SYNOPSIS
This course covers the mechanics and microstructure of structural materials for high-temperature applications. The mechanisms of time-dependent deformation and failure at high homologous temperature are treated in a quantitative manner. Materials used at high temperature (metals, ceramics and their composites) are reviewed, with emphasis on the relationship between microstructure and high-temperature mechanical properties.
Week 1 Introduction, Continuum Approach
Lattice defects relevant to high temperature deformation
Week 2 Dislocation Glide
Dislocation Creep
Week 3 Dislocation Creep
Dispersion Strengthening
Week 4 Diffusional Creep
Deformation Mechanism Maps
Week 5 Midterm Exam
Superplasticity
Week 6 High Temperature Fracture
Steels
Week 7 Nickel-base Superalloys
High Temperature Coatings
Week 8 Intermetallics
Refractory Metals
Week 9 Ceramics
Composites
Week 10 Carbon
A. Mechanics and Mechanisms
I. Continuum mechanics
1. Test techniques
2. Visco-elastic Behavior
II. Lattice Defects
1. Vacancies
1. Diffusion in metals
2. Diffusion in ceramics
2. Grain boundaries
3. Dislocations
1. Slip
2. Climb
3. Orowan equation
III. Deformation Mechanisms
1. Dislocation glide
1. Discrete obstacles
2. Diffuse obstacles
2. Dislocation creep
1. Glide control
2. Climb control
3. Effect of alloying
4. Power-law break-down
5. Harper-Dorn creep
6. Microstructure evolution
7. Dispersion strengthening
3. Diffusional creep
1. Vacancy creep
2. Grain-boundary sliding
3. Grain-boundary dislocations
4. Microstructural effects
4. Deformation mechanism maps
1. Steady-state creep
2. Isomechanical groups
5. Superplasticity
1. Structural superplasticity
2. Internal-stress superplasticity
3. Fracture
4. Superplastic materials
IV. High-temperature fracture
1. Fracture Mechanism Maps
2. Cavity Nucleation
3. Cavity growth
B. Microstructures and Materials
V. Metals
1. Iron-based alloys
1. Low-alloy steels
2. Martensitic steels
3. Ferritic steels
4. Austenitic steels
5. Iron-nickel superalloys
2. Nickel- and cobalt-base superalloys
1. Historical developments
2. Microstructure
3. Properties
4. Processing
5. Coatings
3. Intermetallic alloys
1. Nickel aluminides
2. Iron aluminides
3. Titanium aluminides
4. Other aluminides
5. Silicides
4. Refractory alloys
1. Chromium
2. Niobium