XIII. Point defects and the release of energy from deformed nickel

Abstract

Summary A plastically deformed specimen of nickel is assumed to consist of an assembly of spherical ‘grains’ each of which contains a uniform distribution of point defects. On this model, a calculation is made of the rate of evolution of energy when such a specimen is heated at a uniform rate. The result is compared with experimental data given by Clarebrough, Hargreaves and West and it is shown that the model adequately explains a part of the evolution of energy at low temperatures. The activation energy for migration of the defects is calculated to be 1·0 ev (23 kcal/mole). It is suggested that the defects are probably vacancies but the possibilities that they are interstitials or vacancy pairs are not excluded. On the vacancy hypothesis, the energy stored per vacancy is about 1·6 ev and the size of the ‘grains’ is of the same order as the size of the particles described by Gay and Kelly.