Structural Observations of Amorphous Cu-Ta and Ni-Ta Alloy Powders Subjected to Mechanical Alloying

Abstract

Two mixtures of elemental powders Ni₃₀Ta₇₀ and Cu₃₀Ta₇₀ with a negative and positive heat of mixing, respectively, were subjected to mechanical alloying(MA) and the resulting structural changes have been studied by X-ray diffraction, neutron diffraction and DSC measurements. We found that the amorphization occurs by MA in both samples, in particular, despite the fact that the atomic pair of Cu and Ta is characterized by a positive heat of mixing. The coordination numbers and atomic distances of the Ni-Ni(Cu-Cu), Ni(Cu)-Ta and Ta-Ta pair correlations for the amorphous Ni₃₀Ta₇₀ and Cu₃₀Ta₇₀ phases was deduced by assuming the first nearest neighbors of the total pair distribution function g(r) to consist of the three partial ones, respectively. We concluded that the short range structure is fairly similar in both amorphous phases.