Semi-solid Processing of Alloys (eBook)

Foreword 6
Preface 7
Contents 9
Part I Evolution and Design of Microstructure in Semisolid Alloys D.H. Kirkwood 13
1 Fundamental Aspects 14
1.1 General and Local Equilibrium in Alloy Systems 14
1.2 Nucleation 16
1.2.1 Homogeneous Nucleation 16
The Rate Equation 16
1.2.2 Heterogeneous Nucleation 19
1.2.3 Grain Refinement 20
1.3 Solid–Liquid Interface Structure 22
1.4 Morphological Instability 23
1.5 Grain Multiplication 25
1.6 The Growth and Spheroidization of Equiaxed Grains 26
2 Characterization of Microstructure in Semisolid Slurries 28
2.1 Fraction Solid 28
2.2 The Shape Factor 28
2.3 Contiguity and Continuity 30
3 Evolution of Microstructure in Semisolid Alloys 33
3.1 Introduction 33
3.2 Coarsening in Al–Cu Alloys 34
3.3 Coarsening in Al–Si Alloys 35
3.4 X-ray Microtomography of Alloy Slurries 39
4 Recent Developments in Slurry Formation 44
References for Part I Evolution and Design of Microstructure in Semisolid Alloys 47
Part II Rheology and Modeling M. Suery and H. Atkinson 48
5 Introduction and Definitions for Rheology and Modeling 49
6 Experimental Determination of Rheological Behavior 51
6.1 Partially Solidified Alloys 51
6.1.1 Experimental Methods 51
Rotation and Translation Viscometer 51
Fluidity Tests 53
6.1.2 Results Concerning Viscosity 54
6.1.3 Results on Fluidity 62
6.2 Partially Remelted Alloys 62
6.2.1 Experimental Methods 62
Shear Viscometer 62
Parallel Plate Compression 63
Direct Extrusion 64
Back Extrusion 64
Indentation 64
Drained Compression 65
Tension 66
6.2.2 Results in Terms of Apparent Viscosity 66
Influence of the Morphology of the Solid Phase 66
Influence of Shear Rate 68
Influence of the Solid Fraction 71
6.2.3 Results in Terms of Constitutive Behavior 71
6.3 Comparison Between Partially Solidified and Partially Remelted Alloys 72
6.4 Yield Stress 73
6.5 Concluding Remarks 74
7 Modeling of Semisolid Processing 76
7.1 Introductory Remarks on Modeling 76
7.2 Utility of Modeling 79
7.3 Use of the Structural Parameter for Modeling: Model of Brown and Coworkers 80
7.4 Use of a Yield Stress in Models 81
7.5 Finite Difference Modeling 82
7.5.1 One-phase Finite Difference Modeling 82
7.5.2 Two-phase Finite Difference Modeling 89
7.6 Finite Element Modeling 89
7.6.1 One-phase Finite Element Modeling 89
Zavaliangos and Lawley 89
Backer 89
Alexandrou, Burgos and Coworkers 90
Orgéas and Coworkers 94
7.6.2 Two-phase Finite Element Modeling 97
7.7 Models akin to Forging Models 101
7.7.1 Viscoplastic Constitutive Models 101
7.7.2 Model Based on Viscoelasticity and Thixotropy 101
7.8 Micromodeling 102
7.9 Concluding Remarks on Modeling 104
8 General Conclusions on Rheology and Modeling 105
References for Part II Rheology and Modeling 106
Part III Industrial Applications of Semisolid Processing Ken Young and Plato Kapranos 110
9 Introduction to Industrial Applications of Semisolid Processing 111
10 Raw Material 114
10.1 Semisolid Material Delivery Systems 115
10.2 Vertical Induction Slug Heating 115
10.3 Horizontal Induction Slug Heating 116
10.4 Horizontal Convection Slug Heating 118
10.5 Reheating of Solid Feedstock 118
10.6 Direct Slurry Production: Rheocasting/Thixomoulding 121
10.6.1 New Rheo-Casting Route 121
10.6.2 Semisolid Rheocasting 122
Low-Fraction Solid Slurry 123
10.7 Other Slurry Based systems 124
10.7.1 ``Semisolid'' Slugs from Slurry 124
10.7.2 Direct Slurry Forming 125
10.7.3 Thixomoulding 126
10.7.4 Rheo-Die casting Process 128
11 Process Control in Die Filling and Die Design 130
11.1 Die Temperature Control Systems 131
11.2 Parts Selection for Formability Evaluation 132
11.3 Injection System Evaluation 132
11.4 Fill Test Observations 133
11.5 Venting and Vacuum Assist 135
11.6 Runner, Gate Design and Injection Forces 136
11.7 Surface Quality 137
11.8 Summary of General Process Issues. 138
11.8.1 Raw Materials 138
11.8.2 Alloy Selection 138
12 Component Design Rules 139
12.1 Tolerances 139
12.2 Part Design Rules 139
12.3 Dimensioning 139
12.4 Cost Reductions in Product Design 140
13 Practical Applications in Use Today 141
14 The Future 150
References for Part III Industrial Applications of Semisolid Processing 151
Appendix to Industrial Applications of Semisolid Processing: Mechanical Properties of Some Thixoformed Alloys 151
References 165
Index 167