Atomic mechanisms controlling crystallization behaviour in metals at deep undercoolingsY. Ashkenazy1 and R. S. Averback2
1 Racah Institute of Physics, The Hebrew University of Jerusalem, E.J. Safra Campus - Jerusalem 91904, Israel
2 Department of Materials Science and Engineering, University of Illinois at Urbana Champaign Urbana, IL 61801, USA
received 19 February 2007; accepted in final form 5 June 2007; published July 2007
published online 5 July 2007
Understanding the liquid-solid phase transition has long been of scientific interest, owing to its singular importance in the processing of materials with desired microstructures. Presently, however, little is known about the atomic mechanisms controlling this process. Using molecular dynamics simulations, we find a surprising connection between the crystallization behavior of metals at extreme undercoolings and the properties of interstitial atoms in the crystalline phase. We show first that the activation energy of crystallization in a number of metals at the kinetically controlled regime is precisely the same as the migration energy of self-interstitials atom in the crystalline state. We then show, contrary to the present thought, that the advance of a planar solid-liquid interface in Fe at low temperatures is controlled by thermally activated jumps of a small fraction of the atoms on the liquid side of the interface, and remarkably these atoms have the same dumbbell interstitialcy structure as observed for interstitials in crystalline Fe.
64.70.Dv - Solid-liquid transitions.
68.08.-p - Liquid-solid interfaces.
81.10.-h - Methods of crystal growth; physics of crystal growth.
© Europhysics Letters Association 2007