Mechanisms of Cold Deformation under High Pressure of Superconductive MgB2 Ceramics

Structures of the massive MgB 2 samples deformed in Bridgman anvils that were initially in different structural states, namely, as-synthesized and post-four-stage-treated (via deformation + annealing), have been studied by methods of the X-ray diffraction, scanning and transmission electron microscopy, and measurements of microhardness. The process of the deformation of brittle ceramic samples of MgB 2 under high pressure has been discussed. An analysis of the obtained data has shown that the plastic deformation of the superconductor MgB 2 preliminarily compacted by a four-stage treatment has been implemented in the main through the mutual rotation of crystallites (grains) and by grain-boundary sliding without a noticeable refinement of the grain structure.