Soft magnetic properties of Fe82-83B14-15Si2C0.5-1 amorphous alloys with high saturation magnetization above 1.7 T

With the aim of developing a new inexpensive soft magnetic amorphous alloy exhibiting high saturation magnetic flux density (Bs) above 1.7 T, we examined the formation, thermal stability and magnetic properties for melt-spun Fe-B-Si-C amorphous alloys with high (B + C)/Si content ratios. The high Bs of 1.71-1.73 T exceeding the previously reported Bs was obtained for annealed Fe82-82.5B15Si2C0.5-1 alloys. These high Bs alloys exhibit low coercivity below 8 A/m and good bending ductility. The 82.5Fe alloy with the highest Bs of 1.73 T also has the highest hardness. Besides, the 82.5Fe alloy has the largest nearest neighbor atomic distance among the present alloys. The correlation between the highest Bs and the largest atomic distance is similar for (Fe,Co)83-86B15-16Si1 amorphous alloys. The 82.5Fe and 82Fe alloys are located near the critical composition where the crystallization changes from two stages of α-Fe(Si) + amorphous ⇢ α-Fe(Si) + Fe3(B,C) to a single stage of α-Fe(Si) + Fe3(B,C). These results indicate the importance of the special alloy composition with the largest atomic distance and high stability to primary α-Fe precipitation, in addition to high (B + C)/Si content ratios, for the synthesis of a new ductile amorphous alloy with high Bs and good magnetic softness.