Dislocation-defect analysis during micro-indentation using displacement rate changes

Micro-indentation with step-ramp displacement rate changes has been developed to nullify the machine and specimen compliance and to directly measure the apparent activation work, Delta w', of the deforming material. The Cottrell-Stokes relation is obeyed for an eutectic solder, but in contrast, nominally pure Al in the annealed and pre-rolled states indicate that the type of obstacle barrier continuously changes as a function of strain rate. Thus it is deduced that for high homologous temperature testing, either dislocation-dislocation interactions or jog dragging are detected, whereas at lower temperatures other defects are generated especially when the total plastic volume under the indenter is minute. These results can be correlated to the evolution of debris at high strains detected by tensile tests. (C) 1997 Elsevier Science S.A.