Fe-B-Si-C-Cu amorphous and nanocrystalline alloys with ultrahigh hardness and enhanced soft magnetic properties

Soft magnetic Fe-B-Si-C-Cu amorphous alloys were found to exhibit simultaneously high saturation magnetization above 1.7 T, low coercivity below 5 A/m, high permeability reaching 23100 at 1 kHz and 3500 at 1 MHz as well as high Vickers hardness above 1000 and good bending ductility. Similar good soft magnetic properties were also obtained in annealing-induced nanocluster + amorphous and nanocrystalline alpha-Fe + amorphous phases. The hardness increases rapidly to 1450 when a structure consisting of alpha-Fe + amorphous phases develops, and reaches 1820 for the alpha-Fe + Fe-3(B,C) + Fe2B + amorphous phase mixture obtained just before the disappearance of amorphous phase. The ultimate high hardness is due to the high thermal stability of the finely mixed Fe-3(B,C) and Fe2B phases caused by the addition of carbon. The present Fe-based amorphous alloys are useful for future developments of soft magnetic materials with good bending ductility as well as ultrahigh hardness.