Phase transformations in Ti-6.8Mo-4.5Fe-1.5Al
- Clemson Univ., SC (United States). Dept. of Ceramics and Materials Engineering
Phase transformations during artificial and isothermal aging of Ti-6.8Mo-4.5Fe-1.5Al have been investigated over the temperature range from 300 C to 750 C utilizing hardness measurements, X-ray diffraction, optical microscopy, and electron microscopy. Artificial aging following solution treatment and water quenching initially involved growth of the athermal {omega} phase. This was followed by formation of the {alpha} phase, either in association with the {omega} phase, through homogeneous precipitation within the matrix, or through heterogeneous grain-boundary nucleation. Similarly, isothermal decomposition of the metastable {beta} phase resulted in the precipitation of {omega} phase exhibiting an ellipsoidal morphology. While precipitation of {omega} was immediate at 345 C, an incubation period was observed upon aging at 390 C. Isothermal aging above this temperature involved direct precipitation of the {alpha} phase, either homogeneously within the {beta} matrix or heterogeneously at {beta} grain boundaries. The extent of homogeneous vs heterogeneous {alpha} nucleation during isothermal aging depended upon aging temperature; low aging temperatures promote homogeneous nucleation and higher aging temperatures promote {alpha} heterogeneous nucleation. Finally, continued aging resulted, independent of aging path, in coarsening and spheroidization of the {alpha} phase.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 669740
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 29, Issue 10; Other Information: PBD: Oct 1998
- Country of Publication:
- United States
- Language:
- English
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