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 Co47Fe20.9B21.2Si4.6Nb6.3 bilayer, ribbon, rods with diameter up to 5 mm and [Co47Fe20.9B21.2Si4.6Nb6.3]98Ga2 as-cast ribbon as well as rod with 4 mm diameter were investigated. Co based master ingots with the composition Co47Fe20.9B21.2Si4.6Nb6.3 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 (Tg), crystallization temperature (Tx) and supercooled liquid region (∆Tx = Tx – Tg) 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.

► Glassy CoFeBSiNb(Ga) samples were prepared in ribbon, bilayer and BMG forms (rods).
► Stability, magnetic state and microstructure evolution were analyzed by DSC, TGA and XRD.
► TEM analysis of radial distribution of microstructures in rods was performed.
► Magnetic and structural transitions were correlated with preparation techniques.
► Effect of gallium on Curie temperature and saturation magnetostriction was determined.