Reduced Annealing Time and Enhanced Magnetocaloric Effect of La(Fe, Al) 13 Alloy by La-nonstoichiometry and Si-doping
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Reduced Annealing Time and Enhanced Magnetocaloric Effect of La(Fe, Al)13 Alloy by La‑nonstoichiometry and Si‑doping Liang Yang1 · Jun Li1,2 · Defang Tu1 · Joel C. J. Strickland2 · Qiaodan Hu1 · Hongbiao Dong2 · Jianguo Li1,3 Received: 30 March 2020 / Revised: 21 May 2020 / Accepted: 24 May 2020 © The Chinese Society for Metals (CSM) and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract LaFe13−xMx (M = Si, Al) alloys are promising for use in magnetic refrigeration. However, they require long annealing time (30 days) in order to optimize the magnetocaloric properties. Research has shown that the addition of extra La in off-stoichiometric alloys can greatly shorten the annealing time. Therefore, the purpose of this study is to investigate the influence of the extra addition of La on the annealing properties of a new off-stoichiometric L a1.7Fe11.6Al1.4−xSix (x = 0, 0.1, 0.4) alloys. It was demonstrated that after a 36h annealing time, a large volume fraction of 1:13 magnetocaloric phase was obtained for all alloys. Further microstructural analysis of the off-stoichiometric La1.7Fe11.6Al1.4−xSix alloys revealed a facet-like grain morphology. The La1.7Fe11.6Al1.4 and L a1.7Fe11.6Al1Si0.4 alloys were shown to contain large 1:13 phase precipitates separated in a La-rich matrix, while the La1.7Fe11.6Al1.3Si0.1 alloy had a continuous 1:13 phase matrix with a fine dispersion of La-rich precipitates throughout. When the magnetic field varied between 0 and 2 T, the corresponding magnetic entropy change and relative cooling capacity for the L a1.7Fe11.6Al1.3Si0.1 specimen were determined as 4.58 J/kg K and 173.6 J/kg, respectively. More importantly, the L a1.7Fe11.6Al1.3Si0.1 alloy displayed only a slight volume change when the meta-magnetic phase transition occurred, which is promising for cyclic use. Keywords Solidification · Magnetic properties · Heat treatment · Microstructure · Functional alloys
1 Introduction NaZn13-type LaFe13−xMx (M = Si, Al) alloys are promising for use in magnetic refrigeration due to their inherent magnetocaloric effect (MCE), low cost and environmentally friendly constituting elements [1–5]. Of particular interest are LaFe13−xSix (x ≤ 1.8) alloys which demonstrate a giant MCE, and thus, they have been the focus of a Available online at http://link.springer.com/journal/40195. * Jun Li [email protected] * Qiaodan Hu [email protected] 1
School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2
School of Engineering, University of Leicester, Leicester LE17RH, UK
3
Collaborative Innovation Center for Advanced Ship and Deep‑Sea Exploration, Shanghai Jiao Tong University, Shanghai 200240, China
substantial amount of research [6–9]. The MCE originates from the magnetic phase transition [10]. LaFe13−xSix alloys go through a first-order itinerant electron metamagnetic (IEM) transition from a paramagnetic (PM) to a ferromagnetic (FM) state, which is accompanied by a negative lattice expansion. Because solid refrige
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