Measurement of twinning elements in PST TiAl single crystals

Book · Wed Dec 31 04:00:00 EST 1997

OSTI ID:571764

Lu, L; Pope, D P ^[1]

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1. Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science and Engineering

Twinning is the major deformation mode at room temperature in TiAl polysynthetically twinned (PST) crystals (lamellar structure, TiAl is the major phase and Ti{sub 3}Al is the minor phase). The authors present here the results of Atomic Force Microscope (AFM) observations of deformation twinning displacements measured on the free surfaces of PST single crystals. AFM is used in this experiment because of its very high resolution for topological measurements and its ability to measure surface displacements from very small twins. Measurements were made on samples with different compression axes and surface orientations. When a twin intersects a free surface, a definite displacement is produced which is easily related to the twinning elements. The majority of the surface offsets observed correspond to those for ordinary twinning, within a very small deviation. Thus it is concluded that these are ordinary twins. The widths of the twinning bands are around 300nm, smaller than the widths of the TiAl lamellae. Slip bands are also observed. They are characterized by a much more irregular geometry than the twinning bands. At some places where twins intersect a domain boundary slip bands are produced in the adjacent domain.

• Sponsoring Organization: National Science Foundation, Washington, DC (United States)
• OSTI ID: 571764
• Report Number(s): CONF-961202--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
DEFORMATION
EXPERIMENTAL DATA
INTERMETALLIC COMPOUNDS
SLIP
TITANIUM ALLOYS
TWINNING