Microstuctural developments in rapidly solidified monotectic alloys

Abstract

The origin of the finely dispersed second-phase morphology observed in rapidly solidified near-monotectic alloys of liquid-immiscible systems has been discussed. It is shown that two competing mechanisms, namely (1) phase separation in the liquid state followed by trapping of the dispersed liquid by the growing solid and (2) massive solidification followed by solid state decomposition, exist. A combination of thermodynamics and homogeneous nucleation kinetics can predict the possible origin. This is confirmed by analysing the symmetry of the shape of the dispersoids and invoking the principle of the intersection group. It is also shown that in the case of liquid trapping, a simple analysis based on Ulmann et al.'s work can predict the hierarchy of ease of trapping of the dispersed liquid by different matrices.