NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
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) SuperlatticesIn 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.
Document ID
19880011913
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Reynaud, F.
(NASA Headquarters Washington, DC United States)
Date Acquired
September 5, 2013
Publication Date
May 1, 1988
Subject Category
Metallic Materials
Report/Patent Number
NAS 1.77:20177
NASA-TT-20177
Accession Number
88N21297
Funding Number(s)
CONTRACT_GRANT: NASW-4307
Distribution Limits
Public
Copyright
Public Use Permitted.
Document Inquiry

Available Downloads

There are no available downloads for this record.
No Preview Available