• 한국표면공학회지
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• 제52권4호
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• pp.203-210
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• 2019

In this work, anodizing behavior of 6xxx series aluminum alloys was studied under constant current density and constant voltage conditions in 20% sulfuric acid solution by V-t curves, I-t curves, thickness measurement, observations of surface appearance and cross-sectional observation of anodizing films. The film growth rate of the anodizing films on Al6063, Al6061 and Al6082 obtained at 20 V were $0.63{\mu}m/min$. $0.46{\mu}m/min$ and $0.38{\mu}m/min$, respectively. Time to the initiation of imperfections at the oxide/substrate interface under constant current condition was shortened and colors of anodizing films became darker with the amount of alloying elements in 6xxx series aluminum alloys. Based upon the experimental results obtained in this work, it is concluded that maximum anodizing film thickness without interfacial defects is reduced with increasing amount of alloying elements and brighter anodizing films can be obtained by decreasing amount of alloying elements in the aluminum alloys.

• 열처리공학회지
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• 제9권2호
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• pp.121-129
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• 1996

The solubility of Ti in Al matrix was determined by X-ray diffraction method on two different mechanical alloying systems, i.e Al+$Al_3Ti$ and Al+Ti alloys. Starting powder compositions of two systems were chosen for final volume fraction of $Al_3Ti$ phase being 25%. The solubility of Ti in ${\alpha}$-Al was estimated by the lattice parameter measurement of Al. For Al+$Al_3Ti$ mixture, it appeared that some of $Al_3Ti$ particles decomposed during milling and maximum solubility of Ti in Al was about 0.99%. The majority of $Al_3Ti$ particles were dispersed uniformly in Al matrix, having approximate size of 100~200 nm. On the other hand, higher Ti solubility of 1.24 wt.% was found in Al+Ti system, with starting composition of Al+10 wt.%Ti. After 15 hours of milling, Ti phase was identified as 20 nm sized particles embedded in Al matrix. The annealing of mechanically alloyed powders from Al+$Al_3Ti$ and Al+10 wt.%Ti systems was followed in the temperature range of 200 to $600^{\circ}C$ to study thermal stability of supersaturated solution of Al(Ti). After annealing, the lattice parameter of Al reverted back to that of pure Al, and the peak intensity ratio of $Al_3Ti$/Al was increased more than the original value before annealing. These results suggest that Ti dissolve into alpha-Al solutions during milling, and by annealing, $Do_{22}-Al_3Ti$ phase forms from Al(Ti) solution.

• 소성∙가공
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• 제7권5호
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• pp.465-473
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• 1998

The effect of alloying elements of Ag-Cu-Zr-X brazing alloy on the microstructure and the bond strength of $Al_2O_3/Ni-Cr$ brazed steel joint was investigated. The reaction layer, $ZrO_2$ (a=5.146 ${\AA}$ , b=5.213 ${\AA}$ , c=5.311 ${\AA}$ )was formed at the interface of $Al_2O_3/Ni-Cr$ steel joint by the redox reaction between alumina and Zr. The addition of An and Al to the Ag-Cu-Zr brazing alloy gave rise to changes in the thickness of the reaction product layer and the morphology of the brazement. Sn caused the segregation of Zr was decreased b Al the $ZrO_2$ layer formed at the Ag-Cu-Zr-Al alloy was thinner than that of $ZrO_2$ formed at the Ag-Cu-Zr-An alloy. The fracture shear strength was strongly dependent on the microstructure of the brazement. Brazing with Ag-Cu-Zr-Sn alloy resulted in a better bond strength than with Ag-Cu-Zr or Ag-Cu-Zr-Al alloy.

• 한국주조공학회지
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• 제30권1호
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• pp.29-33
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• 2010

The microstructure of Al-5%Mg based alloy mainly consists of aluminum matrix with a small amount of AlMn phase. The addition of Sc or Zn to the base alloy significantly improved the as-cast tensile strength, while the addition of Fe deteriorated both strength and ductility. Although the Al-5%Mg based alloy was not heat-treatable, aging hardening could be observed in the case that Sc or Zn was added to the base alloy. TEM analysis showed that very fine AlSc or AlMgZn precipitates were formed after T6 heat treatment, resulting in enhanced strength. The corrosion resistance measured as corrosion potential was found to decrease a little by adding Zn, whereas other alloying elements were not clearly influential.

• 한국주조공학회지
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• 제26권6호
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• pp.249-257
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• 2006

The effects of alloying element and the condition of heat-treatment on the strength of squeeze-cast Al-3.0 wt%Si alloy were investigated. The strength of the alloy without grain refinement was increased with increase Cu content upto 3.0 wt% and rather decreased beyond that. The tensile strength of the alloy with grain refinement increased with Cu content upto 3.0 wt% and not changed beyond that. The strength of the alloy without grain refinement increased with the Mg content. The tensile strength with grain refinement increased with the Mg content upto 0.50 wt% and then decreased beyond that. The strength of the grain refined alloy increased by individual and simultaneous additions of Cu and Mg and the maximum strength was obtained with Al-3.0 wt%Si-4.5 wt%Cu-0.50 wt%Mg alloy. The optimum heat-treatment condition for this alloy was obtained.

• 한국주조공학회지
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• 제20권1호
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• pp.38-45
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• 2000

The remelting for recycling or thin aluminum scrap, such as aluminum chip generally involves melting of these pieces submerged in molten salt flux. In this study, the effects of salt flux compositions and alloying elements on the aluminum dropletscoalescence and oxide film removal were studied in 99.8%Al, Al-1.01%Cu, Al-1.03%Si, and Al-1.38%Mg alloys as a function of holding time at $740^{\circ}C$ Salt fluxes based on NaCl-KCl(1:1) with addition of 5wt.% fluorides(NaF, $Na_3AlF_6$, $CaF_2$) or 5 wt.% chloride($MgCl_2$, $AlCl_3$) were used. The experimental results show that NaCl-KCl(1:1) with addition of 5 wt.% fluorides exhibits better coalescence ability than that with chlorides. The oxide film is not removed by NaCl-KCl(1:1) with addition of 5 wt.%chlorides, while it is removed by NaCl-KCl(1:1) with addition of 5 wt.% fluorides. The aluminum droplets coalescence and oxide film removal by salt fluxes are related to interfacial tension tension between metal and salt flux.

• 한국분말재료학회지
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• 제26권2호
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• pp.107-111
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• 2019

The activation energy to create a phase transformation or for the reaction to move to the next stage in the milling process can be calculated from the slop of the DSC plot, obtained at the various heating rates for mechanically activated Al-Ni alloy systems by using Kissinger's equation. The mechanically activated material has been called "the driven material" as it creates new phases or intermetallic compounds of AlNi in Al-Ni alloy systems. The reaction time for phase transformation by milling can be calculated using the activation energy obtained from the above mentioned method and from the real required energy. The real required energy (activation energy) could be calculated by subtracting the loss energy from the total input energy (calculated input energy from electric motor). The loss energy and real required energy divided by the reaction time are considered the "metabolic energy" and "the effective input energy", respectively. The milling time for phase transformation at other Al-Co alloy systems from the calculated data of Al-Ni systems can be predicted accordingly.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.722-723
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• 2006

A new method has been developed to fabricate microcomponents by a combination of photolithography and sintering of metallic powder mixtures, without the need for compression and the addition of Mg. This involves (1) the fabrication of a micromould, (2) mould filling of the powder/binder mixture, (3) debinding and (3) sintering. The starting powdered materials consisted of a mixture of aluminium powder(average size of 2.5 um) and alloying elemental powder of Cu and Sn(less than 70nm), at appropriate proportions to achieve nominal compositions of Al-6wt%Cu, Al-6wt%Cu-3wt%Sn. This paper presents detailed investigation of debinding behaviour and microstructural development.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.514-522
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• 1999

The laser-induced plasma affects greatly on the results of welding process. moreover selective evaporation loss of alloying elements leads to change in chemical composition of weld metal as well as the mechanical properties of welded joint. this study was undertaken to obtain a fundamental knowledge of pulsed laser welding phenomena especially evaporation mechanism of different aluminum alloys. The intensities of molecular spectra of AlO and MgO were different each other depeding on the power density of a laser beam Under the low power density condition the MgO band spectrum was predominant in intensity while the AlO spectra became much stronger with an increase in the power density. These behaviors have been attributed to the difference in evaporation phenomena of Al and Mg metals with different boiling points and latent heats of vaporization. The time-averaged plasma temperature and electron number density were determined by spectroscopic methods and consequently the obtained temperature was $3,280{\pm}150K$ and the electron number density was $1.85{\times}10^{19}\;l/m^3$.

• 한국재료학회지
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• 제10권6호
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• pp.403-408
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• 2000

본 연구에서는 고온용 고강도 Al 합금을 제조하기 위해 Al-Cr-Zr 복합금속분말을 attritor에서 300rpm의 회전속도로 20시간 동안 기계적 합금화방법으로 제조한 후 진공 고온 압축성형하였다. Al-Cr-Zr 합금의 미세구조 및 조직관찰은 XRD, TEM 등을 사용하여 분석하였고, 열적 안정성은 열적 노출시간에 따른 미소경도측정을 통하여 조사하였다. 진공 열간 압축성형 되었을 때 MA Al-Cr-Zr 합금의 이론 밀도의 97%에 이르는 조밀화르 f보였으며, $300^{\circ}C$에서 100시간 열처리 한 경우에는 경도변화가 거의 없었고, $500^{\circ}C$에서 100시간 열처리한 경우에도 감소가 6% 이내로 우수한 열적 안정성을 나타내었다. 이와 같은 MA Al-Cr-Zr 합금의 우수한 열적 안정성은 기계적 합금화에 의해 Al 기지 내에 미세하고 균일하게 분산된 Cr과 Zr이 고온 성형과 열처리 과정에 의해 $Al_3Zr,\;Al_{13}Cr_2$의 금속간 화합물들의 형성되었으며, 열처리 후의 이 합금의 최종 결정립 크기는 150mm 크기 이하이었다.