Previous studies on magnesium single crystals of various crystallographic orientations have deepened the understanding of the deformation mechanisms and the recrystallization behavior of magnesium. The aim of this work was to extend the investigations to bicrystals to study the effect of grain boundaries on deformation behavior. For this purpose, bicrystals with specific grain boundaries were grown using the Bridgman method. In the current experiment deformation specimens were machined from the bicrystal containing 90° ⟨10-10⟩ symmetric tilt boundary and subjected to plane strain compression in a channel-die at room temperature. To investigate the microstructure evolution as a function of strain, the samples were deformed up to selected strains, and examined using optical and electron microscopy, as well as x-ray diffraction (XRD) for macrotexture measurements.
Owing to their initial orientation, the grains of the investigated bicrystal were deformed by simple basal <a> slip. This resulted in the rotation of the c-axes in both grains in opposite directions and created an orientation gradient in the deformed grains. This gradient became larger with decreasing distance to the grain boundary and by increasing deformation strain. The disorientation angle of the grain boundary changed from 90° to 40° at a true strain of -1, which indicates a dramatic change of the grain boundary character by absorption of dislocations. In addition, cracks could be observed at a true strain of -0.4 at the grain boundary, which however did not lead to mechanical failure of the specimen.