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Title: Observations of a dynamical-to-kinematic diffraction transition in plastically deformed polycrystalline intermetallic YCu

Unlike most intermetallic compounds, polycrystalline YCu, a B2 (CsCl-type) intermetallic, is ductile at room temperature. The mechanisms for this behavior are not fully understood. In situ neutron diffraction was used to investigate whether a stress-induced phase transformation or twinning contribute to the ductility; however, neither mechanism was found to be active in YCu. Surprisingly, this study revealed that the intensities of the diffraction peaks increased after plastic deformation. It is thought that annealing the samples created nearly perfect crystallinity, and subsequent deformation reduced this high degree of lattice coherency, resulting in a modified mosaic structure that decreased or eliminated the extinction effect. Analysis of changes in diffraction peak intensity showed a region of primary plasticity that exhibits significant changes in diffraction behavior. Fully annealed samples initially contain diffracting volumes large enough to follow the dynamical theory of diffraction. When loaded beyond the yield point, dislocation motion disrupts the lattice perfection, and the diffracting volume is reduced to the point that diffraction follows the kinematic theory of diffraction. Since the sample preparation and deformation mechanisms present in this study are common in numerous material systems, this dynamical to kinematic diffraction transition should also be considered in other diffraction experiments. These measurementsmore » also suggest the possibility of a new method of investigating structural characteristics. (C) 2014 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.« less
 [1] ;  [2] ;  [2] ;  [1] ;  [1]
  1. Ames Laboratory
  2. Los Alamos National Laboratory
Publication Date:
OSTI Identifier:
Report Number(s):
IS-J 8308
Journal ID: ISSN 1359-6454
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Materialia; Journal Volume: 70
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
36 MATERIALS SCIENCE alloys, CRYSTALS, deformation, diffraction, dynamic, extinction, fracture, kinematic, Mosaic structure, plastic deformation, refinement, yag, YCu intermetallic compound