Synthesis and process characterization of mechanically alloyed amorphous Ni-Nb powders.

Amorphous NixNb1-x powders were prepared by mechanically alloying pure crystalline nickel and niobium powders in the concentration region 0.2 equal or smaller than x equal or smaller than 0.8. This homogeneity range was determined by X-ray analysis and differential scanning calorimetry. The total atomic pair distriubution functions, G(R), were calculated from X-ray diffraction data and the first maximum in G(R) was compared with data of melt-spun samples. The progress of mechanical alloying and of amorphization with increasing milling time was examined by metallography, X-ray analysis and transmission electron microscopy (TEM). The TEM examinations carried out after different milling times show a crystalline lamellar structure as well as the development of an amorphous phase. These results, combined with thermodynamic claculations after Miedema, are discussed within the model of reaction by solid state interdiffusion.