Crystal plasticity and in-situ diffraction-based determination of the dislocation strengthening and load-sharing effects of precipitates in Mg alloy, AZ91

The elasto-viscoplastic self-consistent (EVPSC) polycrystal modeling approach is employed to describe in-situ diffraction tests conducted on textured, as-rolled (non-aged) and aged Mg alloy, AZ91, plate material. The yield strength differential between rolling direction compression (RDc) and normal direction tension (NDt) is well described by the model, indicating that differences are solely related to texture, and not due to any more exotic latent hardening phenomenon. Second phase precipitates induced by aging result in an increase in the critical resolved shear stresses (CRSSes) of basal dislocation slip and {10.2} extension twinning of ∼15 MPa. The precipitates also induce a small, separate increment in the nominal strength of ∼5 MPa, due to load sharing. Confidence in this predicted load sharing effect is provided by the fact that the internal strains within the second phase particles are well-predicted by the model.