Evidence for disordered character of grain boundaries in a Ni{sub 3}Al-based alloy during reordering
- Inst. National Polytechnique de Grenoble, St. Martin d`Heres (France)
Metastable disordered polymorphs of L1{sub 2}-type Ni{sub 3}Al + Fe intermetallics obtained by heavy deformation or rapid solidification reorder upon annealing. In order to understand the mechanism of such reordering, the authors have obtained TEM images of the reordering process during in situ annealing of mostly disordered melt-spun Ni{sub 75}Al{sub 12}Fe{sub 13} which is slightly off-stoichiometric with excess nickel. The results indicate that the grain boundaries in such L1{sub 2}-type Ni{sub 3}Al + Fe alloys are incapable of nucleating chemical long-range order and appear to maintain a disordered f.c.c. character. Reordering starts vis one-dimensional growth of lamellar structures from pre-existing nanometric ordered nuclei behind moving grain boundaries and is consistent with evacuation of excess nickel first to anti-phase domain boundaries and then to grain boundaries. This interpretation is confirmed by a kinetic analysis of magnetization variations during reordering which yields a Johnson-Mehl-Avrami exponent n = 1/2.
- OSTI ID:
- 271692
- Journal Information:
- Acta Materialia, Vol. 44, Issue 1; Other Information: PBD: Jan 1996
- Country of Publication:
- United States
- Language:
- English
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