Prediction of transformation textures in steels

Abstract

Both discrete and continuous mathematical formalisms are employed to simulate texture evolution during the γ-to-α transformation in steels. Five f.c.c. NiCo alloys with different stacking fault energies (SFE's) were previously cold rolled to four reductions (40, 70, 90 and 95%) and their textures characterized by the orientation distribution function (ODF) method. The corresponding b.c.c. transformation textures are calculated from these experimental textures according to three different orientation relationships. The ODF's derived from the Bain relation are much sharper than the ones deduced from the Kurdjumov-Sachs (KS) or the Nishiyama-Wassermann (NW) relations, although the general trends of the three families of textures are similar. Ferrite textures determined on controlled rolled steels, heavily deformed in the unrecrystallized γ region, agree reasonably well with the b.c.c. textures calculated, according to the KS relationship, from the NiCo alloy with similar SFE. The two major ferrite components, namely the {332} 〈113〉 and {113} 〈110〉, are shown to originate from the three main orientations of cold rolled f.c.c. material, i.e. the {112} 〈111〉 (Cu), {110} 〈112〉 (Bs) and {123} 〈634〉 (S). Such ferrite formation from heavily deformed austenite follows the KS relationship without any variant selection. By contrast, the texture of martensite produced from deformed austenite involves significant amounts of selection.