POSSIBILITIES FOR HIGH-TEMPERATURE STRENGTHENING IN IRON ALUMINIDES

Iron aluminides based on Fe3Al and on FeAl offer considerable possibil ities for development as intermediate temperature materials operating in aggressive chemical environments. Two major property limitations re strict their application: low toughness, related to their environmenta l sensitivity, and poor high temperature creep resistance. Considerabl e attention has been given to the intermediate stress but, while many of its characteristics are well documented, there remains considerable uncertainty about the controlling mechanisms. Plastic deformation at temperatures above the stress peak can be analysed in terms of thermal ly-activated, creep-like flow, with a steady evolution during deformat ion of many of the controlling parameters. Two avenues can be explored for improving high temperature behaviour: modify the diffusive flow b ehaviour and restrict dislocation motion at dispersed particles. There is considerable evidence that control of matrix composition can lead to large changes in diffusion parameters and the motion of dislocation s. Dislocation pinning at particles depends on the availability of sui table particle phases, and examples of precipitated carbides, disperse d oxides, and decomposed intermetallic mixtures will be considered. (C ) 1998 Elsevier Science Limited. All rights reserved.