Nanoscale Order in Metallic Glass

1. Nanoscale Order in Metallic Glass Paul M. Voyles, University of Wisconsin- Madison , DMR 0347746 Primary Al crystallization in Al-based metallic glasses offers a unique window into nucleation and crystallization. We have previously used fluctuation electron microscopy, a novel technique for measuring order in glasses, to show that rapidly quenched Al-glass contains crystal nuclei frozen into the structure [1], offering a snapshot of the earliest stages of nucleation. Annealing after quenching allows those nuclei to grow, but only to ~10 nm in diameter before out-diffusion of the rare-earth component limits growth. We have now shown that substituting 1 at.% Cu for Fe in Al88Y7Fe5 changes both the distribution of quenched in nuclei and the resulting crystallized microstructure. Adding Cu increases the number density of nuclei at approximately the same size. After annealing, this results in an increase in the number density of crystals and a reduction in their size. This required developing a new model of the fluctuation microscopy signal for this system, and represents a complete structural understanding of a new microstructure control path. [1] W. G. Stratton et al. APL 86, 141910 (2005). As-quenched:Adding Cudecreases V(k), a measure of the nanometer-scale spatial heterogeneity by increasing the number density of quenched-in nuclei. Crystallized: Adding Cu increases the number density and decreases the size of nanocrystals.

2. Nanoscale Order in Metallic Glass Paul M. Voyles, U. Wisconsin, DMR 0347746 Training the Nanotechnology Workforce To support education in advanced microscopy techniques using TEM and STEM, Voyles has created the Electron Microscopy Database (EMdb), a web clearinghouse for high-quality educational examples. Most teaching examples come from research, and not every teacher has the ongoing research to provide good examples for every technique. EMdb is a way for teachers to exchange examples, including possible exercises, and a way for researchers to leverage their unpublished results for impact in the classroom. Since its announcement at the meeting Microscopy and Microanalysis Aug 5-8, 2007, over 200 users have registered to access EMdb, and three research groups have submitted examples for dissemination.