Elements of Metallurgy and Engineering Alloys
edited by F.C. Campbell
640+ pages
Selected Contents
Part 1: Physical and Mechanical Metallurgy
Chapter 1 – Metallic Structure
- Periodic Table
- Bonding in Solids
- Metallic Bonding
- Ionic Bonding
- Covalent Bonding
- Secondary Bonding
- Crystalline Structure
- Space Lattices and Crystal Systems
- Face-Centered Cubic System
- Hexagonal Close-Packed System
- Body-Centered Cubic System
- Slip Systems
- Allotropy
Chapter 2 – Crystalline Imperfection and Plastic Deformation
- Point Defects
- Line Defects
- They are successfully applied in the aerospace and the chemical industries as well as in other markets such as architecture
- Dislocations and Plastic Flow
- Work Hardening
- Surface or Planar Defects
- Grain Boundaries
- Polycrystalline Metals
- Phase Boundaries
- Twinning
- Stacking Faults
- Volume Defects
Chapter 3 – Solid Solutions
- Interstitial Solid Solutions
- Substitutional Solid Solutions
- Ordered Structures
- Intermediate Phases
- Dislocation Atmospheres and Strain Aging
Chapter 4 – Introduction to Phase Transformation
- Free Energy
- Influence of Microstructure
- Liquid-Solid Phase Transformations
- Solid-State Phase Transformations
- Spinodal Decomposition
- Martensitic Transformation
Chapter 5 – Diffusion
- Mechanisms of Diffusion
- Interstitial Diffusion
- Substitutional Diffusion
- Fick’s Laws of Diffusion
- Fick’s First Law of Diffusion
- Fick’s Second Law of Diffusion
- Several Applications of Fick’s Second Law of Diffusion
- Temperature Dependence of Diffusion
- Intrinsic Diffusion Coefficients (Kirkendall Effect)
- High Diffusion Paths
Chapter 6 – Phase Diagrams
- Phase Rule
- Binary Isomorphous System
- Eutectic Alloy System
- Aluminum-Silicon Eutectic System
- Lead-Tin Eutectic System
- Free Energy of Alloy Systems
- Peritectic Reaction
- Monotectic Reaction
- Intermediate Phases
- Solid-State Reactions
- Eutectoid Reactions
- Ternary Phase Diagrams
Chapter 7 – Solidification and Casting
- The Liquid State
- Solidification Interfaces
- Solidification Structure
- Segregation
- Grain Refinement and Secondary Dendrite Arm Spacing
- Porosity and Shrinkage
- Casting Processes
- Sand Casting
- Plaster and Shell Molding
- Evaporative Pattern Casting
- Investment Casting
- Permanent Mold Casting
- Metallographic and Fractographic Techniques and Microstructures
Chapter 8 – Recovery, Recrystallization, and Grain Growth
- Recovery
- Recrystallization
- Recrystallization – Temperature and Time
- Recrystallization – Purity of Metal
- Recrystallization – Original Grain Size
- Recrystallization – Temperature of Deformation
- Grain Growth
- Normal Grain Growth
- Abnormal Grain Growth
Chapter 9 – Precipitation Hardening
- Particle Hardening
- Theory of Precipitation Hardening
- Precipitation Hardening of Aluminum Alloys
- Solution Heat Treating
- Quenching
- Aging
- Dispersion Hardening
Chapter 12 – Mechanical Behavior
Chapter 13 – Fracture
Chapter 14 – Fatigue
Chapter 15 – Creep
Chapter 16 – Deformation Processing
Chapter 17 – Physical Properties of Metals
Chapter 18 – Corrosion
Part II: Engineering Alloys
Chapter 26 – Aluminum
- Aluminum Metallurgy
- Aluminum Alloys Designation
- Aluminum Alloys
- Wrought Non-Heat-Treatable Alloys
- Wrought Heat-Treatable Alloys
- Melting and Primary Fabrication
- Rolling Plate and Sheet
- Extrusion
- Casting
- Aluminum Casting Alloys
- Aluminum Casting Control
- Heat Treating
- Annealing
- Fabrication
- Corrosion
Chapter 27 – Magnesium and Zinc
Chapter 28 – Titanium
The notes
Chapter 9 contains the best explanation of the essence of precipitation hardening that I have come across.
Here it is.
Precipitation hardening
Precipitation hardening is used extensively to strengthen not only
- aluminum alloys
but also
- magnesium alloys
- nickel-base superalloys
- beryllium-copper alloys and
- precipitation-hardening stainless steels.
In precipitation hardening:
- An alloy is heated to a high enough temperature to take a significant amount of an alloying element into solid solution.
- It is then rapidly cooled (quenched) to room temperature, trapping the alloying elements in solid solution.
- On reheating to an intermediate temperature, the host metal rejects the alloying element in the form of fine precipitates that create matrix strains in the lattice.
- These the fine precipitate particles act as barriers to the motion of dislocations and provide resistance to slip, thereby increasing the strength and hardness.
Particle Hardening
Particle, or dispersion, hardening occurs when extremely small particles are dispersed throughout the matrix. When a dislocation encounters a fine particle, it must either cut through the particle or bow (loop) around it, as shown schematically in Fig. 9.1.
There are two types of particle strengthening:
- Precipitation hardening. Takes place during heat treatment.
- True dispersion hardening. Can be achieved by mechanical alloying and powder metallurgy consolidation.
For effective particle strengthening, the matrix should be soft and ductile, while the particles should be hard and discontinuous (Fig. 9.2). A ductile matrix is better in resisting catastrophic crack propagation. Smaller and more numerous particles are more effective at interfering with dislocations motion then lager and more widely spaced particles.
Fig. 9.1 – Paricle-strengthening
Fig. 9.2 –
Precipitation Hardening of Aluminium Alloys
Aluminium alloys are one of the most series of alloys that can be precipitation hardened, including
- 2xxx (aluminium-copper) alloys
- 6xxx (aluminium-magnesium-silicon) alloys
- 7xxx (aluminium-zinc
- some of the 8xxx (aluminium-lithium) alloys.
Precipitation hardening consists of three steps:
- Solution heat treating
- Rapid quenching
- Ageing
In solution heat treating, the alloy is heated to a temperature that is high enough to put the soluble alloying elements in solution. After holding at the solution-treating temperature long enough for diffusion of solute atoms into the solvent matrix in occur, it is quenched to a lower temperature (e.g., room temperature) to keep the alloying elements trapped in solution. During ageing, the alloying elements trapped in solution precipitate to form a uniform distribution of very fine particles. Some aluminium alloys will harden after a few days at room temperature, a process called natural ageing, while others are artificially aged by heating to an intermediate temperature (Fig. 3).
Fig. 9.3 – Typical age hardening for aluminium:
T1 – natural ageing (room temperature) artificial underageing (low temperature);
T2 – artificial underageing; T3 – artificial top ageing; T4 – artificial overageing
