Strain-hardening rates during the primary stage in high-temperature creep of aluminum

Abstract

The strain-hardening rate, which is not affected by recovery, has been determined during the primary stage of high-temperature creep in polycrystalline aluminum at 600 K under 5 MPa. The strain-hardening rate H 0.4 was evaluated as a function of strain from the instantaneous plastic strain upon the sudden stress change of 0.4 MPa. At the very beginning of deformation H 0.4 is small, but it increases rapidly with strain and reaches to the steady value at around 0.05 strain, which is only about the initial 20% of the primary stage strain or occurs during less than the initial 10% of the primary creep period. The strain rate in creep of pure metals changes according to the change in the recovery rate during most period of the primary stage. The change in the hardening rate affects the change in creep rate only in the very beginning of deformation.