Plastic deformation kinetics of electrodeposited Cu foil at low and intermediate homologous temperatures

The plastic deformation kinetics of electrodeposited (EP) Cu foil (grain size d=0.6 mum) were determined at 296-448 K and compared with those for vapor-deposited (V-P) foil (d=0.5 mum) tested at 77-473 K. The apparent activation volume v=kT partial derivative In (epsilon)over dot/partial derivativesigma for both materials exhibited a minimum at similar to350 K, and at this temperature, there occurred a marked increase in the temperature dependence of the flow stress sigma. The rate-controlling mechanism in both materials at T < 373 K appears to be grain boundary shear induced by dislocation pileups at the grain boundaries. The results at T = 373-473 K suggest that the dislocation pileups are relieved or prevented and that either cross slip or intersection of dislocations is rate controlling with stronger support for the latter. The determination of the rate-controlling mechanism at the higher temperatures is complicated by possible changes in defect structure due to thermal annealing, and therefore, the operative mechanism corresponds to a structure that may differ from the initial, as-deposited condition.