Topological and chemical short-range order in amorphous Ni-Ti alloys

Abstract

Neutron and x‐ray scattering measurements were made on amorphous Ni35Ti65 and Ni40Ti60 alloys prepared by the melt‐spinning process. The x‐ray interference functions (structure factors) Sx(K) are dominated by the topological short‐range order (TSRO)SNN(K), but exhibited a small prepeak. The neutron structure factors Sn(K) are dominated by the CSRO SCC (K)/(c1c2), describing the concentration fluctuations in the alloys. Assuming that the size effect term SNC(K) which describes the correlation between number density and concentration can be approximated by the Percus‐Yevick hard sphere model, the TSRO SNN(K) and CSRO SCC(K)/(c1c2) were evaluated. From their Fourier transforms it became possible to evaluate the chemical short‐range order parameter α which is of the order of −0.1 to −0.15 indicating a preference for unlike nearest neighbors in the amorphous Ni‐Ti alloys.