TY - CONF

T1 - Consideration of the timing of dendrite pinch-off for a flow-driven fragmentation mechanism during the casting process

AU - Zhang, Haijie

AU - Wu, Menghuai

AU - Kharicha, Abdellah

PY - 2024/9

Y1 - 2024/9

N2 - In many engineering castings, forced flow is implemented to promote the equiaxed zone, and the primarysource of the equiaxed is considered to be dendrite fragmentation. It is known that the interdendritic flowin the dendrite growth direction promotes dendrite remelting, creating favorable conditions for dendritefragmentation. Therefore, a flow-driven fragmentation model was primarily proposed, assuming thatfragmentation occurs when the following criterion, (u_l-u_c)⋅∇c_l<0, is fulfilled. Although the above modelhas considered global transport phenomena and their impacts on the local thermodynamic condition for thedendrite remelting, some other microscopic events influencing the fragmentation were ignored orsimplified. One such event is the timing effect of dendrite pinch-off. In this conference contribution, aliterature survey on the study of the dendrite pinch-off is made, and on this base, a modification to theprevious flow-driven fragmentation model is suggested. In addition to the above flow-driven remeltingcriterion, a second condition, i.e., the necessary time for the remelting (t_r) of the dendrite roots to allowthe pinch-off (τ) to occur, is applied to the model. As an evaluation effort, this newly improved model wasused to simulate two engineering castings: one is the directionally solidified superalloy casting, and one isan in-laboratory cast steel ingot. It is verified that a better simulation-experiment agreement is obtainedwith the new model modification

AB - In many engineering castings, forced flow is implemented to promote the equiaxed zone, and the primarysource of the equiaxed is considered to be dendrite fragmentation. It is known that the interdendritic flowin the dendrite growth direction promotes dendrite remelting, creating favorable conditions for dendritefragmentation. Therefore, a flow-driven fragmentation model was primarily proposed, assuming thatfragmentation occurs when the following criterion, (u_l-u_c)⋅∇c_l<0, is fulfilled. Although the above modelhas considered global transport phenomena and their impacts on the local thermodynamic condition for thedendrite remelting, some other microscopic events influencing the fragmentation were ignored orsimplified. One such event is the timing effect of dendrite pinch-off. In this conference contribution, aliterature survey on the study of the dendrite pinch-off is made, and on this base, a modification to theprevious flow-driven fragmentation model is suggested. In addition to the above flow-driven remeltingcriterion, a second condition, i.e., the necessary time for the remelting (t_r) of the dendrite roots to allowthe pinch-off (τ) to occur, is applied to the model. As an evaluation effort, this newly improved model wasused to simulate two engineering castings: one is the directionally solidified superalloy casting, and one isan in-laboratory cast steel ingot. It is verified that a better simulation-experiment agreement is obtainedwith the new model modification

M3 - Paper

T2 - The 8th International Conference on Solidification and Gravity

Y2 - 2 September 2024 through 5 September 2024

ER -