Papers by Keyword: Recrystallization

Abstract: The behaviors of precipitation and recrystallization aging at 900 after cold work in a Fe-18Cr-12Mn-0.48N high-nitrogen austenitic stainless steel were investigated by means of optical microscopy (OM) and transmission electron microscopy (TEM). The results show that precipitation and recrystallization occur simultaneously after aging at 900 for 10min. The precipitates firstly appear at dislocation, sub-boundary and inside the subgrain. Precipitation at these positions hinders the formation of recrystallization nucleus. With aging time increasing, precipitates appear in the recrystallized grain boundary and inside the grain. Precipitation at these positions hinders the growth of the recrystalized grains.

Abstract: The mechanism responsible for the formation of recrystallization texture is still disputed although recrystallization texture has long been a subject of research. This is mainly related to the complexity of recrystallization itself .The mechanism of recrystallization microtexture Cold-rolling low carbon sheet steel based on CSP was investigated by the electron back scatter diffraction(EBSD) was investigated. In addition, the origin of nuclei with specific orientations was studied. The results showed that the formation of recrystallization texture is explained by oriented nucleation and the nucleis show around 50% frequency of 15–60°misorientation with their surrounding deformed matrices. Deformed γ-fibre texture components increase more rapidly during the early stage of recrystallization. In contrast, the deformed α-fibre components, such as {001}<110> components disappear rather rapidly early stage of recrystallization and {112}<110> components increases rapidly late stage of recrystallization and grains growth. By microcosmic orientation distribution analyse find that the new {011}<100> grains are nucleated within shear bands in the deformed {111}<112> grains, New {111}<112> grains are nucleated within deformed {111}<110> grains and new {111}<110> grains originated in the deformed {111}<112> grains .

Abstract: In modern, highly loaded structures of metallic materials, particular standards are required both regarding the strength and deformation properties of individual components as well as in terms of the load carrying capacity of the bonded joints between individual components. This specific subject matter is taken up in the subproject C4 "Setting of Gradient Material Properties and Quality Control of High Tension 3D NVEB-Weld Joints" within the framework of “Collaborative Research Centre” CRC 675 "High strength, locally modified components and structures" in order to correspondingly and individually adapt a component's properties to the loading profile. For this purpose, components having specifically calibrated strength properties are joined into high quality structures. Although still quite new but powerful, and due primarily to its very favourable welding characteristics, the non-vacuum electron beam welding technology is, in this case, to be further developed with respect to an improvement in beam positioning and weld-seam defect inspection. On the other hand, a well-defined, local heat-treatment is to be carried out on individual, work-hardened components to be able to introduce targeted and structured local, load-oriented microstructural changes into the component: thereby locally changing the component's strength and deformation properties with a view to retarding crack growth.

Abstract: The same property of the phase transformations driven by short range diffusion (recrystallization, allotropic transformation, grain coarsening) is that the movements of the grain or the phase boundaries take place by atomic jumps through the boundaries. The probability (frequency) of these jumps depends on only on the energy state of the closenear neighborhood of the atoms. In the operation of cellular automata Consequently, only the closenear neighborhood of the cells is taken into account in the operation of the cellular automaton. This similarity makes applicable the cellular automaton applicable to simulate the aforementioned phase transformation processes. A condition (rule) of the movement of grain and phase boundaries is introduced, which makes it possible to simulate all the all mentioned phase transformation by the same automatona.

Abstract: 3-D FIB-EBSD tomography was used to analyze the structure and crystallography of nuclei, and nucleation process in 3-D space during annealing a cold rolled IF steel. It is revealed that the structure of nucleus at its very initial formation stage can be divided into two parts: (1) nucleation core, having a dislocation-contained subgrain structure, mainly bounded by low angle grain boundary with surrounding deformation subgrain, (2) newly-grown region, having a dislocation free structure, formed from high store energy deformation structures surrounding nucleus, and mainly bounded by high angle grain boundary.

Abstract: A new approach to obtain high strength of non-oriented electrical steel by addition of phosphorus is proposed. The method includes B-additions which suppress grain boundary P segregation, strengthen the grain boundary cohesion and enhance the P solid solution hardening. Two 3% Si steels, a B-free 0.1%P steel and a 20 ppm B-added 0.1%P steel were analyzed. The microstructures were studied by EBSD. The B-addition resulted in a pronounced rotated cube component, {100}<011>, after a hot-band annealing treatment. A -fiber texture was developed in the B-free steel. The B-addition caused a retardation of the recrystallization, allowing for the growth of grains with a lower stored energy, such as rotated cube oriented grains. The steels were further cold rolled and recrystallization annealed to observe a similar effect after large cold reductions. The present contribution focuses on the potential of this concept to obtain high strength 3% Si steels with low core losses.

Abstract: Achieving fine and uniform grains is the most effective way to enhance strength and toughness, which are required properties for pipeline steels. Steels microalloyed with Nb can exhibit a mixed grain structure, which can deteriorate low temperature toughness. In this work the effects of the thermomechanical processing parameters on the prior austenite grain structure before ferrite transformation have been investigated.

Abstract: The development of crystallographic textures of IF and HSLA steels after 20, 50, 70 and 90% cold rolling reductions and subsequent recrystallisation have been investigated using Electron Backscattered Diffraction (EBSD). The HSLA steel was initially processed to give a volume fraction of about 0.2 of fine pearlite colonies, which acted as mechanically hard particles. Both cold rolling and recrystallisation textures are shown to be largely dependent on the rolling reduction for both steels. With increasing rolling reduction, the texture shows gradual intensification of α and γ fibre components. Although PSN was the dominant nucleation site in the HSLA steel during annealing, the α and γ fibres also exist in the recrystallisation textures, but with lower density.

Abstract: The Goss {110}<001> orientation, which is not stable with respect to plane strain rolling, rotates toward the {111}<112> orientation forming a strong maximum. The {111}<112> rolling component returns to the Goss orientation after recrystallization (Rex). On the other hand, the {111}<112> Rex texture developed in 65% rolled iron electrodeposit with a weak {111}<112> texture, and the {111}<110> Rex texture developed in 80% cold rolled electrodeposit having a strong {111}<112> texture. That is, the {110}<001>, {111}<112>, and {111}<110> Rex textures developed in bcc steels having the {111}<112> rolling textures. The results have been discussed by the strain-energy-release-maximization model for Rex texture.

Abstract: The recrystallization behavior of cold-rolled, commercial-purity titanium was studied experimentally and with Monte-Carlo (MC) modeling. Utilization of EBSD-OIM as input for MC modeling resulted in realistic predictions of recrystallization kinetics, microstructure and texture, which were in good agreement with experimental results. MC modeling of recrystallization kinetics predicted that the non-uniform stored energy distribution, heterogeneous nucleation of recrystallization and recovery in combination leads to a negative deviation from linear JMAK kinetics. It was found that concurrent recovery that takes place during recrystallization is an important process that controls both the overall recrystallization kinetics and the deviation of linear JMAK kinetics. On the other hand, the non-uniformly distributed stored energy itself has little effect on the negative deviation from JMAK kinetics but intensifies the deviation when heterogeneous nucleation is combined. Modeling results also revealed that heterogeneous nucleation of recrystallized grains and their early impingement in local areas of high deformation are essential for producing a log-normal distribution of grain size and a typical recrystallization texture of rolled titanium.