Grain size and grain boundary diffusion

krahl

Hi all,

I was wondering if anyone knows of any literature that explains why larger grains "absorb" smaller grains during cross-boundary diffusion in solid state diffusion. I read a book that explains it analogously in terms of pressure differences and boundary tension but I'm not quite happy with that explanation.

Thanks

qazxswedc

Assuming the concentration of solute is constant in the solid solution, the growing of one grain is at the expense of the other grain. This is to reduce the surface energy of the whole system because in equilibrium, a system will choose to 'react' in a way to minimize its free energy. The total interfacial area of large, fewer particles will be smaller than total interfacial area in the system with many small particles. Note that interfacial energy will increase the free energy of the system hence it is preferable to have smallest interfacial energy as possible.

streeters

Yeah, minimising the total free energy is what drives this.

Look at Ostwald Ripening for literature on this.