SCIENTIFIC ORGANIZATION:
Saint-Petersburg State University, St. Petersburg, Russia; Institute of Problems in Mechanical Engineering, St. Petersburg, Russia; Saint-Petersburg State Polytechnical University, St. Petersburg, Russia; Ufa State Aviation Technical University, Ufa, Russia

REPORT FORM:
«Oral report»

AUTHOR(S)
OF THE REPORT:
I.A Ovid’ko, A.G. Sheinerman and R.Z. Valiev

TALKING POINTS:

We consider the models describing the mechanical behavior of nanocrystalline and ultrafine-grained materials at high applied stresses. Within the models the effects of various mechanisms of plastic deformation of nanocrystalline materials on their fracture toughness are analyzed. We demonstrate that grain boundary sliding can dramatically magnify the fracture toughness of nanocrystalline materials. This explains the experimental observations of good plasticity exhibited by some nanocrystalline solids.

In consideration of the mechanical behavior of ultrafine-grained (UFG) alloys, we examine the experimental data on superstrength of such materials processed by severe plastic deformation and the formation of segregations at their GBs. We suggest models describing the emission of dislocations from GBs of UFG alloy and the formation of GB segregations. We also examine the micromechanisms responsible for the superstrength of the above UFG alloys.