Title Page
초록
Abstract
Contents
1. Introduction 14
2. Theoretical background 16
2.1. Metalic Additive Manufacturing 16
2.2. Powder Bed Fusion 17
2.3. Advantage & Disadvantage of EBM 18
2.4. Fe-Cu alloys 19
3. Materials and methods 20
3.1. Materials and EBM process 20
3.2. Microstructure characterization 21
3.3. Cross-correlation EBSD analysis 23
3.4. Mechanical and thermal testing 24
4. Results 26
4.1. Relative density and microstructure 26
4.2. Cu precipitation behavior 28
4.3. Analysis of residual stress around the crack 29
4.4. Mechanical and thermal properties 32
5. Discussion 49
5.1. Effect of scanning speed on relative density and Cu precipitation behavior 49
5.2. Formation mechanism of cracks due to the EBM process 50
5.3. Mechanical and thermal properties 53
6. Conclusions 56
References 58
Table 1. Process parameters and energy density for EBM of the Fe-10Cu alloys. 25
Table 2. The chemical compositions of as-received powder and as-built sample. 34
Fig. 1. Characterization of the Fe-10%Cu alloy powder: backscatter scanning electron images of the powder with (a) low and (b) high magnifications, (c) particle size distribution... 35
Fig. 2. The relative densities of the as-EBMed Fe-10%Cu alloys fabricated at various scanning speeds. 36
Fig. 3. As-polished microstructures of the as-EBMed Fe-10%Cu alloys fabricated at various scanning speeds; (a) 1000, (b) 2000, (c) 3000, (d) 4000, (e) 5000, and (f) 6000 mm/s. (g)... 37
Fig. 4. EBSD-IPF maps of the as-EBMed Fe-10%Cu alloys fabricated at various scanning speeds; (a) 1000, (b) 2000, (c) 3000, (d) 4000, (e) 5000, and (f) 6000 mm/s. The white and... 38
Fig. 5. BSE-SEM images of the as-EBMed Fe-10%Cu alloys constructed at various scanning speeds: (a) 1000, (b) 2000, (c) 3000, (d) 4000, (e) 5000, and (f) 6000 mm/s. (g-j) SEM image... 39
Fig. 6. TEM bright filed image and corresponding EDS element mapping images of the as-EBMed Fe-10%Cu alloys built at the scanning speed of 1000 mm/s show the mixture of... 40
Fig. 7. Phase analysis and dislocation density of the as-EBMed Fe-10%Cu alloys. (a) X-ray diffraction patterns of the powder and the alloys built at different scanning speeds, (b)... 41
Fig. 8. SEM images, IPF maps and KAM maps neighboring cracks of the as-EBMed Fe-10%Cu alloys constructed at (a) 3000, (b) 4000, (c) 5000, and (d) 6000 mm/s. 42
Fig. 9. (a) Three dimensional optical microscope and (b) SEM image of crack initiation and propagation of the as-EBMed Fe-10%Cu alloys built at the scanning speed of 3000 mm/s. 43
Fig. 10. The crack initiation and propagation mechanisms of the as-EBMed Fe-10%Cu alloys. SEM images with (a) low and (b) high magnifications, (c) IPF map and (d) KAM map... 44
Fig. 11. SEM image and corresponding EPMA elemental maps neighboring cracks, as indicated by the red box on Fig. 10d, of the alloy built with 3000 mm·s⁻¹. 45
Fig. 12. (a) IPF map, Von Mises stress map, GND density map, and (b) residual normal stress tensors (σij), residual shear stress tensors (τij), and lattice rotation tensors (ωij) near crack, as...[이미지참조] 46
Fig. 13. Mechanical and thermal properties of as-EBMed Fe-10%Cu alloys fabricated at various scanning speeds. (a) The tensile stress-strain curves and (b) thermal conductivities of... 47
Fig. 14. SEM images of fracture surface of the as-EBMed Fe-10%Cu alloys with two scanning speeds of (a,b) 2000 mm·s⁻¹ and (d,e) 3000 mm·s⁻¹. The dimple structures include... 48
Fig. 15. Schematics of microstructure formation mechanism of Fe-10%Cu alloy fabricated using EBM with (a) low and (b) high scanning speeds. 54
Fig. 16. Comparison of tensile strength and thermal conductivity for various conventional wrought iron alloys and as-EBMed Fe-10%Cu alloys built at scanning... 55