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Phase separation in an Ni–12·5 at.% Al alloy at 575 K
Author(s) -
Epperson J. E.,
Linn J. S.,
Labarbe P. D.
Publication year - 1988
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889888005333
Subject(s) - nucleation , electrical resistivity and conductivity , scattering , small angle scattering , annealing (glass) , alloy , materials science , phase (matter) , supersaturation , analytical chemistry (journal) , transmission electron microscopy , small angle x ray scattering , condensed matter physics , crystallography , chemistry , optics , metallurgy , nanotechnology , physics , organic chemistry , chromatography , quantum mechanics
The phase separation in a supersaturated Ni–12.5 at.% Al alloy has been investigated by high‐angle diffuse scattering, small‐angle scattering, transmission electron microscopy and electrical resistivity methods. High‐angle X‐ray diffuse scattering measured at room temperature on a bulk single‐crystal homogenized and quenched from 1323 K showed well developed short‐range atomic ordering. An electrical resistivity isochrone shows a marked peak at about 675 K. Small‐angle scattering measurements on samples annealed at 823 K clearly indicate that, at this temperature, phase separation occurs by a nucleation and growth process. It has been argued that a cluster coagulation model well represents the processes occurring at 823 K. It is, however, not required that the same process be operational at lower temperatures, particularly below the break in the resistivity isochrone. Measurements for annealing times up to 840 h at 575 K reveal weak small‐angle scattering which has some of the characteristics of a continuous transformation. However, much longer transformation times at the lower temperature will need to be investigated before the possibility that this is only a kinetic effect associated with slow nucleation of the second phase can be ruled out.