Research On Fatigue Properties Of TC4 Titanium Alloy Plate After Superplastic Gas Bulging Forming

As a kind of high benefit components manufacturing technology,superplastic forming(SPF)is focus by all kinds of industries.Because SPF can improve the performance of component,change the design concept of traditional structure and improve the structural integrity,and other advantages.SPF is applied on aero-engine key components,thus higher requirements of structure strength and life assessment applied to SPF structure must be put forward.Based on TC4 titanium alloy plate,this paper researched the influence of fatigue proporties under different reduction ratio under the process of superplastic gas bulging forming.Fatigue life prediction method is established.First of all,by means of superplastic gas bulging forming experiment of TC4 titanium alloy,test specimens of thinning evenly under four kinds(20%,30%,40% and high temperature cycle)of reduction ratio were obtained,metallographic experiment was carried out,and the rules of grain size changing with the reduction ratio was studied.Secondly,mechanism of grain size changing by superplastic gas bulging forming was analysed,superplastic grain growth accompanied by dynamic recrystallization was found during superplastic,finite element software Marc was used simulating the superplastic gas bulging forming experiment,code of superplastic grain growth was written.Simulation results under different reduction ratio agree well with the experiment test results.Axial tensile fatigue test was carried out and the fatigue life curves of TC4 under different reduction ratio were got.Superplastic forming process of different reduction ratio influenced on fatigue life of TC4 was studied.Fatigue life prediction model based on different reduction ratio was set up.Eventually,a fatigue life prediction method of superplastic gas bulging forming of TC4 titanium alloy was set up.