In situ observation of deformation-induced interface migration in a fully-lamellar TiAl alloy

Journal Article · Thu May 01 04:00:00 EDT 1997 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(96)00480-0· OSTI ID:474217

Hsiung, L M; Schwartz, A J; Nieh, T G ^[1]

---

1. Lawrence Livermore National Lab., CA (United States)

It has been reported previously that the mobility of interfacial dislocations plays a dominant role in the creep deformation behavior of a fully-lamellar (FL) TiAl alloy fabricated by powder metallurgy (P/M). Since the motion of lattice dislocations within the {gamma} lamellae is largely restricted by a refined lamellar spacing within the P/M alloy, the deformation strain is mainly accommodated by the motion of the interfacial dislocations. The creep resistance of the P/M alloy significantly increases when the motion of interfacial dislocations in the twin ({gamma}/{gamma}{sub T}) or interphase ({gamma}/{alpha}{sub 2}) interface is effectively hindered by a well developed deformation substructure such as mechanical (deformation) twins. In parallel to this study, other investigation reported in the literature have also suggested that the lamellar interfaces of TiAl are glissile. It is possible that the lamellar interfaces in TiAl, under certain circumstances, could migrate (advance) directly through the cooperative motion of interfacial dislocations. That is, the {gamma}/{gamma}{sub T} or {gamma}/{alpha}{sub 2} interface can migrate through the cooperative motion of interfacial dislocations and lead to the growth or shrinkage of the {gamma} or {alpha}{sub 2} lamellae. Therefore, a deformation-induced interfacial instability in fully-lamellar TiAl alloys could result in a weakening effect when the alloys are employed for engineering applications. Although it is anticipated that the interface migration is prevalent at elevated temperatures, the present study, in fact, addresses the influence of deformation on the stability of lamellar interfaces at room temperature. An in situ straining experiment in a transmission electron microscope was incorporated for the investigation.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 474217
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 9 Vol. 36; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
ANNEALING
CHROMIUM ALLOYS
DEFORMATION
DISLOCATIONS
EXTRUSION
INTERFACES
LAMELLAE
MICROSTRUCTURE
NIOBIUM ALLOYS
POWDERS
SAMPLE PREPARATION
TANTALUM ALLOYS
TITANIUM ALLOYS