Dynamic recovery during and after steady state deformation of Al-11wt%Zn

Abstract

Cylindrical specimens of Al-11wt%Zn were deformed at constant stress and at 523 K in tensile creep tests. The stress dependence of the steady state deformation rate ge s , was determined from stress change tests, ge s shows an exponential stress dependence in the stress range above 10 MPa. The steady state values of the dislocation density in the subgrain interior ( ρ i ) and of the subgrain size were determined by means of transmission electron microscopy. The fundamental equation of steady state deformation ge s = ( b M) Agr − was tested by independent measurement of ge s and gr −. A is of the order of the subgrain size. gr − was determined from the recovery behavior of the dislocation density immediately after steady state deformation. The shape of the recovery curves did not depend on type and amount of stress reduction but was strongly dependent on ge s . These results were confirmed by measurements of the transient creep behavior after reloading the specimens with the initial load. For the exact determination of gr − an interpolation method was used, which is based on the decrease of ρ i during stress relaxation. The shape of the recovery curves and the stress dependence of ge s . A and gr − suggest that recovery during and immediately after steady state deformation is of dynamic nature.