The Isothermal Forming Law And Numerical Simulation Of TC11 Alloy Impeller Component With Complex Shape

Titanium alloy impeller is one of the most important parts of engine, and it has the high requirements for dimensional accuracy, microstructure and mechanical properties. At present this kind of component is manufactured by machining or chemical shining with a low material utilization and efficiency. Furthermore, the inner metal flow lines are cut off because of machining and the performance of blades is severely decreased. Therefore, the processing technology of this kind of components is lag far behind the need of manufacturing development and has been the bottleneck of aerospace engine development. Based on the physical model and numerical simulation, compound forging technology of isothermal and enclosed die forging was carried out in this study to obtain the TC11 alloy impeller with high dimensional accuracy and mechanical properties. The research has important significances on the development and manufacture of aerospace engine impeller and the improvement of weapon equipments.In this investigation, isothermal compression tests were carried out on Gleeble-1500 system at constant strain rate. The influences of deformation temperature, deformation degree and strain rate on the flow stress and microstructure change were analyzed to study the hot deformation mechanisms of the alloy in different conditions. Constitutive equations during deformation in bothα+βphase region andβphase region were constituted and used for equipment selection and finite element simulation. Based on the theory of dynamic material modeling (DMM), processing map of TC11 alloy was established using the data obtained in compression test. Combined with the deformed microstructure observation, relationship between power dissipationηwith hot working parameters, deformation mechanism and microstructure was established. Microstructural deformation mechanism map for TC11 alloy in this study was constructed to determine the safe working region including globularization of plate, dynamic recrystallization and dynamic recovery, and the unstable region including adiabatic shear band, micro crack and flow instability. The optimal hot working range of this alloy was obtained and the precise control of structure and property was realized.In order to study the flow mechanism and deformation rule and control the dimensional accuracy of impeller forging, the calculation model of 3D thermal coupled rigid visco-plastic finite element method (FEM) has been established on the process of hot deformation. The integral forging process of TC11 alloy impeller with radial twisted blades was simulated to display the deformation mechanism and flow defect. These researches laid the foundation for optimizing the forging parameters and die structure.The compound technology of isothermal and enclosed die forging was adopted to precisely forge the TC11 alloy impeller with the satisfied dimension and performance. Combined female die including 17 die sections with same shape was employed to make sure the forged impeller can be taken out from die cavity easily. Different kinds of billets were used in forging in order to obtain the optimal scheme. According to local loading theory, the deformed region and direction were controlled so as to decrease the forging load, improve the die life and performance of forged piece. Different heat treatments were applied to the forged impeller to determine the optimal heat treating regime, and the result showed excellent mechanical properties can be obtained using multiple annealing.