Grain size, stress and creep in polycrystalline solids

Abstract

If a stress sigma is applied to a polycrystal of grain size L, the mode of creep deformation depends on the answers to the following questions: (i) Does sigma exceed the Peierls stress sigma (p); (ii) Does L exceed the dislocation spacing in a Taylor lattice stabilized by sigma (p); (iii) Does Lo exceed the value required for a Frank-Read or Bardeen-Herring source to operate within the grain? (iv) Does L (1/2) sigma exceed the Hall-Petch value required for slip to propagate across a grain boundary? The (L, sigma) plane is thus partitioned into regions in which different creep modes predominate.