Effect of Misorientation on the Compression of Highly Anisotropic Single-Crystal Micropillars

The effect of crystal misorientation, geometrical tilt, and contact misalignment on the compression of highly anisotropic single crystal micropillars was assessed by means of crystal plasticity finite element simulations. The investigation was focused in single crystals with the NaCl structure, like MgO or LiF, which present a marked plastic anisotropy as a result of the large difference in the critical resolved shear stress between the soft {110}< 110 > and the hard {100}< 110 > active slip systems. It was found that contact misalignment led to a large reduction in the initial stiffness of the micropillar in crystals oriented in the soft and hard direction. The crystallographic tilt did not modify, however, the initial crystal stiffness. From the viewpoint of the plastic response, none of the effects analyzed led to significant differences in the flow stress when the single crystals were oriented along the soft [100] direction. Large differences were found, however, if the single crystal was oriented in the hard [111] direction as a result of the activation of the soft slip system. Numerical simulations were in very good agreement with experimental literature data.