Fundamentals of Deformation and Annealing

Paper Title Page

Authors: Roger D. Doherty, D. Stojakovic, Fernando José Gomes Landgraf, Surya R. Kalidindi
Abstract: The ideal sheet texture for electric motor steels, the λ fiber, with 〈001〉 normal to the rolling plane, that can be produced by directional solidification, is largely lost by the required heavy rolling reduction and recrystallization needed to produce thin motor laminations. However by two successive light rolling reductions, followed in each case by recrystallization, the desired texture was largely recovered. Taylor and finite element modeling supported the hypothesis for this successful processing: the low Taylor factor of the λ fiber grains. Although starting from similar grain sizes, the second light deformation produced a much larger recrystallized grain size than did the first light deformation. This result suggests that a lower average Taylor factor in the structure before deformation, resulting in lower stored energy, can increase the recrystallized grain size.
Authors: Jai Gautam, Roumen H. Petrov, Leo Kestens
Abstract: This paper investigates the surface texture evolution during α−γ−α phase transformation. After austenite annealing of the cold rolled sheets a weak texture was formed at the surface of ultra low carbon steel alloyed with Mn and Al. This texture consists of <100>//ND and <110>//ND fiber orientations with an intensity of approximately 2 X random. This surface texture is confined to a mono-layer of surface grains which are in direct contact with the metal/vapour interface. In order to interpret this surface effect, two alternative mechanisms were considered: (i) one assumption attributes the occurrence of the specific surface texture to the minimization of the outer surface energy and (ii) according to an alternative hypothesis the release of elastic work parallel to ND in the surface area is responsible for the observed surface fibers. After analyzing the experimental data it is concluded that the evidence in support of hypothesis (i) is the more convincing in this experiment.
Authors: Peter N. Kalu, Daudi R. Waryoba
Abstract: The texture and microstructure resulting from heavily drawn and annealed oxygen-free high conducting (OFHC) copper wires have been investigated using several microscopical techniques including orientation imaging microscopy and nano-indentation. In the as-drawn condition, the microstructure and texture were heterogeneous across the wires, and consisted of three distinct concentric regimes: the inner core, the mid section, and the outer region. Whilst the microtexture of the inner core was dominated by a strong <111>+weak<100> duplex fiber texture, the mid section and the outer region had a comparatively weak fiber texture. Analysis using a Taylor-type viscoplasticity model revealed that the weak texture observed in this material was a direct consequence of shear deformation during drawing. The recrystallization kinetics of the wires upon isothermal annealing at various temperature was influenced by the deformation heterogeneity, and can be accurately described by a modified JMAK-Microhardness model. In this approach, the JMAK model is expressed in terms of microhardness data, from which the parameters of the different restoration kinetics were determined.
Authors: S.C.V. Lim, Anthony D. Rollett
Abstract: The extraordinary strength values of composites with nano-scale layers or phases have inspired much investigation into the strengthening mechanisms of laminated composites such as Cu-Nb. The annealed microstructure and texture of any material govern its mechanical properties in composites just as much as in single-phase materials yet studies on the development of annealing textures of such deformed layered composites are still very limited as compared to studies of strengthening mechanisms. Recrystallization textures of monolithic pure Cu and alloyed Cu - C19210 as well as when they are reinforced with Nb using roll-bonding are investigated. The rollbonded samples of different layered length scales were deformed to reductions of 70-90% and annealed at 300oC and 800oC for 0.5 hours. We found that the Cube and R-orientation {124}<211> were the dominant components in the recrystallized texture of monolithic pure Cu and alloyed Cu respectively. However, retained rolling texture was obtained for the sub-micron Cu layers of the composites. X-ray analysis and EBSD was used to study the recrystallization evolution of the Cu in the composites. EBSD in particular was also used to observe recrystallization for the sub-micron Cu layers. In this paper we also discuss the effect of the length scale of the Cu layer thickness on the recrystallized texture especially in the sub-micron range.
Authors: Henryk Paul, Julian H. Driver
Abstract: Microstructure and texture development in twinned fcc metals is investigated in order to characterize the influence of micro- and macro-scale brass-type shear bands (SB) on structural and textural changes at large deformations. TEM and SEM analyses are focused on bands developed by plane strain compression in twinned C{112}<111> oriented single crystals. The proposed crystallographic model of the shear banding phenomenon refers to the idea of local lattice reorientation within narrow areas. Most of these rotations occur around the TD||<110> axis with significant further rotations about <112> poles. These two rotations explain the influence of SB’s on the formation of Goss{110}<001> and brass{110}<112>-S{123}<634> texture components clearly observed in highly deformed low SFE metals. At high deformations symmetrically equivalent crystal lattice rotations inside narrow areas lead to the formation of positive and negative macroscopic SBs.
Authors: Jae Young Choi, Chel Min Park, Jong Tae Park, Jae Kwan Kim
Abstract: The effects of hot band annealing temperature on the texture of the 2%Si nonoriented electrical steel were investigated. Slab was hot rolled and then hot band annealed in the temperature range of 900°C~1100°C. The magnetic flux density and the core loss were improved by the hot band annealing because of the texture improvement. As the hot band annealing temperature was increased, the magnetic properties were improved. The microstructure of the hot band was composed of a recrystallized structure at the surface and a deformation structure near the middle plane. These hot bands were completely recrystallized after annealing above 1000°C. The main texture of the hot band was rotated cube and gamma-fibre. After hot band annealing, rotated cube changed to cube texture and gamma-fibre intensity gradually decreased. In the case of non-annealed hot band, rotated cube in the middle plane was changed to near {111}<112>texture and Goss texture in the surface to gamma fibre after final annealing. In the case of the hot band annealed at 900°C, rotated cube near the middle plane changed to Goss texture and Goss texture in the surface to rotated cube after final annealing. After final annealing, the {111} and {112} texture was dramatically decreased as the hot band annealing temperature was higher. The total {100} texture intensity was not changed. Cube texture {100}<001> increased and rotated cube texture {100}<011> decreased. The {110} texture increased after hot band annealing irrespective of temperature. As the hot band annealing temperature was higher, the Goss texture increased, and this increase of Goss texture causes the anisotropy of the magnetic flux density.
Authors: Jong Tae Park, Jae Young Choi, Jae Kwan Kim, Jerzy A. Szpunar
Abstract: In nonoriented electrical steels, the control of texture has received little attention, and hence there is an unexplored possibility to improve the magnetic properties of nonoriented steels through texture control. Furthermore, the formation of recrystallization texture in these steels has not yet been systematically studied. In this study, such systematic investigations are undertaken for nonoriented electrical steels with 2% Si. New information obtained from EBSD measurements on partially recrystallized specimens will allow us to know what is happening during the recrystallization stage. The formation of recrystallization texture is much better explained by oriented nucleation. This is supported by the fact that the area fraction of nuclei or recrystallized grains with specific orientations for all new grains remains almost constant during the progress of recrystallization. Most nuclei have a high misorientation relationship with the surrounding deformed matrix: 25~55. The main texture components of nuclei or recrystallized grains during the progress of recrystallization are Goss and {111}<112>. Deformed {111}<110> and {111}<112> grains generally disappear at the early stage of recrystallization whereas deformed {001}<110> and {112}<110> grains are mostly consumed at the late stage of recrystallization.
Authors: Pablo Rodriguez-Calvillo, Roumen H. Petrov, Yvan Houbaert, Leo Kestens
Abstract: Electrical steels, in particular Fe-Si alloys, are used as magnetic flux carrier in transformers and motors because of their excellent magnetic properties. They owe these magnetic properties in part to the presence of specific texture components such as the Goss ({110} <001>) or the cube components ({001} <010>), but also to the chemical composition which is optimum with 6.5 wt. % Si. This high silicon content provides a stable BCC lattice structure to the alloy over the entire solid state domain, but also renders the material more brittle. This embrittlement, which is induced by ordering phenomena, makes it impossible to produce the alloy in a conventional rolling process unless a specific thermomechanical route at high temperature is applied. In order to examine the working behaviour of high Si electrical steels, a series of room temperature plane strain compression tests was carried out on a Fe-3%Si alloy in hot band condition. The samples were compressed with a constant strain rate of 20 s-1 to a reduction of 10, 35 and 70% and subsequently annealed for different times at 800 and 900°C in an electrical furnace without protecting atmosphere. The hot rolled microstructure displayed an average grain size of 195 7m and the texture showed on the cube component ({001} <010>) of maximum 5x random levels. After plane strain compression the samples developed the conventional α (<110> // RD) / γ (<111> // ND) fibre texture by plastic shear which was also accommodated, in part, by mechanical twinning. With regard to the annealed material, it was observed that the recrystallisation started in grains with the higher stored energy and within the shear bands. After a reduction of 70% the samples that were annealed at 800°C for 4 hours displayed an average grain size of 27 7m and a relative maximum of 4x random on the cube component. Also other less intense components such as the rotated cube ({001} <110>) and the Goss ({110} <001>) were present in the annealing texture. The samples that were annealed at 900°C, after a reduction of 70%, were characterized by an average grain size of 36 7m and by the appearance of the {111} <121> γ fibre component with an intensity of 4.7.
Authors: K. Zhu, Brigitte Bacroix, Thierry Chauveau, D. Chaubet, Olivier Castelnau
Abstract: The evolution of crystallographic texture in a Zr-2Hf alloy has been investigated during deformation, primary recrystallisation and normal grain growth. The as-deformed states (50-90% deformation) are characterized by a major tilted {0001}<1010> texture component and this component is reinforced with increasing deformation. A decrease in the intensity of the tilted {0001}<10 10> component and a continuous increase in the intensity of the tilted {0001}<1120 > component take place during primary recrystallisation. Normal grain growth is associated with the coarsening of grains with the {0001}<1120 > orientation. This texture evolution is interpreted on the basis of the evaluation of the stored energy and the consideration of specific grain boundaries with low energy and/or high mobility.
Authors: Sorphal Chhann, Denis Solas, Anne Laure Etter, Richard Penelle, Thierry Baudin
Abstract: Asymmetrical rolling, in which the circumferential velocities of the working rolls are different, is a method to impose shear deformation and in turn shear deformation texture to sheet through the thickness. The Invar® alloy has been deformed by asymmetrical rolling with a 84% thickness reduction. The texture of the deformed and annealed alloy was measured by X-ray diffraction at different levels through the thickness: upper side- middle- down side, with unidirectional rolling. The deformed texture is a copper type texture but the components were rotated about 5-7° around the Transverse Direction (TD) axis as compared to the ideal position of these components in the pole figure representation. During recrystallization, the rolling components (brass {011}<112>,copper {112}<111>, aluminum {123}<634>) decrease quickly whereas the cube component {001}<100> is preferentially developed after a short annealing time. However, the rolling components do not disappear completely after complete recrystallization (120 minutes annealing). As a consequence the final texture contains a high cube component and rolling components.

Showing 71 to 80 of 94 Paper Titles