lower than that of as-spray 2D70 alloy at room temperature,and the tensile strength of as-spray 2D70 alloy decreases obviously at high temperature.Combined with the Taguchi methed with widely used in engineering field of engineering,the optimum two-stage aging heat treatment process of the spray forming 2D70 alloy was determined.By determining the temperature range of the alloy two-stage aging temperature of 170?,180? and 190?,and the aging time is 6 h,8 h and 10 h.The secondary aging temperature is 230?,240? and 250?,and the aging time is 4 h,6 h and 8 h.Through the orthogonal experiment,the optimum two-stage aging process of the alloy was determined as the first stage aging treatment at 180? for 8 h and the secondary stage aging treatment at240? for 6 h.The tensile strength of the spray forming 2D70 alloy is 406 MPa at room temperature,compared with 430 MPa at room temperature with single stage treatment.It is a slight loss for the elongation increases.However,under high temperature conditions,the tensile strength of the alloy after two-stage aging treatment is 30 MPa-40 MPa higher than that of the alloy after single-stage aging treatment.The main reason for the improvement of the properties of the alloy is that after the spray forming process and the hot extrusion process,insoluble second phase in the alloy,especially the heat-resistant phase Al₉FeNi is broken.Through single-stage aging heat treatment,the properties of the alloy will be further improved,the precipitation phase will increase and rearrange evenly,forming dispersion strengthening.The two-stage aging treatment can make the alloy secondary precipitation in a short time after the second aging treatment,so that the precipitation phase increases,the high temperature strength of the alloy is improved,and the elongation increases.