Influence of microstructure and strain distribution on failure properties in intermetallic TiAl-based alloys

Gamma-TiAl alloys exhibit plastic strains to failure (typically in the range 1-3%) that are lower and more variable than those of conventional structural alloys. We have developed a technique to measure strains at the scale of the microstructure, and have used this technique to assess the variation in failure properties with microstructure. This technique is capable of using the grayscale information in the image of a gridded sample to obtain sub-pixel marker displacements, and can therefore accurately determine small strain values. Microstructures that exhibit large variations in local strain distribution tend to have higher variability in tensile properties, particularly tensile ductility, compared to microstructures that accumulate strain more uniformly. Local grain orientation, segregation, and phase distribution are factors influencing the strain distribution, and therefore the properties of these materials. Orientation and morphology of lamellar plates in lamellar colonies also play a role in influencing the distribution of strain. (C) 2001 Elsevier Science B.V. All rights reserved.