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Solidification Kinetics

  Growth Velocity     6 of 7

If growth is continuous (all adsorption sites equivalent), then a simple model can be used to relate growth velocity to undercooling. (During lateral growth, the velocity is expected to be slower, for a given undercooling, because there are fewer adsorption sites.)
An adsorption event is assumed to be similar to a normal diffusive jump in the liquid.

have_a_go.gif (3415 bytes)This is simulated schematically. When "Adsorb Molecule" is clicked. The advance velocity from adsorption events can be written as the product of jump distance, l*, vibration frequency, w0, and the probability of making a diffusive jump   v_adseq.gif (1582 bytes) Account must also be taken of desorption events. These are less frequent (if the interface is undercooled) because of the larger energy barrier

v_deseq.gif (1785 bytes)


  Kinetics | Redistribution | Cell, dendrite and grain structure | Eutectic

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