Gamma Titanium Aluminide Alloys

Transcription

1 Fritz Appel, Jonathan David Heaton Paul, and Michael Oehring Gamma Titanium Aluminide Alloys Science and Technology WILEY- VCH WILEY-VCH Verlag GmbH & Co. KG aa

2 I' Preface XIII Figures-Tables Acknowledgement List XV 1 Introduction 1 References 3 2 Constitution The Binary Ti-Al Phase Diagram Ternary and Multicomponent Alloy Systems 11 References 20 3 Thermophysical Constants Elastic and Thermal Properties Point Defects Diffusion 29 References 30 4 Phase Transformations and Microstructures Micro structure Formation on Solidification Solid-State Transformations P > a Transformation SO Formation of (cc2 + y) Lamellae Colonies Feathery Structures and Widmannstatten Colonies Massive Transformation 63 References 64 5 Deformation Behavior of Single-Phase Alloys Single-Phase y(tial) Alloys Slip Systems and Deformation Kinematics Planar Faults Planar Dislocation Dissociations in y(tial) Nonplanar Dissociations and Dislocation Locking 85

3 VI j Mechanical Twinning in 7(TiAl) Effects of Orientation and on Temperature Deformation of Y Phase Deformation Behavior of Single-Phase oc2(ti3al) Alloys Slip Systems and Deformation Kinematics Effects of Orientation and Temperature on Deformation of a2 Phase P/B2 Phase Alloys 114 References Deformation Behavior of Two-Phase c^ftijal) + y(tial) Alloys Lamellar Microstructures Interface Structures in Lamellar TiAl Alloys Energetic Aspects of Lamellar Interfaces Coherent and Semicoherent Interfaces Coherency Stresses Plastic Anisotropy Micromechanical Modeling Deformation Mechanisms, Contrasting Single-Phase and Two-Phase Alloys Methodical Aspects of TEM Characterization Deformation of (a2 + 7) Alloys at Room Temperature Independent Slip Systems High-Temperature Deformation of (a2 + 7) Alloys Slip Transfer through Lamellae Generation of Dislocations and Mechanical Twins Dislocation Source Operation in Y(TiAl) Interface-Related Dislocation Generation Twin Nucleation and Growth Twin Intersections Acoustic Emissions Thermal Stability of Twin Structures Glide Resistance and Dislocation Mobility Thermally Activated Deformation Glide Resistance at the Beginning of Deformation Static and Dynamic Strain Aging of TiAl Alloys Diffusion-Assisted Dislocation Climb, Recovery, and Recrystallization Thermal and Athermal Stresses 234 References Strengthening Mechanisms Grain Refinement Work Hardening Work-Hardening Phenomena 255

4 VII Athermal Contributions to Work Hardening Jog Dragging and Debris Hardening Thermal Stability of Deformation Structures High-Temperature Flow Behavior High Strain-Rate Deformation Solution Hardening Elemental Size Misfit of Solute Atoms with the TiAl Matrix Survey of Observations Effect of Solute Niobium Precipitation Hardening Carbide Precipitation in TiAl Alloys Hardening by Carbides Hardening by Borides, Nitrides, Oxides, and Silicides Optimized Nb-Bearing Alloys 292 References Deformation Behavior of Alloys with a Modulated Microstructure Modulated Microstructures Misfitting Interfaces Mechanical Properties 310 References Creep Design Margins and Failure Mechanisms General Creep Behavior The Steady-State or Minimum Creep Rate Single-Phase Y(TiAl) Alloys Two-Phase a2(ti3al) + 7(TiAl) Alloys Experimental Observation of Creep Structures Effect of Microstructure Primary Creep Creep-Induced Degradation of Lamellar Structures Precipitation Effects Associated with the ct2->y Phase Transformation Tertiary Creep Optimized Alloys, Effect of Alloy Composition and Processing Creep Properties of Alloys with a Modulated Microstructure Effect of Stress and Temperature Damage Mechanisms 347 References Fracture Behavior Length Scales in the Fracture of TiAl Alloys Cleavage Fracture 360

5 VIII 10.3 Crack-Tip Plasticity Plastic Zone Interaction of Cracks with Interfaces Crack-Dislocation Interactions Role oftwinning Fracture Toughness, Strength, and Ductility Methodical Aspects Effects of Microstructure and Texture Effect of Temperature and Loading Rate Effect of Predeformation Fracture Behavior of Modulated Alloys Requirements for Ductility and Toughness Assessment of Property Variability Statistical Assessment Variability in Strength and Ductility of TiAl Fracture Toughness Variability of TiAl 396 References Fatigue Definitions The Stress-Life (S-N) Behavior HCF Fatigue Crack Growth Crack-Closure Effects Fatigue at the Threshold Stress Intensity Effects of Temperature and Environment on the Cyclic Crack-Growth Resistance LCF General Considerations Cyclic-Stress Response Cyclic Plasticity Stress-Induced Phase Transformation and Dynamic Recrystallization Thermomechanical Fatigue and Creep Relaxation 428 References Oxidation Behavior and Related Issues Kinetics and Thermodynamics General Aspects Concerning Oxidation Effect of Composition Mechanical Aspects of Oxide Growth Effect of Oxygen and Nitrogen Effect of Other Environmental Factors Subsurface Zone, the Z-Phase, and Silver Additions Effect of Surface Finish 447

6 Ion Implantation Influence of Halogens on Oxidation Embrittlement after High-Temperature Exposure Coatings/Oxidation-Resistant Alloys Summary 458 References Alloy Design Effect of Aluminum Content Important Alloying Elements-General Remarks Cr, Mn, and V Nb, W, Mo, and Ta B, C, and Si Specific Alloy Systems Conventional Alloys High Niobium-Containing Alloys P-Solidifying Alloys Massively Transformed Alloys Summary 476 References Ingot Production and Component Casting Ingot Production Vacuum Arc Melting (VAR) Plasma-Arc Melting (PAM) Induction Skull Melting (ISM) General Comments Casting Investment Casting Gravity Metal Mold Casting (GMM) Centrifugal Casting Countergravity Low-Pressure Casting Directional Casting Summary 515 References Powder Metallurgy Prealloyed Powder Technology Gas Atomization Plasma Inert-Gas Atomization (PIGA) at GKSS Titanium Gas-Atomizer Process (TGA) Electrode Induction Melting Gas Atomization (EIGA) Rotating-Electrode Processes Rotating-Disc Atomization General Aspects of Atomization 532

7 Sheet X Postatomization Processing Hot Isostatic Pressing (HIPing), Hot Working, and Properties Laser-Based Rapid-Prototyping Techniques Metal Injection Molding (MIM) Spray Forming Sheet/Foil Production through (i) HIP of Cast Tapes and (ii) Liquid-Phase Sintering Spark Sintering Summary Elemental-Powder Technology Reactive Sintering Mechanical Properties of Reactive Sintered Material Manufacture of Reactively Sintered Components/Parts Summary Mechanical Alloying 565 References Wrought Processing Flow Behavior under Hot-Working Conditions Flow Curves Constitutive Analysis of the Flow Behavior Conversion of Microstructure Recrystallization of Single-Phase Alloys Multiphase Alloys and Alloying Effects Influence of Lamellar Interfaces Microstructural Evolution during Hot Working above the Eutectoid Temperature Technological Aspects Workability and Primary Processing Workability Ingot Breakdown Texture Evolution Secondary Processing Component Manufacture through Wrought Processing Rolling Production and Selected Mechanical Properties Pack Rolling Rolling Defects Industrial Production of Sheet Mechanical Properties of Sheet Superplastic Behavior Novel Techniques Manufacture of Large "Defect-Free" Components 672 References 673

8 XI 17 Joining Diffusion Bonding Alloy Compositions and Microstructures Microasperity Deformation Diffusion Bonding; Experimental Setup Metallographic Characterization of the Bonding Zone Effect of Alloy Composition Influence of Bonding Time and Stress Mechanical Characterization of the Bonds Brazing and Other Joining Technologies Brazing and Transient Liquid-Phase Joining Other Techniques 704 References Surface Hardening Shot Peening and Roller Burnishing Residual Stresses, Microhardness, and Surface Roughness Surface Deformation Due to Shot Peening Phase Transformation, Recrystallization, and Amorphization Effect of Shot Peening on Fatigue Strength Thermal Stability of the Surface Hardening 724 References Applications, Component Assessment, and Outlook Aerospace Aircraft-Engine Applications Exotic Aerospace Applications Automotive Outlook 736 References 737 Subject Index 739