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Title: Sign reversal of transformation entropy change in Co{sub 2}Cr(Ga,Si) shape memory alloys

In situ X-ray diffraction (XRD) measurements and compression tests were performed on Co{sub 2}Cr(Ga,Si) shape memory alloys. The reentrant martensitic transformation behavior was directly observed during the in situ XRD measurements. The high-temperature parent phase and low-temperature reentrant parent phase were found to have a continuous temperature dependence of lattice parameter, therefore suggesting that they are the same phase in nature. Moreover, compression tests were performed on a parent-phase single crystal sample; an evolution from normal to inverse temperature dependence of critical stress for martensitic transformation was directly observed. Based on the Clausius-Clapeyron analysis, a sign reversal of entropy change can be expected on the same alloy.
Authors:
; ;  [1] ;  [1] ;  [2] ;  [1] ;  [2]
  1. Department of Materials Science, Tohoku University, Sendai 980-8579 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
22485990
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 18; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALLOYS; COMPRESSION; ENTROPY; LATTICE PARAMETERS; MONOCRYSTALS; PHASE TRANSFORMATIONS; SHAPE MEMORY EFFECT; STRESSES; TEMPERATURE DEPENDENCE; X-RAY DIFFRACTION