Crystallization and soft magnetic properties of rapidly solidified Fe 73.5Nb 3Cu 1Si 22.5− XB X ( X=5, 9, 10, 11.25, 19) alloys

Abstract

The metalloids Si and B in the melt-spun Fe 73.5Nb 3Cu 1Si 22.5− X B X ( X=5, 9, 10, 11.25, 19) alloys play a major role in their crystallization and magnetic behaviour. In the present work, the effect of nanocrystallization on the transport properties was studied using thermal variation of electrical resistivity. An X-ray diffractogram study showed that the formation of different phases was controlled by the metalloid content in the alloy. Nanocrystalline α-Fe(Si) and/or Fe 3Si particles were formed in all the measured alloys except the alloy with 19 at% boron where α-Fe phase appeared. The lattice parameter as well as Si content within α-Fe(Si) was also found to depend on the metalloid content of the alloy. The Debye temperature was derived from thermal electrical resistivity study and was found to depend on the metalloid content of the alloys. However, Curie temperature of these alloys was not strongly dependent on the metalloid. The formation of α-Fe(Si) and/or Fe 3Si nanoparticles was responsible for the superior soft magnetic properties of the 9 at% boron alloy annealed around 800 K. The early appearance of boride phases, which have high magnetocrystalline anisotropy, was the cause of deterioration in soft magnetic properties in X=5, 10, 11.25 and 19 alloys.