A study on the Microstructures and the Suppression of Grain Growth in Rapidly Solidified Fe-Si-B(-Cu-Zr-Ca) Base Nanostructured Alloys

Abstract

Magnetic induction and resonance wireless power charging generally operates in a high frequency range, and its efficiency is degraded by the generation of heat at high frequency. This makes it necessary to develop new soft magnetic materials capable of maintaining their characteristics even at high frequency. The purpose of this study is to minimize the heat generated by the eddy currents when charging, and to improve the charging efficiency under an alternating magnetic field. In this study, Fe-Si-B alloys containing Cu, Zr and Ca elements were melt-spun to prepare amorphous ribbons. The amorphous ribbons were heat treated to crystallize nanograins, The structure was analyzed by TEM and EELS, As a result, it was found that Zr was distributed mainly at the grain boundaries after heat treatment, whereas Ca was uniformly distributed only along the grain boundaries. It could be concluded that the Ca and Zr elements effectively suppressed the grain growth, and thus maintained the very fine nanograin structure.