The Flow Behavior and Microstructural Evolution of Ti-5Al-5Mo-5V-3Cr during Subtransus Isothermal Forging

High-strength metastable β alloys, for example, Ti-5Al-5Mo-5V-3Cr, have replaced steel as the material of choice for large components, such as the main truck beam on the latest generation of airframes. The production of these components is carried out by hot near-net-shape forging, during which process variable control is essential to achieve the desired microstructural condition and subsequent mechanical properties. The flow behavior and microstructural evolution during subtransus isothermal forging of Ti-5Al-5Mo-5V-3Cr has been investigated for two different starting microstructures and analysis has incorporated previously published results. The flow behavior, irrespective of initial microstructural condition, is found to be very similar at strains ≥0.35. It is thought that this is due to a common microstructural state being reached, where dynamic recovery of the β phase is the dominating deformation mechanism. At strains <0.35, the flow behavior is believed to be dominated by the morphology and volume fraction of the α phase. Small globular α particles are thought to have little effect on the flow behavior, while the observed flow softening is directly linked to the fragmentation of acicular α precipitates.