ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
High-angle X-ray diffuse scattering has been measured in a volume element in reciprocal space for a Ni-12.7 at.% Al alloy single crystal quenched from 1323 K. The Cowley-Warren order parameters were determined after separation of the first- and second-order size effects, using a procedure based on the Borie-Sparks quadratic approximation of atomic displacements. The experimental order coefficients were used to reconstruct the real-space locally ordered distribution of atoms, from which the spectrum of nearest-neighbor atomic configurations was determined. Some 61% of the Al atoms were found to be in a planar ordered configuration consisting of a nickel atom and four nearest-neighbor aluminum atoms, the basic structural unit of Ni3Al. These planar elementary ordered units were, of course, distributed on the three equivalent {100} planes. While most of the ordered 'domains' consisted of from one to three Ni3Al rings, a few domains were found to contain on the order of a hundred such elementary ordered units. The larger ordered domains may be thought of as embryos of the ordered Ni3Al phase which have formed during quenching of the bulk alloy single crystal. There is evidence that the spatial distribution of ordered domains is not random.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108767383001476
