• 비파괴검사학회지
• /
• 제33권1호
• /
• pp.20-25
• /
• 2013

열화 정도를 예측하기 위한 비파괴기법으로 초음파기법이 널리 적용되고 있다. 초음파 속도와 감쇠 특성은 일반적으로 금속재료의 물성 변화에 따라 변화하기 때문에 초음파 속도와 감쇠 특성을 이용하여 금속재료의 열화 정도를 간접적으로 예측할 수 있다. 따라서, 본 연구에서는 반복하중으로 인하여 피로파괴 발생 가능성이 높은 볼트, 리벳 접합의 구조용재 및 선박 차량에 사용되고 있는 Al6061-T6을 피로수명의 0%, 55%, 70%, 85%인 시험편을 제작하였고, 가공된 시험편의 감쇠 특성을 이용하여 측정된 열화 이미지로 Al6061-T6의 건전부와 열화부를 판단하였으며, 건전부와 열화부의 감쇠 특성 차이를 계산하여 Al6061-T6의 열화 진행 정도를 평가하였다.

• 한국재료학회지
• /
• 제5권7호
• /
• pp.765-774
• /
• 1995

입자강화 알루미늄 복합재료의 고온거동을 조사하기위하여, 온도 623K~823K에서 $10^{-2}$ ~1.0 S$^{-1}$ 변형속도로 열간 압축 가공 시험을 행하여 복합재의 고온유동응력에 미치는 강화입자의 첨가량, 강화입자의 종류 및 크기와 변형속도 및 변형온도 등의 영향을 조사하였다. 강화입자의 체적분율이 증가함에 따라서 고온유동음력은 증가하였으나 항복점에서의 차이가 변형량이 증가되어도 그대로 유지되고 있었다. 변형속도 민감도(m)로 볼때 SiCp첨가된 복합재가 A1$_2$O$_3$p를 첨가한 복합재보다 비교적 균일하게 가공할 수 있음을 알 수 있었으며, 823K에서 최적변형속도는 0.1Sec$^{-1}$ 이었다. 변형에 필요한 활성화 에너지는 A6061기지금속이 290KJmole$^{-1}$, A6061-20vo1% SiCp = 327KJmo1e$^{-1}$, A6061-20vo1% $Al_2$O$_3$= 531KJmole$^{-1}$이었다. 이것은 알루미늄의 자기활성화에너지 138KJmo1e$^{-1}$보다 큰 값으로 A1$_2$O$_3$강화복합재료가 SiCp 강화 복합재료보다 열간가공이 어렵다는 것을 나타내는 것이다.

• 한국가스학회지
• /
• 제19권5호
• /
• pp.41-46
• /
• 2015

알루미늄 6061-T6는 $Mg_2Si$와 ${\beta}-Al_5FeSi$로 구성되며, 피로 손상도가 증가하면 ${\beta}-Al_5FeSi$주변에서 기공이 발생하고 성장하는 것으로 알려져 있다. 본 연구에서는 우선 알루미늄 6061-T6 시편에 대한 SEM 촬영을 통해 이러한 현상을 확인하였다. 이후, 피로 손상도에 따라 이 시편의 전위댐핑 (dislocation damping), 정합변형률 (coherency strain), 및 기공 (void)이 감쇠계수와 비선형인자에 미치는 영향을 실험적으로 관찰하였다. 그 결과 비선형인자는 피로 손상도가 증가에 따라 증가하다가 피로수명 75% 이후에서는 감소하는 것을 확인하였다. 이는 전위댐핑과 정합변형률이 증가할수록 비선형인자는 증가하지만, 기공이 증가하면 초음파의 산란이 커져 비선형인자가 감소하는 것으로 해석할 수 있다. 따라서, 피로에 따라 조직변화가 복잡하게 나타나는 재료의 열화 평가에 있어서는 비선형인자를 주의하여 활용하여야 한다는 결론을 얻었다.

• 한국표면공학회지
• /
• 제41권6호
• /
• pp.341-350
• /
• 2008

In friction stir welding for 6061-T6 with various traveling speed and rotation speed conditions, the best mechanical characteristics presented in traveling speed of 507 mm/min and rotation speed of 1100RPM. The maximum tensile strength and yield strength increased with the increasing of traveling speed. The result of the electrochemical characteristic evaluation in friction stir welding at optimum conditions for 6061-T6 Al alloy presented a good characteristics compare to base metal.

• 한국표면공학회지
• /
• 제52권3호
• /
• pp.117-122
• /
• 2019

In this study, surface porosity and corrosion resistance of PEO coatings prepared on the 6061 Al alloy were investigated in terms of sodium phosphate ($Na_3PO_4$) concentrations in an alkaline solution and $NaAlO_2$ sealing. The surface morphologies of the PEO coatings clearly show that the coatings film formed in $9g\;L^{-1}$ had the lowest porosity. The $NaAlO_2$ sealing was found to remove micropores and cracks existing on the surface of PEO coatings. As a result, the $NaAlO_2$ sealing resulted in the movement of corrosion potential toward more positive value and lower corrosion current density.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 1999년도 춘계학술발표회 초록집
• /
• pp.1-1
• /
• 1999

• Journal of Advanced Marine Engineering and Technology
• /
• 제33권2호
• /
• pp.313-321
• /
• 2009

The construction of fiber-reinforced plastic (FRP) boats is decreasing trend since the application of international regulations on the control of marine environmental pollution, which recommended the use of environmentally friendly materials. The aluminum alloy used with material for ship is a superior to FRP. It is environmental friendly, easy to recycle, and provides a high added value to fishing boats. However, the welding for Al alloy materials have many problems, such as deformation by welding heat and effect of the working environment. In this paper, it was carried out welding by robot with welding material of ER5183 and ER5556 on 6061-T6 Al alloy for ship. The mechanical and electrochemical characteristics evaluated for specimen welded by robot. The cathodic polarization trend for the base metal and welding metal showed the effects of concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation. The hardnesses of welding zone and heat affected zone are lower than that of base metal. At the result of tensile test, the specimen welded with ER5183 presented excellent property compared with ER5556.

• 한국재료학회지
• /
• 제13권1호
• /
• pp.64-68
• /
• 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.

• 열처리공학회지
• /
• 제20권4호
• /
• pp.181-186
• /
• 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
• /
• 제57권3호
• /
• pp.201-207
• /
• 2024

This study compared the chemical resistance properties according to various sealing treatment methods for the anode film formed during the anodization process of Al6061 alloy. Al6061 aluminum was used in four different sealing treatment methods: boiling water sealing, lithium sealing, nickel sealing, and pressurized sealing, and each sample was evaluated for corrosion resistance through a 5% HCl bubble test and the microstructure was observed through a scanning electron microscope(SEM). According to the results, corrosion resistance increased as time and temperature increased in all sealing treatment methods. Relatively, corrosion resistance was high in the order of boiling water sealing, lithium sealing, nickel sealing, and pressure sealing, and the best corrosion resistance was found in pressure sealing. These research results can be helpful in selecting a process necessary to improve the efficiency and performance of anodizing process in the industrial field using aluminum alloys.