On grain refinement of a γ-TiAl alloy using cryo-milling followed by spark plasma sintering

A fully dense fine-grained γ-TiAl based alloy was fabricated by cryo-milling pre-alloyed powders followed by spark plasma sintering. The consolidation was performed at 1050 or 1200 °C. The effect of cryo-milling on the densification kinetics and final microstructure was studied. Results indicate that cryo-milled (8 h) powder is fully densified at a temperature nearly 125 °C lower than that of un-milled powder. The microstructure of the alloy fabricated at different temperatures consisted of fine grains of γ-TiAl and α2 (Ti3Al) phases in different volume fractions. The average grain size of cryo-milled powders compacted at 1050 and 1200 °C were determined as 0.6 and 0.9 μm, respectively. It is inferred that the reduction in crystallite and particle size induced by cryo-milling is the likely reason for such enhancement in densification and grain refinement.