Phase-Field Simulation of Microsegregation and Dendritic Growth During Solidification of Hypoeutectic Al-Cu alloys

Abstract

Prediction of microstructure evolution and microsegregation is one of the most important problems in materials science. The dendritic growth and microsegregation provide a challenging simulation goal for computational models of solidification, in addition to being an important technological feature of many casting processes. The phase-field model offers the prospect of being able to perform realistic simulation experiments on dendrite growth in metallic systems. In this paper, the microsegregation and dendritic growth of hypoeutectic Al-Cu alloys under constant cooling rate was simulated using a phase-field model. The main new feature of the present model is based on the fact that the effect of the growth rate is incorporated via an effective partition coefficient that has been experimentally determined for a range of growth rates. It is shown that both models (Phase-field model and Scheil) have significant deviations from the experimental data when the equilibrium partition coefficient is considered in the calculations. Since the predicted results using the models yielded discrepancies from the experimental data, an experimental equation is adopted for calculating the effective partition coefficient from experimental data. The experimental equation is then adopted in the calculations of phase-field model and Scheil's equation, showing a good agreement with the experimental data.

Investigation of Thermal Parameters Effects on the Microstructure, Microhardness and Microsegregation of Cu-Sn alloy Directionally Solidified under Transient Heat Flow Conditions

“…In addition to solid back-diffusion, there is another phenomenon denominated: solidification kinetics must be considered, as far as it can influence microsegregation profiles. Although the influence of thermal variables, such as temperature gradient and cooling rate on the dendritic arm spacings has been studied, the literature still is scarce on research about the effects of solidification speed on the microsegregation profiles, Ferreira et al 4 , Baptista et al 16 and Baptista et al 19 . An equation for effective partition coefficient (k ef ) as a function of the solidification speed (S S ), was proposed by Burton et al 27 , eq.…”

“…The effect of microsegregation on casting quality has been investigated over the decades by theoretical and experimental models [4][5][6][7][8][9][10][11][12][13][14][15][16] . Ferreira et al 4 used a numerical model to the prediction of microsegregation and dendritic arm spacing during solidification of hypoeutectic Al-Cu alloys. It is shown by performing comparisons between experimental microsegregation results and theoretical models with equilibrium partition coefficient, a reasonable agreement between them.…”

Análise das variáveis térmicas e correlação com os espaçamentos dendríticos e microssegregação na solidificação unidirecional da liga binária Al-4%Cu.

“…Pode-se perceber que, conforme a Figura 3b, notaram-se grãos colunares com uma direcionalidade no sentido vertical, atestando a eficácia da extração de calor no processo de solidificação, conforme em outros estudos (MEZA, 2012;RODRIGUES et al, 2014;BAPTISTA et al, 2018;FERREIRA et al, 2017;BOEIRA, 2006). Observou-se também uma leve inclinação que pode ser causada por perturbações mecânicas externas durante a solidificação, de acordo com Garcia (2007).…”

“…, 2007;FERREIRA et al, 2017. Na Figura 12, é apresentado o perfil de concentração de soluto no sólido (Cs) em função da fração sólida (fs) pela equação experimental, considerando-se as posições de 5, 40 e 80 mm.…”

Analysis of Microsegregation in Al-Si-Cu Ternary Alloys: Interdependence of Solute Composition at the Solubility Limit during Non-Equilibrium Solidification

“…The segregation has gotten the attention of researchers for many years [2][3][4][5] . However, the physical and chemical processes involved are highly complex and have always been an obstacle for modeling.…”