Characterizing Ti39.5Zr39.5Ni21 and Zr64Ni36 supercooled liquids with classical nucleation theory

Mark Sellers, Department of Physics, Washington University
February 9, 2018 at 4:00 pm
204 Crow
Event Description 

Classical nucleation theory describes the formation of post-critical clusters, as seen in the condensation of vapors, the crystallization of liquids, or the phase separation of an alloy. In the 1950s, David Turnbull demonstrated that liquid mercury can be supercooled by over 25% of its melting point before crystallizing—a feat deemed impossible at the time as impurities catalyze nucleation easily in metallic liquids. Since then, supercooling has been shown to be a common property of all liquids. By applying electrostatic levitation techniques and making samples out of high-purity stock, catalysts for nucleation are minimized and large supercoolings can be observed. In this talk, supercooling experiments on two different alloys, Ti39.5Zr39.5Ni21 and Zr64Ni36, will be presented. Using classical nucleation theory and a statistical analysis method developed by Skripov, these supercoolings will be analyzed to extract estimates for the work of cluster formation W* and nucleation rate A*. Typical values range from 30-60kT for W* and 1029-1039 (m3s)-1 for A*. These studies form the basis for future studies exploring the effects of gravitational convection on nucleation and the role of chemical ordering and structure. Experimental challenges will also be detailed.