Chemical Structure of Ni-Ti Neutron Zero Scattering Amorphous Powders Prepared by MA

Abstract

The starting powders of Ni_24.3Ti_75.7 composition were amorphized by mechanical alloying(MA). The concentration-concentration correlation function was directly observed by neutron diffraction, because the average coherent scattering length of the alloy powders is adjusted to be zero, i.e., <b>=0.
The negative peak at r=2.54 Å in the reduced radial concentration correlation function G_CC(r) can be taken as evidence for the preferential formation of the Ni-Ti unlike atom pair, the distance of which is smaller than that calculated from the diameters of Ni and Ti atoms. The Warren chemical short range order parameter of the Ni_24.3Ti_75.7 amorphous alloy was evaluated to be a negative value of -0.097. These findings clearly demonstate the preferential existence of Ni-Ti unlike atom pairs at the nearest neighbor coordination in the Ni_24.3Ti_75.7 amorphous alloy synthesized by MA.