Friction-stress measurements during high-temperature creep of polycrystalline copper

Abstract

A description is given of the high-precision equipment developed to examine the tensile creep behaviour of polycrystalline copper at 686 K. When the dependence of the steady-state creep rate εs on applied stress ε obeys a power law of the form εs ∝ σ4.8 definitive values of the friction stress σ0 can be obtained which allow the creep behaviour to be described as ε ∝ (σ−σ0)4. The σ0 values, measured by making consecutive small stress reductions during creep, appear to characterize the long-range back-stresses associated with the dislocation substructures developed under various creep conditions. The deformation behaviour can then be explained in terms of slip resulting from the operation of dislocation sources developed by recovery-controlled growth and rearrangement of the 3-dimensional dislocation network present.