Study On Stress Aging Behavior Under The Effect Of Electrical Pulses Of2219Aluminum Alloy

:Stress aging under the effect of electrical pulses refers to the application of electrical pulses and stress during aging, the alloy was in the coupling of temperature, electrical pulse and stress, the orientation, type, size, number and morphology of precipitation strengthening phase could be precisely controlled, so as to achieve the purpose of improving the microstructure and properties of alloy. The main research contents and conclusions are as follows:(1) The comparison experiment of stress relaxation aging and creep aging was carried out to establish the strength model of2219aluminum alloy, which was used to predict the evolution of the strength with the aging time during the stress relaxation aging.(2) Developing electrical pulses generator to compare and analyze the effect on microstructure and properties of2219aluminum alloy by electrical pulses aging and conventional aging with stress-free, found that electrical pulse could make lattice distortion zone of Al-Cu alloy become larger, so that the energy of lattice distortion increased, driving force of phase transformation increased, which could improve the nucleation rate of new phase, shorten the arrival time of peak aging.(3) The effect of creep aging under the effect of electrical pulses on the microstructure and properties of2219aluminum alloy has been systematically studied. The results show that:a) Under the coupling effect of different stress and aging temperature, the alloy would achieve different peak strength. When the aging temperature was165℃, the strength of alloy would reach the peak value under the condition of160MPa stress and1000Hz electrical pulse aging12h, the yield strength was357.8MPa, tensile strength was458.2MPa, the mechanical properties of alloy was optimal.b) Through the observation and analysis of microstructure, higher temperature could accelerate the precipitation process of θ’ phase, but when the aging temperature was too higher, the θ’ phase would grow up coarsening, and transform into the θ phase, resulted in the decrease of strengthen; the number of dislocation would increase with the increase of test stress, which promoted the nucleation of the second phase, however, when the applied stress was too large, it would result in6’phase grow coarsening and boundary precipitate free zone widening, as a result, decreasing the strength of the alloy.c) In the initial aging period, the hardness of the alloy increased quickly, the increase rate of the hardness would decrease with the extension of aging time; The strength of the alloy would reach the peak value under the condition of1000Hz electrical pulses and160MPa stress aging6h, yield strength and tensile strength was respectively362.4MPa and467.7MPa, the elongation was12.7%; With the extension of aging time, the alloy was in over aging stage, resulted in the decrease of mechanical properties of the alloy.(4) The age hardening index was n=1.17and the activation energy of alloy was Q=115.4kJ/mol after creep aging treatment under the effect of electrical pulses, while the age hardening index was n=1.13and the activation energy was Q=135.5kJ/mol after conventional aging treatment. It could be found that creep aging under the effect of electrical pulses could reduce the activation energy of aging precipitation, increase the nucleation rate, and then accelerate the process of aging precipitation.