• 동력기계공학회지
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• 제18권2호
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• pp.62-69
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• 2014

In this paper, in order to investigate the effects of marco and microscopic observations of fatigue crack growth in friction stir welded (FSWed) 7075-T651 aluminum alloy plates, fatigue crack growth tests were performed under constant amplitude loading condition at room temperature with three different pre-cack locations, namely base metal (BM-CL) and two kinds of pre-crack locations in welded joints, weld metal (WM-CL) and heat affected zone (HAZ-CL) specimens. The fatigue crack growth behavior of FSWed 7075-T651 aluminum alloy plates were discussed based on the marco and microscopic fractographic observations. The marcoscopic aspects of surface crack growth path for BM-CL and HAZ-CL specimens indicate relatively straight lines, however, the crack growth paths of WM-CL specimens grow first straight and by followed toward the TMAZ and HAZ. The microscopic aspects of fatigue fracture for BM-CL and HAZ-CL specimens indicate typical fatigue striation, but WM-CL showed intergranular fracture pattern by micro structural changes of FSW process.

• 열처리공학회지
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• 제20권6호
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• pp.293-298
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• 2007

Influences of aluminum carbide ($Al_4C_3$) addition on microstructure and damping capacity of Mg-3%Al casting alloy have been investigated based on experimental results of optical micrography, scanning electron microscopy with energy-dispersive spectrometry analysis and damping capacity measurement at RT. The addition of $Al_4C_3$ particles results in an efficient grain refinement. The damping capacity shows an increasing tendency with an increase in $Al_4C_3$ content. The damping value associated with $Al_4C_3$ particles is linearly dependent on the volume fraction of $Al_4C_3$ particles to the 2/3 power, $f_{2/3}$, which corresponds to the total surface area of the particles.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.220-225
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• 2007

The mechanical characteristics of AC4C Aluminum Casting Alloy were investigated by tensile test and impact test. Based on the tensile test' s result, we found that the yield strength of a high speed was about 10% higher than that of a low speed test and the maximum rupture strain mostly occurred in low speed tensile test. The impact energy of curved surface specimen was higher than that of plane surface specimen that can be measured in impact test.

• Journal of Advanced Marine Engineering and Technology
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• 제18권2호
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• pp.41-53
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• 1994

In this paper, rotating-bending fatigue tests of the SiC-whisker- reinforced 6061-T6 aluminum alloy and 6061-T6 alumiunm alloy made by power metallurgy were carried out to investigate the fatigue characteristics of plain and notched specimens at room temperature. The fatigue mechnisms in both materials were clarified through successive surface observations using the plastic replica method. In the case of the SiC-whisker-reinforced composites, there are whisker rich and poor zones and the fatigue crack is nucleated from the end of whiskers near the boundary. On the other hand, in the case of the 6061-T6 aluminum alloy, the fatigue crack is nucleated from defects and propagates by shear. Moreover, the results were discussed based on linear notch mechanics.

• 한국표면공학회지
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• 제51권6호
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• pp.415-420
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• 2018

The possibility of an improvement in heat dissipation performance of aluminum alloy heat sink for shipboard LED luminaries through plasma electrolytic oxidation (PEO) was investigated. Four different PEO coatings were produced on aluminum alloy 5052 in silicate based alkaline solution by varying current density ($50{\sim}200mA/cm^2$). On voltage-time response curves, three stages were clearly distinguished at all current densities, namely an initial linear increase, slowdown of increase rate, and steady state(constant voltage). It was found that the increase in current density caused the breakdown voltage to increase. Two different surface morphologies - coralline porous structure and pancake structure - were confirmed by SEM examination. The coralline porous structure was predominant in the coatings produced at lower current densities (50 and $100mA/cm^2$) while under high current densities(150 and $200mA/cm^2$) the pancake structure became dominant. The coating thickness was measured and found to be in a range between about $13{\mu}m$ and $44{\mu}m$, showing increasing thickness with increasing current density. As a result, $100mA/cm^2$ was proposed as an effective process parameter to improve the heat dissipation performance of aluminum alloy heat sink, which could lower the LED operating temperature by about 30%.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.179-180
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• 2012

Aluminum alloys are widely known as non-ferrous metal with light weight and high strength. Consequently, these materials take center stage in the aircraft and automobile industry. The Al7075 aluminum alloy is based on the Al-Zn-Mg-Cu and one of the strongest wrought aluminum alloys. Aluminum nitride has ten times higher thermal conductivity($319W/m{\cdot}K$) than Al2O3 and also has outstanding electric insulation($1{\times}1014{\Omega}{\cdot}cm$). Furthermore, it has high mechanical property (430 MPa) even though its co-efficient of thermal expansion is less than alumina For these reasons, it has great possibilities to be used for not only the field which needs high strength lightweight but also electronic material field because of its suitability to be applied to the insulator film of PCB or wafer of ceramic with high heat conduction. This paper investigates the mechanical properties and corrosion behavior of aluminum alloy Al7075 deposited with aluminum nitride thin films To improve the surface properties of Al7075 with respect to hardness, and resistance to corrosion, aluminum nitride thin films have been deposited by pulsed DC reactive magnetron sputtering. The pulsed DC power provides arc-free deposition of insulating films.

• 한국주조공학회지
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• 제32권6호
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• pp.269-275
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• 2012

Al-Mg-Si/Al hybrid alloy was prepared by Duo-casting and the mechanical behavior was evaluated based on their microstructure and mechanical properties. The hybrid aluminum alloy included the Al-Mg-Si alloy with fine eutectic structure, pure Al with the columnar and equiaxed crystals, and the macro-interface existing between Al-Mg-Si alloy and pure Al. The growth of columnar grains in pure Al occurred from the macro-interface. The tensile strength, 0.2% proof stress and bending strength of the hybrid aluminum alloy were almost similar to those of pure Al, and the elongation was much higher than the Al-Mg-Si alloy. The fracture of the hybrid alloy took place in pure Al side, indicating that the macro-interface was well bonded and the mechanical behavior strongly depends on the limited deformation in pure Al side.

• 한국자동차공학회논문집
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• 제18권1호
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• pp.120-126
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• 2010

It was known that the excellent wear resistance of hyper eutectic aluminum alloy is based on the primary Si particles which are distributed in the base metal. When the primary Si volume fraction increases, the smaller size have excellent wear resistance characteristics. However, this trend always does not match. There is no investigation result based on the materials and methods for real using parts. In this study, using the automotive parts manufacturer currently in use hyper eutectic Al alloy tensile test specimen type sample was fabricated by 350Ton high pressure die-casting machine. Then, fluidity, tensile, impact and wear resistance properties were evaluated. If the casting quality, primary Si size, fraction and distribution are similar, mechanical properties and wear resistance are equivalent.

• Journal of Welding and Joining
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• 제34권3호
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• pp.23-30
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• 2016

This paper discusses the optimization of friction stir spot welding (FSSW) process parameters for joining Aluminum alloy (AA6061-T6) with Magnesium alloy (AZ31B) sheets. Prior to optimization an empirical relationship was developed to predict the Tensile Shear Fracture Load (TSFL) incorporating the four most important FSSW parameters, i.e., tool rotational speed, plunge rate, dwell time and tool diameter ratio, using response surface methodology (RSM). The experiments were conducted based on four factor, five levels central composite rotatable design (CCD) matrix. The maximum TSFL obtained was 3.61kN, with the tool rotation of 1000 rpm, plunge rate of 16 mm/min, dwell time of 5 sec and tool diameter ratio of 2.5.

• 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.