High Resolution Electron Microscopic Observations of Disordered CuPd Alloys

Abstract

Cu–21.0 at% Pd and Cu–29.8 at% Pd alloys quenched from the disordered state are observed around the [001] direction with tilted dark field and axial bright field lattice imaging techniques to elucidate the structure of short‐range order (8RO) of constituent atoms. The electron micrographs show lattice fringes in some localized regions of 2 to 3 nm in size caused by the interference between the characteristic SRO diffuse streaks and a fundamental spot. This suggests at least the existence of localized ordered regions in disordered alloys. The change of the fringe arrangement with that of Pd content is also detected from the micrographs and the optical diffraction patterns. The results about the atomic arrangement deduced from the micrographs are interpreted with a model on the basis of the correlative microdomain for disordered binary alloys.

Transformation Processes from Short Range Order to L1<SUB>2</SUB> and L1<SUB>2&minus;s</SUB> Ordered States in a Cu-25.7 at%Pt Alloy

“…It seems hard to postulate that the ordered structure within these developed particles is related to Ll0. Tanaka et al (18) discussed an SRO structure in quenched Cu-Pd alloys with high resolution electron microscope observation and obtained almost the same conclusion as the present.…”

Electron-microscope imaging of short-range order in disordered alloys

“…In the dark-field lattice images taken under conditions of diffuse scattering and fundamental reflections, the image features suggested localized ordered structures in a disordered matrix (Van Tendeloo, De Ridder & Amelinckx, 1978;Tanaka, Ohshima, Harada & Mihama, 1979). In the brightfield lattice images taken under conditions of direct wave and diffuse scattering, localized ordered regions were clearly observed with localized lattice-like fringes in disordered Cu-Pd (Tanaka & Ohshima, 1984;Van Tendeloo & Amelinckx, 1983) and Au-Mn alloys (Tanaka, Cowley & Ohshima, 1987).…”