Fatigue of bi-lamellar microstructures
The mechanical properties of Ti-castings with typically coarse lamellar microstructures can be improved by a heat treatment in the {alpha}+{beta}-phase field; during the subsequent cooling, fine {alpha} platelets can be precipitated in the {beta} phase which reduces the slip length effectively. This so-called bi-lamellar modification improves simultaneously the yield stress, the creep resistance and the fatigue strength; the latter, however, not to the full potential with respect to the increase in yield stress. For certain combinations of annealing temperature and cooling rate, the high-cycle fatigue strength of the bi-lamellar condition can be even lower than that of the lamellar condition despite a higher yield stress. The reason was found to be a narrow depleted zone in the {alpha} phase next to the {alpha}/{beta} interface. This soft layer can be healed by an additional heat treatment restoring the equilibrium concentration in the vicinity of the interface.
- Research Organization:
- Technical Univ. Hamburg-Harburg (DE)
- Sponsoring Organization:
- Deutsche Forschungsgemeinschaft DFG (German Research Partnership)
- OSTI ID:
- 20013305
- Country of Publication:
- United States
- Language:
- English
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