New approach to creep of pure metals with special reference to polycrystalline copper

Abstract

A new approach to creep, termed the θ-projection concept, is illustrated by reference to high-precision data obtained for polycrystalline copper. Over wide ranges of stress and temperature, the increase in creep strain ε_c with time t can be described precisely using the equation ε_c=θ₁[1−exp(−θ₂t]+θ₃[exp(θ₄t)−1] where θ₁ and θ₃ define the extent of the primary and tertiary stages with respect to strain and θ₂ and θ₄ quantify the curvatures of the primary and tertiary stages of creep respectively. Once the stress and temperature dependences of the four θ-parameters and the creep ductility are evaluated, the complex stress and temperature dependences of the minimum creep rate and the rupture life, as well as the exact form of the deformation mechanism map expected for polycrystalline copper, can be predicted directly without invoking any change in creep mechanism.

MST/504