Recrystallization and Grain Growth III

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Authors: Sadahiro Tsurekawa, H. Fujii, V.A. Yardley, T. Matsuzaki, T. Watanabe
Abstract: Crystallization kinetics and texture evolution in iron-based amorphous alloys (Fe78Si9B13, Fe73.5Si13.5B9Nb3Cu1) under a magnetic field have been studied. We have found that the application of a magnetic field during crystallization at a temperature ranging the Curie point of the amorphous phase and that of the crystalline bcc-Fe(Si) phase can produce a {110} texture in the alloys. X-ray diffraction with the Schulz method revealed that {110} oriented grains were preferentially nucleated due to the magnetic field. The studies of crystallization kinetics found that the nucleation rate of the α-Fe(Si) phase in amorphous Fe73.5Si13.5B9Nb3Cu1 was enhanced approximately three times as high with the 6T magnetic field than without field. The volume fraction of crystalline α-Fe(Si) phase produced was increased by the magnetic field.
1371
Authors: Y. Choi, Hirofumi Inoue
Abstract: Crystallographic texture of pilgered zirconium alloy tubes was analyzed by neutron diffraction, electron backscatter diffraction (EBSD) and X-ray techniques to study bulk and local texture change with pilgering and heat treatment above re-crystallization temperature. Pilgering resulted in slightly inclining (001) planes to sample normal direction, and aligning effectively (100) planes to the normal of radial direction, respectively. (001) planes of the zirconium tube uniformly exist in radial and tangential directions, however, the (001) planes moved from tangential to radial directions after pilgering followed by heat treatment for 20 hours at 540°C. Some of (001) and (100) planes of pilgered tube were paralleled to longitudinal direction by re-crystallization.
1379
Authors: B.M. Gonzalez, O.J. Santos, C.S.B. Castro, Dagoberto Brandão Santos, Ronaldo Barbosa
Abstract: The mechanical behavior of a fire resistant steel was studied by means of tensile tests performed in the temperature interval from 25 to 600oC, at strain rates from 10-4 to 10-2 s-1, aiming at analyzing the role of alloying elements in the dynamic strain aging (DSA) phenomena occurring in this steel. Typical features of DSA were observed: serrated flow (the Portevin-LeChatelier – PLC effect), the presence of a maximum and a minimum in ultimate tensile strength and elongation versus temperature curves, respectively and a plateau in yield strength versus temperature curves. Apparent activation energies were calculated based on the onset of PLC effect and the maximum in ultimate tensile strength. Results suggest that changes in mechanical properties associated with DSA in the fire resistant steel are related to the dynamic interaction of C-substitutional dipoles and dislocations.
1383
Authors: Katsuya Inoue, Sang Koo Kwon, Kozo Shinoda, Shigeru Suzuki, Yoshio Waseda
Abstract: Solid particles of ferric oxyhydroxides or iron oxide were recrystallized from ferrous and ferric ions dissolved in aqueous solution. There are different structures of α-FeOOH, β-FeOOH and γ-FeOOH in the ferric oxyhydroxides, of which the formation is influenced by reaction conditions such as oxidation rate of ferrous ions. In this work, a few factors affecting the formation of the ferric oxyhydroxides and iron oxides, which was converted from hydrosulfate green rust, has been studied using different methods. The hydrosulfate green rust (GR2) was synthesized from solutions of ferric sulfate (Fe2(SO4)3), ferrous sulfate (FeSO4), and sodium hydroxide (NaOH), and they were oxidized by gas containing oxygen. X-ray diffraction measurements and X-ray absorption spectroscopy were used for analyzing the structure and chemical state of solid particles extracted from the suspension during the oxidation. The morphology of the particles was observed by transmission electron microscopy. The results showed that γ-FeOOH or Fe3O4 particles were formed together with α-FeOOH particles during conversion from the green rust, depending on oxidation temperature, oxygen flow rate and addition of manganese. This indicates that the species of ferric oxyhydroxides or iron oxides formed in aqueous solution is sensitively influenced by reaction conditions.
1389
Authors: Jun Yun Kang, Brigitte Bacroix, Kyu Hwan Oh, Hu Chul Lee
Abstract: The development of deformation texture and microstructure was examined for four different initial textures. IF steel sheets with a majority of α-, ε-, and γ-fiber and near random texture were prepared and cold rolled. The specimens exhibited characteristic behaviors in rolling texture evolution and deformation-induced misorientation development, according to their initial textures, especially at small strain levels. Due to the orientation dependence of intra-granular misorientation accumulation, the different texture evolutions affected the induced misorientation distribution. A larger fraction of γ-fiber orientations was related to more prominent misorientation development, while the initial texture stability simultaneously affected the misorientation development. The unstable, initial ε-fiber texture showed a stronger tendency of misorientation accumulation than the stable α-fiber during the subsequent cold rolling.
1395
Authors: Han Sol Kim, Won Yong Kim
Abstract: Microstructure and texture formation behavior of a gold rod and fine wire which were produced by continuous casting process and drawing, respectively were investigated by means of optical micrographs, TEM images and X-ray pole figure. Well-developed unidirectional structure aligned to casting direction was found in 7 mm gold rod. Higher casting speed was found to be favor in developing the directional microstructure. In the sample with unidirectional microstructure developed in partial it is found that dislocation substructure with nano-size appeared to display a characteristic feature, while no dislocation substructure is seen in the sample with complete unidirectional microstructure. Interface stability between solid and liquid may be responsible for this difference in dislocation substructure. <100> fiber component was observed to be well developed over the whole microstructure in unidirectional sample. With decreasing casting speed <100> fiber component became weak. Two texture components consisting of <111> fiber and <100> fiber were seen in as-drawn samples. For the development of <111> fiber texture component initial texture component plays a more significant role than subsequent annealing process. Annealing heat treatment would be effective way to control the formation of <100> fiber component. On the basis of results obtained it is suggested that both the initial texture and final annealing are important in controlling the texture of gold bonding wire.
1401
Authors: Won Yong Kim, Han Sol Kim
Abstract: Texture and cyclic tensile behavior of Ti-26Nb-0.5Si (denoted as atomic percent) alloys in which the microstructures were varied by quenching, cold rolling and recrystallization heat treatment were investigated in order to understand the relationship between pseudoelastic behavior and texture formation. Three phase mixtures consisting of bcc-structured β phase, orthorhombic structured α" phase and hcp-structured intermediate ω phase were characterized to display the constituent phases. The volume fraction of constituent phases was found to be insensitive to the given materials processing. Two-stage yielding, one at low stress with low strain hardening rate and the other one at high stress with high strain hardening rate, appeared to exhibit a characteristic flow behavior in the present alloys. It is revealed that stress-induced martensite transformation resulting in two-stage yielding was closely associated with pseudoelasticity. On the basis of texture analyses, we have suggested that pseudoelasticity of the present alloys is hindered by the development of {001}<110> rotated cube component.
1407
Authors: H. Landheer, S. Eric Offerman, R.H. Petrov, Leo Kestens
Abstract: The role of the α/γ orientation relationships during ferrite nucleation is investigated. EBSD measurements were performed on an especially developed high purity ternary iron-based alloy with 20 wt.% Cr and 12 wt.% Ni with both austenite and ferrite present at room temperature to measure the orientation relationship between the austenite and ferrite crystallites. The experimental results are compared to the nucleation models of Clemm and Fisher and Aaronson and co-workers.
1413
Authors: S.I. Park, J.H. Kim, Cheol Gi Kim, Chong Oh Kim
Abstract: The monodispersed hydrophilic magnetic fluids with nanometric MO·ferrite (M=Cu, Co, Ca, Ni) particles were prepared by the sonochemical method. The substituted amounts of M elements were analyzed with different x values by ICP-AES quantitatively for MxFe3-xO4 particles.
1419
Authors: Seong Jun Park, Dong Woo Suh, Chang Seok Oh, Sung Joon Kim
Abstract: Low alloy transformation induced plasticity (TRIP) steels have a complex microstructure consisting of ferrite, bainite and retained austenite. Their excellent mechanical properties are ascribed to the martensitic transformation of retained austenite during plastic deformation. In the present contribution, the crystallographic texture of fcc and bcc phases in TRIP steels was measured by means of orientation mapping. The austenite texture was close to a typical rolling texture of fcc metals. For bcc phase, the effects of orientation and grain size on the distribution of pattern quality were investigated. The texture of transformation product phase was separated by grain size. The transformation texture showed stronger α fiber including {113}<110> component than the recrystallization texture. It showed a good agreement with a transformation texture predicted by Kurdjmov-Sachs (KS) relationship without any variant selection.
1423

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