Influence of large and severe plastic deformation mechanisms on structure formation in metals

摘要

A comparison of structural changes during large deformation accumulation in a metal billet by the example of longitudinal rolling and super large intense plastic deformation (SPD) by the case of equal-channel angular pressing (ECAP) has been carried out. It is shown that during rolling large monotonic deformation leads to formation of extremely thin microstrip structure with weakly oriented cells inside, and nonmonotonic SPD by ECAP method to formation of ultrafine grained (UFG) structure. A kinetic equation for the growth of the fraction of extremely thin micro- bands with small cells in them during strain accumulation was obtained in agreement with the experiment. It has been revealed that the reason why it is not possible to refine grains to sizes corresponding to extremely small cells even after superlarge strains at ECAP is the instability of the latter and nonuniform distribution of deformation origin boundaries over the sample cross-section. Recommendations are given to increase the efficiency of the SPD methods.