Different atomic structures observed from ternary Ni-Nb-Ta metallic glasses obtained by ion beam mixing

Abstract

Four sets of ternary Ni-Nb-Ta multilayered samples with overall compositions of Ni₆₉Nb₈Ta₂₃, Ni₅₅Nb₁₃Ta₃₂, Ni₄₂Nb₁₆Ta₄₂ and Ni₂₉Nb₁₈Ta₅₃, respectively were prepared and subjected to 185 keV xenon ion beam mixing. The experimental results showed that in the four Ni-Nb-Ta multilayered samples, metallic glasses could all be obtained at appropriate doses, supporting the prediction directly from a proven realistic Ni-Nb-Ta interatomic potential through molecular dynamics simulations, and that two different atomic structures were observed, as in the corresponding selected area diffraction patterns, the locations of the diffused bands reflected from the metallic glass phases were observed at different angles for the Ni₆₉Nb₈Ta₂₃ and Ni₂₉Nb₁₈Ta₅₃ metallic glasses. Interestingly, Voronoi tellessation analysis indicated that the observed difference in atomic structures could be attributed to the distinct coordinate number spectra, i.e., the spectrum of the Ni₆₉Nb₈Ta₂₃ metallic glass has its coordinate number (CN) equal to 13 as dominating atomic configuration (with a weight of about 27%), whereas for the Ni₂₉Nb₁₈Ta₅₃ metallic glass, CN=14 is the dominating atomic configuration (also about 27%). Moreover, the distinct atomic configurations of the obtained Ni-Nb-Ta metallic glasses could be correlated to the structures of the constituent metals of the ternary Ni-Nb-Ta system, as the first neighbor of fcc is 12 and the sum of the first and second neighbors of bcc is 14, implying the structural heredity did play a role in metallic glass formation.