Unveiling the enhancing mechanism of cyclic stability in Tb doped Ni-Mn-Sn Heusler alloys

• Published in: Materials & design 2024-08, Vol.244, p.113162, Article 113162
• Main Authors: Qian, Hanyang, Cai, Rui, Lu, Xiang, Sun, Wen, Li, Guowei, Wei, Zhiyang, Liu, Jian
• Format: Article
• Language: English
• Subjects: Cyclic stability; Elastocaloric effect; Heusler alloys; Martensitic Transformation; Rare-earth doping; Solid-state refrigeration
• ISSN: 0264-1275
• DOI: 10.1016/j.matdes.2024.113162

[Display omitted] •The effects of Tb doping on the microstructure, stress induced martensitic transformation behaviors, elastocaloric effect and cyclic stability have been systematically investigated.•The in-situ characterization was employed to understand the effects of Tb doping on stress induced martensitic transformation behaviors.•The precipitation of intergranular NiSnTb phase brings in the multipoint nucleation across the specimen, which weakens the strain concentration and suppresses crack tendency.•The multipoint nucleation promotes the transformation volume fraction and (Ni43Mn47Sn10)99.5Tb0.5 yields a |ΔTad/Δεtr| up to 8.7 K %−1, which further alleviates the extension of the cracks.•Large adiabatic temperature changes of ∼ 5.5 K over 1000 cycles with no significant degradation are achieved in a small amount of Tb doped (Ni43Mn47Sn10)99.5Tb0.5. Rare-earth (RE) doping has been demonstrated as a feasible approach to improve the cyclic performance of Ni-Mn-based Heusler alloys, but the current demonstration of underlying mechanism is simply ascribed to strengthening of the grain boundary cohesion. In this work, the effects brought by RE doping on microstructure, stress induced martensitic transformation behavior and cyclic stability of Ni-Mn-based alloys were systematically investigated. By Tb doping, a stable adiabatic temperature change (|ΔTad|) of ∼ 5.5 K over 1000 cycles with no significant degradation was obtained in (Ni43Mn47Sn10)99.5Tb0.5. (1) Through the in-situ digital image correlation strain measurement and in-situ SEM observation upon loading process, it revealed a multipoint nucleation of the martensitic transformation across the specimen arising from the intergranular NiSnTb secondary phase as nucleate sites, which weakens the strain concentration and suppresses the crack tendency. (2) The multipoint nucleation promotes the transformation volume fraction, making the large |ΔTad| could be driven by a small transformation strain (Δεtr) and (Ni43Mn47Sn10)99.5Tb0.5 yields a |ΔTad/Δεtr| up to 8.7 K %−1. Such reduction in applied strain further alleviates the extension of the cracks. Both the two factors brought by Tb doping in (Ni43Mn47Sn10)99.5Tb0.5 give rise to the enhancement in cyclic stability of the large elastocaloric effect.