Study On Microstructures And Macroscopic Properties Of 7075 Aluminum Alloy After Ageing Forming By Ultrasonic Vibration

Modern aircrafts are constantly developing toward the direction of high performance,light weight,super manufacturability,and low maintenance costs.It is particularly important for the overall design of aircraft structures and the selection of materials.Integral siding is the main structural component of modern aircraft,and age forming is the most effective method to integral siding.Now,the study of temperature field and the stress field is the main part for ageing forming.However,researches on the introduction of ultrasound into the aging forming process is very few.This is a kind innovation to traditional ageing forming by the function of ultrasonic wave in the aging forming process,which has important research significance.The paper takes the7075-T651 aluminum alloy as the research object,explores the effect of ultrasonic vibration on the macroscopic and microstructural characteristics of 7075 aluminum alloy after age forming,and explain the influence mechanism on properties of 7075 aluminum alloy after age forming under ultrasound,with the best parameters for aging forming process was obtained by the effect of ultrasonic vibration.Based on the process experiment,It was explored that the influence rule of effect and macro-mechanical properties of 7075 aluminum alloy after age forming by different ultrasonic application time and different ultrasonic vibration when the applied power was 1600 W.The results show that the time of at 12 h makes the best forming effect of the component,the lowest rebound rate was at 48.40%,compared with the ordinary aging forming test piece,the rebound rate was reduced by 12.21%;when the aging temperature of ultrasonic vibration rised to 220?,the rebound rate was reached at a least value of 32.26%.The yield strength and tensile strength was increased with the extension of ultrasonic application time,and was decreased with the increase of ultrasonic vibration aging temperature.However,the variation of elongation of testspecimen between ultrasonic vibration aging treatment with the ordinary aging was very few.The microscopic law of aging formation under ultrasonic wave show that with the prolongation of the ultrasonic action time and the increasement of ultrasonic vibration aging temperature,the precipitation phase and some black second phases may be dissolved or refined,and the amount was decresed and the size was reduced of the point precipitates in the matrix and the second-phase.When the ultrasonic application timewas changed,the number of fractured dimples increased,the depth became deeper,and the dimple size became smaller,which based on ductile fractures mainly.When the ultrasonic vibration be a low temperature,lots of tear marks was appeared,which based on brittle fractures mainly.With the increase of ultrasonic vibration aging temperature,the mode of fracture turns to ductile fracture.The precipitation phase in the intragranular phase of the specimen after ultrasonic vibration aging forming process mainly changes from the spherical GP zone and the transition phase phase to the rod-like equilibrium phase and ?-phase,as well the number of ? phases was increasing.The precipitates at the grain boundaries was growing and coarsening,mainly in a discontinuous distribution,and the width of the grain-free precipitate-free zone(PFZ)has broadened.