Singh, Vajinder and Kumar, Atul and Mondal, Chandan and Bhattacharjee, Pinaki Prasad and Ghosal, P
(2019)
Hot deformation of high-Nb-containing γ-TiAl alloy in the temperature range of 1000–1200 °C: microstructural attributes to hot workability.
SN Applied Sciences, 1 (4).
ISSN 2523-3963
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Abstract
Hot deformation behavior of a high-Nb-containing cast γ-TiAl-based Ti–45Al–8Nb (at.%) alloy has been investigated in the temperature range of 1000–1200 °C and the strain rate range of 0.5–0.005 s−1. The alloy shows an initial microstructure of coarse lamellar ((α2 + γ) and (γ + γ)) colonies. The effect of strain rate and temperature domain on hot deformability of the alloy has been analyzed through a correlation between the apparent activation energy, deformation process maps, and associated microtextural development. The relatively higher apparent activation energy (Q = 553.8 kJ/mol) could be correlated with the fully lamellar α2 + γ microstructure which posses greater resistance to the mobile dislocation. The results are further corroborated by the “instability-dominated” processing maps indicating poor hot deformability of the alloy in the studied temperature–strain rate range. Detailed electron microscopy of the deformed samples indicates that poor workability exhibited as cracks that are predominantly found at the coarse γ-TiAl grains situated at the lamellar boundaries. The crack initiation and propagation mechanisms during hot compression have further been discussed with reference to concurrent dynamic recrystallization. It has been found that “wedge-type” cavitation damage is prevalent during compressive deformation in the temperature range studied here. Such cracking behavior is elucidated in light of the “Semiatin–Seetharaman criterion.”
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