Microsegregation Model Including Convection and Tip Undercooling: Application to Directional Solidification and Welding

• Published in: Materials Vol. 11; no. 7; p. 1252
• Main Authors: Billotte, Thomas, Daloz, Dominique, Rouat, Bernard, Tirand, Guillaume, Kennedy, Jacob R, Robin, Vincent, Zollinger, Julien
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 20-07-2018; MDPI
• Subjects: Alloying elements; Alloys; Computational fluid dynamics; Corrosion; Dendritic structure; Directional solidification; Engineering Sciences; ERNiCrFe-7; Experiments; Filler metals; Fluid flow; FM52 filler metal; Gas tungsten arc welding; Grain boundaries; Hypotheses; Lasers; Materials; Materials science; Mathematical models; microsegregation; Nickel; Parameterization; Process parameters; Software; Solids; Supercooling; tip undercooling; France; Switzerland; FM52 filler metal; microsegregation; tip undercooling; gas tungsten arc welding; ERNiCrFe-7; directional solidification
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma11071252

The microsegregation behavior of alloy filler metal 52 (FM 52) was studied using microprobe analysis on two different solidification processes. First, microsegregation was characterized in samples manufactured by directional solidification, and then by gas tungsten arc welding (GTAW). The experimental results were compared with Thermo-Calc calculations to verify their accuracy. It was confirmed that the thermodynamic database predicts most alloying elements well. Once this data had been determined, several tip undercooling calculations were carried out for different solidification conditions in terms of fluid flow and thermal gradient values. These calculations allowed the authors to develop a parametrization card for the constants of the microsegregation model, according to the process parameters (e.g., convection in melt pool, thermal gradient, and growth velocity). A new model of microsegregation, including convection and tip undercooling, is also proposed. The Tong⁻Beckermann microsegregation model was used individually and coupled with a modified Kurz-Giovanola-Trivedi (KGT) tip undercooling model, in order to take into account the convection in the fluid flow at the dendrite tip. Model predictions were compared to experimental results and showed the microsegregation evolution accurately.