Effect of Mn Substitution on Microstructure Evolution and Magnetic Phase Transition in La(Fe1−xMnx)10.8Co0.7Si1.5 Compounds

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 44; no. 13; pp. 5782 - 5787
• Main Authors: Sun, Song, Ye, Rongchang, Li, Huaifeng, Zhang, Yanpo, Jia, Yuanhang, Wu, Yunfei, Long, Yi
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.12.2013; Springer
• Subjects: Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Exact sciences and technology; Materials Science; Metallic Materials; Metals. Metallurgy; Nanotechnology; Structural Materials; Surfaces and Interfaces; Thin Films; Gray Phase; Curie Temperature; Dark Phase; White Phase; Magnetic Entropy Change; Microstructure; Phase transformation; Magnetic transition
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-013-1925-2

The influences of Mn substitution for Fe on microstructures of La(Fe 1− x Mn x ) 10.8 Co 0.7 Si 1.5 ( x  = 0, 0.01, 0.02, 0.03) alloys in both the as-cast state and the annealed state have been studied. The results show that Mn substitution promotes the fining of the as-cast microstructure and increases the formation of 1:13 phase significantly when annealed. An almost single 1:13 phase is obtained for x  = 0.01 when annealed at 1373 K (1100 °C) for 3 days, while a large amount of impurity phases is still present for x  = 0. By increasing the amount of Mn to x  = 0.02, a more purified annealed microstructure can be obtained. However, further substitution of Mn up to x  = 0.03 is harmful for the formation of 1:13 phase. The Curie temperature T C of the annealed La(Fe 1− x Mn x ) 10.8 Co 0.7 Si 1.5 ( x  = 0, 0.01, 0.02, 0.03) varies monotonously with Mn content x , decreasing from ~279 K (6 °C) for x  = 0 to ~236 K (−37 °C) for x  = 0.03. When x  = 0.01, a higher maximum entropy change (−Δ S ) max of 5.3 J/(kgK) and relative cooling power (RCP) of 166 J/kg can be obtained under a magnetic field of 2T. Further substitution of Mn ( x  = 0.02) results in a slight decrease of (−Δ S ) max , whereas a larger RCP can still be kept.