Measurements of dendrite tip growth and sidebranching in succinonitrile–acetone alloys

Three-dimensional mesoscopic modeling of equiaxed dendritic solidification of a binary alloy

“…The computations were performed for supersaturations in the range of Ω 0 = 0.05-0.25. This is similar to the range of solutal supersaturations of Ω 0 ≈ 0.05-0.45 found in the experiments [18]. These were estimated with the LGK model from the known total undercoolings.…”

“…However, simple solutions do not exist for the envelope shape or the solute flux from a dendrite. Validation is therefore made by comparisons with the recent experiments of Melendez and Beckermann [18]. They performed detailed characterizations of equiaxed dendrites of transparent succinonitrile-acetone alloys growing into a uniformly undercooled melt.…”

“…In the present paper we perform a care- the envelope, the confocal envelope, and the stagnant film thickness, δ. The envelope propagation velocity, ⃗ V n , is obtained by the projection of the tip velocity, ⃗ V tip , from the preferential growth direction forming the smallest angle θ with the envelope normal, ⃗ n. The parameters and scales of equiaxed dendrites measured in the experiments used for validation [18] are also shown: the width of the envelope formed by the active sidebranches, X act , the projection area of the solid, F , and the primary tip radius, R tip .…”

“…We also validate the model for free dendritic growth in a binary alloy over a wide range of undercoolings. This is accomplished through comparisons of 3D simulations to recently published experimental scaling laws giving the shape and the internal solid fraction of freely growing binary alloy dendrites [18] and to classical analytical solutions for the primary dendrite tip speed. We provide generally valid guidelines for the calibration of the numerical and model parameters of the mesoscopic model, enabling reliable control of the accuracy of model predictions over a wide range of undercoolings.…”

“…A simple estimation shows that the threshold between these two regimes is well above a supersaturation of Iv(0.5) = 0.46. Such supersaturations are not of great interest since the experiments used for validation [18] were performed at considerably lower values. In technical processes the supersaturations are even much lower.…”