Abstract
The α→γ phase transformation during rapid quenching and subsequent isothermal aging has been investigated in a Ti-48 at pct Al alloy. The microstructure changes from a completely massively transformed γ-grain structure to a mixed microstructure of the massively transformed γ grains and the untransformed (meaning massively untransformed) fine α 2/γ lamellae with an increase in the cooling rate from the high-temperature α phase field. Fine γ grains are generated from these fine α 2/γ lamellae by subsequent again at 1323 K. The fine γ grains contain many defects, such as dislocations, microtwins (or stacking faults), domain boundaries, and variants, which are frequently observed in the massive γ grains. This result suggests that the formation mechanism of the fine γ grains during aging is similar to that of the massive γ grains. When the fine γ/γ lamellar sample, which is formed by preliminary aging at a lower temperature (1173 K), is aged at a higher temperature (1323 K), apparent changes in microstructure could not be recognized. This result indicates that the fine γ-grain formation is closely related to the α 2 → γ phase transformation in the fine α 2/γ lamellae.
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This article is based on a presentation made in the symposium “Fundamentals of Gamma Titanium Aluminides,” presented at the TMS Annual Meeting, February 10–12, 1997, Orlando, Florida, under the auspices of the ASM/MSD Flow & Fracture and Phase Transformation Committees.
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Kumagai, T., Nakamura, M. Microstructure evolution through the α→γ phase transformation in a Ti-48 At. pct Al alloy. Metall Mater Trans A 29, 19–26 (1998). https://doi.org/10.1007/s11661-998-0155-5
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DOI: https://doi.org/10.1007/s11661-998-0155-5