• 한국표면공학회지
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• 제52권5호
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• pp.275-281
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• 2019

Anodization is widely used to enhance the properties of aluminum, such as hardness, electric resistance, abrasion resistance, corrosion resistance etc. But these properties can be enhanced with additional process. According to the partial crystallization of oxide layer with post heat treatment, enhanced hardness can be expected with partial crystallization. In this study, post heat treatments were applied to the anodized aluminum alloys of Al6061 to achieve the partial crystallization, and crystallizations were evaluated with the reduced breakdown voltages. Interestingly, remarkable enhanced hardness (21~29%), abrasion resistance (26~62%), and reduced breakdown voltage (24~44%) were observed for the sulfuric acid anodized samples when we annealed the anodized samples with 1hour post heat treatment at $360^{\circ}C$. For the Al5052 alloys, a lot of cracks were observed when we applied the post heat treatment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.408-410
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• 2008

The evolution of texture and microstructure during recrystallization was tracked after different cold rolling of aluminum sheets. Texture of the sheet center were differentiated by different strain states due to prior deformation. The evolution of recrystallization texture was studied with the amount of shear applied during cold rolling. The final grain size after recrystallization annealing was varied due to the effective strain during deformation.

• 대한금속재료학회지
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• 제49권11호
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• pp.893-899
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• 2011

Fabrication of a complex aluminum alloy by the ARB process using dissimilar aluminum alloys has been carried out. Two-layer stack ARB was performed for up to six cycles at ambient temperature without a lubricant according to the conventional procedure. Dissimilar aluminum sheets of AA1050 and AA5052 with thickness of 1 mm were degreased and wire-brushed for the ARB process. The sheets were then stacked together and rolled to 50% reduction such that the thickness became 1 mm again. The sheet was then cut into two pieces of identical length and the same procedure was repeated for up to six cycles. A sound complex aluminum alloy sheet was successfully fabricated by the ARB process. The tensile strength increased as the number of ARB cycles was increased, reaching 298 MPa after 5 cycles, which is about 2.2 times that of the initial material. The average grain size was $24{\mu}m$ after 1 cycle, and became $1.8{\mu}m$ after 6 cycles.

• 소성∙가공
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• 제19권8호
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• pp.460-467
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• 2010

It was studied that two plates of aluminum can be welded by extru-riveting experiments with extru-rivet welding dies, and that the welding strength and metal flow on the welding section were analyzed by computer simulation according to the welding variable such as the diameter of extrusion insert dies. It was known by computer simulation that welding strength on the welding section of plates could be influenced by the diameter of extrusion insert dies. And it was known by experiments that two plates of aluminum can be welded on a spot point on aluminum plate by extru-rivet welding process, and that welding strength is higher and higher if the diameter of extrusion insert die is smaller and smaller, and that welding strength is the highest when diameter of extrusion insert dies is ${\emptyset}4.2$mm in the case that the diameter of rivet is 5 mm, when aluminum 5052 two plates with 1.5 mm thickness and one plate with 3mm thickness for rivet plate are used as welding material.

• Journal of Welding and Joining
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• 제27권3호
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• pp.44-51
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• 2009

In this study, welding distortion analysis is performed for various design of tube shape structures which are assembled with aluminum sheet metal. Aluminum 5052 plates of 1mm thickness are used to analyze. An efficient keyhole model, as a welding heat source, is used for the prediction of full penetration weld size and shape which is required for the thermal analysis. The thermal and mechanical material properties are considered as temperature dependent functions, due to the high temperature variations during the welding. The numerical model is calculated by using a commercial software and evaluated with the experiments. The calculation results could make a comparative study in the view of distortion for the various size and shape of structure.

• 소성∙가공
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• 제19권8호
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• pp.452-459
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• 2010

It was investigated that two plates of aluminum can be welded by hot extru-shear welding process with extru-shear welding dies, and that the welding strength and metal flow on the welding section were analyzed by computer simulation according to the welding variables such as inclined angle of cutter and overlapped length of plates and temperature of plates. It was known by computer simulation that welding strength on the welding section of plates could be influenced by the inclined angle of cutter and overlapped length of plates and temperature of plates. And it was known by experiments that two plates of aluminum can be welded on the end sections by hot extru-shear welding process using extru-shear welding dies, and that welding strength is the highest when inclined angle of dies is $70^{\circ}$, and overlapped length is 1.2 mm, and temperature is $520^{\circ}$, when aluminum 5052 two plates with 1.6 mm thickness are used as welding material.

• Journal of Welding and Joining
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• 제22권4호
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• pp.43-49
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• 2004

Conventional method for electrode force application in resistance spot welding(RSW) processes is to use pneumatic cylinder. However, due to its inherent problems in pneumatic power system such as compressibility of air and poor transient response characteristics, new electrode force system with servo control are recently introduced in RSW machine. This machine is called “servogun”. The purpose of this study is to evaluate performance of servogun in case of spot welding of aluminum alloy. Aluminum alloy(A5052) sheets are spot welded using pneumatic gun and servogun. Both results are compared by means of macro cross-section etching test and tensile shear strength test. Numerous previous research have reported nugget with many voids and cracks are not uncommon defects in spot welds with aluminum alloy. The experimental results show similar defects in case of pneumatic gun. In contrast, use of servogun considerably reduced generation of voids and cracks. In case of step-wise increased forging force at the end of welding cycle with servogun, crack-free and void-free nuggets have been observed. The performance of servogun has been also verified by series of tensile shear test. Higher strength values have been achieved with servogun in comparison to that of pneumatic gun.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.178-183
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• 1998

This paper examines the crack growth behavior of 7075-T651 and 5052-H32 aluminum alloys for variable load within tensile load range condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investgated by compliance method. The applied initial stress ratio is R=0.3 and variable load are R=0.65, 0.46. Crack length, stress intensity factor range, ratio of effective stress intensity factor range and crack growth rate etc. are inspected with fracture mechanics estimate.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 추계학술논문요약집
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• pp.179-180
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• 2018

Al - MMC, used as a neutron absorber, shows pitting corrosion and/or galvanic corrosion in 3.5wt.% NaCl solution. If pitting corrosion penetrates the core, neutron absorption performance could be affected. Galvanic corrosion was observed between Al 5052 and Al 1070, and pitting corrosion was observed around $B_4C$.

• 한국기계가공학회지
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• 제13권2호
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• pp.89-93
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• 2014

Variable polarity (VP) arc welding is known as an effective solution for aluminum thanks to the cleaning effect, which means oxide removal, during the DCEP (direct current electrode positive) period. In this research, VP GTAW (gas tungsten arc welding) is adopted for lap joint fillet welding of 3mm thickness 5052 aluminum alloy. Various welding currents and DCEP duty cycles are applied as welding conditions with a fixed welding speed to investigate the influence of DCEP characteristics on weld bead formation. Results show a tendency of higher heat input for higher DCEP duty cycle, which result does not follow conventional arc theory because it is known that DCEN (DC electrode negative) polarity is more efficient for heat input than is DCEP. This phenomenonhas recently been reported by several VP-GTA researchers and is still controversial because the mechanism of oxide removal is not yet clear except for the previous, well-known idea of "ion bombardment", which cannot explain the situation. Finally, proper usage conditions for VP-GTAW are suggested; then, further, related theoretical topics in the field of cathode physics are brieflyintroduced.