Establishment And Application In Numerical Simulation Of The Constitutive Model For Ti-15-3 Alloy At High Temperature

Ti-15-3 alloy is a new metastableβ-type titanium characterized by improved high specific strength (strength-to-weight rate) and cold formability. It has been used extensively in aerospace industry. For understand the deformation behavior and the effect of process parameters on deformation of the Ti-15-3 alloy during hot deforming, The deformation behaviors of Ti-15-3 alloy during hot deformation have been studied systematically by the hot physics simulation experiment on Gleeble-1500 Thermal Simulator,regression analytic method,artificial neural network and the finite element numerical simulation technology. The main contents are as follows:1. The flow stress increases with decreasing deformation temperature and increasing of strain rate. The predominated intenerate mechanisms of Ti-15-3 alloy during hot deformation are dynamic recovery2. The deformation of Ti-15-3 alloy at high temperature is a thermally activated process. The interrelations of flow stress and strain rate can be described by a hyperbolic sine functionε= A[sinh(ασ)]ⁿ exp(-Q/RT) for Ti-15-3 alloy during the process of high temperature deformation. The flow stress at high temperature can be described by Zener-Hollomon parameter Z value.3.The flow stress and strain rate,temperature at high temperature can be described by Inσ= In A₁ + n Inε+ m Inε- bT.4. The flow stress model of Ti-15-3 alloy at high temperature can be established by the artificial neural network which can predict the flow stress more precisely.5. According to the basic principle of rigid-plastic finite element method and considering to quantity of heat transfer and energy transfer during forming. Integrating the constitutive relationship into the FE code, a simulation of deformation with heat transfer has been carried out for the isothermal forging of Ti-15-3 alloy. The effect of process parameters, including the deformation temperature, the punch velocity and friction, strain and temperature raise during isothermal forging has been studied and load-journey curves with different thermal mechanical parameters has been calculated. The results investigated show that punch velocity and deformation temperature have significant effect on the forming. Moreover, the effect of different deformation ways on the deformation process of Ti-15-3 alloy has been given out. This work provides the theory and technique foundation for implementing process optimized design and quality control scheme of Ti-15-3 alloy isothermal forging process.