Microstructure evolution through the {alpha} {r_arrow} {gamma} phase transformation in a Ti-48 at. pct Al alloy

Journal Article · Thu Jan 01 04:00:00 EST 1998 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-998-0155-5· OSTI ID:605806

Kumagai, Tatsuo; Abe, Eiji; Nakamura, Morihiko ^[1]

---

1. National Research Inst. for Metals, Ibaraki (Japan)

The {alpha} {r_arrow} {gamma} 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 {gamma}-grain structure to a mixed microstructure of the massively transformed {gamma} grains and the untransformed (meaning massively untransformed) fine {alpha}{sub 2}/{gamma} lamellae with an increase in the cooling rate from the high-temperature {alpha} phase field. Fine {gamma} grains are generated from these fine {alpha}{sub 2}/{gamma} lamellae by subsequent aging at 1,323 K. The fine {gamma} grains contain many defects, such as dislocations, microtwins (or stacking faults), domain boundaries, and variants, which are frequently observed in the massive {gamma} grains. This result suggests that the formation mechanism of the fine {gamma} grains during aging is similar to that of the massive {gamma} grains. When the fine {gamma}/{gamma} lamellar sample, which is formed by preliminary aging at a lower temperature (1,173 K), is aged at a higher temperature (1,323 K), apparent changes in microstructure could not be recognized. This result indicates that the fine {gamma}-grain formation is closely related to the {alpha}{sub 2} {r_arrow} {gamma} phase transformation in the fine {alpha}{sub 2}/{gamma} lamellae.

• Sponsoring Organization: USDOE
• OSTI ID: 605806
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 1 Vol. 29; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CRYSTAL DEFECTS
CRYSTAL-PHASE TRANSFORMATIONS
HEAT RESISTING ALLOYS
MICROSTRUCTURE
QUENCH AGING
TITANIUM ALLOYS