Deformation banding and nucleation of recrystallisation in if steel

Abstract

In an investigation of the properties of the model proposed by Liu et al. for the development of BCC rolling textures incorporating Deformation Banding (DB) certain crystal rotation paths were encountered which were recognized as being pertinent to the ongoing debate as to the origins of the {l_brace}111{r_brace} recrystallization texture in IF steels. For the case of steel, grain subdivision into bands was observed in longitudinal and rolling plane sections by optical and SEM imaging. It was also progressive, i.e., the number of grains subdividing into these bands increased with strain. At low strains the grains fragmented into regions in which different slip systems were operating, and these grain fragments eventually became well developed bands at higher strains. The early and later stages are both called deformation banding (DB) because they are part of the process which develops pancake elements parallel to the rolling plane and well known by this name to many metallographers. Banding in the longitudinal section follows the principle of the relaxed constraints (RC) model, but without orientation splitting, in other words, banding in these sections is ignored and the DB model is one dimensional. To ensure that DB occurs in the model, a latent hardening parameter,more » L{sub n} is introduced, which is multiplied by the CRSS of slip planes which do not belong to the most heavily stressed slip plane. Since L{sub n} is set at 1.2, this has the effect of limiting the number of slip systems to an average of 2 per band. The simulation can be done with 110, 112, and 123 slip either in combination or singly, and DB occurs from the first increment in strain, with relaxation of the longitudinal elements following the RC procedure.« less