Development of Ferrite Rolling Textures in Low- and Extra Low-Carbon Steels L.S. TOTH, J.J. JONAS, D. DANIEL, and R.K. RAY The texture changes that affect the main ideal orientations displayed by rolled low- and extra low-carbon steels are examined. Predictions are made regarding the stability of these compo- nents using a rate-dependent theory for mixed {112} (111) and {110} (111) slip. Both full con- straint (Taylor) and relaxed constraint (lath and pancake) grain interaction models are employed. It is shown that the experimentally observed texture changes can be reproduced by adopting the deformation modes which require the least plastic work. The orientation dependences of the preferred deformation modes are described together with the relative stabilities of the expected end textures. I. INTRODUCTION THE development of rolling textures in steels has been studied by numerous investigators, tl-~l] In microalloyed grades, such texture development begins during finish rolling in the austenite domain, because static recrystal- lization is suppressed in this temperature range. The de- formation textures formed in this way are retained until the beginning of the 3'-to-a transformation. Although the reorientations taking place during transformation reduce the severity of the austenite textures, orientation distri- bution function (ODF) peaks nevertheless remain, which are then modified and intensified by further rolling in the ferrite phase, t~~ By contrast, in plain carbon steels, austenite textures are much less marked as a result of the randomizing effect of the recrystaUization that takes place between finishing passes, t1~ In both types of material, the final texture present after either warm or cold rolling depends on how individual grains are reoriented during deformation of the a phase. Several experimental and theoretical studies have been carded out to characterize the observed changes. The former include the rolling of samples with strong ideal components t~'4] and the measurement of intensity varia- tions along the fibers as a function of strain.J6.91 The lat- ter have involved simulations based on the Sachs, 121 Taylor, t2'5'sl and relaxed constraint [5,7,sl models of crystal plasticity. However, because of the complexities asso- ciated with grain rotations caused by a combination of austenite rolling, phase transformation, and ferrite roll- ing, the full effect of the latter is not yet completely clear. The present work was undertaken in order to clarify some of the contradictions present in experimental data regarding the orientation changes produced by cold roll- ing. For this purpose, the rate-dependent model of crystallographic glide wos employed, and mixed {112} (111) and {110} (111) slip was assumed to take place. L.S. TOTH, Associate Professor, is with the Institute for General Physics, EBtvfs University, 1445 Budapest, Hungary. J.J. JONAS, CSIRA/NSERC Professor of Steel Processing, and D. DANIEL, Research Associate, are with the Department of Metallurgical Engineering, McGill University, Montreal, PQ H3A 2A7, Canada. R.K. RAY, Professor, is with the Department of Metallurgical Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016, India. Manuscript submitted January 2, 1990. For simulation purposes, various initial textures were studied, which were represented by Gaussian distribu- tions about selected ideal components. The reorientation of these components was then followed as a function of strain using the full constraint (Taylor) and two relaxed constraint (lath and pancake) grain interaction models. It was found that the experimental observations can only be reproduced by employing all three deformation modes. The preferred deformation mode for a given grain is the one that requires the least work (lowest Taylor factor) and therefore depends on orientation. With the aid of this combined model, the movement of grain orientations along the three fibers produced by cold roiling is described and explained in detail. II. THE IDEAL ORIENTATIONS ASSOCIATED WITH BODY-CENTERED CUBIC ROLLING TEXTURES The important components of the rolling texture of low-carbon steels are located along three orientation lines referred to as the a, y, and e fibers, t91 These contain the grains whose (110), (111), and (110) directions are par- allel to the roiling, normal, and transverse directions, respectively. To avoid confusion between the a and 3' fibers and the a and 3' phases in steels, the three fibers are referred to below as the RD, ND, and TD fibers, respectively. All the ideal orientations belonging to the above fibers can be found in the ~b2 = 45 deg section (Bunge notation) of Euler space (Figure 1). The detailed experimental results concerning these orientations, which are available in the literature, provide a good basis for the development of theoretical models and will now be reviewed briefly, v'4'6,9] The grain rotations that affect the fibers were deter- mined by Inagaki and Suda, [11who rolled low- and extra low-carbon steels with specific initial orientations. The expected behavior of grains with these orientations in otherwise random polycrystals were then deduced from the measured orientation changes. Their experimental observations can be summarized as follows. A. RD Fiber (RD II (110)) {110} (110): limited stability until a reduction of 30 pet is attained; then rotation to {111} (110) along the RD METALLURGICAL TRANSACTIONS A VOLUME 21A, NOVEMBER 1990--2985