It was recalled that material which had been subjected to severe plastic deformation could have an average grain size of about 300nm, while the boundaries exhibited very high stress concentrations and extensive disorder. The mechanisms which operated during grain boundary relaxation were studied here. An analysis of hardness variations after various isothermal annealing treatments provided estimates of the apparent activation energy for the mechanism which controlled relaxation. Calorimetry revealed the amount of heat which was released during the relaxation of grain boundary stresses. Direct transmission electron microscopic observations showed that the released heat could be correlated with the energy that was stored in intergranular dislocations.

J.P.Monchoux, J.L.Derep, M.Sarfati: Annales de Chimie, 1996, 21[6-7], 503-13