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

Journal Article · Mon Nov 02 00:00:00 EST 2015 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4934878· OSTI ID:22485990

Xu, Xiao; Omori, Toshihiro; Kainuma, Ryosuke ^[1]; Nagasako, Makoto ^[1]; Kanomata, Takeshi ^[1]

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1. Department of Materials Science, Tohoku University, Sendai 980-8579 (Japan)

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.

• OSTI ID: 22485990
• Journal Information: Applied Physics Letters, Vol. 107, Issue 18; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALLOYS
COMPRESSION
ENTROPY
LATTICE PARAMETERS
MONOCRYSTALS
PHASE TRANSFORMATIONS
SHAPE MEMORY EFFECT
STRESSES
TEMPERATURE DEPENDENCE
X-RAY DIFFRACTION