Microstructure and the thermal stability of rapidly solidified aluminum-rare earth alloys

The effect of rapid solidification by the melt spinning process on the Al-4Er and Al-4La alloys has been studied. Compared to the normally solidified master alloy, rapid solidification processing promotes the formation of an eutectic with suppressed, relatively refined microstructures. Varying relative proportions of microstructures occupy the ribbons longitudinal transverse cross sections; a featureless zone at the contact surface, a columnar zone in the middle and an equiaxed-grain zone with degenerate dendrites at the fres surface. The presence of finely dispersed, coherent Al₃Er secondary equilibrium phase near the contact surface is evident, as well as the formation of a spherical, metastable L₁₁La₃ secondary phase in the near contact zone of the Al-4La alloy. The ribbons microhardness remains fairly stable after isochronal heating up to 300°C and retains, at further elevated temperatures, higher mean values than the master alloy.