  This paper unravels micromechanical aspects of metallic materials whose
microstructure comprises grains of two or more phases. The local plastic
response is determined by (i) the relative misorientation of the slip systems
of individual grains, and (ii) the different mechanical properties of the
phases. The relative importance of these two mechanisms at the meso-scale is
unclear: is the plastic response dominated by the grain's anisotropy, or is
this effect overwhelmed by the mechanical contrast between the two phases? The
answer impacts the modeling of such a material at the meso-scale, but also
gives insights in the resulting fracture mechanisms at that length-scale. Until
now, this question has been addressed only for particular crystallographies and
mechanical properties. In contrast, this paper studies the issue systematically
using a large set of phase distributions, crystallographies, and material
parameters. It is found that the macroscopic and the mesoscopic
(grain-averaged) plastic response of the two extreme modeling choices (crystal
plasticity or isotropic plasticity) converge with increasing phase contrast.
The effect of the crystallography is completely overwhelmed by the phase
contrast when the yield stress of the hard phase is a factor of four higher
compared to the soft phase. When this ratio is lower than two, its influence
may not be neglected. However, even in this regime, fracture initiation is
controlled by the local arrangement of the phases. The latter is quantified in
this paper through the average arrangement of the phases around fracture
initiation sites.
