Internal friction in [gamma]-TiAl at high temperatures
- Max-Planck-Inst. fuer Metallforschung, Stuttgart (Germany)
The internal friction in TiAl polycrystals of technical purity was studied in the temperature range of 300--1500 K using an inverted torsion pendulum. Extruded single-phase [gamma]-TiAl with an aluminium content of 54.1 at.% shows a large, frequency-dependent relaxation maximum near 1300 K during cooling from temperatures above 1400 K, which is neither observed during heating from ambient temperature nor in two-phase [alpha][sub 2]/[gamma]-TiAl alloys with a lower Al content. This relaxation maximum is tentatively ascribed to the motion of grain boundaries or dislocations, which are pinned by precipitates in [gamma]-TiAl. The precipitates dissolve at temperatures above 1350 K and form again below 1200 K. No relaxation is observed in polycrystalline TiAl with a carbon content in the range from 0.009 to 0.22 at.% at temperatures below 900 K. This behavior may be an indication of hardening by finely dispersed precipitates, as observed in TEM and SEM micrographs.
- OSTI ID:
- 6305792
- Journal Information:
- Acta Materialia, Vol. 47:8; ISSN 1359-6454
- Country of Publication:
- United States
- Language:
- English
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