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 ε_s on applied stress ε obeys a power law of the form ε_s ∝ σ^4.8 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.