Yield Loci Calculation of Hexagonal Materials Using a Selfconsistent Polycrystalline Model

Polycrystalline models are used for the calculation of the yield loci of hcp aggregates with different crystallographic textures. Predictions are made using both a classical Taylor Full Constraints (FC) approach and a viscoplastic selfconsistent (VPSC) formulation. Typical deformation modes for low and high temperature are assumed to be active. The vertex configuration of the Single Crystal Yield Surface (SCYS) and the relative activity of different deformation modes as a function of the applied stress are also presented and discussed. For low temperature, when twinning is active, a non centro-symmetric behavior is observed in textured polycrystals along the direction of the -axis texture component. Such effect, associated with the directionality of twinning, is well reproduced by the VPSC model. For high temperature, the predicted yield loci are centro-symmetrical but also strongly dependent on the texture of the aggregate.