KINETICS OF PRECIPITATION IN AL-SC ALLOYS AND LOW-TEMPERATURE SOLID SOLUBILITY OF SCANDIUM IN ALUMINUM STUDIED BY ELECTRICAL-RESISTIVITY MEASUREMENTS

The precipitation kinetics of Al3Sc phases in Al-0.090at.%Sc and Al-0.15at.%Sc alloys were investigated in the aging temperature range from 533 to 733 K mainly by electrical resistivity measurements. The average Sc concentration c(Sc) of the Al-rich matrix was calculated from the value of the resistivity. The results of aging time dependence of c(Sc) and fraction of solute transformed were analysed from the viewpoint of time scaling, the Johnson-Mehl-Avrami equation and the Ostwald ripening theory. The rapid growth stage of the Al3Sc phases was successfully scaled and nearly characterized by the model of diffusion-controlled growth of a fixed number of particles. The solid solubilities of Sc in aluminium from 733 K down to 643 K were estimated by the analysis of c(Sc) of the Al-rich matrix during the Ostwald ripening of the Al3Sc precipitates.