Julie Lévesque

Small-angle X-ray scattering investigation of deformation-induced nanovoids in AA6063 aluminium alloy

Abstract Small-angle X-ray scattering studies of microstructure in metallic systems are prone to contamination by double Bragg scattering from the crystalline matrix. This is particularly problematic to the study of fracture in ductile metals via the nucleation and growth of nanovoids in response to plastic deformation. We show clear evidence of the presence of these scattering artefacts in the scattering data from representative Al systems and describe a simple method of numerically isolating and removing potentially misleading information to reveal the true small angle scattering response of the sample. This data correction process is used to obtain quantitative measurements of the nanovoid volume fraction in deformed AA6063. The SAXS results yield values comparable to existing predictions of the total vacancy volume fraction obtained from the mechanical stress–strain data.

Numerical Modelling of Large Strain Deformation in Magnesium

In this paper, a new constitutive framework based on a rate-dependent crystal plasticity theory is presented to simulate large strain deformation phenomena in HCP metals such as magnesium. In this new model the principal deformation mechanisms considered are crystallographic slip and deformation twinning. The new framework is incorporated into in-house finite element (FE) codes. Simulations of uniaxial tension and compression for the magnesium alloy AM30 are performed and the results are compared with experimental observations of the specimens deformed at 200°C. Limitations of the current modelling approaches are also discussed.

Large Strain Behaviour of ZEK100 Magnesium Alloy at Various Strain Rates

A constitutive framework based on a rate-dependent crystal plasticity theory is employed to simulate large strain deformation in hexagonal closed-packed metals that deform by slip and twinning. The model allows the twinned zones and the parent matrix to rotate independently. ZEK100 magnesium alloy sheets which significant texture weakening compared to AZ31 sheets are investigated using the model. There is considerable in-plane anisotropy and tension compression asymmetry in the flow behavior of ZEK100. Simulations of uniaxial tension in different directions at various strain rates and the accompanying texture evolution are performed and they are in very good agreement with experimental measurements. The effect of strain rate on the activation of the various slip systems and twinning show that differences in the strain rate dependence of yield stress and Rvalues in ZEK100 have their origin in the activation of different deformation mechanisms.