A consideration of mobile dislocation density

Abstract

From the assumption that the yield stress consists of two components and that the mobile dislocation density can vary, it was possible to determine the mobile dislocation density as a function of effective stress or temperature. The results indicate that for Fe the internal stress does not decrease simply, instead it first increases and then decreases, with increasing temperature. In general, the activation parameters were only slightly affected by a variable mobile dislocation density. However, the present results indicate that the dislocation density of Mg is 10/sup 5/ less than that for Fe, which is in agreement with experimental observations. It is proposed that this difference in the density could be the reason for the smaller pre-exponentials for mg as compared to Fe. Present results also indicate that the density of mobile dislocations at macroyielding is independent of the initial dislocation density. Data obtained by Young indicates that the initial dislocation density may vary from 10/sup 2/ to 10/sup 6//cm/sup 2/, but the density at macroyield was /sub approx./10/sup 6//cm/sup 2/ in all cases.