An analysis of the forgeability of Ti-10V-2Fe-3Al β titanium alloy using a combined Estrin Mecking and Avrami material constitutive model

A constitutive model was developed to predict the high temperature sub-transus flow behavior of a metastable β Ti-10V-2Fe-3Al alloy, and its applicability for industrial scale forging process has been evaluated using a finite element simulation. Cylindrical samples extracted from a cogged billet of the alloy after β recrystallisation treatment were subjected to hot compression tests at sub-transus temperatures ranging from 720 °C to 780 °C with an increment of 15 °C under varying strain rates from 0.025 to 0.2 s−1. The sub-transus flow curves of the alloy exhibited work hardening followed by dynamic recovery and flow softening beyond the strain equivalent to peak stress. Formation of low angle grain boundaries within the prior β grains and dynamic recrystallisation of β phase were observed to contribute to the flow softening. A constitutive model based on Estrin Mecking and Avrami methods was developed with minimised number of material constants, using the data derived from the hot compression tests. The model was successfully verified using the deformation behaviour measured for the alloy in the region of interest. The constitutive model was implemented into a finite element package as a user subroutine to predict the flow behaviour of industrial scale billets during open die hot forging processes and validated using experimental trials. A fairly good predictive capability with more than 95% convergence for open die forging was achieved, confirming the suitability of the material model developed for predicting sub-transus forgeability of the Ti-10V-2Fe-3Al alloy during industrial scale forging.