Microstructure and grain boundary pattern in ultrafine-grained Ni processed by severe plastic deformation

An influence of intensive plastic deformation parameters on evolution of microstructure and grain boundary ensemble in ultrafine-grained Ni is investigated. The Ni specimens are prepared by equal-channel angular pressing, torsion under quasi-hydrostatic pressure, their combination and by electrodeposition. The microstructure variation process is followed with the help of electron microscopy. It is ascertained that the evolution of the grain boundary ensemble in the ultrafine-grained and nanocrystalline specimens occurs similar to process of multiple twinning observed in the fcc-materials with the low and medium energies of stacking faults.