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Record 12 of 3152
Electron Diffraction Evidence for the Ordering of Excess Nickel Atoms by Relation to Stoichiometry in Nickel-Rich Beta'-Nial Formation of a Nickel-Aluminum (Ni2al) Superlattices
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Author and Affiliation:
Reynaud, F.(NASA, Washington, DC, United States)
Abstract: In electron diffraction patterns of nickel-rich beta-NiAl alloys, many anomalies are observed. One of these is the appearance of diffuse intensity maxima between the reflexions of the B2 structure. This is explained by the short-range ordering of the excess nickel atoms on the simple cubic sublattice occupied only by aluminum atoms in the stoichiometric, perfectly ordered NiAl alloy. After annealing Ni 37.5 atomic percent Al and Ni 37.75 atomic percent Al for 1 week at 300 and 400 C, the diffuse intensity maxima transformed into sharp superstructure reflexions. These reflexions are explained by the formation of the four possible variants of an ordered hexagonal superstructure corresponding to the Ni2Al composition. This structure is closely related to the Ni2Al3 structure (same space group) formed by the ordering of vacancies on the nickel sublattice in aluminum-rich beta-NiAl alloys.
Publication Date: May 01, 1988
Document ID:
19880011913
(Acquired Nov 04, 1995)
Accession Number: 88N21297
Subject Category: METALLIC MATERIALS
Report/Patent Number: NASA-TT-20177, NAS 1.77:20177
Document Type: Journal Article
Publisher Information: United States
Contract/Grant/Task Num: NASW-4307
Financial Sponsor: NASA; United States
Organization Source: NASA; Washington, DC, United States
Description: 14p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: ALUMINUM ALLOYS; ELECTRON DIFFRACTION; NICKEL ALLOYS; STOICHIOMETRY; VACANCIES (CRYSTAL DEFECTS); BODY CENTERED CUBIC LATTICES; ELECTRON MICROSCOPY
Imprint And Other Notes: Transl. into ENGLISH from Journal of Applied Crystallography (France), v. 9, pt. 4, 1976 p 263-268
Miscellaneous Notes: Transl. by Scientific Translation Service, Santa Barbara, Calif.
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