Role of niobium in the progress of gamma alloy development

Nb has become a critically important alloying element in gamma aluminide alloys, as over the years their compositions have evolved from the initial composition of Ti-48Al-2Cr-2Nb to more recent ones based on Ti-45Al-(5-8)Nb. These changes, originally intended to raise the oxidation resistance, also resulted in increases in yield as well as creep strength levels; however, at the expense of damage tolerance. This paper discusses this complex phenomenon, along with the ways of further enhancing the resistance to oxidation as well as creep, and the processes that may improve the damage tolerance. (AU)