• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.214-215
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• 2009

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.50-50
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• 2000

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.11a
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• pp.39-39
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• 2001

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.82-87
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• 2001

The hot deformation behavior of Ti-6Al-2Sn-4Zr-6Mo(Ti6246) alloy was investigated in both the $\alpha$+$\beta$ and $\beta$-phase fields by conducting compression tests over a strain rate range of $10^{-3}s^{-1}$ to $10^0s^{-1}$. The flow stress was increased with increasing strain rate and decreasing test temperature. The flow curves obtained at temperatures below 90$0^{\circ}C$ exhibited a flow softening. However, in the $\beta$-phase field, above 95$0^{\circ}C$, the flow stress increased monotonically with plastic strain approaching steady state values. Constitutive equations for the dependence of flow stress on strain, strain rate, and temperature were developed through the analysis of the flow curves.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.1
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• pp.10-16
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• 1998

The softening behavior of squeeze cast Mg-Li-Al and Mg-Li-Al-Zr alloys have been investigated. The highest hardness values of Mg-Li-Al and Mg-Li-Al-Zr alloys were obtained after solution treatment at $400^{\circ}C$ for 1 hour. The hardness value, however, decreased as the aging temperature and time increased. Microstructural and calorometric analyses showed that quenched-microstructure changed from primary (${\alpha}$ and ${\beta}$)+secondary ${\alpha}$ to primary(${\alpha}$ and ${\beta}$)+secondary ${\alpha}+{\theta}$ after aging. The softening during aging was due to the coarsening of ${\theta}$ precipitates.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.481-488
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• 1998

The active metal brazing was applied to bond Alumina and Ni-Cr steel by Ag-Cu-Zr-Sn alloy and the interfacial microstructure and reaction mechanism were investigated. Polycrystalline monoclinic $ZrO_2$ with a very fine grain of 100-150 nm formed at the alumina grain boundary contacted with Zr segregation layer at the interface. The $ZrO_2$ layer containing the inclusions and cracks were developed at the boundary of inclusion/$ZrO_2$ due to the difference in specific volume. The development of $ZrO_2$ at the interface was successfully explained by the preferential penetration of $ZrO_2$ at the interface was successfully explained by the preferential penetration of Zr atoms a higher concentration of oxygen and a high diffusion rate of Al ions into molten brazing alloy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.246-249
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• 2000

The effects of Zr on the mechanical workability and tensile strength of Cu-Ni-Mn-Sn-Al alloys have been investigated and the following results were obtained. The mechanical workability of Cu-Ni-Mn-Sn-Al alloys are increased with addition of Zr. And the surface cracks of specimen were not produced in Zr added Alloys. Especially in condition of hot-worked beyond the 90% working ratio, Zr contained specimen showed intra-granule crack propagation but Zr-free specimen showed inter-granule mode. The tensile strength have maximum value in 0.05% Zr contained alloy. The aging mechanism of Cu-Ni-Mn-Sn-Al alloys were varied by Zr addition.

• Journal of Korea Foundry Society
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• v.15 no.2
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• pp.194-200
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• 1995

Rapidly Solidified (RS) Al-Zr base splats with various alloy contents were prepared by atomization-splat quenching method to understand the continuous and discontinuous precipitation in the aged alloys. And the RS alloys were consolidated by hot extrusion and swaging to analyze the effect of plastic deformation on the precipitation behavior. Discontinuous precipitation dominated at relatively low temperature in the Al-Zr alloy, whereas both V additions to Al-Zr alloys and hot metal working appeared to suppress the discontinuous precipitation. As continuous precipitation is favored in the grain interiors, the driving force for discontinuous precipitation become to disappear with a further process.

• Korean Journal of Materials Research
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• v.27 no.10
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• pp.563-568
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• 2017

In this study, the coating of an Al-Cr layer on the surface of a Zircaloy-4 alloy was carried out through plasma pretreatment coating and a laser surface melting process. Two different conditions for laser treatment, severe or minimal surface melting of the Zr alloy substrate, were applied to form the final coating. When there was significant surface melting of the Zr alloy, the solidification microstructure of the newly formed coating layer was mainly composed of needle-shaped $Al_3Zr$, Al(Cr) and $Al_7Cr$ phases. On the other hand, the solidification microstructure of the coating layer was mainly composed of Al(Cr) and $Al_7Cr$ phases when there was minimal surface melting of Zr base in the laser process. However, when the coating was maintained at $1100^{\circ}C$ for 2 hours, significant inter-diffusion occurred between the phases in the coating. As a result, the upper part of the coating layer was observed to mainly consist of $Al_3Zr$ and $Al_8Cr_5$ phases, regardless of the laser treatment conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.12
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• pp.1099-1104
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• 2007

In order to develop non-heated STAl(super thermal resistant Aluminum alloy) for ampacity gain conductor, the systematic research was carried out. Especailly, the effect of a very small amount of Zr, Sc element in EC grade Al ingot on mechanical and electrical properties was our priority. As a result, it was found that the strength and recrystallization temperature of designed alloy was gradually increased with Zr, Sc addition up to 0.3 wt.%. However, the electric conductivity showed no drastic change. The tensile strength and recrystalliztion temperature, $17.75{\sim}20.05\;kgf/mm^2$ and $420{\sim}520\;^{\circ}C$, was obtained at 0.3 wt.% Zr, Sc addition, respectively. Particles of the $Al_3Zr$ and $Al_3Sc$ phase affected the ambient and elevated-temperature strength of the alloys.