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Title: Evolution of L1/sub 2/ Ordered Domains in FCC Cu3Au Alloy

Abstract

No abstract prepared.

Authors:
;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
902867
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physics: Condensed Matter; Journal Volume: 19; Journal Issue: 2007; Related Information: Article No. 086201
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALLOYS; PHYSICS; NATIONAL RENEWABLE ENERGY LABORATORY; Basic Sciences; Solid State Theory

Citation Formats

Sanati, M., and Zunger, A. Evolution of L1/sub 2/ Ordered Domains in FCC Cu3Au Alloy. United States: N. p., 2007. Web.
Sanati, M., & Zunger, A. Evolution of L1/sub 2/ Ordered Domains in FCC Cu3Au Alloy. United States.
Sanati, M., and Zunger, A. Mon . "Evolution of L1/sub 2/ Ordered Domains in FCC Cu3Au Alloy". United States. doi:.
@article{osti_902867,
title = {Evolution of L1/sub 2/ Ordered Domains in FCC Cu3Au Alloy},
author = {Sanati, M. and Zunger, A.},
abstractNote = {No abstract prepared.},
doi = {},
journal = {Journal of Physics: Condensed Matter},
number = 2007,
volume = 19,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Atomic ordering of a disordered fcc phase into the L1[sub 0] phase is accompanied by a reduction in point group symmetry as well as in translational symmetry (Fm[bar 3]m ---> P4/mm). The reduction in point group symmetry renders three rotational modifications (or three crystallographic variants) of the L1[sub 0] phase; in terms of spatial regions, this results in three kinds of structural domains. An important point here is that each of the structural domains is distorted along its own tetragonal axis and, thus, the L1[sub 0] single phase is an aggregate of the domains of three different distortion directions. Undermore » this circumstance, the relative volume fraction of the variants, the habit plane between structural domains and the shape of a structural domain plate, which constitute essential features of the microstructures of the L1[sub 0] phase, can not be arbitrary, but are subject to the systematics governed by minimization of the elastic strain energy. In this report, the authors discuss a few characteristics of these morphological features, as observed in thin (<100 [mu]m) specimens of L1[sub 0] single phase Fe-Pd alloys.« less
  • Thermal expansion measurements have been performed on an L1{sub 2} ordered and a quenched Ni{sub 2}Mn alloy and the role of electrons, phonons and magnetic moments on their thermodynamic properties has been studied using theoretical models. The authors show that with increasing atomic disorder the itinerant nature of the electron moments decreases. They furthermore show that magnetic interactions do not influence the chemical ordering of Ni{sub 3}Mn, while lattice vibrations play an important role in its ordering transition.
  • It is well known that the yield strength of L1{sub 2} ordered intermetallic compound Ni{sub 3}Al increases anomalously with increasing temperature. Therefore, Ni{sub 3}Al increases anomalously with increasing temperature. Therefore, Ni{sub 3}Al alloys have potentially attractive properties for components used at high temperature and have received considerable attention during the past few decades. However, polycrystalline Ni{sub 3}Al exhibits intergranular embrittlement at room temperature. In addition to the microalloying with boron, which significantly improves the ductility of Ni{sub 3}Al, addition of ternary elements is performed to improve the mechanical properties of Ni{sub 3}Al alloys. According to Chiba et al., these ternarymore » elements have been classified as {gamma} formers, which substitute the Ni sublattice, such as Pd, Pt, Co, and Cu, or {gamma} formers which substitute the Al sublattice, such as Zr, Hf, Ta, and Ti, and the ductility of Ni{sub 3}Al can be enhanced by alloying with {gamma} formers, while Ni{sub 3}Al remains brittle if doped with {gamma} formers. In the present article, the influence of Pd doping on the structure of the antiphase boundary (APB)-coupled dislocations and the APB energies in the deformed Ni{sub 3}Al alloy is reported.« less
  • In solid state phase transformations, the evolution of one state into another is realized through the motion of atoms. Such atomic motion may be either diffusional or displacive in nature. Phase transformation are often considered to involve only one type of atomic motion, but there has been mounting experimental evidence and implications above the interplay or the combination of both kinds. In principle, combined diffusional and displacive atomic motion is possible when a phase transformation involves a rearrangement of the crystal lattice as well as the reconfiguration of atoms such as decomposition or atomic ordering. Recently, the authors have conductedmore » an experimental study of a phase transformation of this class (decomposition of a hyper-eutectoid CuBe alloy) and have substantiated diffusional and displacive atomic motion in conjunction with the formation of polytwin precipitate plates. In the present work, they examine the possibility of the transformation between the L1[sub 2] and the DO[sub 19] phase states (ordered derivatives of fcc and of hcp, respectively) through the combination of displacive and diffusional atomic motion. The particular situation they are considering is when the stability of the L1[sub 2] precipitate phase is perturbed by the shear deformation that is responsible for the transformation of the matrix fcc to hcp. In what follows, they will first introduced experimental findings from recent TEM study of a CoCrTa ternary alloy. They then discuss the implications of these finding by examining the transformation crystallography of the L1[sub 2] ordered structure.« less
  • Recent studies have demonstrated that a large number of ordered intermetallics exhibit environmental embrittlement in air at ambient temperatures. The embrittlement involves the decomposition of water vapor at metal surface, resulting in the generation of atomic hydrogen that diffuses into the alloys and causes brittle intergranular fracture. The authors' recent studies have shown that Ll[sub 2]-ordered (Co, Fe)[sub 3]V alloys containing 25 at. % V exhibit the environmental embrittlement. For instance (Co[sub 78]Fe[sub 22])[sub 3]V alloy showed a high ductility of 36% when tested in vacuum at room temperature, whereas the ductility decreased to 20 and 16% when tested inmore » air and distilled water, respectively. In this paper, the study of environmental embrittlement in (Co,Fe)[sub 3]V is extended to include effects of alloy stoichiometry. Hypostroichiometric alloys containing less than 25 at.% V were prepared and tensile tested in various environments at room temperature. The results are compared with those from the stoichiometric (CO,Fe)[sub 3]V alloy and other Ll[sub 2] intermetallics and discussed based on available models predicting the grain-boundary cohesive strength.« less