Current understanding of creep behaviour of near γ-titanium aluminides

Abstract

The literature dealing with creep of near γ-TiAl alloys is reviewed, including single and multiphase compositions. The characteristics of creep in the primary or transient, minimum strain rate or pseudo-steady state, and tertiary creep regimes are presented. Considerable experimental evidence indicates that a temperature-stress domain exists in which creep is controlled by dislocation climb. For multiphase compositions, the effect of microstructure on creep is discussed, with emphasis on the predominantly lamellar microstructure, which exhibits superior creep resistance. The influence of composition on creep resistance is presented in terms of intrinsic and extrinsic effects, and the associated role of β phase is discussed. Models for the creep of lamellar structures are reviewed. The current state of knowledge regarding creep of near γ-TiAl alloys precludes quantitative conclusions; however preliminary design of creep resistant microstructures is possible.