The mechanical properties of grain boundaries and the development of grain-boundary sliding were studied in pure Zn using precision micro-indentation technique, optical, electron and atomic-force microscopy. Results had shown the different dependencies of the microhardness values upon the indentation depth for grain boundaries and individual grains. When the size of the plastic zone around the imprint was comparable to the grain size, grain boundaries acted as barriers for dislocation sliding bands and twins. With applying the higher load, more grains were involved in the process of deformation, but microhardness did not increase. That was explained by the activation of grain-boundary sliding, leading to the relaxation processes. In its turn, the microhardness values measured at low loads in the vicinity to grain boundaries and triple junctions were higher than those measured in the grain interior. Thus, movement of the ensemble of defects to the grain boundaries during micro-indentation was the activating factor for grain-boundary sliding in polycrystalline Zn. At the same time, during spreading of the deformation at low loads in the vicinity to grain boundaries the activation of grain-boundary sliding was not observed.

Micromechanical Properties of Grain Boundaries and Triple Junctions in Polycrystalline Metal Exhibiting Grain-Boundary Sliding at 293K. F.Muktepavela, G.Bakradze, V.Sursaeva: Journal of Materials Science, 2008, 43[11], 3848-54