Acta Metallurgica Sinica (English Letters) ›› 2020, Vol. 33 ›› Issue (11): 1535-1542.DOI: 10.1007/s40195-020-01107-y

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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   

  1. 1School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
    2School of Engineering, University of Leicester, Leicester, LE17RH, UK
    3Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai Jiao Tong University, Shanghai, 200240, China
  • Received:2020-03-30 Revised:2020-05-21 Accepted:2020-05-24 Online:2020-11-10 Published:2020-11-17
  • Contact: Jun Li,Qiaodan Hu

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 La1.7Fe11.6Al1.4-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 La1.7Fe11.6Al1Si0.4 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 La1.7Fe11.6Al1.3Si0.1 specimen were determined as 4.58 J/kg K and 173.6 J/kg, respectively. More importantly, the La1.7Fe11.6Al1.3Si0.1 alloy displayed only a slight volume change when the meta-magnetic phase transition occurred, which is promising for cyclic use.

Key words: Solidification, Magnetic properties, Heat treatment, Microstructure, Functional alloys