Abstract Scope |
In situ characterization of grain boundary tensile strain indicates that disconnection nucleation is rate limiting up to high local stresses, typically >100 MPa. To explain polycrystalline GB creep, which occurs at lower applied stresses, a stress concentration term was adapted from prior literature and demonstrated to predict creep response well. Metal-oxides represent an interesting test of the physical model because climb mediating disconnections should be unfavorable in the interface relative to lattice dislocations. Indeed, bicrystal strain experiments indicate that interfacial sliding is facile, but axial strain is not observed under any testing conditions; instead all plasticity localizes in the metal lattice at all temperatures. The results generally support the hypothesis that nucleation of climb mediating disconnections is an important pre-requisite to tensile creep. |