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Chapter 1 Introduction 1
1£®1 Background 2
1£®2 Motivation 3
1£®3 Outline 4
Chapter 2 Investigation of the flow field in Laser-based Powder Bed Fusion
manufacturing 5
2£®1 Introduction 7
2£®2 Simulation model of the L-PBF printer 10
2£®2£®1 Problem description 10
2£®2£®2 Geometric model of the L-PBF printer 11
2£®2£®3 Numerical model of the L-PBF printer 12
2£®3 Simulation results 16
2£®3£®1 Distribution of the flow field 16
2£®3£®2 Distribution of the temperature field 21
2£®3£®3 Distribution of spatter particles 23
2£®4 Conclusions 28
References 30
Chapter 3 Investigation of optimizing the flow field with fluid cover in
Laser-based Powder Bed Fusion manufacturing process 33
3£®1 Introduction 35
3£®2 Simulation model of L-PBF printer 37
3£®2£®1 Geometry of L-PBF printer with a fluid stabilizing cover 37
3£®2£®2 Numerical model of printer with a fluid stabilizing cover 37
3£®2£®3 Mesh of L-PBF printer with a fluid stabilizing cover 39
3£®2£®4 Model of the fluid stabilizing cover and particles 40
3£®3 Simulation results and discussion 43
3£®3£®1 Influence of the fluid stabilizing cover on the flow field 43
3£®3£®2 Influence of fluid stabilizing cover on particle distribution and removing rate 47
3£®4 Summary and conclusions 51
References 53
Chapter 4 Numerical investigation of controlling spatters with negative pressure
pipe in Laser-based Powder Bed Fusion process 54
4£®1 Introduction 56
4£®2 Simulation model of L-PBF printer 59
4£®2£®1 Geometric model of L-PBF printer 59
4£®2£®2 Numerical model of L-PBF printer 61
4£®3 Simulation results and discussions 64
4£®3£®1 Effect of pipe diameter 68
4£®3£®2 Effect of outlet flow rate 70
4£®3£®3 Effect of initial particle velocity 74
4£®4 Summary and conclusions 76
References 78
Chapter 5 Evolution of molten pool during Laser-based Powder Bed Fusion of
Ti-6Al-4V 80
5£®1 Introduction 82
5£®2 Modeling approach and numerical simulation 85
5£®2£®1 Model establishing and assumptions 85
5£®2£®2 Governing equations 87
5£®2£®3 Heat source model 87
5£®2£®4 Phase change 88
5£®2£®5 Boundary conditions setup 89
5£®2£®6 Mesh generation 90
5£®3 Experimental procedures 91
5£®4 Results and discussions 92
5£®4£®1 Surface temperature distribution and morphology 92
5£®4£®2 Formation and solidification of the molten pool 94
5£®4£®3 Development of the evaporation region 98
5£®5 Conclusions 101
References 103
Chapter 6 Simulation of surface deformation control during Laser-based
Powder Bed Fusion Al-Si-10Mg powder using an external magnetic field 107
6£®1 Introduction 109
6£®2 Modeling and simulation 112
6£®2£®1 Modeling of L-PBF 112
6£®2£®2 Mesh model and basic assumptions 113
6£®2£®3 Heat transfer conditions 114
6£®2£®4 Marangoni convection 115
6£®2£®5 Phase-change material 115
6£®2£®6 Lorentz force 116
6£®3 Results 118
6£®3£®1 Velocity field in the molten pool 118
6£®3£®2 Lorentz force in the MP 121
6£®3£®3 Surface deformation of the sample 123
6£®4 Conclusions 127
References 128
Chapter 7 Influence of laser post- processing on pore evolution of Ti-6Al-4V
alloy by Laser-based Powder Bed Fusion 131
7£®1 Introduction 133
7£®2 Experimental procedures 136
7£®2£®1 Sample fabrication 136
7£®2£®2 Determination of porosity by micro-CT 137
7£®3 Modeling and simulation 140
7£®3£®1 Numerical model 140
7£®3£®2 Moving Gaussian heat source 143
7£®3£®3 Thermal boundary conditions 143
7£®3£®4 Marangoni effect£¬ surface tension and recoil pressure 144
7£®4 Numerical results and discussion 145
7£®5 Conclusions 152
References 153
Chapter 8 Evolution of multi pores in Ti-6Al-4V/Al-Si-10Mg alloy during laser
post-processing 157
8£®1 Introduction 159
8£®2 Experimental procedures 162
8£®2£®1 Sample preparation 162
8£®2£®2 Detection of porosity by mirco-CT 162
8£®3 Model and simulation 165
8£®3£®1 Simulation model 165
8£®3£®2 Gaussian heat source 167
8£®3£®3 Latent heat of phase change 168
8£®3£®4 Level-set method 169
8£®3£®5 Boundary conditions 169
8£®4 Numerical results and discussion 171
8£®5 Conclusions 177
References 179
Chapter 9 Investigation of laser polishing of four Laser-based Powder Bed
Fusion alloy samples 182
9£®1 Introduction 184
9£®2 Model and theoretical calculation 188
9£®2£®1 Physical model and assumptions 188
9£®2£®2 Governing equations and boundary conditions 190
9£®2£®3 Simulation results 192
9£®3 Experimental methods 195
9£®3£®1 Sample fabrication 195
9£®3£®2 Morphology observation by 3D optical profiler 198
9£®3£®3 Experimental results 199
9£®4 Conclusions 206
References 208