Taylor hardening in five-power-law creep of metals and Class M alloys

Previous work on aluminum and stainless steel show that the density of dislocations within the subgrain interior (or the network dislocations) are associated with the rate-controlling process for five-power-law creep-plasticity. Furthermore, the hardening in stainless stress is shown to be consistent with the Taylor relation if a linear superposition of lattice hardening (tau(o), or the stress necessary to cause dislocation motion in the absence of a dislocation substructure) and the dislocation hardening (alphaMGbrho(1/2)) is assumed. It is now shown that the same relationship appears valid for aluminum with the same values of alpha observed in other metals, where dislocation hardening is established. It appears that the constant, alpha, is temperature independent and, thus, the dislocation hardening is athermal. It is also shown that constant-stress creep behavior, where the total interior dislocation density decreases during primary (hardening stage) creep, is consistent with Taylor hardening. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.