Effects of alloying on crack-tip deformation and shielding in gamma-based titanium aluminides
- Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering
Alloys based on gamma titanium aluminide (TiAl) are being considered as structural materials in a number of aerospace and automotive applications. The effects of ternary alloying of Ti-48Al (with 1--3 at.% Mn, Cr and V), and micro-alloying with 0.2% W, on crack-tip deformation and shielding mechanisms are discussed in this paper, for failure under cyclic (fatigue) loading. Crack-tip deformation mechanisms are elucidated by crack-tip transmission electron microscopy examination. Twin process zone dimensions and the degree of deformation-induced twinning are also determined via optical interference and transmission electron microscopy techniques, respectively. A micromechanics-based model is proposed for the estimation of twin toughening ratios under monotonic or cyclic loading. The model, which is based on non-linear fracture mechanics concepts, assumes an average smeared plastic stress distribution across the twin process zone. Differences in the resistance to crack growth in the ternary alloys are related to intrinsic microstructural features and crack-tip shielding phenomena.
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States); Ohio State Univ., Columbus, OH (United States)
- OSTI ID:
- 483613
- Journal Information:
- Acta Materialia, Vol. 45, Issue 3; Other Information: PBD: Mar 1997
- Country of Publication:
- United States
- Language:
- English
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