Pure material, containing about 200pp[at]Fe in solution, was shown to creep about 106 times slower at 200C than did the same material when it contained a negligible amount of Fe in solution. A high creep resistance of the Al-200ppm[at]Fe alloy was attributed to the presence of sub-grain boundaries which contained Fe solute atoms. It was proposed that the opposing stress fields, arising from sub-grain boundaries and from piled-up dislocations during creep, were cyclically relaxed by Fe solute diffusion so as to allow climb of the lead dislocation in the pile-up. The mechanism was a form of mechanical ratcheting. The model correctly predicted that the creep rate was controlled by the rate of Fe solute diffusion, and by a temperature dependence that was equal to the activation energy (221kJ/mol) for Fe diffusion.

Solute-Diffusion Controlled Dislocation Creep in Pure Aluminium Containing 0.026at%Fe. O.D.Sherby, A.Goldberg, O.A.Ruano: Philosophical Magazine, 2004, 84[23], 2417-34