• 열처리공학회지
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• 제20권1호
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• pp.1-10
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• 2007

The deformation behaviors of full annealed and T6 treated 6061, 7075 aluminum tubes are investigated at various temperature performing uniaxial tensile test. Full annealed Al 6061 and Al7075 tubes, and T6 treated Al7075 tube don't show sharp local necking with an elongation of 50% at $300^{\circ}C$. So it is expected that influenced by elevated tempterature. At $300^{\circ}C$ and strain rate of 0.001/s, many micro-cracks are observed in T6 treated Al 6061 tube, which is believed to be responsible for the decrease of total elongation.

• 소성∙가공
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• 제30권1호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.150-153
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• 2007

Apply electromagnetic stirring system to making rheology slurry of Al7075. This experiment has important element which is the relation between solid fraction percent and melt temperature of Al7075. The rheology slurry of Al7075 eliminated liquid phase to include alloying element of copper and zinc by squeeze casting process. In result the most structure was composed entirely of globular primary $\alpha$. Used this material for this study. This study made a comparison of mechanical property according to heat treatment T6 at each melt temperature ($619^{\circ}C$ and $615^{\circ}C$). The microstructure and component are observed how heat treatment T6 weight with the mechanical property by SEM-EDS.

• 한국생산제조학회지
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• 제22권5호
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• pp.865-870
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• 2013

In recent years, aluminum processing has been increasing in the aerospace, vehicle, airplane industries etc., because aluminum has abundant resources and has a high specific strength. Aluminum alloys have a high coefficient of thermal expansion therefore, it is necessary to consider the temperature problem in the cutting process. The objective of this research is to investigate the machinability of a hardened aluminum alloy Al7075-T6 by using cryogenic heat treatment. The machining test is conducted by comparing the cutting force and surface roughness, corresponding to various cutting conditions of depth of cut, cutting speed, and feed rate, with those of Al7075-T0.

• 동력기계공학회지
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• 제15권2호
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• pp.61-68
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• 2011

This paper investigates the tensile properties of the friction stir welded joints of Al 7075-T651 aluminum plate according to the welding conditions. A 7075-T651 aluminum alloy plate with a thickness of 6.0 mm was used in this investigation. For the friction stir welding (FSW) process, a tool with shoulder diameter of 20 mm and probe diameter of 9 mm was used. The rotation speed and traverse speed conditions were changed in this study, the other welding conditions are constant. The welding direction was aligned with the material rolling direction, and dimension of the FSW plate were $250{\times}100{\times}6\;mm$. As far as this work is concerned, the optimal FSW conditions are determined as the rotation speed, 600 rpm and traverse speed 0.8 mm/sec or the rotation speed, 800 rpm and traverse speed 0.5 mm/sec.

• 대한기계학회논문집A
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• 제34권8호
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• pp.981-987
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• 2010

Split Hopkinson Pressure Bar(SHPB) 실험기법은 고변형률 하중 조건하에서 변형하는 여러 가지 공업 재료의 변형 거동 특성을 규명하는데 가장 널리 사용되는 실험 방법 중의 하나이다. 본 논문에서는 봉을 통하여 전파하는 응력파의 모양과 라이징 시간을 제어할 수 있는 pulse shaper를 사용하는 수정 SHPB 실험기법을 이용하였다. 수정 SHPB 실험 장치에 고온 장치를 부착하고 알루미늄 합금 7075-T6의 고변형률 하에서의 고온 변형거동에 대한 연구를 수행하였다. 고온 수정 SHPB 실험 장치를 이용하여 알루미늄 합금 7075-T6의 온도와 변형률속도에 따른 기계적 특성을 규명하고, 실험적으로 얻어진 데이터를 Johnson-Cook 구성방정식을 적용하여 알루미늄 합금 7075-T6의 동적 거동을 모델 하는 변수를 결정하였다.

• 한국주조공학회지
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• 제1권2호
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• pp.10-18
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• 1981

In this paper tensile strength and fatigue propagation rate were investigated by aging treatment $(T_6)$ and thermomechanical treatment (TMT) of 7075-Al Alloy specimen. The results of teat showed that TMT improved tensile strength and fatigue crack propagation due to bomogenization of microstructure. In TMT, the results of comparison between T-H' AHA and T-AHA and $T-AH{\cdot}{\cdot}{\cdot}$and $T-HA{\cdot}{\cdot}{\cdot}$were showed that T-AHA and $T-AH{\cdot}{\cdot}{\cdot}$treatments, after solution treatment, which are aging treated before rolling have higher tensile strength. Our investigation on high temperature stability at the Specimen for $T_6$, T-AHA, $T-AH{\cdot}{\cdot}{\cdot}$treatments resulted in rapid reduction of tensile strength over $150^{\circ}C$, but the reduction of tensile strength for specimen of TMT was smoothed than $T_6$.

• 대한기계학회논문집A
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• 제27권6호
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• pp.960-968
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• 2003

The objective of this study is to investigate the effect of AE activities in the crack opening and closure during the fatigue test. The laboratory experiments for various materials and test conditions were carrie out to identify AE characteristics of fatigue crack propagation. Compact tension specimens of SWS 490B and Al 7075-T6 alloy were prepared for fatigue test. AE activities were analyzed based on the phase of the loading cycle. In case of SWS 490B, the most of AE was generated when the crack began opening and the crack closed fully, whereas a few in the full opening of the crack. On the other hand, in case of Al 7075-T6, a distinct AE activity was observed during crack opening process. AE activity in the peak loading of cycle was different with each specimen. However, in the same material, AE activity was not affected by the change of cyclic frequency (0.1, 0.2, 1.0 ㎐). It was found that AE activities during crack opening and closure depend on material properties such as micro-structure, yield strength and elongation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.758-759
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• 2012

• 한국군사과학기술학회지
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• 제1권1호
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• pp.154-165
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• 1998

본 논문에서는 Mongrel원리를 적용한 6절점 삼각형 특이 요소와 8절점 사각형 요소를 사용하여 등방성 재료의 평면균열문제에 대한 응력확대계수를 직,간접적으로 구함으로서 그 수렴성을 입증하였다. 평면균열문제의 경우, 전 영역의 균열크기에 걸쳐 동일한 분할 형태와 요소 수에서 Mongrel 특이요소를 균열끝 요소로 사용하여 직접 구한 응력확대계수가 J-적분을 통해 간접 계산된 응력확대계수에 비해 정해에 잘 일치하였다. 또한 항공기 수명관리의 핵심이라 할 수 있는 피로균열 성장해석을 위한 기초실험으로서 F-5 날개 스파 Al 7075-T6의 CT시편을 채취하여 파괴인성실험을 수행한 결과 L-T방향 파괴인성치는 31.06 ksi.inch$\frac{1}{2}$ 이었다.