期刊
ACTA MATERIALIA
卷 81, 期 -, 页码 9-20出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2014.08.006
关键词
Elastocaloric effect; Ti-Ni; Film; Local strain distribution; Shape memory alloy (SMA)
资金
- German Science Foundation (DFG) [SPP1599]
The time-resolved strain and temperature profiles of magnetron-sputtered pseudoelastic TiNi films of 20 mu m thickness are investigated during tensile stress cycling for different strain rates. Based on simultaneous infrared thermography and digital image correlation, a good correlation between the evolution of temperature profiles and the local formation and propagation of Luders-like strain bands is observed. The evolution of temperature profiles can be quantitatively described by a phenomenological Tanaka-type model of the martensitic transformation combined with a heat transfer model taking into account the local interaction between transformed and untransformed regions in the transformation kinetics. The investigated film samples exhibit an undercooling of -16 K upon mechanical unloading under adiabatic conditions at a strain rate of 0.2 s(-1). A coefficient of performance of 7.7 is determined. Due to the high surface-to-volume ratio, the films show fast heat exchange in air of the order of 1.5 s. Based on these results, the prospects of SMA film-based elastocaloric cooling are discussed. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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