Influence of B Doping on the Microstructure and Magnetocaloric Effect of La-Fe-Si Alloys

The influences of small dose B doping and heat treatment on the microstructure and magnetocaloric properties of La-Fe-Si melt spun ribbons were investigated. The results show that the doping of B promotes the formation of the La(Fe,Si)13 phase, and the La-Fe-Si-B alloys have already acquired more La(Fe,Si)13 phase before heat treatment than La-Fe-Si alloys. During the solidification process, the alloy has the most La(Fe,Si)13 phase when B doping content is 0.08. B doping is beneficial to refining the microstructure during rapid solidification; the refined microstructure shortens the element diffusion path of peritectoid reaction in the following process of heat treatment (α-Fe + LaFeSi → La(Fe, Si)13) and is in favor of the formation of La(Fe,Si)13 phase. In the process of heat treatment, the microstructures of La-Fe-Si alloys are optimized by B doping, and their Curie temperature and magnetocaloric effect are improved. The Curie temperature of the ribbons changes from 210 K to 233 K, and the maximum isothermal magnet entropy change increases from 5.47 J/kg∙K to 9.40 J/kg∙K when B content increases from 0 to 0.08. © 2018, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.