Synthesis of Giant Magnetostrictive Iron-rich Sm-Fe Alloy by Unidirectional Solidification in Microgravity

Int. J. Microgravity Sci. Appl. 2011_s057
Sm-Fe magnetostrictive material was produced by unidirectional solidification of Sm-Fe alloy with atomic ratio from 1/2 to 2/17 in microgravity within ±4x10-3g for 1.43s obtained using 10-m drop tower and with fluctuating gravity between 0.1 and 0.02g obtained by parabolic flight. SmFe2 and a small amount of Sm2Fe17 as well as Fe were formed from unidirectional solidification in microgravity of Sm-7Fe alloy, obtained using the drop tower and parabolic flight. The structure consisted of sheet dendrites of SmFe2 and Fe-rich Sm-Fe layers between the sheet dendrites having no gaps with an orientation along the solidification direction. A crystalline orientation of <111> of SmFe2 along the solidification direction was found in the products formed in microgravity using the drop tower, but not in those using parabolic flight. The formation mechanisms of SmFe2 sheet dendrites can be explained by microsegregation caused by the lack of convection in melt in microgravity. In contrast, Sm2Fe17 and a small amount of Fe were formed in normal-gravity, and the resulting structure consisted of sheet dendrites without orientation. Magnetostriction of -3328ppm at the outer magnetic fields of 0.12T was achieved on a sample synthesized by unidirectional solidification of Sm-7Fe in microgravity obtained using the drop tower.

© The Japan Society of Microgravity Applicaiton

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