| Abstract Scope |
Solidification of single phase alloys occurs in a number of distinctive stages: prenucleation, heterogeneous nucleation, grain initiation, spherical growth, morphological instability, dendritic growth and grain impingement. Early stages of solidification refer to the process between prenucleation and the point of morphological instability. Since the majority of the historic research has been concentrated on dendritic growth, our current understanding of early stages of solidification has been very limited albeit it contributes dominantly to the formation of the solidified microstructure. In this contribution we present an overview of the recent advances in understanding early stages solidification, focusing on heterogeneous nucleation, grain initiation and their effect on grain refinement. We show that: (1) more significant grain refinement can be achieved by impeding rather than enhancing heterogeneous nucleation (2) Al- and Mg-alloys do not need grain refiners since they contain sufficient native solid particles to achieve grain refinement. |