Synthesis of Structure Controlled Magnetostrictive Materials by Use of Microgravity and Magnetic Fields

Abstract

Tb-2Fe and Sm-2Fe molten alloys with a 1:2 molar ratio were unidirectionally solidified separately in microgravity and normal gravity in concurrence with a magnetic flux (0-0.12T). The Tb-2Fe molten alloy was solidified unidirectionally in microgravity with a 0.1T magnetic flux and the solidification product, TbFe2, had dominant [111] crystallographic alignment and the microstructure was lamellar with an average lamellar thickness of 30μm oriented along the solidification direction. The single phase SmFe2 was synthesized by unidirectional solidification in microgravity with a magnetic flux of 0T, and the microstructure was lamellar. The average SmFe2 lamella thickness was 30μm and each lamella possessed a <111> crystallographic alignment along the direction of cooling. The unidirectional solidification of Sm-2Fe molten alloys in normal gravity or in microgravity with a magnetic field resulted in Sm2Fe17 and Fe crystalline phases. The magnetostriction of TbFe2 solidified unidirectionally in microgravity with a 0.1T magnetic flux was 4,500ppm with an external 1.6T static magnetic flux. In TbFe2 solidified in normal gravity, the maximum magnetostriction remained at 2,000ppm with an external 1.6T static magnetic flux. The magnetostriction of single phase SmFe2 solidified unidirectionally in microgravity with a magnetic flux of 0T was -3,200ppm with an external 0.09T static magnetic flux.