|About this Abstract
||2016 TMS Annual Meeting & Exhibition
||Frontiers in Solidification: An MPMD Symposium in Honor of Michel Rappaz
||Multiscale Modeling of Columnar to Equiaxed Transition
||Alain Karma, Pierre-Antoine Geslin
|On-Site Speaker (Planned)
The columnar to equiaxed transition (CET) is a widely observed and technologically important microstructural transition strongly impacting the grain structure of dendritic alloys. This talk discusses new quantitative insights into this complex transition obtained using a coarse-grained approach that tracks the diffusion-controlled dynamics of branches of the hierarchically structured dendritic network, thereby bridging the well-separated scales traditionally simulated by phase-field and grain structure models. We extend this dendritic needle network (DNN) model to incorporate the nucleation and growth of equiaxed grains of different orientations and use it to investigate the CET during directional solidification of binary alloys in two dimensions. Results identify different types of sharp and progressive CET as a function of growth rate, temperature gradient, nucleant concentration and undercooling, including the industrially relevant case of athermal heterogeneous nucleation.