Fracture criterion of Ti40 alloy based on the Zener-Hollomon parameter at hot forming

By means of simulative hot compression tests in conjunction with the finite element method, the fracture criterion of burn resistant titanium alloy Ti40 at the temperature range of 900-1100°C and strain rate range of 0.01-10 s^-1 duringt hot forming was investigated. The results show that a single variable Zener-Hollomon parameter that accounts for a combined effect of temperature and strain rate, was introduced to indicate the critical fracture strain ε_f, and the relation between them was a linear. The fracture behavior of Ti40 alloy was analyzed by Oyane criteria which is used extensively for cold forming. It was found that Oyane criteria can accurately predict the location of crack initiation of Ti40 alloy during hot compression tests. Meanwhile, the fracture critical value of C_f increased with the increasing of temperatures and decreasing of strain rates, and a linear relation with lnZ is also found. The fracture criteria of Ti40 alloy obtained at high temperature deformation can reflect the relationship between deformation parameter and the fracture critical value of C_f much more clearly, it should be a powerful tool to predict the fracture of Ti40 alloy at hot forming successfully.