Solid state amorphization in the amorphous alloy Co66Nb22B12 by mechanical alloying

Resumen

Elemental mixtures of powders Co, Nb and B with a stoichiometric composition of Nb-Co-B were prepared from the mechanical processing in a ball mill. The evolution of the structure of the starting powders and ground mixtures were characterized by X-ray diffraction and Differential Scanning Calorimetry and Scanning Electron Microscopy and spectroscopy Dispersion Energy (SEM / EDS). The alloy amorphous Co-Nb-B previously activated by high energy milling balls, involves two consecutive reactions amorphization. The mechanical grinding, first leads to amorphization reaction between layers of Co and B with a strong thermodynamic driving force, as well as for the rapid kinetics of Co-B amorphization compared with amorphized Co-Nb intermetallic phases. In further grinding the kinetic requirements for amorphization of Co-Nb reaction is observed and, consequently, the appearance and an Nb-B compound in the form of amorphous phase. The two amorphous phases resulting homogenized for a long grinding time.