Watching microstructure evolve in three dimensions10/22/2015
"Watching Microstructure Evolve in Three Dimensions"
The microstructure-properties link is at the core of the materials science and engineering paradigm. Understanding the factors controlling the formation of microstructure in an engineering material has been hampered by the inability to record the evolution of a microstructure as a function of time. With the advent of high-energy x-ray sources it is now possible to follow microstructural evolution in three dimensions and as a function of time (4D). The ability to observe and quantify the evolution of a microstructure provides fundamentally new insights into this complex process. This is especially true of those microstructures that are produced during solidification. 4D x-ray tomography provides new insights into dendritic growth in technologically relevant metallic alloys, and shows the importance of crystal defects in the growth of Si particles from Al-Si melts. The big-data challenge associated with these experiments, and the important role of computer simulation will also be discussed.
The Voorhees research group is focused on the kinetics of phase transformations using experiment, simulation, and theory. These phase transformations range from the growth of nanowires from the vapor and graphene, to the solidification of alloys. We measure the evolution of interfacial morphology during phase transformations using techniques such as time resolved three-dimensional X-ray tomography and automated serial sectioning. Our recent studies on simulations of phase transformations include work on a method to follow the atomic structure of a material on diffusional time scales and the growth of oxides on metal surfaces. We also combine the experiments with simulations by using the measured three-dimensional interfacial morphologies as initial conditions in simulations and then comparing the results of the simulations and experiment at some later time. Through our involvement in Northwestern’s Center for Hierarchical Materials Design, we use these models to design materials with novel properties, such as Si-based insitu composite materials.