B0724 Effects of hydrogen in aluminium and its alloys

289 Pages·2004·4.93 MB·English

by  David E. J. Talbot

The Effects of Hydrogen in Aluminium and its Alloys

The Effects of Hydrogen in
Aluminium and its Alloys
D.E.J. Talbot
MANEY
FOR THE INSTITUTE OF MATERIALS, MINERALS AND MINING
B0724
First published in 2004 for
The Institute of Materials, Minerals and Mining by
Maney Publishing
1Carlton House Terrace
London SWIY 5DB
Maney Publishing is the trading name of
W. S. Maney and Son Ltd
Hudson Road
Leeds LS9 7DL
© 10M3 2004
All rights reserved
ISBN 1-902653-73-4
Typeset in India by Emptek Inc.
Printed and bound in the UK by
The Charlesworth Group
Contents
Preface xiii
Acknow ledgement xiv
1.0 OVERVIEW OF THE EFFECTS OF OCCLUDED HYDROGEN 1
1.1 STATES OF OCCLUSION 2
1.1.1 Nature of Hydrogen 2
1.1.2 Solutions 3
1.1.3 Hydrogen Traps 3
1.2 QUANTITATIVE ApPROACHES 4
1.2.1 Hydrogen Contents 4
1.2.2 Solubilities 4
1.2.3 Diffusivity 5
1.3 ENVIRONMENTAL SOURCES OF HYDROGEN 5
1.3.1 Humidity 5
1.3.2 Rolled Surfaces 6
1.4 CONTROL OF ARTIFACTS ASSOCIATED WITH HYDROGEN 7
1.4.1 Interdendritic Porosity 7
1.4.2 Secondary Porosity 7
1.4.3 Extraneous Sites for Defects 8
1.4.4 Inherited Characteristics 8
1.5 REFERENCES 8
2.0 ALUMINIUM AND ITS ALLOYS 11
2.1 STRUCTURE AND PROPERTIES OF ALUMINIUM 11
2.1.1 Physical States 11
2.1.2 Crystal Structure 12
2.1.3 Chemical Properties 12
2.2 SUMMARY OF COMMERCIAL ALLOYS AND ApPLICATIONS 13
2.2.1 Alloy Systems 13
2.2.2 Alloys Used without Heat-Treatment 14
2.2.2.1 Commercial Pure Aluminium Grades
(AA 1100 Alloy Series) 14
2.2.2.2 The Aluminium-Manganese Alloy AA 3003 14
2.2.2.3 Aluminium-Magnesium Alloys (AA 5000 Series) 16
2.2.2.4 The Aluminium-Magnesium-Manganese
Alloy AA 3004 17
2.2.3 Heat Treatable (Ageing) Alloys 17
2.2.3.1 Aluminium-Copper-Magnesium Alloys (e.g. AA 2024) 18
vi EFFECTS OF HYDROGEN IN ALUMINIUM AND ITS ALLOYS
2.2.3.2 Aluminium-Zinc-Magnesium Alloys (e.g. AA 7075) 18
2.2.3.3 Aluminium-Magnesium-Silicon Alloys (e.g. AA 6061) 18
2.2.3.4 Aluminium Alloys Containing Lithium 19
2.2.4 Casting Alloys 19
2.3 REFERENCES 19
3.0 SUMMARY OF MANUFACTURING ROUTES AND
PROCEDURES 21
3.1 EXTRACTIVEMETALLURGYOFALUMINIUM 21
3.1.1 Extraction of Alumina from Bauxite by the Bayer Processl 21
3.1.2 Extraction of Aluminium by the Hall-Herault Processl 22
3.1.2.1 The Reduction Cell 22
3.1.2.2 Metal Purity 23
3.2 INGOTCASTING 23
3.2.1 Melting and Preparation of the Liquid Metal 24
3.2.2 Delivery of Liquid Metal from Furnace to Moulds 24
3.2.3 The Direct Chill CDC) Semicontinuous Process 24
3.2.3.1 Regular DC Casting 24
3.2.3.2 Low Head Casting 25
3.2.3.3 Level Transfer Casting 26
3.3 ROLLINGFLATPRODUCTS 26
3.3.1 Hot Rolling 26
3.3.2 Cold Rolling 27
3.3.3 Foil Rolling 27
3.4 FABRICATIONOF RODS TUBESAND SECTIONS 27
3.4.1 Extrusion 27
3.4.2 Rod and Section Rolling 28
3.4.3 Tube and Wire Drawing 28
3.5 FOUNDRYPRODUCTS 28
3.6 FORGING 29
3.7 RECYCLING 29
3.8 REFERENCES 30
4.0 HYDROGEN OCCLUSION IN ALUMINIUM AND
ITS ALLOYS 31
4.1 DILUTE SOLUTIONSOF HYDROGENINALUMINIUM 31
4.1.1 Thermodynamics of Dissolution 31
4.1.1.1 Selection of Standard States 31
4.1.1.2 Pressure-Dependence of Solubility and
.Sievert's Isotherm 32
4.1.1.3 Temperature-Dependence of Solubility and the
Van't Hoff Isobar 32
EFFECTS OF HYDROGEN IN ALUMINIUM AND ITS ALLOYS vii
4.1.2 Some Fundamental Aspects of Hydrogen Solutions 33
4.1.2.1 Electronic Approach to the Enthalpy of Solution 34
4.1.2.2 Statistical Approach to Solubility 35
4.1.2.3 Crystallographic Aspects of Hydrogen Solutions 38
4.2 SPONTANEOUSBREAKDOWNOF SUPERSATURATEDSOLUTIONS 42
4.2.1 Nucleation and Growth of Hydrogen-Filled Micropores 43
4.2.3 Pore Stability Diagram 46
4.3 HYDROGENTRAP SITES 46
4.3.1 Diatomic Traps 46
4.3.1.1 Microporosity 46
4.3.1.2 Extraneous Artifacts 46
4.3.2 Monatomic Traps 47
4.3.3 Chemical Traps 49
4.3.3.1 The Stability of Lithium Hydride in
Aluminium-Lithium Alloys 49
4.3.3.2 The Stability of Sodium Hydride in
Aluminium and itsAlloys 50
4.4 QUANTITATIVEDESCRIPTIONOF OCCLUDEDHYDROGENIN INDUSTRY 52
4.4.1 Determinate and Indeterminate Occluded Systems 52
4.4.2 Hydrogen Content 54
4.5 REFERENCES 54
5. THE DETERMINATION OF HYDROGEN IN ALUMINIUM
AND ITS ALLOYS 57
5.1 GENERALPRINCIPLES 57
5.1.1 Collection Methods 57
5.1.2 Methods Based on Measurements of Hydrogen Activity 58
5.2 THE VACUUMEXTRACTIONTECHNIQUE 58
5.2.1 Operating Principles 58
5.2.2 Equipment 59
5.2.2.1 Gas Collection and Analysis System 59
5.2.2.2 Arrangements for Heating Samples 62
5.2.3 Procedures 62
5.2.3.1 Sample Preparation 62
5.2.3.2 Conditioning the Sample Tube 63
5.2.3.3 Extraction of Hydrogen 64
5.2.3.4 Correction for Residual Gases 64
5.2.3.5 Correction for Extraneous Hydrogen 64
5.2.3.6 Care and Maintenance of Sample Tubes 65
5.2.4 On-Line Data Processing by Computer 66
5.2.5 Validity of Results 69
5.2.5.1 Reproducibility of the Method 69
5.2.5.2 Absolute Accuracy 69
viii EFFECTS OF HYDROGEN INALUMINIUM AND ITS ALLOYS
5.3 THE TELEGAS 69
5.3.1 Validation of Principle 70
5.3.2 Micro Carrier Gas System 71
5.3.3 Practical Operation and Characteristics 74
5.3.3.1 Operation 74
5.3.3.2 Accuracy 75
5.3.3.3 Example of Telegas Application in
Industrial Experiments 75
5.3.3.4 Further Developments 76
5.4 RAPIDCARRIERGAS METHOD 77
5.5 ApPLICATIONOF REDUCEDPRESSURETo LIQUIDMETALSAMPLES 78
5.6 ASSESSMENTOF ApPLICATIONS 79
5.7 REFERENCES 80
6. SOLUBILITIES OF HYDROGEN IN ALUMINIUM AND ITS
ALLOYS 81
6.1 TECHNIQUESFOR MEASURINGSOLUBILITIES 81
6.1.1 Sieverts' Method 81
6.1.1.1 Equipment 82
6.1.1.2 Procedures 82
6.1.1.3 Validity of Sieverts' Method 84
6.1.2 Absorption- Desorption Methods 84
6.1.2.1 Equipment 84
6.1.2.2 Procedures 85
6.1.3 Procedures for Alloys with Active Volatile Components 87
6.1.4 Reliability of Determinations 88
6.2 PRESENTATIONOF VALUESFOR SOLUBILITY 88
6.2.1 Conventional Descriptions of Solutions 88
6.2.2 Practical System Based on Hydrogen Content 89
6.2.3 Relation of Hydrogen Content to Molality and Mole Fraction 89
6.3 CRITICALASSESSMENTSOF PUBLISHEDVALUESFOR SOLUBILITIES 90
6.3.1 Pure Aluminium 90
6.3.1.1 Pure Liquid Aluminium 90
6.3.1.2 Pure Solid Aluminium 93
6.3.1.3 Comparison of Solubilities in Liquid and
Solid Pure Aluminium 95
6.3.2 Aluminium-Copper and Aluminium-Silicon Alloys 96
6.3.2.1 Liquid Aluminium Copper Alloys 97
6.3.2.2 Liquid Aluminium-Silicon Alloys 99
6.3.3 Aluminium-Lithium Alloys 100
6.3.3.1 Liquid Aluminium-Lithium Alloys 101
6.3.3.2 Nature of Hydrogen Solutions in
Liquid Aluminium Alloys Containing Lithium 105
EFFECTS OF HYDROGEN INALUMINIUM AND ITS ALLOYS
IX
6.3.3.3 Solid Aluminium-Lithium Alloys 107
6.3.3.4 Association of Solute Hydrogen
with Lithium-Rich Clusters 119
6.3.3.5 Nature of Hydrogen Solutions in Solid
Aluminium Alloys Containing Lithium 123
6.4 REFERENCES 128
7.0 THE DIFFUSION OF HYDROGEN IN ALUMINIUM
AND ITS ALLOYS 131
7.1 MATHEMATICSOFDIFFUSION 131
7.1.1 Diffusion in a Uniform Isotropic Medium 131
7.1.1.1 Absorption in or Desorption from an
Infinite Plane Sheet 132
7.1.1.2 Absorption in or Desorption from an
Infinite Cylinder 133
7.1.1.3 Dimensionless Parameters 134
7.1.2 Diffusion in a Field of Traps 134
7.1.2.1 Linear Isotherm 137
7.1.2.2 Non-Linear Isotherm 138
7.2 DETERMINATIONOF DIFFUSIVITYCOEFFICIENTS 139
7.2.1 Approach 139
7.2.2 Procedures for the Solid Metal 140
7.2.3 Evaluation of Diffusion Coefficients 140
7.3 DIFFUSIVITYIN ALUMINIUM 141
7.3.1 True Diffusivity in Solid Pure Aluminium 141
7.3.2 Diffusivity in Manufactured Products 143
7.3.3 Diffusion with Enhanced Trapping 145
7.3.4 Diffusivity of Hydrogen in Pure Liquid Aluminium 147
7.4 DIFFUSIVITYIN SOLIDALUMINIUMLITHIUMALLOYS 148
7.4.1 Measured Values 148
7.4.2 Mathematical Analysis 150
7.5 REFERENCES 151
8. ABSORPTION OF HYDROGEN IN ALUMINIUM
AND ITS ALLOYS 153
8.1 INDUSTRIALHYDROGENSOURCES 154
8.2 THE CAPACITYOFTHEMETAL TOACCEPT HYDROGEN 155
8.3 HYDROGENABSORPTIONBYLIQUID METAL 157
8.3.1 Practical Considerations 157
8.3.1.1 Furnace Atmospheres 157
8.3.1.2 Charge Materials 157
8.3.2 Reaction Kinetics 158
8.3.2.1 Oxygen Activity Gradients in Oxidation
Products on Aluminium 158