Study On Creep Behavior Of TC4 Titanium Alloy Forgings Under Non-isothermal Forging

TC4 titanium alloy has high specific strength,good corrosion resistance,good creep strength,endurance strength and fatigue strength,so it is the preferred structural material for steam turbine blades.However,in the medium and high pressure stage of large steam turbine,the creep deformation of TC4 titanium alloy is inevitable.The creep properties of materials are not only related to the service environment,but also closely related to the forming process.In the field of industry,the core parts of equipment are mostly formed by forging.Considering the problems of efficiency and cost,the frequently-used forging process of TC4 titanium alloy is non isothermal forging.Most of the existing researches focus on the effect of forging process parameters on the microstructure and mechanical properties of TC4 titanium alloy,but the effect of forging process parameters on its high temperature service properties is rare,especially its creep behavior.Therefore,the influence of forging process parameters on the creep behavior of TC4 titanium alloys is analyzed in this paper to find the optimal matching between reasonable forging process and creep behavior.The main research contents are as follows:(1)According to the engineering practice and the characteristics of TC4 titanium alloy,the key forging parameters(deformation temperature and deformation degree)are selected,and the appropriate non isothermal forging process experiment is developed.High temperature uniaxial tensile tests were carried out on the TC4 titanium alloy forgings,and the corresponding mechanical properties were obtained,which laid a foundation for the implementation of creep test.(2)Based on the analysis and research of the existing creep models,the creep tests of TC4 titanium alloy forgings under different deformation temperature and deformation degree were designed,and the creep strain time curves were drawn.By analyzing the influence of different deformation temperature and deformation degree on the creep behavior of TC4 titanium alloy forgings,the corresponding mathematical equation describing the creep behavior of TC4 titanium alloy forgings was established.The influence of different forging process parameters on the key parameters of creep equation was clarified,and the creep deformation mechanism of TC4 titanium alloy forging under non isothermal forging was discussed.(3)Based on the effect of forging process parameters on the creep behavior of TC4 titanium alloy forgings,the best process parameters group with better creep performance of TC4 titanium alloy forgings was obtained and determined.Combined with the relevant creep mathematical equations,the simulation model was established,and the creep numerical simulation analysis of TC4 titanium alloy forgings under the relevant process parameters group was carried out,the characteristic parameters of creep limit behavior are obtained.The research in this paper clearly shows that the forging process parameters have an significant influence on the creep behavior of TC4 titanium alloy in high temperature service environment,which has important engineering guiding significance for the reasonable selection and optimization of the corresponding forging process parameters according to the different requirements of TC4 titanium alloy forgings' actual service performance.