It was recalled that, when low-temperature deformation was governed by dislocation motion, the grain boundaries (which acted as obstacles to slip) affected the distribution and density of dislocations. The stored energy of cold work, which was a function of the dislocation density was also affected by the grain size. It was noted that the increase in stored energy with increasing strain fell into 3 distinct regimes. The total stored energy could be divided into 2 components. These were the stored energy that arose from statistically-stored dislocation, which increased with increasing strain, and the stored energy which arose from geometrically necessary dislocations and which increased sharply to a strain of about 10% before saturating. The saturation value of the stored energy that arose from geometrically necessary dislocations was inversely proportional to the grain size.

D.Mandal, I.Baker: Scripta Metallurgica et Materialia, 1995, 33[5], 831-6