Exploitation of Field-Assisted Sintering Technology (FAST) to Produce Pre-Forged Billets from Metastable Beta Titanium Alloy Powder

Abstract

Powder produced by gas atomisation of metastable beta alloy Ti-5Al-5Mo-5V-3Cr has been consolidated using field-assisted sintering technology (FAST) to examine the suitability of the process to produce pre-forged billets as opposed to the conventional multi-step Kroll-VAR-forging route. FAST testing was performed using an FCT Systeme GmbH spark plasma sintering furnace type HP D 25 at The University of Sheffield. The dwell temperature was varied between 800 and 1200°C and the dwell time between 3 and 60 minutes. The process was found to allow very precise control over the beta grain size in Ti-5Al-5Mo-5V-3Cr by variation of the dwell time and dwell temperature, producing grain sizes between ~40 and ~350 μm. However, it was found that the grain size was increased more by increasing the dwell temperature than increasing the dwell time. The porosity was found to be between 99.5 and 100 % for all dwell temperatures at dwell times of 30 minutes or above. FAST has the ability to produce almost fully consolidated Ti-5Al-5Mo-5V-3Cr pre-forged material from powder with a controlled beta grain size, which is not possible by other methods.