Rate of diffusion creep accompanied by grain boundary sliding in elongated microstructures

The instantaneous creep rate is evaluated for various two-dimensional elongated microstructures, when deformation occurs by grain boundary diffusion accompanied by grain boundary sliding. The strain contributions of grain boundary diffusion and grain boundary sliding are evaluated separatively, and the total creep rate is obtained as a sum of the two. The analysis for the diffusion on elliptical grain shows an increasing creep rate with grain elongation, while the creep rate for hexagonal microstructures increases or decreases depending on grain orientation. It is shown that the instantaneous creep rate calculated for hexagonal microstructures is reasonably consistent with the reported values in a steady state. The instantaneous creep rate in a polycrystal decreases with grain elongation, but the decrement is small enough to allow the application of the original constitutive equation to diffusion creep without significant modification.