Research On Low Cycle Fatigue Behavior And Prediction Method For Ti₂AlNb At High Temperature

Ti₂AlNb based alloy is a new type of high temperature alloy with low density,specific strength and high stiffness.It is the most development potential of high temperature light alloys in recent years.The Ti₂AlNb based alloy has been gradually used in high temperature engine parts,and high temperature fatigue is one of the main failure modes of high temperature components,this paper is based on the alloy at high temperature low cycle fatigue research in view of this situation,the main research contents include:1.The tensile tests of Ti₂AlNb based alloy are investigated at the temperature range of 500? ⁷00?,the high temperature low cycle fatigue tests are carried out to obtain the stress-strain data of the alloy.Through the analysis of the experimental results,it is found that the alloy is a cyclic hardening material with Masing characteristics.2.Based on the experimental data and the chaboche visco plastic unified constitutive model this paper modifies the model by introducing the temperature variables and researches Ti₂AlNb based alloy in high temperature low cycle fatigue deformation in the process of true stress-strain relationship.The results show that the unified viscoplastic constitutive model can well describe the uniaxial tension and high temperature cyclic deformation behavior of the Ti₂AlNb base alloy.3.The equation of MansonCoffin,Walker strain model,and the energy method are used to predict high temperature fatigue life of Ti₂AlNb based alloy.This paper analyzes the feasibility of several forecasting methods and improves energy method based on the theory of energy dissipation.Through the comparison with several models,the prediction of the modified energy method is more accurate and applicability.4.Based on the static strength analysis of the compressor blade of a certain type of engine,this paper uses the modified energy method to predict the life of the compressor blade.The calculation results show that compared with the raw materials,the Ti₂AlNb based alloy has a higher specific strength and safety factor,and has good engineering application value.