Beryllium Science and Technology : Volume 1

This beryllium treatise was made possible by the expertise and hard work of members of the Joint US-UK Working Group on Beryllium (JOWOG 22), which was set up in the 1960s to allow a controlled exchange of technical information on the science and application of beryllium between the two countries. The leading roles in JOWOG 22 of Dr. Lee Roberts of the Lawrence Livermore Laboratory and Dr. Geoffrey Ellis ofthe Atomic Weapons Research Establishment (A WRE) at Aldermaston are particularly noteworthy. Excerpts from so me of the material in this book were presented at an international conference "Beryllium 77" in London in October 1977. The conference, which was superbly organized by Dr. John Martin and his co­ workers at A WRE, was sponsored by the Metals Society and the Institu­ tion of Metallurgists, and was particularly instructive in revealing the unexpectedly strong position of the USSR in some aspects of beryllium physical metallurgy and ductility improvement. Advance publicity for this book was also provided by presentations at the AlME 1977 annual meeting in Atlanta, Georgia. The presentations were co-sponsored by the Metal­ lurgy and Non-Ferrous Metals Committees at the request of committee members John E. Smugeresky and Gilbert J. London. D. Webster G. J. London vii Contents 1 • Introduction .... . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . .

1 • Introduction.- 2 • Flow and Fracture of Single Crystals.- 1. Introduction.- 2. Nature of Interatomic Bondings in Beryllium.- 3. General Mechanical Behavior of Hexagonal Metals with Respect to Beryllium.- 3.1. Crystallography.- 3.2. Deformation Modes.- 3.3. Stacking Faults.- 3.4. Primary Slip Systems.- 3.5. Secondary Slip Systems.- 3.6. Fracture Modes.- 3.7. Conclusion.- 4. General Aspects for Testing Beryllium Single Crystals.- 4.1. Crystal Orientation.- 4.2. Geometry of Specimens.- 4.3. Strain Rate.- 4.4. Strain Resolution.- 4.5. Purity.- 5. Basal Slip (0001) ?112?0?.- 5.1. Critical Resolved Shear Stress.- 5.2. Stress-Strain Behavior.- 5.3. Strain at Fracture.- 6. Prismatic Slip {101?0} ?112?0?.- 6.1. Critical Resolved Shear Stress.- 6.2. Stress-Strain Behavior.- 6.3. Strain at Fracture.- 7. Pyramidal Slip {112?2} ?112?3?.- 7.1. Critical Resolved Shear Stress.- 7.2. Stress-Strain Behavior.- 7.3. Strain at Fracture and Pyramidal Fracture.- 8. Twinning.- 9. Fracture.- 9.1. Basal Cleavage.- 9.2. {112?0} Prismatic Cleavage.- 9.3. Pyramidal Fracture.- 9.4. Twin Boundary Cleavage.- 10. The Brittleness Problem in Beryllium.- References.- 3 • Flow and Fracture of Polycrystalline Beryllium.- 1. Introduction.- 2. Atomic Structure.- 3. Single Crystals.- 3.1. Deformation and Failure Mechanisms.- 3.2. Purity.- 3.3. Taylor-von Mises Criterion.- 4. Bicrystals.- 4.1. Deformation Behavior.- 5. Polycrystals.- 5.1. Single Crystal-Poly crystal Correlation.- 5.2. Ductility Improvement.- 6. Structures.- 7. Summary.- References.- 4 • Grain Size Effects.- 1. Introduction.- 2. Polycrystalline Strength.- 2.1. Taylor Orientation Factor.- 2.2. Resistance of Grain Boundaries to Deformation.- 2.3. Grain Boundary Structure.- 3. Grain Size Development and Measurement in Beryllium.- 3.1. Grain Size Development.- 3.2. Grain Size Measurement.- 4. Uniaxial Tensile Properties.- 4.1. Strengths.- 4.2. Ductility.- 4.3. Brittle-to-Ductile Transition.- 5. Other Properties.- 5.1. Indentation Hardness.- 5.2. Impact Properties.- 5.3. Superplasticity.- 6. Summary.- References.- 5 • Impurity Effects in Beryllium.- 1. Introduction.- 2. Distribution of Impurity Phases.- 2.1. General Remarks.- 2.2. Low-Solubility Metallic Impurities.- 2.3. Soluble Metallic Impurities.- 2.4. Nonmetallic Impurities.- 2.5. The Ternary Al-Fe-Be Compound.- 3. Effect of Specific Impurities upon Mechanical Behavior.- 3.1. Fe/Al Effects at Room and Elevated Temperatures.- 3.2. Yield Point Phenomena.- 3.3. Effects of BeO.- 3.4. Effects of Low-Melting Impurities and BeO in High-Temperature Creep and Beryllium Powder Consolidation.- 4. Overall Purity Levels and Mechanical Behavior.- References.- 6 • Recrystallization and Grain Growth in Beryllium.- 1. Introduction.- 2. Recrystallization.- 2.1. Microstructural Changes during Recrystallization.- 2.2. Property Changes during and after Recrystallization.- 2.3. Factors Affecting Recrystallization Temperature.- 3. Grain Growth.- 4. Recommendations for Future Work.- 5. Summary.- References.- 7 • Constitution of Beryllium and Its Alloys.- 1. Introduction.- 2. Crystal Structure.- 3. Electronic Structure.- 3.1. Influence of Temperature and Pressure.- 3.2. Influence of Alloying.- 4. Phase Stability.- 4.1. Phase Transformations.- 4.2. Heat Capacity.- 4.3. Vapor Pressure.- 4.4. Enthalpy and Entropy.- 4.5. Relative Phase Stability.- 4.6. Influence of Pressure.- 4.7. Influence of Alloying.- 5. Solid Solubility.- 6. Intermetallic Phases.- 7. Binary Phase Diagrams.- 7.1. Silver-Beryllium.- 7.2. Aluminum-Beryllium.- 7.3. Boron-Beryllium.- 7.4. Beryllium-Cobalt.- 7.5. Beryllium-Copper.- 7.6. Beryllium-Iron.- 7.7. Beryllium-Nickel.- 7.8. Beryllium-Silicon.- 8. Ternary Phase Diagrams and Intermetallic Phases.- Bibliography of Ternary Beryllium Phase Diagrams.- References.- 8 • Elevated Temperature Behavior.- 1. Introduction.- 2. High-Purity Beryllium.- 2.1. Definition.- 2.2. Tensile Properties.- 2.3. Creep.- 3. Low-Purity (Ingot) Beryllium.- 3.1. Definition.- 3.2. Impurity Reactions and Effects.- 3.3. Texture.- 3.4. Tensile Properties at Elevated Temperatures.- 3.5. Creep.- 4. Powder-Source Beryllium.- 4.1. Impurity Effects.- 4.2. Grain Size and Recrystallization.- 4.3. Substructure.- 4.4. Texture.- 4.5. Tensile Properties.- 4.6. Creep.- 5. Recommendations for Future Work.- References.