The investigation on the unstable flow behavior of Ti17 alloy in α+β phase field using processing map

In this study, five existing instability criteria (Prasad's, Murty's, Sematin's, Gegel's and Malas's criterion) were employed to delineate the unstable flow regions for Ti17 alloy during hot deformation. Experimental stress-strain data obtained from isothermal hot compression tests in the temperature range of 780-860°C and strain rate range of 0.001-10s^-1 were utilized to develop the instability maps. These domains were validated through detailed microstructure observation. The material exhibited stable flow at lower strain rates while adiabatic shear band and flow localization occurred at higher strain rates (≥1s^-1). It was observed that the maps at strain of 0.9 developed by Prasad's and Murty's criteria have a good ability for predicting unstable flow at high strain rates and entire temperatures. However, the Semiatin's criterion under-predicts the instability regions in the test temperatures and strain rates. On the contrary, the Gegel's and Malas's criteria over-predict the instability domains, especially for the low strain rate region.