표제지
국문요약
영문요약
목차
제1장 서론 및 연구 배경 21
1.1. 연구 배경 및 목적 22
1.2. 연구 내용 및 구성 27
참고문헌 28
제2장 이론적 배경 29
2.1. 알루미늄 합금의 구분 30
2.1.1. 알루미늄 합금의 특징 30
2.1.2. 주조재 알루미늄 합금 31
2.1.3. 전신재 알루미늄 합금 34
2.2. 주조재 알루미늄 합금의 주요 이차상 37
2.2.1. 공정상 37
2.2.2. 초정상 40
2.2.3. 석출상 41
2.3. 주조재 알루미늄 합금의 이차상 형상 제어 43
2.3.1. 액상 제어 43
2.3.2. 열처리 46
2.3.3. 미량 원소 첨가 48
2.3.4. 가공열처리 52
2.3.5. 외부 에너지 인가 54
참고문헌 56
제3장 AlMg5Si2Mn 알루미늄 합금의 미세조직, 가공성 및 기계적 특성에 미치는 Pre-homogenization deformation 공정의 영향 60
3.1. 서론 61
3.2. 실험방법 63
3.3. 실험결과 및 고찰 65
3.3.1. 균질화 열처리 전 냉간 가공에 의한 미세조직 변화 65
3.3.2. 이차상 형상 제어에 따른 압연 가공성 변화 73
3.3.3. 최종 판재의 미세조직 및 기계적 특성 75
3.4. 결론 79
참고문헌 80
제4장 Pre-homogenization deformation 공정의 냉간 가공량 차이에 따른 AlMg5Si2Mn 알루미늄 합금의 미세조직 및 기계적 특성 변화 83
4.1. 서론 84
4.2. 실험방법 85
4.3. 실험결과 및 고찰 89
4.3.1. 균질화 열처리 전 냉간 가공량 차이에 따른 미세조직 변화 89
4.3.2. 균질화 열처리 전 냉간 가공량 차이에 따른 압출재의 미세조직 및 기계적 특성 95
4.4. 결론 104
참고문헌 105
제5장 가공열처리 및 Sr 첨가에 따른 Al-Si-Cu계 알루미늄 합금의 미세조직, 가공성 및 기계적 특성 변화 108
5.1. 서론 109
5.2. 실험방법 110
5.3. 실험결과 113
5.3.1. 균질화 열처리 및 Sr 첨가에 따른 미세조직 변화 113
5.3.2. Sr 첨가에 따른 압연 가공성 변화 116
5.3.3. 최종 판재의 기계적 특성 118
5.4. 고찰 120
5.4.1. 공정 Si 상 미세화 120
5.4.2. 압연 가공성 향상 122
5.4.3. 인장 특성 향상 126
5.4.4. 주조 기반 공정 소재와의 기계적 특성 비교 132
5.5. 결론 134
참고문헌 135
제6장 종합 결론 139
Table 2.1. Classification according to chemical composition of cast aluminum alloys(KS/JIS). 31
Table 2.2. Classification according to chemical composition of die-cast aluminum alloys(KS/JIS). 32
Table 2.3. Influence of specific tramp elements on cast aluminum alloys. 33
Table 2.4. Classification according to chemical composition of wrought aluminum alloys(AA standard). 34
Table 3.1. Chemical composition of AlMg5Si2Mn alloy determined by optical emission spectroscopy(OES) analysis (mass fraction, wt.%). 64
Table 3.2. Volumes and interconnectivity of Mg₂Si particles of AlMg5Si2Mn alloys in as-cast, PA and PB treated samples. 69
Table 3.3. Tensile properties of the cast slab and the PB treated and rolled sheets. 78
Table 4.1. Nominal and analyzed chemical composition of the AlMg5Si2Mn alloy(mass fraction, wt.%). 86
Table 4.2. Tensile properties of the AlMg5Si2Mn alloy extrudates with different amounts of PHD for as-extruded, T4 heat-treated, and T6... 97
Table 5.1. Chemical composition of ALDC12 aluminum alloys determinded by inductively coupled plasma-optical emission... 111
Table 5.2. Tensile properties of the cast and sheet samples under various heat treatment conditions (YS : yield strength, TS : tensile... 118
Table 5.3. Volumes and interconnectivity of eutectic Si particles of ALDC12 alloys represented in Figure 5.9. 125
Figure 1.1. Assessment of lightweight materials for automotive industries. 23
Figure 1.2. Development of primary and recycled aluminum through 2050, based on numbers in 2019 for end-of-life product collection... 24
Figure 1.3. Numbers from 2019 showing the distribution of the global aluminum post-consumer scrap intake as a function of manufacturing... 25
Figure 1.4. Example revealing the dual effect of aluminum alloys made from scrap; weight reduction and the associated fuel savings(left) plus... 25
Figure 2.1. Classification of aluminum alloys. 30
Figure 2.2. Alloying elements in wrought aluminum alloys and their critical limits. 36
Figure 2.3. Comparison of tensile properties for 1XXX to 8XXX wrought aluminum alloys. 36
Figure 2.4. Representation of part of the Al-Cu system between aluminum and θ(Al₂Cu). Letters in the diagram highlight different... 37
Figure 2.5. Schematic of the four broad categories of eutectic structures; (a) lamellar, (b) rod-like, (c) globular, (d) acicular. 38
Figure 2.6. Schematic illustration showing the relationships among preparation method, microstructure and mechanical properties of Al-Si alloy. 39
Figure 2.7. Schematic illustration showing the effect of Gd addition and thermo-mechanical processing on microstructure and mechanical... 39
Figure 2.8. Microstructure of hyper-eutectic Al-Si alloys with different Mg contents; (a) Al-16Si-1Mg-1Cu, (b) Al-16Si-3Mg-1Cu,... 40
Figure 2.9. Schematic illustration showing the effect of liquid state manipulations on microstructure and mechanical properties of... 41
Figure 2.10. Basic steps of precipitation hardening of Al-Cu alloy. 42
Figure 2.11. Effect of heat-treatment on microstructure and hardness of Al-Si-Cu and Al-Si-Mg alloys. 42
Figure 2.12. Micrographs of Al-16wt.%Si alloy air-cooled and cast into sand/metal mold with increasing the melt overheating temperature... 44
Figure 2.13. Mechanical properties of AA511.0 alloy (Al-4.35Si-0.5Si) in the as-cast state at different temperatures of melt overheating; (a)... 44
Figure 2.14. Schematic diagram of the melt structure(Black spots illustrating the segregated atom clusters). 45
Figure 2.15. Optical micrographs of (a) sample A(760 ℃), (b) sample B(950-760 ℃) and (c) sample C(1150-760 ℃); (d) typical changes... 45
Figure 2.16. The dissolution and spheroidizing processes of Mg₂Si dendrites. 46
Figure 2.17. Microstructures of the Al-xSi-0.45Mg alloys without and with Sr addition after various solution treatment times at 538 ℃. 47
Figure 2.18. Elongation of the Al-xSi-0.45Mg alloys without and with Sr addition after a T61 heat treatment carried out at different solution... 47
Figure 2.19. Summary of the modification potency of elements for eutectic Si in Al-Si alloys from the literature in the period from May... 48
Figure 2.20. Optical and SEM micrographs showing the size and distribution of the eutectic Si in the Al-10.5Si-2.0Cu alloys with... 49
Figure 2.21. Variation of (a) the tensile strength and (b) the elongation of the Al-10.5Si-2.0Cu alloys with different Sr contents and... 50
Figure 2.22. Optical microstructure of Al-15Mg₂Si composites after T6 heat treatment; (a, b) with 0.1wt.% as-cast Sr addition, (c, d) with... 51
Figure 2.23. Microstructures of Al-12%Si-0.2%Mg alloy; (a) as-cast, (b) as-homogenized, (c) and (d) as-hot-extruded. 53
Figure 2.24. Tensile properties of (a) ESA(hot-extruded, solutionized and aged) and (b) CSA(as-cast, solutionized and aged) of... 53
Figure 2.25. Optical micrographs(x100) showing the microstructures of the as-cast A390 alloys; (a) without UST and (b) with UST. 55
Figure 2.26. Strain versus stress curves of the as-cast A390 alloys with and without UST. 55
Figure 3.1. Flow chart of the fabrication of AlMg5Si2Mn alloy sheets using different homogenization methods. 64
Figure 3.2. DSC heating curve of the as-cast AlMg5Si2Mn alloy. 66
Figure 3.3. Thermodynamically predicted mass fraction of the second phases during solidification of the AlMg5Si2Mn alloy. 66
Figure 3.4. Microstructure of (a) as-cast(with XRD results) and treated (b) PA, and (c) PB AlMg5Si2Mn alloy. 67
Figure 3.5. Histograms for (a) length, (b) diameter and (c) aspect ratio of Mg₂Si particles in as-cast and homogenized AlMg5Si2Mn... 68
Figure 3.6. 3D reconstructed images of the eutectic Mg₂Si in homogenized AlMg5Si2Mn alloys; (a) as-cast(=10.7vol.%), (b) PA... 69
Figure 3.7. Microstructure of AlMg5Si2Mn alloy slab after being cold rolled, showing dimensional reductions of 3% prior to homogenization... 71
Figure 3.8. Schematic representation of the effect of homogenization treatment on the spheroidization sequences of eutectic Mg₂Si in PA and... 72
Figure 3.9. (a) PA treated slab after hot rolling, (b) optical micrograph of cracked part, marked by the dashed rectangle in (a), (c) PB treated... 73
Figure 3.10. Stress-strain curves of PA and PB treated AlMg5Si2Mn alloy slabs at 300 and 400 ℃. 74
Figure 3.11. Microstructural changes of Mg₂Si particle((a)-(d)) and crystal grains((e)-(h)) during solution heat treatment at 580 ℃ for 0... 75
Figure 3.12. (a) Morphologies of Mg₂Si particles, and (b) grain size of matrix, as a function of solution treatment time at 580 ℃. 76
Figure 4.1. Flow chart of the fabrication method for extruded AlMg5Si2Mn alloys including different amount of PHD. 86
Figure 4.2. Schematic representation of the domain used for FE simulation with the dimensions of the billet used for the PHD treatment. 87
Figure 4.3. (a) As-cast microstructure and (b) XRD results of the AlMg5Si2Mn alloy. 89
Figure 4.4. Strain distribution in the AlMg5Si2Mn alloy billets after PHD treatment with different reduction conditions, as calculated by FE... 90
Figure 4.5. Microstructure of the (a, c) top and (b, d) center regions of the billet in the as-cast condition(0% PHD treatment); (a, b) before,... 91
Figure 4.6. Microstructure of the (a, c) top and (b, d) center regions of the billet with 5% PHD treatment; (a, b) before, and (c, d) after... 91
Figure 4.7. Microstructure of the (a, c) top and (b, d) center regions of the billet with 10% PHD treatment; (a, b) before, and (c, d) after... 92
Figure 4.8. Effect of the amount of PHD treatment on the average diameter and sphericity of the Mg₂Si particles at the top and center of... 93
Figure 4.9. 3D reconstructed images of the eutectic Mg₂Si phase in homogenized AlMg5Si2Mn alloy; (a) 0%, (b) 5%, and (c) 10% PHD treatments. 94
Figure 4.10. Microstructure of the AlMg5Si2Mn alloy extrudates with (a, d) 0%, (b, e) 5%, and (c, f) 10% PHD treatments; (a, b, c) before,... 96
Figure 4.11. Effect of the amount of PHD on the average diameter and sphericity of the Mg₂Si particles in as-extruded and solution... 96
Figure 4.12. Grain structure of the AlMg5Si2Mn alloy extrudates with (a, d) 0%, (b, e) 5%, and (c, f) 10% PHD treatment; (a, b, c) before,... 97
Figure 4.13. Tensile stress-strain curves of the AlMg5Si2Mn alloy extrudates with different amount of PHD for (a) as-extruded, (b) T4... 98
Figure 4.14. Microstructure near the tensile fracture surface of the T4 heat-treated AlMg5Si2Mn alloy extrudates; (a) 0%, (b) 5%, and (c)... 100
Figure 4.15. Schematic representation of crack tip blunting behaviors during tensile loading caused by (a) particle cracking and (b) interface... 101
Figure 4.16. Mechanical properties of the AlMg5Si2Mn alloy according to fabrication methods(PMC[13,51], HPDC[25,51], rolling[13], and... 103
Figure 5.1. Flow chart of the fabrication method for the cast and thermo-mechanically treated ALDC12 alloys. 111
Figure 5.2. Solid fraction-temperature curves and fractions of secondary phases at the end of solidification calculated under the Scheil... 113
Figure 5.3. Microstructure of ALDC12 alloys before and after homogenization heat treatment at 520 ℃ for 12 h; (a) as-cast... 114
Figure 5.4. Effect of heat treatment time and Sr addition on the average diameter and aspect ratio of the Si particles in ALDC12 alloys. 115
Figure 5.5. Fraction of cracked surface(edge cracks) of ALDC12 alloys after hot and cold rolling(fraction of cracked surface = average... 116
Figure 5.6. Microstructure of the (a, c) ALDC12 and (b, d) ALDC12+Sr alloys; (a, b) before, and (c, d) after solution heat... 117
Figure 5.7. Tensile properties of the cast and sheet samples under various heat treatment conditions(w/o Sr : without Sr, w/ Sr : with Sr);... 119
Figure 5.8. Histograms for (a, b) diameter and (c, d) aspect ration of Si particles in homogenized, hot-rolled, cold-rolled and... 121
Figure 5.9. 3D reconstruction images of the eutectic Si in (a, b, c, d) ALDC12 and (e, f, g, h) ALDC12+Sr alloys; (a, e) as-cast, (b, f)... 124
Figure 5.10. Microstructure near the tensile fracture surface of the (a, b, c) ALDC12 and (d, e, f) ALDC12+Sr alloys(observed parallel to the... 127
Figure 5.11. Tensile fracture surface of the (a, b, c) ALDC12 and (d, e, f) ALDC12+Sr alloys(observed perpendicular to the loading... 128
Figure 5.12. Grain structure of the (a, c) ALDC12 and (b, d) ALDC12+Sr alloys; (a, b) as-cast samples, and (c, d) sheet samples... 130
Figure 5.13. Schematic representation of the effect of thermo-mechanical treatment and Sr addition on tensile properties of ALDC12 alloys. 131
Figure 5.14. Tensile properties of the ALDC12 alloys according to fabrication methods (DC : die-casting[22,23,25,53], MC : mold casting... 133
Figure 6.1. Schematic representation of the effects of pre-homogenization deformation(PHD) treatment, modifying agent and thermo-mechanical... 141
Figure 6.2. Comparison of tensile properties(tensile strength versus elongation) between commercial wrought aluminum alloys used in the... 142