1- Diffusion
2- Corrosion
3- decrease of dislocation
4- increase of vacancy
5-Phase Transformation
6- precipitation or resolved precipitation
7- Oxidation
1. Concentration gradient, and energy to break current bond + energy to move from one position to the next.
2. Electrochemical potential, and activation energy of the chemical reaction involved (for diffusion-limited corrosion, see 1).
3. Higher stability of undislocated material (less stress), and energy to move dislocations.
4. More energy available to form vacancies, and greater contribution of entropy to free energy favouring more vacancies as these give more disorder. Ea is still Ea to form vacancy, though this may be decreased by entropy.
5. What transformation? There are many
6. Decrease of chemical potential when going from solute to precipitate. Ea is either that of diffusion or that of nucleiation.
7. Concentration of oxidising species, or more accurately their chemical potential. Ea is that of oxidation reaction, or that of diffusion depending on which is limiting.
All of this though can be found in textbooks. I'd recommend you look there and/or add to this question which particular material system you're interested in.
Porter and Easterling for 1,5,6
Mechanical Metallurgy by Dieter for 3.
You'll need to google the others yourself. Also wikipedia is a good start.
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