The γ-to-α transformation of hot rolled austenite

Abstract

A phase transformation model is described that is based entirely on the presence of dislocations in deformed austenite. Each of the 24 possible burgers vectors associated with the glide dislocations in a given crystal leads to the presence of a particular “positive slip” transformation variant. These are illustrated for the seven main components of the fcc rolling fibre and are shown to be responsible for the presence of the so-called transformed brass component. The transformed copper component, on the other hand, is demonstrated to arise entirely from the reaction of in-plane glide dislocations. The superposition of the positive slip and reaction variants is shown to lead to an overall texture that is in excellent agreement with experimental observations. Such calculations involve the weighting of each variant according to the intensity of the parent orientation from which it is derived as well as of the relevant slip activity. The calculations indicate that the texture of rolled austenite resembles that of rolled brass much more than rolled copper. They also demonstrate that the rejected negative slip variants are associated with high intensities of the (100) component (and the presence of the (100) ), which are not observed experimentally and that the rejected miscellaneous components would lead to the presence of the rotated Goss, (110) , which is also absent in experimental textures. Analysis of the full three-dimensional ODF verifies that the ϕ2=45° cross-section is sufficient to display all the important characteristics of the transformation texture.