Advanced intermetallic alloys—beyond gamma titanium aluminides

Recent studies have shown that Nb-base refractory intermetallic materials may be viable for service at temperatures that compete with the nickel-based superalloys in structural applications. While advanced intermetallics in monolithic form have limited prospects for providing the required balance of properties for use at high operating temperatures, two-phase or multiphase intermetallic systems composed of a ductile, Nb-base refractory phase in equilibrium with one or more silicide intermetallics show promise for further development as structural materials. Exploratory efforts on these systems have indicated that damage tolerance, creep resistance and oxidation tolerance may be obtained and controlled simultaneously. In turn, these findings have led to alloy development strategies and approaches which are currently under investigation and are expected to lead to focused research on a small set of alloys. This manuscript presents an overview of recent results on selected Nb-base intermetallic systems with particular emphasis on phase equilibria and mechanical behavior.