• Journal of Welding and Joining
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• v.23 no.6
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• pp.93-98
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• 2005

The purpose of this study is to investigate the characteristics of pb-free $Zn-(3\~6)\%Al-(1\~6)\%Cu$ solder alloys for ultra high temperature(>573K) which applied to air craft, space satellite, automotive, oil, gas well exploration and data logging of geo-thermal wells. Melting range, solderability, electric resistivity, microstructure and mechanical properties were examined with solder alloys casted in Ar gas atmosphere. $Zn-4\%Al-(1\~3)\%Cu,\;Zn-5\%Al-(2\~4)\%Cu\;and\;Zn-6\%Al-(3\~5)\%Cu$ alloys satisfied the optimum melting range of 643 to 673k for ultra high temperature solder. A melting temperature increased with increasing Cu content, but decreased with increasing Al content. The spreadability was improved with increasing hi content. But the content of Cu had no effect on the spreadability. The electric resistivity was lowered with increasing Al and decreasing Cu content. In all Zn-Al-Cu solder alloys, primary dendritic $\varepsilon$ phase(Zn-Cu), dendritic $\eta$ phase(Zn-Cu-Al), $\alpha(Al-Zn)-\eta$ eutectic and eutectoid phase were observed. The addition of Al increased the volume fraction of eutectic and eutectoid phase and it decreased f phases. Also, the addition of Cu increased slightly the volume fraction of e, the eutectic and eutectoid phases. With increasing total content of Al and Cu, a hardness and a tensile strength were linearly increased, but anelongation was linearly decreased.

• Korean Journal of Materials Research
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• v.16 no.2
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• pp.137-143
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• 2006

The effects of Cu and Fe additions on the thermal stability, microstructure and mechanical properties of $Al_{85}-Ni_{8.5}-Mm_{6.5},\;Al_{84}-Ni_{8.5}-Mm_{6.5}Cu_1,\;Al_{84}-Ni_{8.5}-M_{m6.5}Fe_1$ alloys, manufactured by gas atomization, degassing and hot-extrusion were investigated. Gas atomization, with a wide super-cooled liquid region, allowed the alloy powders to exhibit varying microstructure depending primarily on the powder size and composition. Al hotextruded alloys consisted of homogeneously-distributed fine-grained fcc-Al matrix and intermetallic compounds. A substitution of 1 at.% Al by Cu increased the thermal stability of the amorphous phase and produced alloy microstructure with smaller fcc-Al grains. On the other hand, the same substitution of 1 at.% Al by Fe decreased the stability of the amorphous phase and produced larger fcc-Al grains. The formation of intermetallic compounds such as $Al_3Ni,\;Al_{11}Ce_3\;and\;Al_{11}La_3$ was suppressed by the addition of Cu or Fe. Among the three alloys examined, the highest Vickers hardness and compressive strength were obtained for $Al_{84}-Ni_{8.5}-M_{m6.5}Cu_1$ alloy, and related to the finest fcc-Al grain size attained from increased thermal stability with Cu addition.

• Korean Journal of Metals and Materials
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• v.49 no.8
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• pp.642-648
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• 2011

This paper describes an experimental study on ultrasonic welding of similar and dissimilar metals. There are optimum welding conditions which are found for welding of Al/Al and Al/Cu. It evaluated weldability using tensile test, SEM observation and EDX-ray analysis. Both ultrasonic welding of Al/Al and Al/Cu have amplitude as the variable factor. Al/Cu welding was examined again with welding time as variable factor to find the best conditions. The more welding time or amplitude increase, the better weldability. The optimum conditions for ultrasonic welding of Al/Al were formed at pressure 0.25 MPa, welding time 0.25 sec, amplitude 90%. Pressure 0.25 MPa, welding time 0.4 sec, amplitude 80% are optimized for Al/Cu ultrasonic metal welding and solid-state diffusion generated by ultrasonic vibration and frictional heat is confirmed at the welded interface.

• Journal of Korea Foundry Society
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• v.41 no.6
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• pp.528-534
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• 2021

To confirm effects of natural and artificial aging of precipitate on thermal diffusivity and hardness, the studied Al-Mg-Si alloy were manufactured by gravity casting method with 0.6 wt% and 1.0 wt% additional Cu element. The samples were used for measuring thermal diffusivity and hardness. The addition of Cu, promoted by intermediates such as Q'' and θ'' phases, contributing to the improvement of hardness and high-temperature thermal diffusivity. The natural aging decreased the hardness of the Al-Mg-Si-Cu alloys with increasing time, but did not affect the thermal diffusivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.386-391
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• 2003

Sing1e crystal $CuAlSe_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $410^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $CuAlSe_2$source at $680^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence(PL) and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $CuAlSe_2$ thin films measured with Hall effect by van der Pauw method are $9.24{\times}10^{16}\;cm^{-3}$ and $295\;cm^2/V{\cdot}\;s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuAlSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;2.8382\;eV\;-\;(8.86\;{\times}\;10^{-4}\;eV/K)T^2/(T\;+\;155K)$. After the as-grown single crystal $CuAlSe_2$ thin films were annealed in Cu-, Se-, and Al-atmospheres, the origin of point defects of single crystal $CuAlSe_2$ thin films has been investigated by PL at 10 K. The native defects of $V_{Cd}$, $V_{Se}$, $Cd_{int}$, and $Se_{int}$ obtained by PL measurements were classified as donors or accepters. And we concluded that the heat-treatment in the Cu-atmosphere converted single crystal $CuAlSe_2$ thin films to an optical n-type. Also, we confirmed that Al in $CuAlSe_2/GaAs$ did not form the native defects because Al in single crystal $CuAlSe_2$ thin films existed in the form of stable bonds.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.871-880
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• 2003

Single crystal CuAlSe$_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at 410 C with hot wall epitaxy (HWE) system by evaporating CuAlSe$_2$ source at 680 C. The crystalline structure of the single crystal thin films was investigated by the photoluminescence(PL) and double crystal X -ray diffraction (DCXD). The carrier density and mobility of single crystal CuAlSe$_2$ thin films measured with Hall effect by van der Pauw method are 9.24${\times}$10$\^$16/ cm$\^$-3/ and 295 cm$^2$/V $.$ s at 293 K, respectively. The temperature dependence of the energy band gap of the CuAlSe$_2$ obtained from the absorption spectra was well described by the Varshni's relation, Eg(T) = 2.8382 eV - (8.86 ${\times}$ 10$\^$-4/ eV/K)T$^2$/(T + 155K). After the as-grown single crystal CuAlSe$_2$ thin films were annealed in Cu-, Se-, and Al-atmospheres, the origin of point defects of single crystal CuAlSe$_2$ thin films has been investigated by PL at 10 K. The native defects of V$\_$cd/, V$\_$se/, Cd$\_$int/, and Se$\_$int/ obtained by PL measurements were classified as donors or acceptors. And we concluded that the heat-treatment in the Cu-atmosphere converted single crystal CuAlSe$_2$ thin films to an optical n-type. Also, we confirmed that Al in CuAlSe$_2$/GaAs did not form the native defects because Al in single crystal CuAlSe$_2$ thin films existed in the form of stable bonds.

• Korean Journal of Metals and Materials
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• v.47 no.4
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• pp.223-227
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• 2009

The precipitates, hardness, and tensile properties of Al-6.2Si-2.9Cu AC2B alloy were investigated with respect to solution treatment time at $500^{\circ}C$. $Al(Cu)-Al_2Cu$ eutectic, Si, ${\theta}-(Al_2Cu)$, and $Q-(Al_5Cu_2Mg_8Si_6)$ phases were observed in the as-cast specimen. With increasing the solution treatment time at $500^{\circ}C$, the $Al(Cu)-Al_2Cu$ eutectic and ${\theta}-(Al_2Cu)$ phases were gradually reduced and finally almost disappeared in 5 h. The mechanical properties, such as hardness, tensile strength, and elongation, were improved with solution treatment time until about 5 h due to the dissolution of the $Al_2Cu$ particles. With further holding time, the mechanical properties did not change much. The solution treated specimens for over 5 h at $500^{\circ}C$ exhibit almost the same tensile properties even after aging at $250^{\circ}C$ for 3.5 h. Accordingly, the optimal solution treatment condition of the Al-Si-Cu AC2B alloy is considered to be 5 h at $500^{\circ}C$.

• Journal of Powder Materials
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• v.9 no.1
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• pp.19-24
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• 2002

This paper reports the results of an investigation into the effect of Cu additions upon the nano-crystallization behaviour of an Al-Y-Ni alloy. 1 at.% Cu was added to a base alloy of Al/sub 88/Y₄Ni/sub 8/ either by substitution for Al to form Al/sub 87/Y₄Ni/sub 8/Cu₁, or by substitution for Ni to form Al/sub 88/Y₄Ni/sub 7/Cu₁. Consistent with previous findings in the literature, the substitution of Cu for Al was found to increase the thermal stability of the amorphous phase whereas the substitution of Cu for Ni was found to decrease its thermal stability. Comparing the microstructures of these alloys after heat treatment to produce equivalent volume fractions of Al nanocrystals showed average grain sizes of 14 nm, 12 nm and 9 nm for the alloys Al/sub 88/Y₄Ni/sub 8/, Al/sub 87/Y₄Ni/sub 8/Cu₁respectively. The effect of Cu in refining the size of the nanocrystals was attributed to enhanced nucleation increasing the number density of the nanocrystals, rather than diffusion limited or interface limited growth.

• Journal of Powder Materials
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• v.13 no.1 s.54
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• pp.33-38
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• 2006

The effect of Cu content on microstructure and mechanical properties of nano-sized Cu dispersed $Al_2O_3(Al_2O_3/Cu)$ nanocomposites was investigated. The nanocomposites with Cu content of 2.5 to 10 vol% were prepared by reduction and hot-pressing of $Al_2O_3/CuO$ powder mixtures. The nanocomposites with Cu content of 2.5 and 5vol% exhibited the maximum fracture strength of 820MPa and enhanced toughness compared with monolithic $Al_2O_3$. The strengthening was mainly attributed to the refinement of $Al_2O_3$ matrix grains. The toughening mechanism was discussed by the observed microstructural feature based on crack bridging.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.3
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• pp.150-158
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• 2022

The effects of scandium addition on the Al-6Si-2Cu Alloy were investigated. The Al-6Si-2Cu-Sc alloy was prepared by gravity die casting process. In this study, scandium was added at 0.2 wt%, 0.4 wt%, 0.8 wt%, and 1.0 wt%. The microstructure of Al-6Si-2Cu-Sc alloy was investigated using Optical Microscope, Field Emission Scanning Electron Microscope, Electron Back Scatter Diffraction, and Transmission Electron microscope. The microstructure of Al-6Si-2Cu alloy with scandium added changed from dendrite structure to equiaxed crystal structure in specimens of 0.4 wt% Sc or more, and coarse needle-shape eutectic Si and β-Al₅FeSi phases were segmented and refined. The nanosized Al₃Sc intermetallic compound was observed to be uniformly distributed in the modified Al matrix.