• Journal of the Korean institute of surface engineering
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• v.50 no.6
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• pp.447-454
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• 2017

Al1050 and Al7075 alloy specimens were exposed to atmospheric conditions for maximum 12 months and analyzed by Transmission Electron Microscopy (TEM) to characterize the early-stage corrosion behavior and thin surface oxide layers. By comparing of oxide films between Al1050 and Al7075 alloys, it is concluded that Al7075 has a relatively thicker surface oxide film than Al1050 but Al1050 has relatively more significant oxygen penetration through grain boundaries. The oxygen penetration through grain boundaries appeared to be influenced by intermetallic particles at the grain boundary. In the case of aluminum alloys, localized corrosion like pitting or intergranular corrosion should be considered as well as uniform corrosion when estimating the atmospheric corrosion rate.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1998.04b
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• pp.14-14
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• 1998

• Journal of Korea Foundry Society
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• v.37 no.2
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• pp.38-44
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• 2017

Given that the conventional extrusion of high-strength Al alloys such as 7075 aluminum alloys is difficult due to their very low extrudability as compared to that of 6061 aluminum alloys, thixo-extrusion can be used to obtain a high-strength material easily at a lower extrusion pressure as compared to conventional extrusion. In this study, hot- and thixo-extruded 7075 aluminum alloys are prepared by a vertical forward extrusion process and their microstructures, hardness levels, and compressive properties are investigated. Hot-extruded alloy bars are assessed to obtain a microstructure elongated in the extrusion direction, whereas with thixo-extruded alloy bars, it was possible to obtain a microstructure having fine and equiaxed grains by dynamic recrystallization. The resulting isotropy and improved formability at the hot deformation temperature of the thixo-extruded alloy were attributed to the fine and equiaxed grains formed by the thixo-extrusion process.

• Transactions of Materials Processing
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• v.30 no.1
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• pp.5-15
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• 2021

The effects of heat treatments (T6 and T73) on the microstructure, mechanical properties, and high cycle fatigue behavior of modified AA7075 alloys were investigated. A modified 7075 alloy was manufactured using modified-Mg (Mg-Al2Ca) instead of the conventional element Mg. Based on the microstructure, the average grain size was 4.5 ㎛ (T6) and 5.2 ㎛ (T73). Regardless of heat treatment, the modified AA7075 alloys consisted of Al matrix containing homogeneously distributed Al2CuMg and MgZn2 phases with reduced Fe-intermetallic compound. Room temperature tensile tests showed that the properties of modified 7075-T6 (Y.S.: 622MPa, T.S: 675MPa, elongation: 15.4%) were superior to those of T73 alloy (Y.S.: 492MPa, T.S: 548MPa, elongation: 12.8%). Experimental data show that the fatigue life of T6 was 400 MPa, about 64% of its yield strength. However, the fatigue life of T73 alloy was 330 MPa and 67%. Irrespective of the stress level, all crack initiation points were located on the specimen surface, and no inclusions acting as stress concentrators were seen. Superior mechanical properties and high cycle fatigue behavior of modified AA7075-T6 alloy are attributed to the fine grains and homogeneous distribution of small second phases such as MgZn2 and Al2CuMg, in addition to reduced Fe-intermetallic compounds.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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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.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.184-187
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• 2006

The effects of scandium content and extrusion parameters on Al-Zn-Mg-(Sc) alloys were examined. Three kinds of Al-Zn-Mg-(Sc) alloys with up to 0.30 wt.% Sc were prepared. The compression test was conducted to investigate the microstructure evolution during hot deformation. Despite of microstructural differences in the alloys, deformation behaviors were very similar. After extrusion at $350^{\circ}C$ with the ram speed of 15mm/sec, AA7075 showed a moderate surface quality compared with other Sc containing alloys, which was attributed to low flow stresses. AA7075 showed coarse-grained bands in surface region. With the ram speed of 1.5mm/sec at $350^{\circ}C$, the surface quality of the alloys was sound due to low friction stresses and deformation heating. As the Sc content increased, tensile strengths and elongations at room temperature improved.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.194-200
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• 1993

Grinding experiments for Al 7075 alloy were carried out to study the influence of grinding conditions and supply methods of grinding fluid on residual stress and surface roughness and grinding force. The residual stress was measured by an X-ray method. The supply method of grinding fluid with a guide nozzle has large decrease value of the tensile residual stress and of grinding force than a normal nozzle. In sparking out state of the grinding work, it is desirable to decrease the depth of cut and the workpiece feedrate for improving surface roughness and mechanical properties.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.62-71
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• 2019

Al1050 and Al7075 alloy specimens were exposed to atmospheric conditions for 24 months and analyzed by Transmission Electron Microscopy to characterize their corrosion behavior and oxide film characteristics, especially focusing on intergranular corrosion or oxidation. In general, the intergranular oxygen penetration depth of Al1050 was deeper than Al7075. Since O and Si signals were overlapped at the oxidized grain boundaries of Al1050 and Mg is not included in Al1050, it is concluded that Si segregated along the grain boundaries directly impacts on the intergranular corrosion of Al1050. Cr-Si or Mg-Si intermetallic particles were not observed along the grain boundaries of Al7050, but Mg-Si particle was barely observed in the matrix. 10-nm size Mg-Zn particles were also found all over the matrix. Mg was mainly observed along the oxidized grain boundary of Al7075, but Si was not detected due to the Mg-Si particle formation in the matrix and relatively low concentration of Si in Al7075. Therefore, it is thought that Mg plays an important role in the intergranular corrosion of Al7075 under atmospheric corrosion conditions.

• Journal of the Korean institute of surface engineering
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• v.27 no.4
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• pp.215-222
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• 1994

The role dispersoids has been studied in a number of researches as a key point for the high strength application of dispersion strengthened aluminum alloy. The mechanical alloying(MA) process with high mechanical properties of dispersion strengthened MA Al-8Ti-1B alloys were invested in order to evaluate their stress corrosion cracking(SCC) application. SCC properties of the mechanically alloyed Al-8Ti-1B were studied using slow strain rate test(SSRT). In this study Al-8Ti-1B alloy were more susceptible to SCC in solutions of pH=2.01 and 13.2 than pH=6.81 solution. In this study Al-8Ti-1B alloys by MA had more SCC resistance than Al-8Ti alloys or Al 7075-T73 alloys. So Al-8Ti-1B alloys by MA had more resistance in SSRT SCC susceptinility test than any other above alloying metals.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.227-230
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• 2009

The aim of this study was to improve extrudability limit, eliminate welding line and obtain optimum thixoextrusion conditions for manufacturing tubes of 7075 Al wrought alloy. By thixoextrusion, it was possible to improve deformability, control isotropy with extrusion direction, eliminate welding line (seamless) and save cost due to low energy consumption compared with conventional extrusion processes. The welded part was not observed at the welding line area. The grains of thixoextruded tube were homogeneously distributed and equiaxed grains were observed. Therefore, thixoextrusion is the most effective variable for the control of the magnitude of the welding line.