Effects of Dynamical Deformation Ageing on Structure and Texture of Hot-Rolled Sheets from Alloyed BCC Metals

Plasticity of metals with the BCC crystalline lattice is very sensitive to interstitial elements (C, N, O and some others), which interact with moving dislocations under rolling, essentially restrict their mobility and at definite temperatures are capable to move together with them, braking the deformation process. Sheets of alloyed Cr, rolled at elevated temperatures by different regimes, were subjected to systematic layer-by-layer study by means of X-ray methods with the aim to compare structure and texture features of successive layers and to reveal effects of interaction between dislocations and interstitials. The rolling texture of surface layers sharply differs from that of the inner layer and includes components, typical for FCC metals. The crystallographic analysis of lattice rotations under rolling shows that the texture inversion, observed in the surface layer, is a result of the collective dislocation climb, which becomes the preferential deformation mechanism under conditions of increased content of interstitials, increased temperatures and all-round compression within the zone, directly adjacent to the roll. Rolling with inappropriate reductions per pass, promoting predominant deformation of the surface layer, operates as “a pump”, injecting extrinsic atoms from the outside to the bulk of metal.