Preparation of thin ribbon and bulk glassy alloys in CoFeBSiNb(Ga) using planar flow casting and suction casting methods

Co-based ferromagnetic bulk glassy alloy (BGA) system is promising for future applications as new structural and functional materials. In the present paper as-cast Co ₄₇Fe _20.9B _21.2Si _4.6Nb _6.3 bilayer, ribbon, rods with diameter up to 5 mm and [Co ₄₇Fe _20.9B _21.2Si _4.6Nb _6.3] ₉₈Ga ₂ as-cast ribbon as well as rod with 4 mm diameter were investigated. Co based master ingots with the composition Co ₄₇Fe _20.9B _21.2Si _4.6Nb _6.3 have been prepared in a vacuum furnace. The as-prepared master ingots were then purified by fluxing. Small amount of gallium (2 at.%) was added into one part of the purified master alloy. Ribbons, bilayer and bulk samples in form of rods were prepared by subsequent planar flow casting and suction casting method, respectively. Glassy structure of as-cast samples was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability associated with glass transition temperature (T _g ), crystallization temperature (T _x) and supercooled liquid region (∆T _x = T _x – T _g ) were examined by differential scanning calorimetry (DSC). The Curie temperature of the investigated ribbons and rods was determined by magnetic thermogravimetry analysis (TGA). Using special disc-shaped samples field dependencies of magnetostriction in parallel and perpendicular directions of the applied magnetic field were obtained by direct measurement.