|About this Abstract
||2019 TMS Annual Meeting & Exhibition
||Solidification Processing of Light Metals and Alloys: An MPMD Symposium in Honor of David StJohn
||Heterogeneous Nucleation in Peritectic Systems
||John H. Perepezko, Rohit Trivedi
|On-Site Speaker (Planned)
||John H. Perepezko
The nucleation behavior has been examined during directional solidification experiments in a model Sn-Cd peritectic system where a non-steady-state, banded structure in which repeated bands of primary alpha-phase and the peritectic beta-phase form normal to the growth direction. The measured nucleation undercooling for each phase was found to be very small, from a fraction of a degree to one degree at the container wall. The relevant contact angles have been measured and it is shown that the very small nucleation undercooling values for the two phases are not consistent with the predictions of the classical heterogeneous nucleation theory. A new mechanism of nucleation has been developed to account for the observed behaviour in which preexisting clusters in the liquid near the wall and at the wall interface-junction coalesce to become critical clusters when a definite undercooling is reached at the triple point.