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

Abstract

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.