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Lowering temperature below the equilibrium solidification temperature nucleation occurs more readily

Lowering temperature below the equilibrium solidification temperature nucleation occurs more readily

Lowering temperature below the equilibrium solidification temperature nucleation occurs more readily

(OP)
In the book science and engineering of William Callister in the pages 315 an 316 at the final paragraph the book says that the critical radius r* and the Gibbs free energy G* are decreasing functions of temperature, the higher the temperature the lower the critical radius r* and the Gibbs free energy G*. After that the book mention a plot that has two profiles of Gibbs free energy G* Vs critical radius r* corresponding of two different temperatures T1 & T2 in which T2>T1, the profile of temperature T1 looks displayed to the right because of r* and G* are greater for lower T1. After this the book says “ lowering the temperature at temperatures below the equilibrium solidifiaction temperature (Tm) nucleation occurs more readily” and I don’t understand and find the connection of this part with the other parts of this parragraph.

RE: Lowering temperature below the equilibrium solidification temperature nucleation occurs more readily

Read books by Flemings , and by Winegard. You will get a clear understanding of nucleation and growth phenomenon. You will also get to understand undercooling effect, about which you are asking.

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RE: Lowering temperature below the equilibrium solidification temperature nucleation occurs more readily

I am not able to see your link to comment on the figures that you have noted. That said, the plot of G vs r is typically used just to show the inflection point noted as r* where the precipitate becomes energetically stable, and any increase in r will result in a lowering of the total free energy. Lowering the temperature drives the chemical free energy term. Chemical energy is a volumetric term and will vary with the cube of r while interfacial and strain energy are surface terms and vary with the square of r, so unless the surface terms are significantly effected a lower temperature will give finer and faster precipitation in general.

It sounds like possibly the figure you are referring to is mislabeled but I cannot see to verify.

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