표제지
목차
Abstract 8
1. 서론 11
2. 이론적 배경 14
2-1. Sc 첨가의 영향 14
2-2. RRA(Retrogression and Reaging) 처리의 효과 17
3. 실험방법 21
3-1. 시편제조 21
3-2. 열처리 21
3-3. 기계적 성질 21
3-4. 응력부식균열(Stress Corrosion Cracking) 저항성 22
3-5. 미세 조직 관찰 22
4. 결과 및 고찰 25
4-1. 미세조직관찰 25
4-2. EPMA (Electron probe X-ray Microanalyzer : 전자탐침미세분석기) 관찰 25
4-3. 시효 거동 30
4-4. RRA 처리 및 강도 변화 34
4-5. 기계적 성질 39
4-6. 전기 전도도 및 SCC 저항성 검토 39
4-7. 파단면 관찰 46
5. 결론 52
6. 참고 문헌 53
Table 1. Chemical composition of alloys. 23
Table 2. Peak hardness and Age hardening amount of alloys. 33
Table 3. Tensile strength and elongation value of RRA treated alloys… 41
Table 4. Comparison for SCC(Stress Corrosion Cracking) Resistance… 45
Fig. 1. Typical shape of aircraft extrusion parts 13
Fig. 2. Al₃Sc of Phase Diagram 16
Fig. 3. Steps of RRA Treatment 20
Fig. 4. Schematic illustration of various heat treatments 24
Fig. 5. Optical microstructures of As-extruded K alloy on… 26
Fig. 6. Optical microstructures of (a),(b) K alloy and (c),(d) Al7075 after 76 treatment 27
Fig. 7. Optical microstructures of (a),(b) K alloy and (c),(d) A17075 after RRA treatment. 28
Fig. 8. EPMA analysis of RRA treated of K alloy retrogression at 180℃ and 200℃. 29
Fig. 9. Age hardening curves of K alloy and Al 7075 32
Fig. 10. Retrogression and reaging curves of K alloy and Al 7075 at 180℃. 36
Fig. 11. Retrogression and reaging curves of K alloy and Al 7075 at 200℃. 37
Fig. 12. Retrogression and reaging curves of K alloy and Al 7075 at 220℃. 38
Fig. 13. Mechanical properties of as-extruded and T6 and RRA treated alloys 42
Fig. 14. Conductivity corves of K alloy at 180℃ and 220℃ 44
Fig. 15. SEM micrographs of K alloy (a)T6 and (b)RRA treatment… 47
Fig. 16. SEM micrographs of K alloy retrogression treatment at 180℃ for 30min 48
Fig. 17. SEM micrographs of K alloy T6 treatment at 120℃ for 24 hours. 49
Fig. 18. SEM micrographs of Al 7075 retrogression treatment at 180℃ for 30min. 50
Fig. 19. SEM micrographs of Al 7075 T6 treatment at 120℃ for 24 hours. 51