The evolution of microstructure and texture in two ferritic stainless steels was investigated in order to identify the existence of grain colonies associated with ridging and their origin. Special attentions were placed upon examining how the columnar crystals with an initial [001]//ND orientation in continuously-cast slabs can affect the formation of the grain colonies or band structures in the cold-rolled sheet specimens. The rolling and recrystallization textures at each process stage were examined by the orientation distribution function (ODF). Micro-texture measurements using an electron back-scattered diffraction (EBSD) technique were carried out on the ND, RD, and TD section, respectively. The existence of grain colonies having both {001}͗110͘ and {112}͗110͘ orientations at the central region of the sheets was clearly identified. These orientations were caused by both the crystal rotation toward a-fibre texture, which is stable orientation during rolling and the suppressed recrystallization. The relation between the presence of grain colonies and ridging phenomena was discussed.KEY WORDS: microtexture; ridging; grain colony; EBSD; stainless steel. 30 scanning electron microscope permitted the automatic micro-texture analysis by the on-line interpretation of the electron back-scattered diffraction (EBSD) patterns. Texture measurements were also made with an automated pole figure goniometer using MoKa radiation. The X-ray diffraction data were obtained on the mid-thickness sections of the ND plane. Orientation distribution function (ODF) was obtained from (110), (200), and (211) three pole figures. For the evaluation of the degree of ridging, uniaxial tensile tests were performed at a strain rate of 10 mm/min and interrupted at a strain of 0.15. The surface roughness due to ridging was measured using a Surftest 501 (Series 178) manufactured by Mitutoyo surface measuring instrument. ResultsFigure 2 shows the microstructural variation observed on the mid-thickness of ND plane at each process stage of 409L and 430 steels. In 409L steel, the initial columnar structure was elongated upon rolling. The initial columnar structure was found to be remained in a band shape in HRA and CRA conditions (Figs. 2(b) and 2(c)). However, in the case of 430 steel, the band structure originated from the initial columnar structure was reduced significantly, as shown in Fig. 2(f), due to the existence of austenitic phase in the hot rolling stage.Texture evolution of the two steels was also examined at each process stage. Figure 3 shows the variation of fibre intensities measured on the ND plane of central layer depending on process stage of 409L and 430 steels. The difference in fibre intensities was pronounced in a-fibre between the two steels, while that of g-fibre was negligible. The a-fibre intensities of 409L steel were found greater in both HRA and CRA condition than those of 430 steel. The a-fibre intensities measured at the CRA condition were relatively low in comparison to those measured at the HRA condition in both ste...

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The dielectric constant of amorphous Bi 4 Ti 3 O 12 prepared by a rapid quenching method was measured. It was found that the as-quenched sample shows a distinct dielectric anomaly at approximately 600 • C. With further heating, the dielectric constant shows an anomalously high value above 750 • C. In the sample heated to the 900 • C range, the recovery of the ferroelectric Bi 4 Ti 3 O 12 crystalline phase was confirmed by observing the dielectric anomaly at the Curie point.

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