Structure of Grains and Internal Stress Fields in Ultrafine Grained Ni Produced by Severe Plastic Deformation

Abstract

The prospect of obtaining large volumes of materials with submicron grain size has become increasingly real. The equal channel angular (ECA) pressing appears to be among the most successful methods for producing such materials [1]. The structure of the materials obtained by this method has been the subject of intensive investigation [2–5]. In most cases the description of the structure of such materials has been qualitative. Recently detailed quantitative investigations of materials produced by ECA pressing, were reported [6, 7]. At the same time investigations of the structure of materials deformed by tension, compression, rolling and torsion up to great degrees of deformation have also become more quantitative as well (see, for example, [8–10]). For practical application of ultrafine-grained materials data on their structural stability is rather important. The later is closely connected, firstly, with the internal stress fields and, secondly, with the size distribution function for the substructure parameters [11]. Consequently, in such investigations the measurement of such parameters should be carried out statistically.