1005813 Averback

1. Self-organization during severe plastic deformationRobert Averback, University of Illinois at Urbana-Champaign, DMR 1005813 • Processing nanostructured materials from a top-down approach is fundamental to developing new high-strength structural materials. Here we show that by using severe plastic deformation, for example by ball mill, accumulative roll bonding, etc., immiscible alloys will self-organize into nanocomposites. The key findings are: • Shear mixing is superdiffusive, which means that the relative motion of atoms depends on their distance apart. • When combined with thermal diffusion, the two different dynamics result in self-organization. • We offer a theory that predicts the length scale of the phase separation. It shows that the length scale can be pre-selected by varying the ratio of the shearing rate to the thermal diffusion rate. • Computer simulation, shown at right, confirms this theory. • These findings will lead to new top-down schemes for processing, bulk nanocrystalline composite materials with unique properties. KMC simulation of a steady state microstructure of a 50:50 binary alloy with positive heat of mixing. The underlying graph shows the correspondence between these observed length scales (y axis) and the microstructural length scales predicted by our new model

2. Self-organization during severe plastic deformationRobert Averback, University of Illinois at Urbana-Champaign, DMR 1005813 • Computational materials science has become an integral part of materials research and indeed critical to this DMR project. We are implementing this technology into our traditional course on “Introduction to Thermodynamics.” The program has two primary goals: • Provide a deeper understanding of the concepts of classical thermodynamics by relating abstract macroscopic variables to an atomistic description of materials processes. • Develop interest amongst undergraduate students in an increasingly important tool in materials research and technology. • The programs leverage modern HTML5 technologies to deliver a plugin free cross-platform experience. The simulations are implemented in Javascript and the codes use the same design principles employed in modern production MD codes. The source code, which is heavily documented, is available to all students. A visual molecular dynamics simulation was developed to accompany an undergraduate thermodynamics course. The students perform simple experiments exploring ideal gasses and Lennard-Jones systems: heat of formation, heat capacities and phase equilibria are a few examples. Atoms are visualized using hardware accelerated WebGL in the browser and can be rotated and inspected from any direction.