title page

Contents

Chapter 1. Introduction 14

1.1. Titanium matrix composites 16

1.1.1. Continuous fiber reinforced titanium matrix composites. 17

1.1.2. Cold and hot isostatic pressing 20

1.1.3. Self-propagating high temperature synthesis 22

1.1.4. Exothermic dispersion 26

1.2. Casting of titanium matrix composites 29

1.2.1. Melting of titanium 29

1.2.1.1. Vacuum arc remelting 31

1.2.1.2. Electron beam melting 33

1.2.1.3. Plasma arc melting 34

1.2.1.4. Induction skull melting 35

1.2.1.5. Vacuum induction melting 37

1.2.2. Casting method of titanium 38

1.2.2.1. Static casting 39

1.2.2.2. Centrifugal casting 39

1.2.2.3. Vacuum die-casting 42

1.2.2.4. Countergravity low-pressure vacuum melting process 43

1.2.3. Mold for titanium 43

1.2.3.1. Permanent mold 45

1.2.3.2. Rammed graphite mold 45

1.2.3.3. Oxides mold 46

1.3. Research issues 47

1.3.1. Ex-situ routes 47

1.3.2. In-situ routes 50

1.3.3. Alpha-case formation 50

1.4. Research identification 51

Chapter 2. Alpha-case Formation Mechanism on Ti Casting 53

2.1. Introduction 53

2.2. Experimental procedures 54

2.2.1. Evaluation of the α-case reaction 54

2.2.2. Alpha-case controlled SKK mold fabrication 55

2.2.3. In-situ synthesis of alpha-case controlled SKK mold 57

2.3. Results and discussion 57

2.3.1. Evaluation of the α-case reaction 57

2.3.2. Alpha-case formation mechanism 59

2.3.3. Development of α-case controlled SKK mold 67

2.3.4. Noble synthesis of the α-case controlled SKK mold 75

2.4. Summary 79

Chapter 3. In-situ synthesis and net-shape forming of TMCs 81

3.1. Introduction 81

3.2. Experimental procedures 83

3.2.1. Investment mold preparation 83

3.2.2. In-situ synthesis and net-shape forming of TMCs 83

3.2.3. Modeling of TMCs shot sleeve casting 86

3.3. Results and discussion 89

3.3.1. In-situ synthesis of TMCs 89

3.3.2. Net-shape forming of TMCs 96

3.3.3. Modeling of TMCs shot sleeve casting 99

3.4. Summary 111

Chapter 4. Evaluation the properties of TMCs 113

4.1. Introduction 113

4.2. Experimental procedures 115

4.2.1. Preparation of TMCs for the properties evaluation 115

4.2.2. Evaluation of the interfacial reaction 115

4.2.3. Evaluation of the mechanical properties 116

4.3. Results and discussion 122

4.3.1. Interfacial reaction 122

4.3.2. Mechanical properties of TMCs 128

4.4. Summary 142

Chapter 5. Conclusion 145

Reference 148

Appendix - Research Achievements 154

한글초록 167

Table 1.1. Typical characteristics of the SHS process. 25

Table 1.2. Comparison of melting method of titanium 30

Table 3.1. The required materials database for MagmasoftR simulation(이미지참조) 88

Table 4.1. Chemical compositions of A380 alloy. 117

Table 4.2. Chemical compositions of H13 tool steel. 117

Table 4.3. Chemical compositions of AISI 52100 steel. 120

Table 4.4. Mechanical properties of AISI 52100 steel. 120

Fig. 1.1. Fabrication method for continuous fiber reinforced titanium matrix composites 19

Fig. 1.2. Schematic diagram of cold and hot isostatic pressing (CHIP) process in Dynamat technology. 21

Fig. 1.3. Schematic diagram of a typical self-propagating high temperature synthesis procedure. 24

Fig. 1.4. Schematic diagram of a basic reaction mode of exothermic dispersion (XD™) process. 28

Fig. 1.5. Schematic diagram of a vacuum arc remelting (VAR) procedure 32

Fig. 1.6. Schematic diagram of a induction skull melting (ISM) procedure 36

Fig. 1.7. Schematic diagram of a vertical type centrifugal casting procedure. 40

Fig. 1.8. Schematic diagram of a horizontal type centrifugal casting procedure. 41

Fig. 1.9. Schematic diagram of a countergravity low-pressure vacuum (CLV) melting process. 44

Fig. 1.10. Schematic diagram of stress-strain response and damage events under transverse tension (I : no damage, II : interface shear fracture, III : debonding, and IV : plastic deformation of the matrix). 48

Fig. 1.11. Microstructure of TiC in a titanium matrix manufactured by CHIP process. 49

Fig. 2.1. Schematic diagram of drop casting procedure of titanium with a plasma arc melting furnace. 56

Fig. 2.2. Microstructure of the interface between Ti and Al₂O₃ mold, and hardness profile. 58

Fig. 2.3. Comparison of elemental mapping images of O, Al and Si in Ti castings into Al₂O₃ mold and BEI image by EPMA. 60

Fig. 2.4. Bright field TEM image of the α-case region. 62

Fig. 2.5. Results of analytical transmission electron microscopy of (a) ring and spot patterns on the TEM image without C2 aperture on the bright field image, and (b) spot pattern on the TEM image was HCP phase in the [2∏0]...(이미지참조) 63

Fig. 2.6. Convergent beam electron diffraction analysis with primitive unit cell volume method (a) The measured primitive unit cell volume, 61.08 ang³ (CL=521.4 mm, D₁=D₂=6.5 mm, ANG=60°, CRAD=23 mm, λ=0.0251 Å), and... 65

Fig. 2.7. Schematic diagram of the interstitial and substitutional α-case formation mechanism of titanium castings. 66

Fig. 2.8. Illustration of the diffraction patterns and replots for identifying phases in 50 wt% titanium and Al₂O₃ mixed by colloidal silica before curing. 68

Fig. 2.9. X-ray diffraction pattern of synthesized α-case controlled SKK mold materials. 70

Fig. 2.10. Illustration of the diffraction patterns and replots for identifying phases from 10 wt% to 50 wt% titanium and Al₂O₃ after curing at 1223 K for 2 hrs. 71

Fig. 2.11. Comparison of externals of titanium castings (a) CaO stabilized ZrO₂ mold, and (b) the α-case controlled SKK mold. 72

Fig. 2.12. Microstructure and hardness profile between pure titanium and α-case controlled SKK mold. 73

Fig. 2.13. Microstructure of the interface between (TiC+TiB) reinforced TMCs and α-case controlled SKK mold. 74

Fig. 2.14. Illustration of the diffraction patterns and replots for identifying the synthesized phases between TiO₂ and aluminum powders. 76

Fig. 2.15. Microstructure and hardness profile between pure titanium and noble route α-case controlled SKK mold. 78

Fig. 3.1. Permanent mold for shot sleeve wax pattern. 84

Fig. 3.2. Photographs α-case controlled molds of shot sleeve investment casting for (a) static casting and (b) centrifugal casting. 85

Fig. 3.3. Preprocess of the gating system for the static casting of TMCs shot sleeve. 87

Fig. 3.4. SEM image of microstructure of in-situ synthesized (TiC+TiB) reinforced TMCs. 90

Fig. 3.5. Comparison of elemental mapping images of C, B and Ti by EPMA. 91

Fig. 3.6. The results of TEM analysis 93

Fig. 3.7. The results of TEM analysis 94

Fig. 3.8. Photographs of (TiC+TiB) reinforced TMCs shot sleeve castings poured into α-case controlled mold by (a) static casting and (b) centrifugal casting. 98

Fig. 3.9. Filling result shows that the molten TMCs filled completely without defects such as misrun and cold-shuts. 100

Fig. 3.10. User definition of heat transfer coefficient between TMCs and mold. 101

Fig. 3.11. Warning message "mesh inconsistent or solidification during filling" of TMCs static casting. 102

Fig. 3.12. Filling result after 80% of the filling shows the turbulent flow and solidification of TMCs melts were generated during filling. 103

Fig. 3.13. Solidification result shows the directional solidification was not developed in the static gating system. 104

Fig. 3.14. Preprocess of the gating system for the horizontal centrifugal casting of TMCs shot sleeve. 106

Fig. 3.15. Filling result after 80% of the filling shows the stable laminar flow of TMCs melts was generated during filling. 107

Fig. 3.16. Filling time result sliced with z axis shows the stable laminar flow of TMCs melts was generated during filling. 108

Fig. 3.17. Solidification result sliced with z axis of centrifugal casting of TMCs shows the sound directional solidification was generated. 110

Fig. 4.1. Photograph of Al₂O₃ mold for evaluation of interfacial reaction between molten A380 and TMCs, and H13 tool steel. 118

Fig. 4.2. Schematic diagram of disk type sliding wear tester. 119

Fig. 4.3. Microstructures of the interfacial morphology of (a) H13 tool steel and (b) (TiC+TiB) reinforced TMCs in molten A380 alloy for 1200 s at 993K. 123

Fig. 4.4. Depth of interfacial reaction layer of H13 tool steel and (TiC+TiB) reinforced TMCs in molten A 380 at 993 K for times varying from 0 to 1200 s. 124

Fig. 4.5. (a) Microstructure of the eroded H13 tool steel by molten A380, and the spalling of the interfacial reaction products and (b) EPMA elemental mapping images of Fe on the interfacial reaction for 900 s at 993 K. 125

Fig. 4.6. Schematic diagram of the order of interfacial reaction process between H13 tool steel and A380 alloy (XY : initial interface). 127

Fig. 4.7. Variation of friction coefficient of H13 tool steel and (TiC+TiB) reinforced TMCs against AISI 52100 steel ball diamond cone 129

Fig. 4.8. Wear volume of H13 tool steel and (TiC+TiB) reinforced TMCs in the cone-on-disk type at the load of 20 N. 130

Fig. 4.9. SEM image of wear track morphology of H13 tool steel after ball-on-disk type sliding test at the load of 20 N. 132

Fig. 4.10. SEM image of wear track morphology of TMCs after ball-on-disk type sliding test at the load of 20 N. 133

Fig. 4.11. SEM image of wear track morphology of H13 tool steel after cone-on-disk type sliding test at the load of 10 N. 134

Fig. 4.12. SEM image of wear track morphology of TMCs after cone-on-disk type sliding test at the load of 10 N. 135

Fig. 4.13. Tensile strength and elongation of cp Ti and (TiC+TiB) reinforced TMCs in the room temperature. 137

Fig. 4.14. SEM images of the fracture surface after tensile test of (a) pure titanium and (b) TMCs. 139

Fig. 4.15. SEM image of fractography of TMCs shows the clear interfacial microstructures. 140