Mechanically Alloyed Oxide Dispersion Strengthened Metals

Atom probe image of MA957

MA956 Chou & Bhadeshia, 1994

MA956 Chou & Bhadeshia, 1994

o o A B A B 1-x Gibbs free energy per mole Concentration x of B   free energy of mechanical mixture G* x Mechanical Mixture

o o A B A B x Gibbs free energy per mole Composition   G{x} free energy of mechanical mixture ∆G M free energy of solution G*

+=

For a random mixture, number of configurations given by:

Boltzmann

Classical theory for entropy of mixing

Solution-like behaviour when particles about 1000 atoms in size Free energy of mixing due to configurational entropy alone

Enthalpy

Surface per unit volume SvSv Particle size Solution formation impossible!

coherent incoherent

Single barrier to solution formation when components attract Badmos and Bhadeshia, 1997

Double barrier to solution formation when components immiscible Badmos and Bhadeshia, 1997

o o A B A B Composition   free energy of solution

o o A B A B Gibbs free energy per mole   Concentration x of B Paradox at concentration extremities vanishes in the discrete model of concentration