High resolution study of ordering reactions in gold--chromium alloys

Journal Article · Wed Oct 01 04:00:00 EDT 1975 · Metall. Trans., A; (United States)

DOI:https://doi.org/10.1007/BF02646857· OSTI ID:5000535

Dutkiewicz, J; Thomas, G

The ordering reactions in Au/sub 4/Cr and Au/sub 3/Cr alloys have been investigated using high resolution dark field and lattice imaging techniques. In all cases the ordered structures can be described in terms of compositional modulations as occur during spinodal decomposition. In alloys quenched from above the critical temperature sro microdomains of size 10 to 15A have been resolved with structures represented by modulations in composition along (420). After aging the Au/sub 4/Cr alloy below T/sub c/ the D1a lro phase appears as ordered domains of size 50 to 100A showing composition modulations with wavelength of 5d(531). These domains grow in size up to 500A becoming finally the Dla fully ordered structure. A new observation has been made in the Au/sub 3/Cr alloy, viz., that the lro structure is nonstoichiometric Ll/sub 0/ with lambda/sub (001) = 4A. The transformation from sro in this alloy occurs with the formation of a transitional ordered phase, (similar to DO/sub 22/), which can be described in terms of composition modulations along (001), with wavelength equal to the c parameter (8A) of the DO/sub 22/ structure. Lattice imaging of the two variants of superlattice planes in ordered Au/sub 4/Cr enabled the atomic arrangement in the area of translational and rotational antiphase boundaries to be determined. (auth)

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 5000535
• Journal Information: Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 6A:10; ISSN MTTAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
CHROMIUM ALLOYS
CRITICAL TEMPERATURE
DOMAIN STRUCTURE
GOLD ALLOYS
INTERMETALLIC COMPOUNDS
LATTICE PARAMETERS
ORDER PARAMETERS
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
STOICHIOMETRY
SUPERLATTICES
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE