Structural state and decomposition kinetics in rapidly quenched Al-Sc, Al-Mg-Sc alloys

The ability of Al-Sc and AI-Mg-Sc alloys to be supersaturated by the Sc has been studied in dependence on the Sc content (0.3, 0.6, 1 wt.%) and cooling rate during the crystallization. Properties of alloys prepared by rapid quenching from liquid state at 1000 and 1400 degreesC with the temperature rate nu=(1-5).10(5) K/s were compared with the ones of the bulk materials quenched from the solid state with the temperature rate 60 K/s. TEM revealed that rows of fine Al3Sc precipitation form peculiar spiral "waves" structure. The nature of this structure is discussed. It was found by hardness measurements and resistance method that the increase of the cooling rate in four orders resulted in the decrease of grain size in order. It was observed that refining effect of Sc was reduced with the cooling rate increase.