David Turnbull (1915-2007). Pioneer of the kinetics of phase transformations in condensed matter
Entry by Emily Redston, AP 225, Fall 2011
Work in progress
David Turnbull (1915-2007). Pioneer of the kinetics of phase transformations in condensed matter by F. Spaepen and M.J. Aziz, Nature Materials 6: 556 (2007).
We have frequently discussed the importance of phase diagrams in class. However, while these equilibrium diagrams are undeniably useful in themselves, it is oftentimes important to think about the effect of the kinetics of the system. David Turnbull (after whom McKay 402 is named) is one in a line of distinguished physical chemists, going back to J. W. Gibbs, who have profoundly influenced materials science. His work laid the basis of our understanding of the kinetics of phase transformations in condensed matter. In particular, he made seminal contribution to solidification theory and glass formation.He also made key contributions to grain-boundary diffusion, fast diffusion of noble metals in semiconductors and polyvalent metals, crystal growth, grain growth and recrystallization.
At the 1948 dinner meeting of the Science of Metals Club, Turnbull told his audience that he had undercooled liquid mercury several tens of degrees below its thermodynamic crystallization temperature by dispersing it into small droplets. At the end of the talk he speculated that, if similarly treated, not just mercury, but also metals that crystallized into simpler structures would exhibit such large liquid undercoolings. Nonetheless, David Harker's challenge to David Turnbull, his colleague at the General Electric Research Laboratory, was clear: "If you can undercool molten copper by more than a few degrees, I'll eat my hat!". After the meeting, Turnbull quickly showed with a hot-stage microscope that small droplets of copper, silver, gold and many other metals could be cooled to temperatures far below their crystallization points. Harker graciously accepted the results: he appeared at the next meeting with a hat made of Swiss cheese.