Preparation and characterisation of Co-Fe-Ni-M-Si-B (M = Zr, Ti) amorphous powders by wet mechanical alloying

Co-based amorphous alloys were prepared via wet mechanical alloying process starting from elemental powders. The reference alloy Co70Fe4Ni2Si15B9 (at. %) as well as the alloys derived from this composition by the substitution of 5 at.% of Zr or Ti for Si or B (Co70Fe4Ni2Si15B4Zr5, Co70Fe4Ni2Si15B4Ti5, Co70Fe4Ni2Si10B9Zr5 and Co70Fe4Ni2Si10B9Ti5) are obtained in amorphous state, according to X-ray diffraction (XRD) investigation, after 40 h of milling. The calculated amount of amorphous fraction reaches 99% after 40 h of milling. The largest increase of the crystallisation temperature was induced by the substitution of Zr or Ti for Si while, regardless of the type of substitution, an important increase of the Curie temperature of the alloy was obtained. A Co-based solid solution, with Co2Si and Co2B phases, result after crystallisation of the amorphous alloys as proved by XRD investigations. Saturation magnetisation of the alloys decreases upon increasing milling time, however it remains larger than the saturation magnetisation of the reference alloy. This was discussed in correlation with the specificity of the wet mechanical alloying process and the influence of the chemical bonding between Co and metalloids atoms over the magnetic moment of Co. (C) 2016 Elsevier B.V. All rights reserved.