Hot Forgeability of Titanium Alloy Ti–6Al–2.2Mo–1.4Cr–0.4Fe–0.3Si Alloy: An Approach Using Processing Map

Abstract

Titanium alloy, Ti–6Al–2.2Mo–1.4Cr–0.4Fe–0.3Si (BT3-1), is a two phase α + β alloy developed for applications in rocket engines, gas turbine engines, and aircraft frames for service up to a temperature of 450 °C. The hot workability of this alloy has been studied through isothermal hot compression testing in the temperature and strain rate \((\dot{\varepsilon })\) range of 800 °C to 1000 °C and 10⁻³ to 10 s⁻¹, respectively, in a thermomechanical simulator. Processing maps using dynamic material model has been generated and different regions of the map were correlated with microstructural observations. The flow stress data were fitted in Arrhenius strain-compensated model and constitutive equations were developed. Optical microstructures revealed elongated grains, kinking of α phase, flow localisation, and adiabatic shear bands at lower temperatures. Super-plasticity was found to be operative at low temperature of 850 °C and \(\dot{\varepsilon }\) 10⁻³ s⁻¹, whereas dynamic recrystallization (DRX) was dominating at high temperatures of 950 °C to 1000 °C and \(\dot{\varepsilon }\) of 10⁻³ s⁻¹. Finite element analysis showed the flow localization in the unstable regions of processing map. Enhanced hot workability was achieved above 950°C in the \(\dot{\varepsilon }\) of 10⁻²−10⁻³ s⁻¹ due to initiation of DRX in view of an increase in the β phase fraction.

Graphical Abstract