Structure of a Vapor-Quenched AgCu Alloy

Abstract

Ag—52 at.% Cu films were prepared by coevaporation onto 0.005 in. thick vitreous silica plates held at liquid-nitrogen temperature. The interference function I(K), where K=4π sinθ/λ, was evaluated from the elastic x-ray scattering of the film and compared with I(K) of the liquid alloy, measured at 1000°C, and with a model I(K) based on fcc microcrystals containing 125 atoms. The Fourier transforms of K[I(K)—1] yielded the reduced distribution functions G(r) =4πr[ρ(r)—ρ0]V(r), where ρ(r) is the weighted atomic density at a distance r from any reference atom, ρ0 is the average atomic density, and V(r) is the size factor of the diffracting domains. Both I(K) and G(r) indicate that the alloy film cannot be characterized as amorphous but is micropolycrystalline with fcc structure. The size of the microcrystals can be estimated from G(r), i.e., from the value of r beyond which G(r) is zero within the scatter of the experimental points. A value of less than 16 Å has thus been found. I(K) and G(r) of the liquid alloy are characteristic of the close-packed liquid metals with a distance of less than 15 Å beyond which no short-range order can be detected.

Electron-irradiation-induced structural change in Zr–Hf–Nb alloy

“…The peak position ratio of the first peak to the second peak (q 1st :q 2nd ) is 1.66 and that of the first peak to the sub-peak of the second peak (q 1st :q 2nd-sub ) is 1.99. These values are comparable to those obtained for an amorphous phase in metals [5] and a nanocrystalline specimen in the CueAg alloys obtained by the sputtering process [6]. It is well known that many amorphous transition metals and their alloys are typically characterized by the existence of sub-peaks with positions out of the second peak.…”

Electrodeposited Al–Mn alloys with microcrystalline, nanocrystalline, amorphous and nano-quasicrystalline structures

“…Thus, although Grushko and Stafford [2,4] and Takayama et al [11] have identified an ''amorphous" second phase in Al-Mn deposits, the broad diffraction halo of this phase could also correspond to an extremely fine ensemble of quasicrystalline domains [15]. Such ''micro-quasicrystalline" (or, more aptly, ''nano-quasicrystalline") structures have been observed in Al-Mn alloys produced by techniques other than electrodeposition, and are indeed characterized by a broad, amorphous-like diffraction halo at the primary reflection.…”

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

“…Previously, the structure of a vapor-quenched AgCu alloy had been compared to the liquid Ag-Cu alloy of similar composition (Wagner, Light, Halder & Lukens, 1968). The interference function I(K) of this solid film is shown in Fig.…”