• Title/Summary/Keyword: Al-Zn-Mg Aluminum Alloy

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A Study on Forming of Al-Zn-Mg-Sc Aluminum Alloy Bolts (Al-Zn-Mg-Sc 알루미늄 합금 볼트 성형에 관한 연구)

  • Yoon, D.J.;Hahm, S.Y.;Lee, Y.S.
    • Transactions of Materials Processing
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    • v.21 no.7
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    • pp.447-452
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    • 2012
  • This paper is concerned with forming of Al-Zn-Mg-Sc aluminum alloy bolts, focusing on the effects of heat treatment and age-hardening on the formability and ductile damage evolution. Both experimental and finite element studies were performed. From the experiments, it is observed that the heat treatment or the normalization of Al-Zn-Mg-Sc aluminum alloy increases its formability dramatically resulting in successful bolt forming, while the effects of age-hardening at room temperature on the stress-strain relationship and formability are not very critical. Deformation characteristics such as distribution of effective stress and strain, material flow, and ductile damage evolution during bolt forming are examined using a commercial finite element package, Deform-2D. It should be noted that the extrusion load predicted by the finite element method matches well the experiment results. The finite element predictions on the deformation characteristics support the experimental observations such as fracture of bolt head flange, material flow, and distribution of hardness.

Microstructure and Properties of High Strength High Ductility Al-Mg-Zn Casting Alloy (고강도 고인성 Al-Mg-Zn 주조합금의 미세조직 및 특성)

  • Kim, Jeong-Min;Ha, Tae-Hyung
    • Journal of Korea Foundry Society
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    • v.36 no.6
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    • pp.181-186
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    • 2016
  • The typical microstructure of Al-5%Mg-2%Zn cast alloy mainly consists of an aluminum matrix with a small amount of AlMgZn 2nd phase. The secondary dendrite arm spacing and the grain size of the cast alloy tend to be inversely proportional to the section thickness of casting; however, the tensile properties cannot be said to be clearly related to the cast microstructure. After T6 heat treatment, the tensile strength of the alloy was enhanced significantly. TEM analysis results show that very fine AlMgZn precipitates were formed after the heat treatment. The corrosion resistance, measured according to the corrosion potential, was found to increase slightly after the conducting of heat treatment.

Characterization of Extrusion Parts for after Pre-aging Treatment in an Al-4.8Zn-1.3Mg Alloy (안정화 열처리에 의한 Al-4.8Zn-1.3Mg계 합금 압출재 특성 평가)

  • Lee, Chang-Yeon
    • Journal of the Korean Society of Mechanical Technology
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    • v.20 no.6
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    • pp.818-823
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    • 2018
  • In this study, the effect of pre-aging treatment for inhibition of natural aging of Al-4.8Zn-1.3Mg alloy by extrusion process was investigated. Firstly, the as-cast microstructure of Al-4.8Zn-1.3Mg alloy billet and its evolution during homogenization($460^{\circ}C$, $4h+510^{\circ}C$, 5h) were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), hardness analysis. The as-cast microstructures of Al-4.8Zn-1.3Mg alloy reveal $Mg_2Zn$, $Al_5Cu$, $Al_{13}Cu$ formed between dendrities. After homogenization, MgZn, $Al_4Cu$, $Al_{13}Cu$ phases precipitated into the matrix. In addition, standard deviation of homogenized billet was improved than as-cast billet from 2.62 to 0.99. According to pre-aging($100^{\circ}C$, 1h) Al-4.8Zn-1.3Mg alloy by extrusion process, yield strength and tensile strength deviation improved more than condition by natural aging.

Differences in Cold Rolling Workability and Mechanical Properties between Al-Mg-Si and Al-Mg-Zn System Alloys with Cold Rolling (냉간압연가공에 따른 Al-5.5Mg-2.9Si계와 Al-7Mg-0.9Zn계 합금의 압연가공성 및 기계적 특성 차이)

  • Yang, Ji-Hun;Lee, Seong-Hee
    • Korean Journal of Materials Research
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    • v.26 no.11
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    • pp.628-634
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    • 2016
  • The cold rolling workability and mechanical properties of two new alloys, designed and cast Al-5.5Mg-2.9Si and Al-7Mg-0.9Zn alloys, were investigated in detail. The two alloy sheets of 4 mm thickness, 30 mm width and 100 mm length were reduced to a thickness of 1 mm by multi-pass rolling at ambient temperature. The rolling workability was better for the Al-7Mg-0.9Zn alloy than for the Al-5.5Mg-2.9Si alloy; in case of the former alloy, edge cracks began to occur at 50% rolling reduction, and their number and length increased with rolling reduction; however, in the latter alloy, the sheets did not have any cracks even at higher rolling reduction. The mechanical properties of tensile strength and elongation were also better in the Al-7Mg-0.9Zn alloy than in Al-5.5Mg-2.9Si alloy. Work hardening ability after cold rolling was also higher in the Al-7Mg-0.9Zn alloy than in the Al-5.5Mg-2.9Si alloy. At the same time, the texture development was very similar for both alloys; typical rolling texture developed in both alloys. These differences in the two alloys can primarily be explained by the existence of precipitates of $Mg_2Si$. It is concluded that the Al-7Mg-0.9Zn alloy is better than the Al-5.5Mg-2.9Si alloy in terms of mechanical properties.

Distribution Behavior of Solute Element in Al-Mg-Zn Alloy Continuous Cast Billet During Homogenization Treatment (Al-Mg-Zn계 알루미늄 합금 연주 빌렛 균질화처리과정 중 용질원소 거동변화)

  • Myoung-Gyun Kim
    • Journal of Korea Foundry Society
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    • v.43 no.6
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    • pp.286-293
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    • 2023
  • In this study, we investigated the microstructural evolution of Al-Mg-Zn aluminum alloy billet during homogenization treatment using OM, SEM, EDS and DSC. There were numerous phases found, such as; AlMgZn, AlMgFe, and AlMgZnSi phases, in the grain of the cast billet. After 6 hours homogenization treatment, Zn was mostly dissolved, whereas, Mg and Si were only partly dissolved. Accordingly, only AlMgFe and AlMgSi remained. After 18 hours, all of the leftover Mg and Si were dissolved, leaving only AlMgFe, which was also found after 24 hours. The results of the alloy design program, JMatPro showed that Mg dissloved more rapidly than Zn. According to the homogenization kinetic equation, Mg and Zn are completely dissolved within 1.9 and 3.5 hours, respectively.

Effects of Alloying Elements on the Properties and Aging Hardening of Al-5%Mg Based Casting Alloys (Al-5%Mg계 주조합금의 물성 및 시효경화특성에 미치는 합금원소의 영향)

  • Kim, Jeong-Min;Park, Joon-Sik;Cho, Jae-Ik;Kim, Hyun-Gil
    • Journal of Korea Foundry Society
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    • v.30 no.1
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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.

Stress Corrosion Cracking of High Strength Al-Zn-Mg-Cu Aluminum Alloy with Different Compositions (고강도 Al-Zn-Mg-Cu 합금에서 조성에 따른 응력부식균열 특성)

  • Kim, Jun-Tak;Kim, Sang-Ho
    • Journal of the Korean institute of surface engineering
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    • v.41 no.3
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    • pp.109-113
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    • 2008
  • High strength 7xxx series Al-Zn-Mg alloy have been investigated for using light weight automotive parts especially for bump back beam. The composition of commercial 7xxx aluminum has the Zn/Mg ratio about 3 and Cu over 2 wt%, but this composition isn't adequate for appling to automotive bump back beam due to its high resistance to extrusion and bad weldability. In this study the Zn/Mg ratio was increased for better extrusion and Cu content was reduced for better welding. With this new composition we investigated the effect of composition on the resistivity against stress corrosion cracking. As the Zn/Mg ratio is increased fracture energy obtained by slow strain rate test was decreased, which means degradation of SCC resistance. While the fracture energy was increased with Cu contents although it is below 1%, which means improvement of SCC resistance. These effects of composition change on the SCC resistivity were identified by observing the fracture surface and crack propagation.

Effects of Alloying Elements on the Properties of High Strength and High Thermal Conductivity Al-Zn-Mg-Fe Alloy for Die Casting (다이캐스팅용 Al-Zn-Mg-Fe 합금의 특성에 미치는 Zn 및 Mg 첨가의 영향)

  • Kim, Ki-Tae;Lim, Young-Suk;Shin, Je-Sik;Ko, Se-Hyun;Kim, Jeong-Min
    • Journal of Korea Foundry Society
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    • v.33 no.4
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    • pp.171-180
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    • 2013
  • The effects of alloying elements on the solidification characteristics, microstructure, thermal conductivity, and tensile strength of Al-Zn-Mg-Fe alloys were investigated for the development of high strength and high thermal conductivity aluminium alloy for die casting. The amounts of Zn and Mg in Al-Zn-Mg-Fe alloys had little effect on the liquidus/solidus temperature, the latent heat for solidification, the energy release for solidification and the fluidity of Al-Zn-Mg-Fe alloys. Thermo-physical modelling of Al-Zn-Mg-Fe alloys by the JMatPro program showed $MgZn_2$, AlCuMgZn and $Al_3Fe$ phases in the microstructure of the alloys. Increased amounts of Mg in Al-Zn-Mg-Fe alloys resulted in phase transformation, such as $MgZn_2{\Rightarrow}MgZn_2+AlCuMgZn{\Rightarrow}AlCuMgZn$ in the microstructure of the alloys. Increased amounts of Zn and Mg in Al-Zn-Mg-Fe alloys resulted in a gradual reduction of the thermal conductivity of the alloys. Increased amounts of Zn and Mg in Al-Zn-Mg-Fe alloys had little effect on the tensile strength of the alloys.

The Effect of Al and Sn Additions on Corrosion Behavior of Permanent Mold Casting Magnesium Alloy (금형 주조한 마그네슘 합금의 부식 거동에 미치는 Al 및 Sn의 영향)

  • Kim, Byeong Ho;Seo, Jae Hyun;Park, Kyung Chul
    • Journal of Korea Foundry Society
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    • v.35 no.2
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    • pp.36-43
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    • 2015
  • In this study, the influences of aluminum and tin additions (individual and combined) on corrosion behavior of magnesium alloy have been determined. The studied alloys were fabricated by permanent mold casting method to measure the corrosion properties, a potentiodynamic test, hydrogen evolution test and immersion test were carried out in a 3.5% NaCl solution at pH 7.2. From the results of microstructure analysis, the Mg-9Al-1Zn alloy was found to be composed of ${\alpha}$-Mg and rod-like $Mg_{17}Al_{12}$ phase and the Mg-5Sn-5Al-1Zn alloy was found to be composed of ${\alpha}$-Mg, rod-like $Mg_{17}Al_{12}$ and $Mg_2Sn$ phases. In the case of the Mg-9Sn-1Zn alloy, the microstructure was composed of ${\alpha}$-Mg and eutectic $Mg_2Sn$ phase. With Sn addition (individual and combined), the corrosion resistance of the Mg alloys improved.

Effect of Casting Temperature and Speed on Formation of Surface Defect in Al-8Zn-2Mg-2Cu Billets Fabricated by Direct-Chill Casting Process (수직 연속주조 공정으로 제조된 Al-8Zn-2Mg-2Cu 빌렛의 표면 결함 형성에 미치는 주조 온도와 주조 속도의 영향)

  • Lee, Yoon-Ho;Kim, Yong-You;Lee, Sang-Hwa;Kim, Min-Seok;Euh, Kwangjun;Lee, Dong-Geun
    • Journal of Korea Foundry Society
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    • v.41 no.3
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    • pp.241-251
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    • 2021
  • 7000-series aluminum alloys are noted for their superior strength compared with other Al alloys, and their billets are generally fabricated by direct-chill (DC) casting. Surface defects in a DC-cast aluminum billet are mainly related to exudation and the meniscus freezing phenomenon, which are influenced by alloy compositions, casting speed, and casting temperature. 7000-series aluminum alloys have a wide freezing range during solidification, which makes it easy for casting defects to occur. In this study, we investigated surface defect evolution in casting billets of Al-8Zn-2Mg-2Cu alloy fabricated by a DC casting process. The billets showed "wavy" or "dotted" surfaces. The wavy surface was formed by meniscus freezing at a lower casting speed (200 mm/min) and temperature (655 ℃). In the wavy surface, refined dendritic cells were observed in a concave region due to the constitutional supercooling caused by meniscus freezing. Meanwhile, at a higher casting temperature (675 ℃), the dotted surface was formed by pore formation. In the dotted surfaces in the billet formed at a high casting speed (230 mm/min), an exudation layer was formed by the high metallostatic head pressure. The dotted region and the smooth region had a refined dendritic morphology and a columnar morphology at the exudation layer, respectively. This is attributed to the formation of gas pores in the dotted region.