Microstructure morphology of shock-induced melt and rapid resolidification in bismuth

With the growing importance of nanotechnology, there is increased emphasis on rapid solidification processing to produce materials microstructures with a finer length scale. However, few studies have focused on the question of how a material restructures itself on the microstructural scale when it refreezes at very high cooling rates. Here we report on the development of microstructures in pure bismuth metal as it is subjected to rapid shock-driven melting and subsequent resolidification (on release of pressure), where the estimated effective undercooling rates are on the order of 10(10) K/s, orders of magnitude faster than any achieved before in bulk material. Microscopic examination of the recovered material indicates that the melting transformation was far from homogeneous, and substantial morphological changes are observed compared to the starting microstructure. (c) 2007 American Institute of Physics.