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Al 7003 합금의 열처리(T5, T6)에 따른 인장 및 고주기 피로 변형 거동
김민종(M. J. Kim),김관영(K. Y. Kim),어광준(K. J. Euh),이기안(K. A. Lee) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
Tensile and high-cycle fatigue defomation behavior due to heat treatment (T5, T6) on Al 7003 alloy were investigated. Aluminum 7003 alloy was produced through casting and extruding, and then heat treatments of T5(90 ℃, 5hrs. + 150 ℃, 16hrs.) and T6 (470 ℃, 3hrs., 80 ℃ and WQ solution processing, 14hrs + 120 ℃, 42hrs.) followed respectively. Using the two kinds of Al 7003 alloys to which different heat treatments were applied, microstructure analysis, tensile tests, room-temperature high-cycle tests, etc., were performed. The observation of microstructure showed that the average grain size was 3.8 μm for T5 alloy and 4.1 μm for T6 alloy. Both kinds of heat-treated alloys were analyzed to be Al-matrix and to have MgZn₂ and Fe-intermetallic phase; MgZn₂ with T6 condition had finer and more regular distribution compared to the one with T5 condition. The tensile results showed the following properties under the T5 heat treatment condition: tensile strength of 359.0MPa; yield strength of 326.1MPa, and; ductility of 28.0%. On the other hand, under the T6 condition, tensile strength was 411.6MPa, yield strength was 373.6MPa, and ductility was 26.3%. In other words, under the T6 heat treatment condition, relatively higher strength and minor decrease in ductility were obtained compared to those under the T5 condition. The high-cycle fatigue results showed that the fatigue limit (10<SUP>7</SUP>cycle) under the T5 heat treatment condition was 290MPa, and the fatigue limit (10<SUP>7</SUP>cycle) under the T6 condition was 320WPa. Under all stress conditions, the fatigue life of T6 alloy was verified to be longer than that of T5 alloy. Based on the observation on tensile and fatigue fracture surfaces, the excellent properties of the T6 heat-treated alloy were confirmed to cone from the effective reinforcement phases with small and uniform distribution generated by the heat treatment under such condition. Based on these results, Al 7003 alloy`s tensile and fatigue deformation mechanisms were also discussed.
주조용 A356 합금의 피로 변형 거동에 미치는 기공 및 열처리의 영향
이영재(Y. J. Lee),김선호(S. H. Kim),어광준(K. J. Euh),조규상(K. S. Cho),이기안(K. A. Lee) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
The effect of heat treatment on the high-cycle fatigue behavior of A356 casting aluminum alloys was investigated in this study. Microstructure examination, tensile and high-cycle fatigue test were conducted on both Al-Si-Mg casted (F) and heat-treated (T6) conditions. The high-cycle fatigue results indicated that the fatigue strength of the A356-T6 alloy was higher than that of the A356-F alloys. The SEM fractography results showed that porosity affected detrimental effect on the fatigue life: 79% of all tested samples fractured as a result of porosity which acted as the main crack initiation site. It was found that fatigue life decreased as the size of pore increased. The mechanisms of fatigue crack initiation and propagation of A356 alloy, which is correlated with pore and microstructure, was also discussed.
Twin roll strip casting 공정으로 제조된 Al 3527K 합금의 인장 및 피로 변형 거동
함기수(G. S. Ham),백민석(M. S. Baek),어광준(K. J. Euh),임영목(Y. M. Rhyim),이기안(K. A. Lee) 한국소성가공학회 2016 한국소성가공학회 학술대회 논문집 Vol.2016 No.4
This study investigated tensile and fatigue properties of Al 3527K alloy manufactured by strip casting process. Al 3527K alloy (as strip casted (F material)) produced by twin roll strip casting and H heat treated (480°C, 6hr, AC) alloy were examined and compared. Microstructure observation results revealed that both alloys (F and H) featured rapid solidification microstructures. In addition, both alloys were identified to be composed of Al, Al6(Mn, Fe) and AlFeMnSi phases. As H heat treatment was applied, Al 3527K-H alloy formed a more even phase distribution than Al 3527K-F alloy. The tensile properties showed that H heat treatment resulted in increase of strength and decrease of elongation. In tensile fracture surface observation, both alloys showed typical ductile fracture modes. The F alloy was measured to have a dimple size of 6.8㎛ on average, and the H alloy measured 4.2㎛ on average in fracture surfaces. High-cycle fatigue tests were performed using ISTRON 8501, and the test conditions were stress ratio R=0.1, 10 Hz at room temperature. The fatigue limit showed that H heat treatment resulted in increase of fatigue properties at all stress condition. Furthermore, F alloy featured a larger deviation in fatigue life in all identical stress conditions compared to the O alloy. This study also discussed the fatigue deformation behavior of Al 3527K alloy manufactured by strip casting through the abovementioned mechanical properties as well as the tensile and fatigue fractographies.
Al 7003 합금의 인장 및 피로 특성에 미치는 열처리(T5, T6)의 영향
김민종 ( M J Kim ),김관영 ( K Y Kim ),어광준 ( G J Euh ),임영목 ( Y M Rhym ),이기안 ( K A Lee ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.3
A7003 alloy underwent T5 and T6 heat treatments (T5: 90 ℃ for 5 hrs and 150 ℃ for 16 hrs; T6: 470 ℃ for 3 hrs followed by artificial aging at 80 ℃ for 14 hrs, and 120 ℃ for 42 hrs); the tensile and fatigue properties of the treated materials were then examined. High-cycle fatigue tests were conducted at R (stress ratio)=0.1, and f (frequency)=20 Hz. The average grain size of A7003-T5 alloy was 3.8 μm, and that of A7003-T6 alloy was 4.1 μm. Both of the alloys were found to have MgZn2 (?), Fe-based intermetallic phases in their aluminum matrix. A7003-T6 alloy had finer MgZn2 (?) phases distributed more evenly than A7003-T5 alloy. Tensile test results showed that A7003-T6 alloy had higher strength (Y.S. & T.S.) and lower elongation compared to those of A7003-T5 alloy. High cycle fatigue results showed that A7003-T6 alloy had longer fatigue limit (320 MPa) than that (290 MPa) of T5 alloy. A7003-T6 alloy was found to perform better in all other fatigue stress conditions, too. Based on the observation of tensile and fatigue fracture surfaces, the correlations between microstructures made by heat treatments and mechanical/fatigue properties were also investigated along with the fatigue deformation mechanism of A7003 alloy.(Received April 22, 2014)
S. C. Yun(윤신천),K. J. Euh(어광준),H. W. Kim(김형욱),K. A. Lee(이기안) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.10
This study attempted to produce a clad sheet with strip casted AA3527 alloy and AA4343 alloy, and attempted to investigate the effect of intermediate heat treatment and brazing treatment on the mechanical properties (hardness, tensile properties) of 3527/4343 aluminum clad sheet. The core sheet (manufactured by strip casting), AA3527 alloy (composition: Al-0.54Si-0.55Fe-0.76Cu-1.18Mn-0.03Mg-0.32Cr-0.08Ti), and surface thin sheet for brazing, AA4343 alloy (composition: Al-7.38Si-0.138Fe-0.01Ti) underwent hot rolling and cold rolling, and then a roll bonding for finishing. The overall thickness of the clad sheet was measured at approximately 0.22mm (AA3527: 0.20mm, AA4343: 0.02mm). The intermediate heat treatments were conducted on the conditions of 360℃-400℃/14 hours. Then, the samples underwent 100 minutes of brazing treatment at temperatures of 610℃. In the 3527 alloy region, Al, Al6Mn and AlFeMnSi phases were observed. In the case of 4343 region, Al, eutectic Si, AlFeSi phases were identified. The microstructure observation results represented partial recovery and recrystalization at temperatures of 360℃ and 380℃ heat treatment conditions, and complete recrystalization was observed at 400℃ condition. Tensile and yield strengths decreased (249.8MPa->203MPa, 203.8MPa->88MPa) and elongation increased (7.6%->10.4%) as heat treatment temperature increased. After brazing treatment, recrystalization and grain growth appears regardless of intermediate heat treatment temperature. Erosion in directed from partial 4343 alloy region to 3527 alloy region was occasionally found. Tensile properties after brazing are identified to be similar regardless of intermediate heat treatment conditions