EFFECT OF GRAIN-SIZE, PARTICLE-SIZE AND GAMMA'-VOLUME FRACTION ON STRAIN RELAXATION IN NI-CR BASE ALLOYS

Anelastic strain has been measured using the stress drop technique on experimental NiCr base alloys hardened by different γ′ precipitate volume fractions over a range of stress. The test temperature was usually 800 °C. The dependence of anelastic strain on grain size, particle size and γ′ volume fraction at different stresses and temperatures has been studied. Grain size strongly affects the total relaxed strain and the slow-stage strain rate, but it seems to have little influence on the fast-stage strain rate. The precipitate volume fraction and particle size influence the relaxed strain rate of the slow stage but do not affect the total relaxed strain. The anelastic relaxation can be separated into a fast and a slow stage; a model based on different deformation mechanisms, which permits measurements of mobile dislocation fractions, has been proposed to explain the two stages. © 1979.