Atypical defects in a B2 Fe-40Al-0.7C-0.5B alloy
The nature of defects in a quaternary Fe-40Al-0.7C-0.5B alloy was examined by transmission electron microscopy (TEM) techniques including weak beam microscopy and z-contrast imaging. Complex {l{underscore}brace}001{r{underscore}brace} stacking faults were observed in certain conditions in these alloys that were not previously noted in a ternary Fe-40Al-0.6C alloy. These faults exhibit a 1/2{lt}001{gt} displacement vector that lies in the plane of the fault and structurally misses an aluminum layer. Six variants of this fault type are present. These faults are absent in brine-quenched and furnace-cooled alloys, but are readily observed in the air-cooled condition. In addition to the usual {l{underscore}angle}111{r{underscore}angle} superdislocations that are APB-dissociated into {1/2}{l{underscore}angle}111{r{underscore}angle} superpartials, dissociated {l{underscore}angle}100{r{underscore}angle} dislocations (into two {1/2}{l{underscore}angle}100{r{underscore}angle} partials) are also observed under certain conditions. Quenched and aged alloys show dissociated {l{underscore}angle}001{r{underscore}angle} loops. The absence of such defects in the B-free alloy and following certain heat treatments in the B-containing alloy, suggests that boron may be segregating to the cube planes and lowering the interfacial energy on these planes. The presence of dissociated {l{underscore}angle}001{r{underscore}angle} loops in the quenched and aged alloy also suggests the formation of B-vacancy complexes that coalesce during aging, forming such dissociated loops.
- Research Organization:
- Brown Univ., Providence, RI (US)
- Sponsoring Organization:
- US Department of the Navy, Office of Naval Research (ONR)
- OSTI ID:
- 20001594
- Report Number(s):
- CONF-981104-; ISBN 1-55899-458-0; ISSN 1067-9995; TRN: IM0001%%31
- Resource Relation:
- Conference: High-Temperature Ordered Intermetallic Alloys VIII, Materials Research Society Symposium Proceedings, Boston, MA (US), 11/30/1998--12/03/1998; Other Information: PBD: 1999; Related Information: In: High-temperature ordered intermetallic alloys VIII. Materials Research Society symposium proceedings: Volume 552, by George, E.P.; Mills, M.J.; Yamaguchi, Masaharu [eds.], [600] pages.
- Country of Publication:
- United States
- Language:
- English
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