CURRENT UNDERSTANDING OF CREEP-BEHAVIOR OF NEAR GAMMA-TITANIUM ALUMINIDES

The literature dealing with creep of near gamma-TiAl alloys is reviewe d, including single and multiphase compositions. The characteristics o f creep in the primary or transient, minimum strain rate or pseudo-ste ady state, and tertiary creep regimes are presented. Considerable expe rimental evidence indicates that a temperature-stress domain exists in which creep is controlled by dislocation climb. For multiphase compos itions, the effect of microstructure on creep is discussed, with empha sis on the predominantly lamellar microstructure, which exhibits super ior creep resistance. The influence of composition on creep resistance is presented in terms of intrinsic and extrinsic effects, and the ass ociated role of beta phase is discussed. Models for the creep of lamel lar structures are reviewed, The current state of knowledge regarding creep of near gamma-TiAl alloys precludes quantitative conclusions; ho wever preliminary design of creep resistant microstructures is possibl e. (C) 1995 The Government of Canada.