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Microstructural characterization and creep behaviour of as-cast titanium aluminide Ti–48Al–2V

Sujata, M and Sastry, DH and Ramachandra, C (2004) Microstructural characterization and creep behaviour of as-cast titanium aluminide Ti–48Al–2V. In: Intermetallics, 12 (7-9). pp. 691-697.

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Abstract

Solidification paths were established in a two-phase $(\alpha_2 + \gamma)$ alloy of nominal composition Ti–48Al–2V (at.%). The alloy buttons were prepared by vacuum arc melting. The phases present in the alloy were characterized by X-ray diffraction, optical microscopy and scanning electron microscopy. Room temperature microstructure of the alloy consisted of colonies of $(\alpha_2 + \gamma)$ lath dendrites and interdendritic $\gamma$ segregate. The $(\alpha_2 + \gamma)$ lath colony size was determined to be about 76 mm. Based on the dendritic morphologies and the orientation of the $(\alpha_2/\gamma)$ lath striations observed in the shrinkage cavities, it was established that primary $\beta$ solidification occurs in the alloy. Creep behavior of the alloy in the as-cast condition was studied by employing the impression creep technique in the temperature range of 1033–1098 K and in the stress range of 187–420 MPa. The alloy exhibited power law creep in this regime. The stress dependence of the steady-state creep rate showed a stress exponent value of 4.0–4.6 and the activation energy for creep was found to be in the range of 320– 340 kJ mol2$^{-1}.$ This value is slightly higher than that for diffusion of Ti in single phase $\gamma$ (TiAl). These results suggest the operation of a diffusion-controlled creep mechanism in the alloy. Microstructure of the deformed region under the indenter revealed formation of fine-scale lamellae and randomly oriented grains as a result of creep. The creep parameters obtained in the present study are compared with those in the literature on lamellar $(\alpha_2/\gamma)$ alloys.

Item Type: Journal Article
Additional Information: The copyright belongs to Elsevier.
Keywords: A. Titanium aluminides, based on TiAl;B. Creep (properties and mechanisms);B. Phase transformation;D. Microstructure
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 25 Apr 2006
Last Modified: 19 Sep 2010 04:25
URI: http://eprints.iisc.ernet.in/id/eprint/6434

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