A comparison between the structures of amorphous and liquid Ag–Cu and Cu–Mg alloys

Amorphous films of AgCu and CuMg₂, approximately 3000 Å in thickness, were prepared by co-evaporation of Ag and Cu, and Cu and Mg, respectively, onto 25 μm thick Be sheets, held at liquid nitrogen temperature. Mo Kα X-rays were used as a radiation probe to determine the structure of the films, at room temperature, and of the liquid alloys of Cu with 50 at.% Ag and with 0 and 67 at.% Mg at 50°C above the liquidus temperature. With the transmission technique, the interference functions (or structure factors) I(K) were determined in the range of K = 4π sin θ/λ between 0.8 Å⁻¹ and 12.5 Å⁻¹, and then Fourier transformed to obtain the radial distribution functions (RDF). The I(K) and RDF of the amorphous AgCu and CuMg₂ films were compared with those of the liquid Ag–Cu and Cu–Mg alloys, respectively. It was found that the structures of the amorphous and liquid Ag–Cu alloys were similar with a more well defined short-range order occurring in the solid alloys, whose I(K) exhibited the well known shoulder on the second peak. The I(K) and RDF of the amorphous CuMg₂ and the liquid Cu–Mg alloys cannot be explained by a common structure, although I(K) showed a small premaximum below the first main peak in both the amorphous and liquid alloys, a feature observed in many liquid Mg alloys.