On the occurrence of buoyancy-induced oscillatory growth instability during directional solidification of alloys
Monday, June 19, 2023, 9:00 AM - 9:20 AM
Max Bell Theatre
Ahmed Kaci Boukellal

Recent solidification experiments combined with X-ray in situ radiography have identified an oscillatory growth instability during the directional solidification of Ni-based superalloy CMSX4 under a given range of cooling rates [Reinhart et al. Acta Materialia 194 (2020) 68-79]. From a modeling perspective, the quantitative simulation of dendritic growth under convective conditions remains challenging, due to the multiple length scales involved. Using the dendritic needle network (DNN) model, coupled with an efficient Navier-Stokes solver, we reproduced the buoyancy-induced growth oscillations observed during CMSX4 directional solidification [Isensee, Tourret. Acta Materialia 234 (2022) 118035]. These results have shown that, for a given alloy and temperature gradient, oscillations occur in a narrow range of cooling rates (i.e. growth velocity) and that the selected primary dendrite arm spacing (PDAS) also plays a crucial role in the activation of the flow leading to the oscillations. In the present work, using DNN simulations, we extend this study by performing a full mapping of oscillatory states as a function of PDAS and growth velocity, in order to identify the regions of occurrence of the different oscillatory behaviors (sustained, damped, etc.) as well as their effect on the oscillation characteristics (e.g. frequency).

Moderated by: Andre Phillion / Matt Krane