Abstract
Hot forging is an important process for shaping and property control of lightweight titanium aluminide parts. Dynamic recrystallization and phase transformations play an essential role for the resulting grain size and accordingly the mechanical properties. Due to the fact that titanium aluminides require forging under isothermal conditions, reliable process modeling is needed to predict the microstructure evolution, to optimize the process time and to avoid excessive die loads. In the present study an isothermal forging process of a compressor blade made of TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B, at. %) is modeled using the Finite Element (FE) – Software Q-Form. A microstructure model describing the microstructure evolution during forging is presented. To calibrate the model, the high-temperature deformation behavior was investigated using isothermal compression tests. The tests were carried out at temperatures from 1150°C to 1300°C, applying strain rates ranging from 0.001s-1 to 0.5s-1, up to a true strain of 0.9. The experimentally determined flow stress data were described with model equations determined form the course of the strain hardening rate in Kocks-Mecking plots. An isothermal forging process of a compressor blade was carried out and used to validate the results from the FE simulations.