EFFECT OF COOLING RATE ON MAGNETIC PROPERTIES, SIZE AND TYPE OF STRUCTURAL DEFECTS IN THE VOLUME OF BULK AMORPHOUS Fe_(36)Co_(36)B_(19)Si_5Nb_4 ALLOY IN THE FORM OF RODS OF VARIOUS DIAMETERS

摘要

This paper presents the results of microstructure and magnetic properties analysis for bulk amorphous samples of Fe_(36)Co_(36)B_(19)Si_5Nb_4 alloy in the form of rods of 1 mm, 2 mm, and 3 mm diameters in the as-cast state, produced using the method of injecting liquid alloy into cooled copper mold. The main purpose of the research was to examine the effect of solidification speed of the liquid material into amorphous state on the shape of initial magnetization curve as well as to determine the type and size of structural defects occurring in the volume of the material. In order to achieve these objectives, the magnetization measurements were carried out, which according to H. Kronmiiller's theory on magnetization behavior near the area called reaching the ferromagnetic saturation, allow to determine the type, size, and surface density of structural defects occurring in the volume of the sample. The analysis of reduced magnetization curves indicates that solidification speed of the liquid alloy into the amorphous state is the main determining factor for the shape of initial magnetization curve and for the type and size of structural defects formed in the sample, which affects such magnetic parameters as: coercive field (H_c) or saturation magnetization (M_S).