• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2001년도 추계학술발표대회 개요집
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• pp.206-208
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• 2001

• 한국산학기술학회논문지
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• 제17권9호
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• pp.663-668
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• 2016

연료의 경제성을 증가시키는 것이 신차 개발에 필수불가결한 이슈가 되고 있으며 연료 경제성을 개선하기 위한 가장 중요한 문제는 차량 무게를 감소시키는 것이다. 본 연구에서는 연료 경제성을 증가시키기 위하여 알루미늄 합금 소재와 같은 경량 소재를 사용하여 무게를 감량시키는 것에 관한 연구를 진행하였다. 이를 위하여 너클(knuckle)의 경량화 설계과정을 주철 소재인 기존 재질 대신에 310 MPa 급의 알루미늄 6061-T6 합금으로 대체함으로써 설계 형상의 변경에 따라 von-Mises stress의 변화를 살펴보는 방법을 통하여 제시하고자 한다. 재료의 변화에 따른 너클 동강성 해석결과를 비교하였으며 FCD600 주철 소재 대비 6061 알루미늄 합금으로 설계된 너클의 동강성은 약 30% 내외 더 우수한 것으로 나타났다. 보통 동강성의 경우 진동에도 영향을 주기 때문에 동강성이 큰 경우 진동적으로도 우수한 경향을 나타낸다. 본 연구를 통하여 경량화 설계에 대한 가이드가 되는 성과를 얻을 수 있었으며 차량용 너클 개발을 위한 최적 설계 조건을 제시하는 데 기여하고자 한다.

• 대한금속재료학회지
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• 제47권3호
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• pp.175-181
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• 2009

Mechanical properties and precipitation behavior of backward extruded 6061 Al alloy for pressure vessel were investigated using tensile test, transmission electron microscopy (TEM) and differential scanning calorimeter (DSC). In this study, solution heat treatment (SHT) was performed at $535^{\circ}C$ for 30~90 min and aging treatment was conducted at 177 and $190^{\circ}C$ for 1~7 h. Maximum tensile strength of $36.6kgf/mm^2$ and yield strength of $33.29kgf/mm^2$ were achieved at the aging time of 5 h at $190^{\circ}C$. TEM observation showed that fine needle-like ${\beta}^{{\prime}{\prime}}$ phase which has 35~45 nm of length was uniformly distributed in the aged 6061 Al alloy specimen. From tensile test, TEM and DSC analysis, it is expected that aging time of 2~5 h at $190^{\circ}C$ is suitable for the extruded A6061 used as pressure vessels.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.254-257
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• 2007

In this study, hydroformability and mechanical properties of pre- and post- heat treated Al6061 tubes at different extrusion type were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, uni-axial tensile test and free bulge test were performed at room temperature and $200^{\circ}C$. Also mechanical properties of hydroformed part at various pre- and post-heat treatments were estimated by tensile test. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube at $200^{\circ}C$. As for the heat treatment, hydroformability of full annealed tube is 25% higher than that of extruded tube. The tensile strength and elongation were more than 330MPa and 12%, respectively, when hydroformed part was post-T6 treated after hydroforming of pre- full annealed tube. However, hydroformed part using T6 pre treated tube represents high strength and low elongation, 8%. Therefore, the T6 treatment after hydroforming for as-extruded tube is cost-effective. Hydroformability of Al6061 tube showed similar value for both extrusion types. But flow stress of seam tube showed $20{\sim}50MPa$ lower value.

• 한국재료학회지
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• 제13권1호
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• pp.64-68
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• 2003

The 1.6 vol% and 2.5 vol% TiNi/6061Al composites were fabricated by permanent mold casting for investigating the effect of heat treatment on tensile strength for composites. The tensile strength without T6 treatment at 293 K was increased with increasing the volume fraction of TiNi fiber and at 363 K the higher the pre-strain, the higher the tensile strength. The tensile strength of the composite with $T_{6}$ treatment at 293 K was found to increase with increasing both the amount of pre-strain and the volume fraction of TiNi fiber and was higher than that without $T_{6}$ treatment. It should be noted that the tensile strength 2.5vol%TiNi/6061Al composites rolled at a 38% reduction ratio was the maximum value of 298 MPa. The tensile strength of composites decreased with increasing the reduction ratio over 38% because of the rupture of TiNi fiber.

• 소성∙가공
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• 제14권1호
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• pp.71-77
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• 2005

Thermal stability and dry sliding wear behavior of ultra-fine grained 6061 Al alloy fabricated by an accumulative roll-bonding (ARB) process have been investigated. After 4 ARB cycles, an ultra-fine grained microstructure of the 6061 Al alloy composed of grains with average size of 500nm, and separated mostly by high-angle boundaries was obtained. Though hardness and tensile strength of the ARB processed Al alloy increased with ARB cycles up to 4 cycles, the processed alloy exhibited decreased ductility and little strain hardening. Thermal stability of the ARB-processed microstructure was studied by annealing of the severely deformed alloy at $423K{\sim}573K$. The refined microstructure of the alloy remained stable up to 473K, and the peak aging treatment of the alloy at 450K for 8 hrs increased the thermal stability of the alloy. Sliding-wear rates of the alloy increased with the number of ARB cycles in spite of the increased hardness with the cycles. Wear mechanisms of the ultra-fine grained alloy were investigated by examining worn surfaces, wear debris, and cross-sections by a scanning electron microscopy (SEM).

• 소성∙가공
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• 제16권5호통권95호
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• pp.354-359
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• 2007

Effects of forging and mechanical properties of 6061 aluminum alloy wheel for automobiles were investigated in the present study. Microstructural and tensile characteristics of automobile wheel after hot forging process using dynamic screw press were analyzed to evaluate effect of metal flow on mechanical properties. The results showed advanced mechanical properties of 6061 alloy wheel because of $Mg_2Si$ precipitation by T6, elongated grain by forging, and work hardening by dense metal flow, etc. Hot compression tests were conducted in order to characterize high temperature compression deformation behaviors and microstructural variation in the range of $300{\sim}450^{\circ}C$, in the strain rate range of $10^{-3}{\sim}10^1\;sec^{-1}$. As strain rate increased, maximum compression stress increased but it was shown the reverse linear relation between temperature and maximum stress irrelevant to strain rate variation. On the other hand, temperature and yield stress didn't have any linear relation and its relation showed big deviation by a function of strain rate and test temperature.

• 열처리공학회지
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• 제20권4호
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• pp.181-186
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• 2007

Effect of heat treatment conditions on formability and property of warm hydroformed parts for Al 6061 extruded tubes was investigated in this study. For the investigation, as-extruded, fully annealed and T6-treated Al 6061 seamless tubes were prepared. To evaluate the warm hydroformability, uni-axial tensile test and free bulge test were performed at various pre- and post-heat treatment conditions. And the tensile test specimens were obtained from hexagonal prototype hydroformed parts at $250^{\circ}C$. As a result, hydroformability of fully annealed tube is 25% higher than that of extruded tube. The tensile strength and strain of hydroformed part reach to 330 MPa and 12%, respectively, when the part was T6 treated after warm hydroforming. However, the hydroformability of T6 pre-treated tube is relatively low due to the decreased elongation, 8%.

• 한국표면공학회지
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• 제55권5호
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• pp.273-283
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• 2022

Al6061 aluminum alloy specimens were exposed to atmospheric conditions for maximum 24 months. 24-month exposure specimen showed some more frequent and larger size of corrosion products and pitting on the surface compared with the 12-month exposure specimens. The XRD examination revealed the dominant surface oxide phases of Al₂O₃ and Al(OH)₃. The oxide thickness at uniform oxidation (or non-pitting) region was not much changed over exposure time. The 1.2 ㎛ deep oxygen penetration area was found in the 12-months exposed specimen near the thin uniform aluminum oxide film. The line-EDS was conducted through the penetration regions and non-penetrated grain boundary. There were signs of O and Si concentration through the penetration region, whereas non-penetration region showed no concentration of O or Si. It was confirmed that pitting is a more severe degradation mode in Al6061 (max. >4 ㎛ deep) compared with the uniform oxidation (max. ~200 nm deep) up to 24-months exposure.

• 한국기계가공학회지
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• 제14권2호
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• pp.59-66
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• 2015

The production of high value-added products requires efficient processing and this constant demand for complex shape processing has led to the need for hybrid processing. In this study, the surface characteristics of hybrid machining, which combines wire-cut E.D.M and vibration, are examined. The selected experimental parameters are verticality, waveform, amplitude, peak current and frequency. The experimental results provide a guideline for selecting reasonable machining parameters. Surface roughness was improved by increasing the amplitude of the vibration.