A novel powder metallurgy processing approach to prepare fine-grained Ti-rich TiAl-based alloys from pre-alloyed powders

A relatively simple yet attractive and efficient powder metallurgy processing method, based on mechanical milling and spark plasma sintering of PREP (Plasma Rotating Electrode Processed) pre-alloyed powders, has been proposed to prepare full density fine-grained Ti-rich Ti-Al alloys with controlled microstructure. Full density fine-grained Ti-rich Ti-Al alloy compacts, with grain size in the range of 2-4 μm, were successfully prepared from dendritic coarse PREP pre-alloyed powders, which are otherwise difficult to consolidate, by mechanical milling followed by spark plasma sintering at moderate consolidation conditions. It has been demonstrated that the microstructure, i.e. lamellar or equiaxed, depends on the extent of mechanical milling. The fine-grained Ti-Al compacts exhibited extremely good mechanical properties. An attempt has been made to correlate the effect of mechanical milling on the microstructure and properties of the sintered Ti-Al compacts.