• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.241-246
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• 2000

We fabricated Bi-2223 multi-filaments superconductor tape and evaluated the effect of twisting on the microstructural evolution and critical current. Twist pitches of the tapes are in the range of 70- 8mm and uniformly deformed. It was observed that grain size and the degree of texture decreased as decreasing pitch probably due to the formation of the irregular interface between Ag and filaments. In addition critical current of the tapes decreased to 6.5 A with decreasing pitch to 8mm, showing 48% of degradation compared to the untwisted tapes decreased to 6.5 A with decreasing pitch to 8mm, showing 48% of degradation compared to the untwisted tape(12.5 A). These reduction of critical current may be related to the interface irregularity smaller grain size worse texture and the presence of cracks due to the induced strain during twisting processing.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.226-228
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• 2007

During asymmetrical cold rolling in AA 5052 sheet a reduction per a rolling pass was varied to investigate the effect of the ratio of the contact length between the roll and sample ($l_c$) to the sheet thickness (d) on the formation of shear textures. In order to intensify the shear deformation during asymmetrical rolling, AA 5052 sheet was asymmetrically cold rolled without lubrication by using different roll velocities of upper and lower rolls. Asymmetrical rolling with $l_c$/d=1.8 led to the formation of texture gradients throughout the sheet thickness in which the outer thickness layers depicted shear textures and the center thickness layers displayed a rolling texture. Asymmetrical rolling with $l_c$/d=3.1 gave rise to the formation of shear textures in the whole through-thickness layer. The strain states associated with asymmetrical rolling were investigated by the finite element method (FEM) simulation. FEM results indicated that the evolution of deformation texture in a thickness layer is strongly governed by integrated values of strain rates and along the streamline in the roll gap.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.421-424
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• 2009

Superplastic deformation behavior and texture evolution after equal channel angular pressing (ECAP) of Zn-0.3Al alloy were investigated in this study. ECAP was conducted at temperatures from $40^{\circ}C$ to $160^{\circ}C$ on the plate type specimens of 5 mm thickness and 20 mm width. The specimens obtained by ECAP showed typical texture with basal poles tilted away from the ND toward ED. A series of compression and tensile tests was carried out at temperatures from RT to $200^{\circ}C$ under the strain rate from 0.03 to 10/s. After ECAP of the Zn-Al alloy, elongation was dramatically increased up to 1000% at above $60^{\circ}C$. The effects of ECAP on the texture and anisotropy in the superplastic deformation bebavior were found to be negligible.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.63-71
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• 2004

Recently, a sheet forming process of Mg alloys is highlighted again due to increasing demand for Mg wrought alloys in the applications of casings of mobile electronics and outer-skins of light-weight transportation. Microstructure control is essential for the enhancement of workability and formability of Mg alloy sheets. In this research, AZ31 Mg alloy sheets were prepared by hot rolling process and the rolling condition dependency of the microstructure and texture evolution was studied by employing a conventional rolling mill as well as an asymmetric rolling mill. When rolled through multiple passes with a small reduction per pass, fine-grained and homogeneous microstructure evolved by repetitive dynamic and static recrystallization. With higher rolling temperature, dynamic recrystallization was initiated in lower reduction. However with increasing reduction per pass, deformation was locallized in band-like regions, which provided favorable nucleation sites f3r dynamic recrystallization. Through post annealing process, the microstructures could be transformed to more equiaxed and homogeneous grain structures. Textures of the rolled sheets were characterized by $\{0002\}$ basal plane textures and retained even after post annealing. On the other hand, asymmetrically rolled and subsequently annealed sheets exhibited unique annealing texture, where $\{0002\}$ orientation was rotated to some extent to the rolling direction and its intensity was reduced.

• Korean Journal of Materials Research
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• v.32 no.2
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• pp.72-79
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• 2022

A cold roll-bonding process using AA1050, AA5052 and AA6061 alloy sheets is performed without lubrication. The roll-bonded specimen is a multi-layer complex aluminum alloy sheet in which the AA1050, AA5052 and AA6061 sheets are alternately stacked. The microstructural evolution with the increase of annealing temperature for the roll-bonded aluminum sheet is investigated in detail. The roll-bonded aluminum sheet shows a typical deformation structure in which the grains are elongated in the rolling direction over all regions. However, microstructural evolution of the annealed specimen is different depending on the type of material, resulting in a heterogeneous microstructure in the thickness direction of the layered aluminum sheet. Complete recrystallization occurs at 250 ℃ in the AA5052 region, which is lower by 100K than that of the AA1050 region. Variation of the misorientation angle distribution and texture development with increase of annealing temperature also differ depending on the type of material. Differences of microstructural evolution between aluminum alloys with increase of annealing temperature can be mainly explained in terms of amounts of impurities and initial grain size.

• Progress in Superconductivity
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• v.5 no.1
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• pp.70-74
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• 2003

We fabricated cube textured Ni substrate for YBCO coated conductor and evaluated the effects of processing parameters on microstructural evolution and texture formation. Ni-rods as an initial specimen were prepared by two different methods, i.e., powder metallurgy(PM) and plasma arc melting(PAM). Subsequently, the rods were cold rolled to 100 $\mu\textrm{m}$ thick substrate and annealed at temperatures of $700∼1200^{\circ}C$. The texture of the substrate was characterized by pole-figure. It was observed that the texture of substrate made by P/M did not significantly varied with annealing temperature of 600∼$l100^{\circ}C$ and the full-width at half-maximums (FWHM) of both in-plane and out-of-plane were 9$^{\circ}$∼$10^{\circ}$. On the other hand, the texture of substrate made by PAM was more dependent on the annealing temperature and the corresponding values were $9^{\circ}$ ∼$13^{\circ}$ at the temperature range. In addition, recrystallization twin texture, (221)＜221＞, was formed as the temperature increased further. OM profiles showed that the grain size of substrate made by P/M was smaller than that made by PAM and this difference was correlated to the microstructure of initial specimens.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.6
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• pp.256-262
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• 2019

The microstructural features and texture development by both hot rolling and hot forging in ${\gamma}-TiAl$ alloy were investigated. In addition, additional heat treatment after hot forging was conducted to recognize change of the microstructure and texture evolution. The obtained microstructural features through dynamic recrystallization after hot deformed ${\gamma}-TiAl$ were quite different because two kinds of formation process were occurred depending on deformation condition. However, analyzed texture tends to be random orientation due to intermediate annealing up to ${\alpha}+{\beta}$ region during the hot deformation process. After additional heat treatment, microstructure transformed into fully lamellar microstructure and randomly oriented texture was also observed due to the same reason as before. Tensile test at room temperature demonstrated that anisotropy of mechanical properties were not appeared and transgranular fracture was occurred between interface of ${\alpha}_2/{\gamma}$. As a result, it could be suggested that microstructural features influenced much more than texture development on mechanical properties at room temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.96-98
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• 2003

The evolution of texture and microstructure during continuous confined strip shearing (CCSS) in aluminum 3003 alloy sheets was investigated. The tools of CCSS based on the equal channel angular pressing (ECAP) were designed to provide a constant shear deformation of the order of 0.5 per pass while preserving the original sheet shape. FEM results indicated that the shear formation is not homogeneous throughout the sample thickness, in particular at the surface layers. A randomization of textures took place during the CCSS deformation. Observations by TEM and EBSD revealed the formation of sub-micrometer sized grains after CCSS.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.72-74
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• 2003

We fabricated textured Ag substrates for coated conductor and evaluated the effects of annealing temperature on microstructural evolution, texture formation, and surface morphology. A strong {110}〈110〉 textured Ag substrate was obtained by cold rolling and annealing at 80$0^{\circ}C$: the full-width at half-maximum(FWHM) value of {110}〈110〉 poles was as sharp as 10$^{\circ}$. Surface morphology was evaluated by using Atomic force microscopy(AFM). Root-mean-square(RMS) roughness of the substrate annealed at 80$0^{\circ}C$ was 39.2 nm. The substrate of strong texture and smooth surface, fabricated in our study, is considered to be suitable for use as a substrate for deposition of superconductor films.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1086-1093
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• 2011

To fabricate the aluminum alloys with good drawability, the textures evolution of the AA5182 sheets due to the change of lid parameter after rolling and subsequent annealing was studied. The measurement of the deformation textures was carried out for the sheets with high reduction ratio and the change of the recrystallization texture was investigated after heat-treatments of the rolled sheets in various I/d parameters. Rolling without lubrication and subsequent annealing led to the formation of favorable rot-$C_{ND}$ {001}<110> and ${\gamma}$-fiber ND//<111> textures in AA5182 sheets. From the results, the ${\gamma}$-fiber ND//<111> component well evolved during rolling at high lid parameter of 6.77. The initial shear deformation texture, especially, ${\gamma}$-fiber ND//<111> was not rotated during heat treatment in holding time of 180~7,200 seconds on AA5182 with I/d parameter of 6.77. Therefore, the AA5182 sheets were fabricated by controlling I/d parameter having well evolved ${\gamma}$-fiber ND//<111> which was advantageous in good drawability of the sheets.