Deformation twin interactions with grain boundary particles in multi-phase magnesium alloys

Deformation twinning is necessary for achieving strain in plastically hard directions in magnesium alloys under ambient conditions, but can also contribute to void formation and crack propagation that lead to early failure. This is especially true for instances of twin transmission between grains, which result in longer continuous twin boundaries and higher twin volume fractions. Coarse grain boundary particles have the potential to modify twinning behavior, but this effect has not been studied. This work uses a Crystal Plasticity – Fast Fourier Transform model to predict twinning behavior and transmission likelihood, parameterized to simulate different morphologies of the β-phase intermetallic common to Mg-Al alloys. Of these microstructures, those with particles directly in the path of impingement were found to decrease the stresses generated in the neighboring grain, similarly decreasing the likelihood of twin transmission across the boundary. Size and aspect ratio were found to play key roles in determining the resultant stress, but are dependent upon the orientation of the neighboring grain. Particles located near the impingement site were found to exacerbate the stress state and make transmission more likely. Instances where transmission was likely to be prevented were also predicted to undergo reduced twin thickening.