• 한국기계기술학회지
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• 제20권6호
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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.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1000-1001
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• 2006

Two atomized alloy powders were pre-compacted by cold and subsequently hot forged at temperatures ranging from 653K to 845K. The addition of Cu and Mg causes a decrease in the eutectic reaction temperature of Al-10Si-5Fe-1Zr alloy from 841K to 786K and results in a decrease of flow stress at the given forging temperature. TEM observation revealed that in addition to Al-Fe based intermetallics, $Al_2Cu$ and $Al_2CuMg$ intermetallics appeared. The volume fraction of intermetallic dispersoids increased by the addition of Cu and Mg. Compressive strength of the present alloys was closely related to the volume fraction of intermetallic dispersoids.

• 열처리공학회지
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• 제7권1호
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• pp.17-24
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• 1994

The evaluation and analysis of diffusivity of lithium for coarsening and coarsening kinetics of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy aged at $170^{\circ}C$ have been investigated by transmission electron microscopy. With ageing time, ${\delta}^{\prime}$ precipitate coaesened to followed $\bar{\gamma}{\propto}t^{1/3}$ and coarsening kinetics was found to be obeyed to the Lifshitz-Slyozov-Wagner(LSW) theory and diffusivity of lithium for coarsening of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy was obtained to be $5.85{\times}10^{-17}{\sim}1.53{\times}10^{-16}$ by experimental coarsening rate constant and various coarsening kinetic theory. Diffusivity of lithium measured by using various model but MLSW and Tsumuraya (VI) et al. model in Al-Li-Cu-Mg-Zr alloy is similar to that calculated by the Costas's diffusivity equation. It was, therefore, suggested that additing to the Cu, Mg and Zr element in Al-Li system have no great effect on diiffusivity of lithium for coarsening of ${\delta}^{\prime}$ This suggest that in matrix.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.382-387
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• 2004

Nanoindentation technique has been used to measure the mechanical properties of aluminium alloy foam cell walls. Al-Si-Cu-Mg alloy foams of different compositions and different cell morphologies were produced using powder metallurgical method. Cell morphology of the foam was controlled during production by varying foaming time and temperature. Mechanical properties such as hardness and Young's modulus were calculated using two different methods: a continuous stiffness measurement (CSM) and an unloading stiffness measurement (USM) method. Experimental results showed that hardness and Young's modulus of Al-5%(wt.)Si-4%Cu-4%Mg (544 alloy) precursor and foam walls are higher than those of Al-3%Si-2%Cu-2%Mg (322 alloy) precursor and foam walls. It was noticed that mechanical properties of cell wall are different from those of precursor materials.

• Applied Microscopy
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• 제36권2호
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• pp.47-55
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• 2006

이 논문에서 Al-2.5Cu-1.5Mg wt.% 합금에서 미세한 Cu 석출물에 대한 투과전자현미경 관찰이 보고 되었다. 이 새로운 관찰은 시료에 오염된 산화물을 제거하기 위해 ion milling을 하고 곧바로 시료 관찰을 했을 때 우연히 이루어 졌다. 특히 이 Cu석출물은 $150^{\circ}C$에서 100시간 aging한 시료에서 분명하게 관찰되었다. 그리고 ion milling 전 시료표면에서 분명히 관측되는 산화물은 $Cu_2O$임이 확실히 밝혀졌다. 이러한 분석과정은 회절 환 패턴의 정밀 분석을 요구함으로 이에 대한 시뮬레이션에 필요한 이론적 공식도 만들었다. 마지막으로 이 합금에 대한 예기치 않은 ion milling효과와 그 중요성이 논의되었다.

• 한국주조공학회지
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• 제41권1호
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• pp.3-10
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• 2021

알루미늄 합금과 주철의 복합주조 공정 중에는 주철로부터 철 성분이 용해되어 알루미늄 용탕에 혼입될 수 있으므로 다양한 Fe함유 금속간 화합물이 형성되며, 이로 인해 알루미늄 합금의 인장 특성이 크게 저하 될 수 있다. 반면 불순물로 첨가되는 Fe와 는 달리 Cu의 경우 알루미늄 합금의 기계적 물성을 향상시키기 위해 첨가되는 합금원소이다. 본 연구에서는 Fe와 Cu의 첨가로 인한 알루미늄 합금의 미세조직 및 인장특성의 변화를 조사하였다. 첨가된 Fe 함량이 1% 이상일 경우 조대한 Al₅FeSi 상과 같은 Fe 함유 화합물들이 다량 형성되어 인장 특성이 현저히 감소하는 것으로 나타났다. Cu가 첨가 된 알루미늄 합금의 경우 Al2Cu 상이 추가로 형성되었으며, 인장 강도가 뚜렷하게 향상되는 결과를 보였다.

• 한국주조공학회지
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• 제30권4호
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• pp.137-141
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• 2010

The effects of Zn amounts on the castability and tensile properties of Al-Zn-Mg-Cu alloys were investigated for development of high strength die casting aluminium alloys. Al-Zn-Mg-Cu alloys with 3.5% Zn showed high cast cracking tendency and poor mold filling behaviour. Al-Zn-Mg-Cu alloys with 5wt% Zn and 7wt% Zn had the tensile strengths of 300~400MPa and the elongations of 2~18%. The effect of Zn on the tensile strength of Al-Zn-Mg-Cu alloys was insignificant, but Al-Zn-Mg-Cu alloy with high Zn amount had lower elongation.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2002년도 춘계 학술발표강연 및 논문개요집
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• pp.78-78
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• 2002

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1998년도 특별강연 및 춘계학술발표 개요집
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• pp.108-111
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• 1998

• Journal of Welding and Joining
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• 제15권4호
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• pp.166-177
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• 1997

The high strength AlZnMgCu0.5 alloy is a light metal with good age hardenability, and has a high tensile and yielding strength. Therefore, it can be used for structures requiring high speciple strength. Even though high strength AlZnMgCu alloy has good mechanical properties, it has a lot of problems in TIG and MIG welding processes. Since lots of high heat absorption is introduced into the weldment during TIG and MIG processes, the microstructural variation and hot cracks take place in heat affected zone. Therefore, the mechanical properties of high strength AlZnMgCu0.5 alloy can be degraded in weldment and heat affected zone. Welding process utilizing high density heat source such as electron beam should be developed to reduce pore and hot cracking, whichare usually accompanied by MIG and TIG welding processes. In this work, electron beam welding process were used with or without AlMg4.5Mn as filler material to avoid the degradation of mechanical properties. Mechanical and metallurgical characteristics were also studied in electron beam weldment and heat affected zone. Moreover hot cracking mechanism was also investigated.