Recovery behaviour after stress reductions during the steady state creep of Al-14wt.%Zn

Abstract

Stress reduction tests were carried out during the steady state creep of Al-14wt.%Zn under different constant applied stresses σ app reduced in steps of (0.3-0.1) σ app to determine the internal stress σ in, the flow stress σ flow(= σ app − σ in) and the density ϱ is of mobile dislocations under a steady state strain rate at the dissolution temperatures of Guinier-Preston (GP) zones and β phase. After a small stress reduction, the internal stress σ in and the dislocation density ϱ i in the subgrain interior were found to decrease rapidly to a minimum value at the dissolution temperatures of GP zones and β phase, while the steady state strain rate ϵ dot st , the flow stress σ flow and the density ϱ is of mobile dislocations were found to increase to a peak value at these dissolution temperatures. The results support the concept that the dynamic recovery behaviour of mobile dislocations and the flow stress which drives these dislocations are strongly dependent on the applied and internal stresses during the dissolution of GP zones and β phase.