• 열처리공학회지
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• 제19권5호
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• pp.257-261
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• 2006

Scandium(Sc) in Al-Zn-Mg-Cu based Al alloy on precipitation phenomenon was compared to a 7001(Al-7.2%Zn-3.2%Mg-1.8%Cu) Al alloy. GP zone and ${\eta}^{\prime}$ phases were the main strengthening phases at low aging temperature under $100^{\circ}C$, but ${\eta}^{\prime}$ and $Al_3Sc$ phases were the main strengthening phases at high aging temperature above $1600^{\circ}C$ in Sc added 7000(Al-7.7%Zn-2.0%Mg-1.9%Cu-0.1%Zr) Al alloy. With the addition of 0.1%Sc in 7000 Al alloy, the activation energy for the GP zone, ${\eta}^{\prime}$ and ${\eta}$ phase decreased compared to the 7001 Al alloy. This result indicates that the Sc accelerated the precipitation for the GP zone, ${\eta}^{\prime}$ and ${\eta}$ phases in 7000 Al alloy. Al-7.7%Zn-2.0%Mg-1.9%Cu-0.1%Zr-0.1 Sc alloy has higher strength than 7001 Al alloy, which has high strength.

• 소성∙가공
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• 제8권5호
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• pp.482-490
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• 1999

7000 series Al alloy with good mechanical properties has been focused with tendency to reduce the components weight of aircraft and automobile. However, it is difficult to manufacture a sound extruded product because of segregation, grain growth, casting defect, surface defect, decreasing extrudability and so on. The objective of this study is to manufacture a new 7000 al alloy more than the extrudability of A7N01 and A7003 through controlling the weight (%) Mg, Zn, Si. Hot extrusion experiments on the axisymmetric rod are performed in 500℃ and also performed analysis of the same process using unmerical analysis method, a coupled rigid-thermoviscoplastic finite element method. Extrusion limit diagram was obtained for the developed alloy by FE-simulation in order to define the relationship of extrusion speed and initial billet temperature.

• 한국주조공학회지
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• 제41권3호
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• pp.241-251
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• 2021

7000계 알루미늄 합금은 다른 Al 합금에 비해 강도가 우수하여 주목을 받고있으며, 7000계 알루미늄 빌렛은 일반적으로 Direct-Chill (DC) 주조 공정을 통해 제조된다. DC 주조 공정으로 제조된 알루미늄 빌렛의 표면 결함은 주로 Exudation과 Meniscus freezing 현상과 관련이 있으며, 이는 합금 성분, 주조 속도 및 주조 온도의 영향을 받는다. 특히, 7000계 알루미늄 합금은 응고 과정에서 응고 온도 범위가 넓어 주조 결함이 발생하기 쉽다. 본 연구에서는 DC 주조 공정에 의해 제조된 Al-8Zn-2Mg-2Cu 합금 빌렛에 대한 표면 결함 변화에 대하여 조사하였다. 빌렛의 표면은 "Wavy" 또는 "Dot" 표면으로 관찰되었다. Wavy 표면은 낮은 주조 속도(200mm/min)와 온도(655℃)에서 Meniscus freezing 현상에 의해 형성되었으며, Concave 영역에서 Meniscus freezing 현상으로 인한 조성작 과냉으로 인해 미세한 수지상 조직이 관찰되었다. 반면에, 주조 온도가 높은 조건(675℃)에서는 Dot 표면이 기공 형성에 의해 형성되었으며, 높은 주조 속도(230mm/min)에서 제조된 Dot 표면을 갖는 빌렛에서는 높은 금속 수두압에 의해 Exudation 층이 형성되었다. Exudation 층의 Dot 영역과 Smooth 영역은 각각 미세한 수지상 형태와 주상정 형태의 조직이 관찰되었으며 이는 Dot 영역에서 가스 기공의 형성에 의한 결과이다.

• 한국주조공학회지
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• 제32권4호
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• pp.181-189
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• 2012

The microstructures of self-designed 7000 series Aluminium alloys added with Sc are observed. Moreover, the mechanical properties of the Sc-added Aluminium alloys are evaluated as a function of tensile temperature to establish the conditions of a following extrusion process. New casting conditions in the aluminium alloys added with Sc could be established by changing the casting speed and stirring time in the existing casting conditions of Aluminium alloys. The Sc addition results in $Al_3(Sc,Zr)$ precipitates in the cast alloys, and leads to the formation of equal-axed grains and fine grains. After homogenization heat treatment at $450^{\circ}C$, the Sc-added Aluminium alloys showed the highest elongation values in the temperature ranging from $300{\sim}400^{\circ}C$.

• 수산해양기술연구
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• 제28권1호
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• pp.53-60
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• 1992

In this study, cathodic protection experiment was carried out by Al-alloy sacrificial anode in marine environments which have specific resistance($\rho$) if 25~7000$\Omega$.cm and investigated protection potential, current density and loss rate of Al-alloy sacrificial anode. The main results resistance($\rho$) of 400$\Omega$.cm, the cathodic protection potential appears high about-720 mV(SCE). But below specific resistance($\rho$) of 300$\Omega$.cm, the cathodic protection potential appears low about-770 mV(SCE) and simultaneously, cathode is protected sufficiently. 2) The loss rate of Al-Alloy sacrificial anode became large with decreasing specific resistance and increasing the ratio(A sub(c)/A sub(a) of bared surface area of anode and cathode. 3) The loss rate of Al-alloy sacrificial anode(w) to the mean current density of anode(i) is as follows. w=ai+b (a, b : experimental constants)

• 열처리공학회지
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• 제6권1호
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• pp.9-16
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• 1993

To investigate the properties of diffusion bonding of 7050 Al alloy, the diffusion bonding joints have been produced in self-made diffusion bonding hot-press which admits a defined application of the bonding pressure during the heating phase and also rapid cooling after the bonding process with various bonding condition. The strength of the bond increases with increasing the bonding time and temperature. Shear test at toom temperature showed that high strength up to 70% that of parent metal (320 MPa), 220 MPa for the specimen bonded 14 hr at $560^{\circ}C$, with 3 MPa. In this case, however, there is large deformation more than 20% reduction in thickness. The results were correlated with joint characteristics found by optical microstructure and by fractography by SEM. When the strengths of the bonds are more than 50% that of parent metal, a great deal of dimples stretched along the direction of shear stress are observed over the fractured surface of the bond. On the microstructure of the bond line, initial mophology of the bond line disapeared for the grain boundary migration with increasing the bonding time.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 1998년도 추계 학술논문발표회 논문집
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• pp.9-14
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• 1998

고강도 알루미늄 합금은 기술의 진보에 따라서 이용도가 높은 매우 중요한 재료로서, 잘 알려진 적용분야로서는 항공우주산업, 고속회전체, 항공기용재 등으로 많이 사용되고 있다. 고강도 알루미늄 합금은 Al-Cu-Mg(2000 series)를 기초로 둔것과 Al-Zn-Mg-Cu(7000 series)를 기초로 둔 것등이 있다. (중략)

• Journal of Welding and Joining
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• 제12권1호
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• pp.28-37
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• 1994

본 소고에서는 Al-Zn-Mg 계통의 고강도 알루미늄합금의 제조과정에서 실시하는 열처리 공정을 통해 얻어지는 시효경화 효과, 합금원소 첨가에 따른 석출물의 생성과 이에 따른 석출경화 효과와 용착금속의 응고균열 발생과의 상호관계를 조사하고 용접열영향부의 용질원자 확산과 입계의 liquid film에 의한 액화(liquation) 균열의 생성을 분석하여 설명하고자 한다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2003년도 international symposium on advanced powder metallurgy
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• pp.130-131
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• 2003

• 한국주조공학회지
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• 제34권2호
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• pp.54-59
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• 2014

In this study, the extruded Al-6.3Zn-2.4Mg alloys were selected among the 7000 series aluminum alloys sensitive to hydrogen environment in order to examine the effects of both the aging conditions and the length of hydrogen charging period on the mechanical properties of the alloy. The specimens were aged for 24hours at $100^{\circ}C$ (under aging (UA)), $120^{\circ}C$ (peak aging (PA)), and $160^{\circ}C$ (over aging (OA)), respectively. Charging tests were performed at RT for 12, 24, 36 hours under potentiostatic conditions (-2000 mV vs (Ag/AgCl)) for 12, 24 and 36 hours in 1M $H_2SO_4$ and 0.1%$NH_4SCN$ solution. The fracture surface was examined by scanning electron microscopy (SEM). X-ray diffraction (XRD) pattern in peak aged sample was obtained before and after hydrogen charging from extruded Al-6.3Zn-2.4Mg alloys. The decreasing rate of tensile strength and elongation is represented in order of over aging < under aging < peak aging, and it is believed that the hydrogen recharge is more sensitive to elongation than tensile strength. The formation of $AlH_3$ in hydrogen charged Al-6.3Zn-2.4Mg alloys has been confirmed by X-ray diffraction studies.