• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.313-316
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• 2008

This work sought to examine the suitability of twin roll strip casting for Ag-27%Cu-25%Zn-3%Sn brazing alloy (BAg-7A) and to investigate the mechanical properties and microstructure of the strip. The effect of aging heat treatment on the properties was also studied,. This new manufacturing process has applications in the production of the brazing alloy. XRD and microstructural analysis of the Ag-27%Cu-25%Zn-3%Sn strip represented eutectic microstructure of a Cu-rich phase and a Ag-rich matrix regardless of heat treatment. The results of mechanical tests showed tensile strength of 470MPa, a significant enhancement, and an 18% elongation of the twin roll casted strip, due mainly to the solid solution strengthening of Zn atoms (${\sim}20%$) in the Cu-rich phases. Tensile results showed gradually decreasing strengths and increasing elongation with aging heat treatment. Microstructural evolution and fractography were also investigated and related to the mechanical properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.104-107
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• 2001

In order to investigate the effect of Ge addition to the Cu matrix on the microstructure and the critical current density, four kinds of internal tin processed Nb$_3$Sn strands with pure Cu and Cu 0.2, 0.4, 0.6 wt % Ge alloys were drawn to 0.8 mm diameter. The microstructure and critical current of internal tin processed Nb$_3$Sn wires that were heat treated at temperatures ranging from 68$0^{\circ}C$ to 74$0^{\circ}C$ for 240h were investigated. The Ge addition to the matrix did not make workability worse. A Ge rich layer in the Cu-Ge matrix suppressed the growth of the Nb$_3$Sn layer and promoted grain coarsening. The greater the Ge content in the matrix, the lower the net Jc result after Nb$_3$sn reaction heat treatment. There was no significant variation in Jc observed with heat treatment temperature ranging from 68$0^{\circ}C$ to 74$0^{\circ}C$. The values of AC loss of Ge added wires were decreased to 40 % compare with no addition wire. Low AC loss was due to segregation of Ge rich layer in the Cu-Ge matrix. If Ge added wire with thin Nb filaments were fabricated, slow diffusion rate of Sn would be overcome and decreased AC loss that is weak Point of internal tin method.

• BMB Reports
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• v.28 no.4
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• pp.311-315
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• 1995

Exogenous $Cu^{2+}$ or $Zn^{2+}$ at micromolar concentration had a strong inhibitory effect on detergent-solubilized cytochrome c oxidase. A similar effect was observed when $Cu^{2+}$ was added to vesicular cytochrome c oxidase, although the extent of inhibition was significantly larger for the uncoupled state than for the coupled state. Interestingly, the inhibition by $Zn^{2+}$ was almost negligible for both the coupled and uncoupled states. These results suggest that the binding sites for $Cu^{2+}$ ions are exposed to the extravesicular side. whereas those for $Zn^{2+}$ are exposed to the matrix side. The EPR spectra of bound $Cu^{2+}$ ions at 77 K indicate that each of the first two $Cu^{2+}$ ions is ligated by three or four histidine residues, as evidenced by distinct $^{14}N$ superhyperfine splitting. These $Cu^{2+}$ ions can not be removed readily by EDTA and inhibit the enzyme activity by as much as 80%.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.2
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• pp.79-85
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• 2024

The effects of annealing heat treatment and the addition of Cu element on the shape memory effect of the NiTi-based alloy were investigated by analyzing differential scanning calorimeter results and characterizing recovery rate through 3D scanning after Vickers hardness test. Through 3D scanning of impressions after Vickers hardness test, the strain recovery rates for specimens without annealing treatment and annealed specimens at 400, 450, and 500℃ were measured as 45.96%, 46.76%, 52.37%, and 43.57%, respectively. This is because as the annealing temperature increases, both B19' and NiTi₂ phases, which can impede martensitic transformation, are incorporated within the NiTi matrix. Particularly, additional phase transformation from R-phase to B19' observed in specimens annealed at 400 and 450℃ significantly contributes to the improvement in strain recovery rates. Additionally, the results regarding the Cu element content indicate that when the total content of Ni and Cu is below 49.6 at.%, the precipitation of fine B19' and NiTi₂ phases within the matrix can greatly influence the transformation enthalpy and temperature range, resulting in relatively lower strain recovery rates in NiTi alloys with a small amount of Cu element produced in this study.

• Journal of Powder Materials
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• v.7 no.1
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• pp.12-18
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• 2000

Effects of the microstrucrure of rapidy solidified Al-Pb-Cu-Mg alloys on the wear investigated. In order to overcome the miscility gap between Al and pb under equilibrium conditions, both in the solid and the liquid states, the alloy were rapidy solidifies to produce them in a segregation-free condition. Although the Pb particles showed relatively fine dispersion in the Al matrix in all the alloys by this process. the Al-16Pb alloy was found to have the most favorable microstructure with discretre with discrete Pb particles of abount 0.5 ${\mu}$m in size. With the addition of Cu and Cu-Mg to Al-16Pb, cellular structures were newly formed; not seen in the binary Al-Pb alloy. Wear properties of the Al-Pb binary alloys measured as a function of the sliding speen, sliding distance, and applied load showed that the Al-16Pb alloy has the best wear resistance, as expected from the fine microstructural features in this alloy. The were resistance of the alloy containing Cu-and Cu-Mg was higher than that of the Al-16Pvb alloy, due to matrix strengthening by precipitation hardeing. The wear mechanism was identified by examining the traces and wear debris.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.1
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• pp.10-16
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• 2010

The microstructure of Cu-Mg-P alloy sheet consisted of Cu matrix and very fine MgP precipitate, and it has been observed that the microstructure remains virtually unchanged by Ag additions up to 2%. Ag solutes were dissolved into the matrix and hardly found in the precipitates. The hardness increased with increase of the Ag content, while the conductivity slightly decreased. Strain hardening through cold rolling was found to be effective in improving the hardness, especially in high-Ag alloys. Aging treatment was conducted either before the first cold rolling or between the first and the final cold rolling, and the conductivity was significantly higher at the former case, regardless of the Ag content. Softening of Cu-Mg-P alloy sheet was remarkable above $400^{\circ}C$ and the Ag content did not show any significant effect on it.

• Korean Journal of Metals and Materials
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• v.47 no.4
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• pp.217-222
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• 2009

Cu as a tramp element has been reported to encourage transverse cracking upon straightening operation during continuous casting or mini-mill processing. Therefore, the hot workability of steels containing Cu should be investigated. The purpose of the present study was to examine the effect of Cu contents on the hot ductility of low carbon steels by using hot compression test. Hot compression test was carried out using a Gleeble. The specimens were heated to $1300^{\circ}C$ for solution treatment and then held for 300s before cooling at a rate of $1^{\circ}C/s$ to test temperatures in the range of $650{\sim}1150^{\circ}C$ ($50^{\circ}C$ intervals) with strain rate of $5{\times}10^{-3}/s$. In Cu containing steels, the hot ductility was decreased with increasing Cu content at high temperature region which is to be attributed to copper enriched phase formed at scale/steel interface, and low hot ductility with increasing Cu content at low temperature region is attributable to the strengthening of matrix by the formation of ${\varepsilon}-Cu$. The width of ductility trough region was decreased with increasing Cu content.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.69-76
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• 1999

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of upset pressure on friction weldability. Under the condition of friction time 0.8sec, upset pressure 150MPa, the tensile strength and Charpy impact value of the friction welded joint were 336MPa, $400KJ/m^2$ respectively. And highest temperature of the weld measured was below $800^{circ}K$ which is very lower than melting point of Cu($1356^{circ}K$). Under the same conditions, W grains picked up in Cu matrix from Cu-W profitably affected on these mechanical fracture, and were dispersed in Cu by plastic flow during brake time.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.1
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• pp.47-58
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• 2004

Loss factors of A356, Mn-Cu alloy and aluminum matrix composites reinforced with $SiC_p$ and Ni-coated graphite particles at various contents have been investigated using clamped-free cantilever beam method. The loss factors of half-power bandwidth of the specimens were measured over a wide range of frequencies from 50 to 3300Hz. Among the specimens, Al-10%$SiC_p$-10%$C_p$ showed the highest loss factor at the mode I, while Mn-Cu alloy showed the highest loss factors at the modes II and III. Consequently, at the mode I the Al-10%$SiC_p$--10%$C_p$ showed the loss factor of 0.00093, which is 2.64 and 1.58 times higher than those of A356 and Mn-Cu alloy, respectively.

• Journal of Powder Materials
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• v.13 no.5 s.58
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• pp.366-370
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• 2006

The microstructure and mechanical properties of hot-pressed $Al_2O_3/Cu$ composites with a different sintering temperature have been studied. The size of matrix grain and Cu dispersion in composites increased with increase in sintering temperature. Fracture toughness of the composite sintered at high temperature exhibited an enhanced value. The toughness increase was explained by the thermal residual stress, crack bridging and crack branching by the formation of microcrack. The nanocomposite, hot-pressed at $1450^{\circ}C$, showed the maximum fracture strength of 707 MPa. The strengthening was mainly attributed to the refinement of matrix grains and the increased toughness.