The Influence of Field‐Assisted Sintering Technology (FAST) Temperature and Cooling Rate on the Microstructural Evolution in Gamma‐Titanium Aluminide Alloy GE4822

Field‐Assisted Sintering Technology (FAST) has potential as a pre‐processing step for forging γ‐titanium aluminides, but its influence on the microstructural evolution of these intermetallics remains incompletely understood. This study investigates the effect of FAST dwell temperature and subsequent cooling rate on γ‐lamellar colony size and volume fraction in γ‐titanium aluminide alloy GE4822. Dwell temperatures were set between 1300 and 1400 °C, followed by controlled cooling at 0.1, 0.5, 1, 2 or 3 °C/s, with a free‐cooling condition applied at each temperature. The γ‐lamellar colony size and volume fraction were measured after dwell and cooling. At dwell temperatures below 1350 °C, γ‐lamellar volume fractions remained low, regardless of cooling rate. Conversely, dwell temperatures of 1375 °C or higher produced consistently high volume fractions, with colony size increasing at slower cooling rates. The greatest microstructural sensitivity occurred at 1350 °C, where increasing the cooling rate from 1 to 2 °C/s reduced the γ‐lamellar fraction from ∼80% to ∼10% and colony size from 200 μm to less than 50 μm. Substantial γ‐lamellae colony volume fractions only formed when cooled through the α‐transus, approximated at 1335 °C.