Quantitative Phase-field Simulation of Dendritic Equiaxed Growth and Comparison with in Situ Observation on Al-4 wt.% Cu Alloy by Means of Synchrotron X-ray Radiography

Dendritic equiaxed growth from the melt by continuous cooling-down is investigated by quantitative 2D phase-field simulations. The results are compared with detailed data from solidification experiments on Al-4 wt.% Cu alloy with in situ X-ray monitoring. In a first step, the simulation of an isolated equiaxed alloy dendrite growing freely in < 100 >-direction in the melt is performed. Then, the impingement between two grains is considered by simulating two dendritic crystals growing towards each other in < 100 >-direction. From the phase-field simulations, the time evolution of the equiaxed crystals is characterized by measuring the lengths and tip velocities of the primary dendrite arms in free growth and in the presence of neighbor interaction, which enables the analysis of growth dynamics. In a second part, the results of the phase-field simulations are compared to data extracted from an experiment on Al - 4 wt.% Cu alloys carried out at the European Synchrotron Radiation Facility (ESRF), with in situ and real-time characterization by means of X-ray radiography, and to analytical relationship for dendrite tip growth. The limitations of 2D-phase-field simulations to fully describe the dynamic formation and interaction of dendritic equiaxed grains are briefly discussed.