Lattice-Diffusion Creep Mechanism Not Based on Stress Heterogeneity

摘要

In has been deduced that there is a serious problem in the assumption of the vacancy concentration gradient based on the stress heterogeneity in the Nabarro-Herring mechanism for lattice-diffusion creep. A new lattice-diffusion creep mechanism which is not dependent on the diffusion mechanism and hence is nt based on the vacancy concentration gradient has been Based on this new mechanism, the correlation of the strain rate with applied stress, atomic volume, diffusivity, grian size and temperature has been described as an equation, in the case of uniaxial tensile creep on a cube-shaped grain. The resultant equation was identical with that in Nabarro-Herring mechanism except the sactor that deends on the shape of the grain. In the new mechanism, the diffusion was presumed to be caused by a force which appliesw each atom in the grain in the direction perpendicular to the tensile axis. This force was thought to arise to keep the grain volume constant during the plastic deformation. Another mechanism proposed by Kimura has been referred to. Both Kimura's and the authors' mechanisms have been considered to be more plausible than the Nabarro-Herring mechanism in that they are not based on stress heterogeneity, lathough modification by a further study is needed to correlate the elementary processof diffusion, i.e., vacancy mechamism.