Evolution of a Defect Structure during Creep Tests of Ultrafine-Grained Metals and Alloys Produced by Severe Plastic Deformation

The structural factors that lead to a decrease in the mechanostability of ultrafine-grained (UFG) metals and alloys during creep tests at increased temperatures have been revealed using small-angle X-ray scattering, electron microscopy, and the measurements of the density. An important factor is found to be nanopores that form during severe plastic deformation. The development of these nanopores in grain boundaries, which form during the creep, occurs by a diffusion mechanism and leads to the fracture. The role of disperse inclusions and high-angle grain boundaries in the strength of UFG metals and alloys during their “short-time” and long-term loadings is considered.