Work-hardening rates during the high temperature creep of aluminium determined from the instantaneous strain on sudden stress changes

Abstract

The work-hardening rates during the creep of polycrystalline aluminium were determined from instantaneous plastic strains in stress change tests in the temperature range 455–650 K under stresses for which the steady state creep rates lie within the range 5 × 10 −7 − 2 × 10 −5 s −1. The true work-hardening rates h were estimated by extrapolating the apparent values which were determined from the instantaneous plastic strains occurring during about 0.02 s after the stress increases ranging from 0.1 to 1 MPa. The values of h are of the order of Young's modulus and depend markedly on temperature and stress. The need not only to improve the existing theories of recovery creep but also to extend the present fine structure observations is suggested.