Evaluation of microstructure and phase relations in a powder processed Ti-44Al-12Nb alloy
- Univ. of Nevada, Reno, NV (United States). Dept. of Chemical and Metallurgical Engineering
- Lawrence Berkeley Lab., CA (United States). Materials Science Div.
Titanium aluminides based on the ordered face-centered tetragonal {gamma}TiAl phase possess attractive properties, such as low density, high melting point, good elevated temperature strength, modulus retention, and oxidation resistance, making these alloys potential high-temperature structural materials. These alloys can be processed by both ingot metallurgy and powder metallurgy routes. In the present study, three variations of the powder metallurgy route were studied to process a Ti-44Al-12Nb (at.%) alloy: (a) cold pressing followed by reaction sintering (CP process); (b) cold pressing, vacuum hot pressing, and then sintering (HP process); and (c) arc melting, hydride-dehydride process to make the alloy powder, cold isostatic pressing, and then sintering (AM process). Microstructural and phase relations were studied by x-ray diffraction (XRD) analysis, optical microscopy, scanning electron microscopy with an energy-dispersive spectrometer (SEM-EDS), and electron probe microanalysis (EPMA). The phases identified were Ti{sub 3}Al and TiAl; an additional Nb{sub 2}Al phase was observed in the HP sample. The microstructures of CP and HP processed samples are porous and chemically inhomogeneous whereas the AM processed sample revealed fine equiaxed microstructure. This refinement of the microstructure is attributed to the fine, homogeneous powder produced by the hydride-dehydride process and the high compaction pressures.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 39823
- Journal Information:
- Journal of Materials Engineering and Performance, Vol. 4, Issue 1; Other Information: PBD: Feb 1995
- Country of Publication:
- United States
- Language:
- English
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