Prediction of the cyclic stress–strain curve of polycrystalline nickel

Abstract

The cyclic stress–strain curve (CSSC) of polycrystalline nickel is predicted in the framework of Taylor type models. Particular attention is paid to a modified Taylor model (MTM) which takes into account recent experimental findings: (i) the dislocation patterns in the individual grains are essentially determined by the axial grain orientation, (ii) the observed structures resemble the dislocation patterns formed in single crystals with corresponding axial orientations. The proposed MTM uses the CSSCs of [001], [ 1 ̄ 11] and [011] monocrystals and the CSSC of crystals oriented for single slip as hardening relations. In a more elaborated MTM more than four hardening laws are taken into account. For comparison a self-consistent Sachs model is considered which treats each individual grain as an inclusion in a homogeneously deformed matrix. The more detailed MTM is shown to provide the best agreement between the predicted and measured polycrystal CSSC.