Necking and spheroidization of {alpha}{sub 2} plates in lamellar microstructure of a hot-deformed two-phase TiAl alloy during annealing

Journal Article · Fri Mar 13 04:00:00 EST 1998 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(98)00028-1· OSTI ID:619471

Zhang, L C ^[1]; Chen, G L; Wang, J G ^[1]; Ye, H Q ^[2]

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1. Univ. of Science and Technology, Beijing (China). State Key Lab. for Advanced Metals and Materials
2. Academia Sinica, Shenyang (China). Lab. of Atomic Imaging of Solids

It is well known that two-phase TiAl alloys exhibit better mechanical properties than single phase {gamma}-TiAl alloys. Recently Kim reported that the thermomechanical treatments (TMT) or thermomechanical processing (TMP) for TiAl alloys can significantly change the microstructures resulting in an improved balanced mechanical properties. Besides changes in grain size, lamellar spacing and the ratio of {gamma} to {alpha}{sub 2} lamellae, TMT or TMP may also lead to the formation of numerous dislocations and deformation twins, and various nonequilibrium structures of lamellar interfaces. Chen et al. have observed by high-resolution transmission electron microscopy (HRTEM) that hot-deformation results in {alpha}{sub 2}/{gamma} and {gamma}/{gamma} interfaces with numerous ledges, so the boundary plane is no longer parallel to the (111){sub {gamma}} or (0001){sub {alpha}{sub 2}} plane, and some interfacial ledges correspond to 1/3 [111] Frank partial dislocations in {gamma} plate, as consistent with the deviation of (111){sub {gamma}} from being parallel to (0001){sub {alpha}{sub 2}} plane near the {alpha}{sub 2}/{gamma} interface. The thermal instability of the deformed {alpha}{sub 2}/{gamma} lamellar microstructure, such as necking and spheroidization of {alpha}{sub 2} plates, formation of subgrains in plates and recrystallization, has been recently studied. However, no report has been made on the detailed evolution of deformed microstructure during annealing. This paper reports some TEM observations on necking and spheroidization of {alpha}{sub 2} plates in a hot-deformed two-phase TiAl alloy upon subsequent short-time annealing.

• OSTI ID: 619471
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 8 Vol. 38; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
DEFORMATION
INTERMETALLIC COMPOUNDS
MICROSTRUCTURE
MORPHOLOGY
THERMOMECHANICAL TREATMENTS
TITANIUM ALLOYS