Understanding the Influence of Thermal Gradients during Large-Scale FAST/SPS on Final Microstructure after Secondary Hot Rolling of Ti-5Al-5V-5Mo-3Cr (FAST-roll)

The potential of Field Assisted Sintering Technology (FAST) as a high value manufacturing process for metals is now being realised, with the focus shifting towards the production of larger samples. The challenges presented by thermal gradients leading to grain size and mechanical property heterogeneity within larger parts is well documented. Several methods to reduce such thermal gradients have been developed but often require more complex and costly tooling design. However, the influence of initial grain size heterogeneity on the final part properties after secondary thermomechanical processing is currently unknown. Here, we apply hot rolling to a FAST-produced Ti-5Al-5V-5Mo-3Cr billet (83 mm diameter, 90 mm height) processed with a non-optimised tooling setup and processing parameters. Analysis of grain size, microstructure and hardness was performed at multiple locations in the as-FAST and FAST-rolled conditions. These results provide an indication of the importance of the initial grain size in titanium alloy FAST/SPS parts prior to secondary thermomechanical processing operations.