RECOVERY OF AlMg ALLOYS f FLOW STRESS AND STRAIN-HARDENING PROPERTIES

摘要

The recovery of Al--2.5 wt/100 Mg alloys cold-rolled to several strains between 0.l and 3 has been studied essentially using tensile tests. The yield stress and strain-hardening properties are studied as a func- tion of the initial prestrain, and of the temperature and the duration of annealing treatments. A theoretical model based on the dislocation structure is proposed. The kinetic evolution of the yield stress is related to the variation of the total dislocation density as a single structural parameter. The pseudo-logarithmic time decay is explained on the basis of a relaxation of the internal stresses by thermally activated dislocation motion. A strain-hardening model is proposed based on Kocks' constitutive law of plasticity, where the dislocation storage and dislocation annihilation parameters are adapted to a heterogeneous cell/subgrain dislocation structure. The adjustment of the model to the work-hardening behaviour is in agreement with TEM observations.