• Korean Journal of Materials Research
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• v.17 no.5
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• pp.244-249
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• 2007

The properties of anodized films on aluminum 6061 alloy in single electrolyte of sulfuric acid and mixed electrolyte of sulfuric-boric acid and sulfuric-boric-nitric acid have been studied. Polarization tests in NaC solution were used to investigate the corrosion performance. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM and EDS. The results obtained have indicated that oxide films growth have been promoted by nitric acid and anodized films in mixed electrolyte have superior corrosion resistance. In case of anodic films formed in mixed electrolyte, some grooves and numerous crazings were also observed at the surface.

• Journal of Powder Materials
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• v.7 no.2
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• pp.71-77
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• 2000

A process has been successfully used to manufacture 6061/Graphite composite material and the Graphite particles are distributed uniformly within the Al alloy matrix. The 6061 powders was mixed with natural Graphite particles in a ball milling blender and cold compacted specimens were extruded into rods 15mm in diameter at 450$^{\circ}C$. The results showed that tensile properties of the composites with Graphite content have been reduced. The emergence of fine microstructures appeared to be related to the graphite volume. Heat-treated composites were found to possess good mechanical properties as compared with those of non heated composites. A model was used that the tensile strength of the composites would be estimated from the theoretical calculation and experimental data.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.393-399
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• 2018

Formation behavior of aluminum anodic oxide (AAO) films on Al6061 alloy was studied in view of thickness, morphology and defects in the anodic films in 20 vol.% sulfuric acid solution at a constant current density of $40mA/cm^2$, using voltage-time curve, observation of anodized specimen colors and surface and cross-sectional morphologies of anodic films with anodization time. With increasing anodizing time, voltage for film formation increased exponentially after about 12 min and its increasing rate decreased after 25 min, followed by a rapid decrease of the voltage after about 28 min. Surface color of anodized specimen became darker with increasing anodizing time up to about 20 min, while it appeared to be brighter with increasing anodizing time after 20 min. The darkened and brightened surfaces with anodizing time are attributed to an increase in thickness of porous anodic oxide film and a chemical damage of the films due to heat generated by increased resistance of the film, respectively. Cross-sectional observation of AAO films revealed the formation of defects of crack shape at the metal/oxide interface after 15 min which prevents the growth of AAO films. Width and length of the crack-like defect increased with anodizing time up to 25 min of anodizing, and finally the outer part of AAO films was partly dissolved or detached after 30 min of anodizing, resulting in non-uniform surface structures of the AAO films.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.307-310
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• 2005

Ageing behavior of the Al-Mg-Si alloy was modeled for the use of optimization of Al forging product. Typical precipitates of Al-Mg-Si alloy are a wide variety of metastable phases (e.g. GP zones, $\beta',\beta'$). These rod shaped particles take a role to hinder the dislocation movement. The precipitation sequence in Al-Mg-Si alloys is quite complex and the strength of precipitate particles differs with the ageing condition. In the present study, the ageing behavior of Al-Mg-Si alloy was investigated by using an industrial grade Al 6061 alloy forged product, which was a perform for an Al impeller for turbo charger. The precipitate hardening models by Esmaeili's approach were used for the analysis of ageing behavior.

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.955-961
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• 2002

2.7vol%TiNi/6061 Al composites with TiNi shape memory alloy as reinforcement were fabricated by vacuum hot press. It was investigated by OM, SEM, EPMA and XRD analysis for the behavior of diffusion layer formation on various heat treatment condition. Thickness of diffusion layer was increased proportionally according to heat treatment time. The layer was formed by the mutual diffusion of TiNi and Al. The diffusion rate from TiNi fiber to Al matrix was faster than that of reverse diffusion path. The more diffused layer was formed in Al matrix. The diffusion at interface layer was consisted of $A1_3$Ti, $Al_3$Ni analyzed by EPMA, XRD results.

• Composites Research
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• v.33 no.5
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• pp.241-246
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• 2020

In this study, aluminum (Al) alloy matrix composites in which B₄C particles were uniformly dispersed was manufactured through stir casting followed by hot rolling process. The microstructure, mechanical properties, and wear resistance properties of the prepared composites were analyzed. The composite in which the 40 ㎛ sized B₄C particles were uniformly dispersed increased the tensile strength and improved wear performance as the volume ratio of the reinforcement increased. In the case of the 20 vol.% composite, the tensile strength was 292 MPa, which was 155% higher than that of the Al6061. As a result of the wear resistance test, the wear width and depth of the 20 vol.% B₄C/Al6061 composites were 856 ㎛, and 36 ㎛, and the friction coefficient was 0.382, which were considerably superior to Al6061.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1345-1354
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• 2019

Clogging of sump strainers that filter the recirculation water in containment after a loss-of-coolant accident (LOCA) seriously impedes the continued cooling of nuclear reactor cores. In experiments examining the corrosion of aluminium alloy 6061, a common material in containment equipment, in borated solutions simulating the water chemistry of sump water after a LOCA, we found that Fe-bearing intermetallic particles, which were initially buried in the Al matrix, were progressively exposed as corrosion continued. Their cathodic nature $vis-{\grave{a}}-vis$ the Al matrix provoked continuous trenching around them until they were finally released into the test solution. Such particles released from Al alloy components in a reactor containment after a LOCA will be transported to the sump entrance with the recirculation flow and trapped by the debris bed that typically forms on the strainer surface, potentially aggravating strainer clogging. These Fe-bearing intermetallic particles, many of which had a rod or thin strip-like geometry, were identified to be mainly the cubic phase ${\alpha}_c-Al(Fe,Mn)Si$ with an average size of about $2.15{\mu}m$; 11.5 g of particles with a volume of about $3.2cm^3$ would be released with the dissolution of every 1 kg 6061 aluminium alloy.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.127-130
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• 2004

In the recent years, lightweight components fabricated with aluminum alloys have been applied into building the automobiles. Among the several competing fabrication methods, hot forging is taken as the most reliable technique to produce suspension parts such as control arms. Generally, Al forging products have been used widely for the aircraft building with the extruded stock as a starting material. For the economical base, however, the cast stocks turn to be as the forging stocks recently after a continuously casting technique was developed to produce quite a uniform microstructure enough to use for the forging process. Even more, there is a tendency to omit the homogenization step before forging, which is considered to be an indispensable process for all kinds of Al alloy, In the present study, a series of compression test was carried out to find out how the cast structure and the following heat treatments influence the deformation behavior, that is, forging characteristic.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.6
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• pp.401-409
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• 2016

The formation of micro-burrs in micro-milling processes causes several problems related to productivity and surface integrity. It should be minimized and suppressed by effective monitoring of the cutting conditions. This paper presents the correlation between the micro-burr length and cutting signals in the micro-milling process of an Al alloy (Al6061-T6). The acoustic emission (AE) signals and cutting force signals are acquired during the experiments. The characteristics of the cutting signals are obtained by analyzing the AE root mean square value and resultant cutting force. In addition, the micro-burr length is measured according to the cutting conditions by analyzing a scanning electron microscopy image of the machined surface. The results of this study can be used to enhance the surface quality of micro parts.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.297-297
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• 2011