5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

With the advent of high-energy X-ray sources, it is now possible to follow solidification processes in three dimensions and as a function of time. The ability to observe and quantify the solidification process in metals on sub-second time scales and micron spatial scales in three dimensions provide fundamentally new insights into this complex phase transformation. Only through three-dimensional measurements is it possible to quantify the complicated interfacial morphology and topology of solidification microstructures. We illustrate the power of this approach by examining solidification processes over a range of time scales. At the shortest timescales, the morphologies of free-growing hyperbranched dendrites in Al-Zn and Al-Zn-Cr alloys are examined. Unlike classical dendrite morphologies, by scaling the interfacial shape distribution with a time-dependent characteristic length we find that the morphology of these dendrites is approximately self-similar during growth. At longer time scales, the evolution of the topology of a dendritic mush and processes that alter it, such as fragmentation, is examined. Finally, spatial correlations of interfacial curvature are used to explain why the t1/3 temporal power law for the evolution of a characteristic length scale during coarsening is so robustly observed even when the microstructure of the mush is not self-similar, and thus when theory predicts that a temporal power law should not exist.