• Korean Journal of Materials Research
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• v.28 no.9
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• pp.534-538
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• 2018

The annealing characteristics of a cold rolled Al-6.5Mg-1.5Zn alloy newly designed as an automobile material is investigated in detail. The aluminum alloy in the ingot state is cut to a thickness of 4 mm, a total width of 30 mm and a length of 100 mm and then reduced to a thickness of 1 mm (reduction of 75 %) by multi-pass rolling at room temperature. Annealing after rolling is performed at temperatures ranging from 200 to $400^{\circ}C$ for 1 hour. The tensile strength of the annealed material tends to decrease with the annealing temperature and shows a maximum tensile strength of 482MPa in the material annealed at $200^{\circ}C$. The tensile elongation of the annealed material increases with the annealing temperature, while the tensile strength does not, and reaches a maximum value of 26 % at the $350^{\circ}C$ annealed material. For the microstructure, recovery and recrystallization actively occur as the annealing temperature increases. The recrystallization begins to occur at $300^{\circ}C$ and is completed at $350^{\circ}C$, which results in the formation of a fine grained structure. After the rolling, the rolling texture of {112}<111>(Cu-Orientation) develops, but after the annealing a specific texture does not develop.

• 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.

• Korean Journal of Materials Research
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• v.4 no.1
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• pp.44-54
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• 1994

Effects of cooling rate, cold reduction %, continuous annealing treatments on the recrystallization texture structure of the A1 killed extra low carbon steel sheet contaning Ti, Nb, and B were investigated. The texture coefficient ratio TC (222)/TC (200) tends to increase with decreasing the cooling rate of the coling process and increasing cold reduction %. However, the texture coefficient ratio tends to decrease as the cold reduction % increases from 80% to 90%, which may be due to the change of the primary texture structure from {554} (225) to {ill] (1 1%). The optimum fabrication procedures for the steel sheet with a maximum texture coefficient ratio may be : furnance cooling after the coiling treatment, 80% cold reduction and the continuous annealing treatment of holding at 80O0C for 1 min., water quenching and then holding at $450^{\circ}C$ for 5min.

• Progress in Superconductivity
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• v.6 no.2
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• pp.133-137
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• 2005

We fabricated the Au/Ni template for YBCO coated conductors and evaluated texture formation and the microstructural evolution. The cube textured Ni substrate was fabricated by rolling and recrystallization annealing, and subsequently Au layer formed on the substrate by electroless-plating method. The texture was evaluated by pole-figure with x-ray goniometer with orientation distribution function (ODF) analysis. The surface roughness and grain boundary morphology of template were characterized by atomic force microscopy (AFM) We observed that Au layer deposited epitaxially on Ni substrate and formed a strong cube texture when plating time was optimized. The full-width at half-maximum (FWHM) was $8.4^{\circ}$ for out-of-plane and $9.98^{\circ}$ for in-plane texture for plating time of 30 min. Microstructural observation showed that the Au layer was homogeneous and dense without formation of crack/microcrack. In addition, we observed that root-mean-square (RMS) and depth of grain boundary were 14.6 nm and 160 $\AA$ for the Au layer, respectively, while those were 27.0 nm and 800 $\AA$ for the Ni substrate, indicating that the electoless-plated Au layer had relatively smooth surface and effectively mollified grain groove.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.16-20
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• 2002

Bi-axially textured Ni tapes for YBCO coated conductors were Prepared by cold rolling and heat treatment of Ni Powder compacts. The Ni powder used in this study was 5 urn in particle size and 99.99 % in purity. The process of this study consists of filling of hi powder into a rubber mold, cold-isostatically Pressing and sintering of the powder compacts at 110$0^{\circ}C$ for 6h in 96 % Ar - 4 % H$_2$ atmosphere. The sintered compacts were cold rolled with a 5 % step reduction ratio into a 100 micron-thick tapes and then heat-treated at 100$0^{\circ}C$ for various time periods. The (200) texture of Ni tape was successfully developed through the recrystallization heat treatment of the cold rolled Ni tapes. At 100$0^{\circ}C$, the degree of texture of the heat-treated Ni tapes seems not to be significantly affected by the heat-treatment time. The short heat treatment of S min was sufficient to develop the complete (200) cube texture. The degree of in-Plane and out-of-plane texture of the prepared Ni tapes was 8-10$^{\circ}$. The heat treated Ni tapes consisted of equiaxed grains with a size 50-70 microns. and the AFM sol-face roughness was as smooth as 3 nm.

• Transactions of Materials Processing
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• v.21 no.4
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• pp.240-245
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• 2012

With the increasing demand for light-weight materials to reduce fuel consumption, the automobile industry has extensively studied magnesium alloys which are light weight metals. The intrinsic poor formability and poor ductility at ambient temperature due to the hexagonal close-packed (HCP) crystal structure and the associated insufficient number of independent slip systems restricts the practical usage of these alloys. Hot working of magnesium alloys using a forging or extrusion enables net-shape manufacturing with enhanced formability and ductility since there are several operative non-basal slip systems in addition to basal slip plane, which increases the workability. In this research, the thermomechanical properties of AZ80 Mg alloy were obtained by compression testing at the various temperatures and strain rates. Optical microscopy and EBSD were used to study the microstructural behavior such as misorientation distribution and dynamic recrystallization. The results were correlated to the hardening and the softening of the alloy. The experimental data in conjunction with a physical explanation provide the optimal conditions for net-shape forging under hot or warm temperatures through control of the grain refinement and the working conditions.

• Transactions of Materials Processing
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• v.31 no.2
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• pp.73-80
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• 2022

In this study, a developed Mg-5Bi-2Al-0.4Mn (BAM520, wt%) alloy was successfully extruded at an extremely high speed of 70 m/min. Microstructural evolution during extrusion and the microstructural characteristics and tensile properties of the very-high-speed extruded BAM520 alloy were then investigated. The homogenized BAM520 billet contained only thermally stable Mg₃Bi₂ phase particles without any Mg₁₇Al₁₂ phase with a low melting temperature. Therefore, the BAM520 alloy exhibited excellent extrudability. The very-high-speed extruded BAM520 alloy had a completely recrystallized grain structure and a typical basal fiber texture. Despite the extremely high extrusion speed of 70 m/min, the extruded BAM520 alloy had a high ultimate tensile strength of 280 MPa due to combined strengthening effects of a small grain size, numerous fine Mg₃Bi₂ particles, and strong basal texture.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.19-22
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• 2006

Desirable substrates for $YBa_2Cu_3O_{7-\delta}$ coated conductor are highly cube textured Ni or Ni-alloy tapes, which can be produced by cold rolling and recrystallization annealing. We have fabricated hi-axially textured pure Ni tapes for the application of coated conductors. The sintered Ni rod was cold-rolled into the thin tapes of $50{\mu}m$ thickness and the tapes were heat-treated for texture development with line-focused infrared heater. The temperature was maintained at $800\sim1050^{\circ}C$, using 1kW double ended linear halogen lamp in $96%Ar-4%H_2$ atmosphere The biaxially tortured Ni tapes were successfully formed by line-focused infrared heat treatment The texture of the annealed Ni tapes was analysed using the GADDS (general area detector diffraction system). The full width at half maximum values of phi and omega scan for the Ni tapes were less than $10^{\circ}$ and the grain size was $20-50{\mu}m$.

• Journal of the Korean Magnetics Society
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• v.4 no.4
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• pp.319-325
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• 1994

Permalloy films were deposited by an RF magnetron sputtering method using several different targets which had been cold-rolled and annealed at various temperatures to give different microstructure and texture. The grain refinement occurs at high temperature annealing due to recrystallization and subsequently the initial (110) target texture transforms to the random texture. The coercive forces of thin films fabricated using targets which are not recrystallized are below 0.2 Oe in the AI pressure range of 1~5 mTorr and the lowest coercive force achieved is 0.07 Oe. The low value of coercive force, 0.25 Oe, is only obtained at the sputtering conditions of 400 W and 1 mTorr, and 300 W and 5 mTorr when recrystallized targets are used. The internal stress changes from compressive to tensile as the Ar pressure increases, the stress-free being at 5 mTorr. The changes of coercive force and permeability can be well interpreted by the differences from the composition and the internal stress.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.647-655
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• 2019

In order to analyze the effect of hot asymmetric rolling on the microstructure and texture of aluminum alloy and to investigate the effect of the texture on the formability and plastic anisotropy of aluminum alloy, aluminum 6061 alloy is asymmetrically rolled at room temperature, $200^{\circ}C$, $350^{\circ}C$, and $500^{\circ}C$, and the results are compared with symmetrically rolled results. In the case of asymmetric rolling, the equivalent strain (${\varepsilon}_{eq}$) is greatest in the upper roll part where the rotational speed of the roll is high and increases with increasing rolling temperature. The increase rate of the mean misorientation angle with increasing temperature is larger than that during symmetrical rolling, and dynamic recrystallization occurs the most when asymmetrical rolling is performed at $500^{\circ}C$. In the case of hot symmetric rolling, the {001}<110> rotated cube orientation mainly develops, but in the case of hot asymmetric rolling, the {111}<110> orientation develops along with the {001}<100> cube orientation. The hot asymmetric rolling improves the formability (${\bar{r}}$) of the aluminum 6061 alloy to 0.9 and reduces the plastic anisotropy (${\Delta}r$) to near zero due to the {111}<110> shear orientation that develops by asymmetric rolling.