Etude de la structure fine de la phase riche en plomb de l'eutectique Pb-Sn a structure lamellaire

Abstract

Scanning microscope investigation of lamellar Pb-Sn eutectics showed that tin elimination from lead-rich Pb lamellae is quite different from that observed in massive supersaturated solid solutions: no tin precipitation occurs, but a slow tin diffusion into tin-rich Sn lamellae, together with a concentration gradient inside Pb lamellae. The concentration gradient profile, and an approximation of the value of diffusion coefficient, which is 6 orders of magnitude smaller than the one obtained in massive supersaturated solid solutions, were determined by X-ray diffraction. Single crystal Pb lamellae contain few defects, and the intergranular diffusion becomes of the same order of magnitude as the volume diffusion.