Elastocaloric cooling capacity of shape memory alloys – Role of deformation temperatures, mechanical cycling, stress hysteresis and inhomogeneity of transformation. (15th August 2017)

• Record Type: Journal Article
• Authors: Wu, Y.; Ertekin, E.; Sehitoglu, H.
• Is Part Of: Acta materialia. Volume 135(2017)
• Page Start: 158
• Page End: 176
• Publication Date: 2017-08-15
• Subjects: Elastocaloric (EC) effect -- Superelasticity (SE) -- Entropy change -- Temperature span -- Functional fatigue resistance -- Hysteresis; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2017.06.012
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Elastocaloric (EC) effect refers to the rapid cooling in shape memory alloys (SMAs) during reverse transformation from martensite to austenite under adiabatic conditions. We present a very comprehensive study of the EC response far extending the existing literature by studying the effect of loading states (tension and compression), long-term cycling, strain localization, and deformation temperatures in several SMAs including CuZnAl, NiTi, NiTiCu, Ni2 FeGa and NiTiHf13.3 . We found a temperature change of 14.2 °C in CuZnAl, 18.2 °C in NiTi, 15.2 °C in NiTiCu, 13.5 °C in Ni2 FeGa, and 6.95 °C in NiTiHf13.3 upon reverse transformation depending on the entropy change (as high as 60 J/kg K), the stress hysteresis, the inhomogeneity of the transformation and the number of superelastic cycles. A gradual deterioration of the EC effect in tension develops, while in compression the EC effect can be sustained much longer (in excess of 10 4 cycles). The Ni2 FeGa SMAs possess an operational EC temperature window of nearly 200 °C, which is the widest among the chosen SMAs. With over one hundred experiments reported in one study, this paper represents an authoritative summary of the EC capabilities of a wide range of SMAs. Graphical abstract: Image 1