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Effect of Microgravity and Magnetic Field on the Metallic and Crystalline Structure of Magnetostrictive SmFe 2 Synthesized by Unidirectional Solidification
Author(s) -
OKUTANI TAKESHI,
NAGAI HIDEAKI,
MAMIYA MIKITO,
SHIBUYA MASACHIKA,
CASTILLO MARTIN
Publication year - 2006
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1362.004
Subject(s) - lamellar structure , materials science , nucleation , microstructure , magnetic field , directional solidification , crystallography , composite material , chemistry , physics , quantum mechanics , organic chemistry
The Sm‐2Fe molten alloy with 1:2 molar ratio was unidirectionally solidified in both microgravity and normal gravity in concurrence with a magnetic flux (0–0.12 T). The compound SmFe 2 was produced by the unidirectional solidification in microgravity with a magnetic flux of 0T and exhibited a lamellar microstructure. The average lamellar thickness was 30 μm and each lamella possessed a <111> crystallographic alignment along major axis aligned in the direction of cooling. Unidirectional solidification in microgravity with a magnetic field of 0.04 T produced crystalline SmFe 2 and Fe phases. The microstructure of this product was lamellar with an average lamellar thickness of 17 μm and no crystalline alignment. Unidirectional solidification in microgravity with a magnetic flux ranging from 0.06 to 0.12 T and in normal gravity with a magnetic flux ranging from 0 to 0.12 T produced crystalline Sm 2 Fe 17 and Fe. During unidirectional solidification in microgravity without a magnetic flux, few nucleation sites were formed and rapid crystal growth occurred, consequently forming large‐grain SmFe 2 . The produced SmFe 2 had a lamellar structure with a dominant <111> crystallographic alignment in the direction of cooling. Convection in the molten state and where a magnetic flux was present caused homogeneous nucleation, forming Sm 2 Fe 17 with a disordered structure and crystalline alignment coinciding with the formation of the dendritic Fe.