Chemical short-range order in (Ti 76Ni 24) x(Ti 70Cu 30) 1− x neutron zero scattering amorphous alloys

Abstract

(Ti 76Ni 24) x (Ti 70Cu 30) 1− x neutron zero scattering amorphous alloys were synthesized by mechanical alloying. Neutron diffraction in this system allows one to observe directly the concentration-concentration correlation functions, since the averaged neutron scattering amplitudes of the amorphous alloys are zero. Positive and negative peaks in the first neighboring atoms in G CC( r) for the Ti 70Cu 30 amorphous alloy can be identified as the CuCu and CuTi correlations, respectively. The positive peak at 2.4 Å rapidly diminishes with increasing Ni content. For the Ti 76Ni 24 amorphous alloy, only a negative peak is observed in the nearest neighbor, indicating that the Ni atoms are no longer in hard contact with each other. The chemical short-range order parameter, α, calculated from the Warren definition is negative for all pseudo-binary Ti(Cu,Ni) amorphous alloys. The value of α is found to decrease rapidly with increasing Ni content. The results indicate that an increase in the chemical short-range order by alloying with Ni element is ascribed to the stronger affinity of a Ni atom with a Ti atom than that of a Cu atom.