40 Questions
What is another term used to refer to phase diagrams?
Constitutional diagrams
What is the basis for classification of phases based on atomic order?
Amorphous, Crystalline, Quasi-crystalline
What is an example of a system with two components that are elements?
Au-Cu system
What is the term used to describe the change of one phase into another?
Phase transformation
What is a phase in the context of materials science?
A physically homogeneous and distinct portion of a material system
What type of phase diagrams involve time?
Time-Temperature-Transformation (TTT) diagrams and Continuous-Cooling-Transformation (CCT) diagrams
What is the purpose of the tie line in a phase diagram?
To determine the chemical composition of the phases
What is the term used to describe the system in which the solid solubility of one component in another is limited?
Non-isomorphous system
What is the Lever Rule used for?
To determine the relative amounts of each phase
What is the characteristic of a eutectic alloy?
It freezes at a single temperature
What occurs in a Peritectic reaction?
The liquid reacts with one solid to produce another solid
Why is it difficult to equilibrate peritectic reactions?
Because of the rate-limiting step of solid-state diffusion
What is the term for the maximum concentration of solute atoms that can dissolve in a solvent to form a solid solution?
Solubility Limit
What is the term for the component of a solution that is present in a greater or major extent?
Solvent
What is the term for the distribution of phases and defects in a material?
Microstructure
What is the term for a map that shows the relationship between phases in equilibrium in a system as a function of temperature, pressure, and composition?
Phase Diagram
What is the term for a system with two components?
Binary System
What is the term for a phase diagram where there is complete solid and liquid solubility between two components?
Isomorphous Phase Diagram
What is the rate limiting step in peritectic reactions?
Solid state diffusion
What is the term used to describe the property of metals that can exist in more than one type of crystal structure?
Allotropy
What is the composition of cementite in terms of carbon content?
6.67% carbon
What is the crystal structure of ferrite?
B.C.C.
What is the maximum solubility of carbon in ferrite at 723°C?
0.025% carbon
What is the reason for considering cementite as a part of the phase diagram?
It is a metastable phase with a slow decomposition rate
What is the approximate tensile strength of pearlite?
120,000 psi
What is the crystal structure of austenite?
Face centered cubic
What is the minimum temperature at which ferrite is stable?
1394°C
What is the purpose of the TTT diagram?
To determine the kinetics of isothermal transformations
What is the method used to determine the TTT diagram?
Molten salt bath technique combined with metallography and hardness measurements
What is the characteristic of ledeburite?
It contains small islands of austenite dispersed in the carbide phase
What is the phase that forms when Austenite is quenched below a certain temperature?
Martensite
What is the temperature range in which bainite forms?
Around 510°C
What is the primary advantage of composite materials in aerospace applications?
High strength-to-weight ratio
What is the characteristic of composite materials that allows them to be tailored to meet specific requirements?
Tailored properties
What is the advantage of composite materials in marine applications?
Corrosion resistance
What is the term used to describe engineered materials made from two or more constituent materials with significantly different physical or chemical properties?
Composites
What is the reason why composite materials are used in sports equipment?
Lightweight nature
What is the phase that forms when Austenite is quenched to a temperature above Ms?
Bainite
What is the application of composite materials in the construction industry?
All of the above
What determines the fraction of Martensite formed?
Temperature to which we quench
Study Notes
Introduction to Phase Diagrams
- A phase diagram is a graphical representation of the equilibrium relationships between phases in a system
- It is used to identify the phases present in a system at a given temperature and composition
- Phase diagrams can be unary (one component), binary (two components), or ternary (three components)
Components of a System
- A system consists of independent chemical species, which can be elements, ions, or compounds
- Examples:
- Au-Cu system: components are Au and Cu (elements)
- Ice-water system: component is H2O (compound)
- Al2O3-Cr2O3 system: components are Al2O3 and Cr2O3
Phases
- A phase is a physically homogeneous and distinct portion of a material system
- Phases can be classified based on:
- State: gas, liquid, solid
- Atomic order: amorphous, quasi-crystalline, crystalline
- Band structure: insulating, semiconducting, semi-metallic, metallic
- Property: para-electric, ferromagnetic, superconducting
- Stability: stable, metastable, unstable
- Size/geometry of an entity: nano-crystalline, mesoporous, layered
Phase Transformations
- Phase transformation is the change of one phase into another
- Examples:
- Solid → Liquid → Gas
Solvent and Solute
- Solvent: the component present in a greater extent in a solution
- Solute: the component present in a lesser extent in a solution
Phase Diagrams
- Unary phase diagram: a phase diagram with one component
- Binary phase diagram: a phase diagram with two components
- Isomorphous phase diagram: a phase diagram with complete solid and liquid solubility
- Eutectic phase diagram: a phase diagram with limited solid solubility and one composition at which the liquid freezes at a single temperature
- Peritectic phase diagram: a phase diagram with complete liquid solubility and a reaction between the liquid and a solid to produce another solid
Tie Line and Lever Rule
- Tie line: a horizontal line drawn at a specified temperature to determine the chemical composition of phases in equilibrium
- Lever rule: a method to determine the relative amounts of each phase in equilibrium
Eutectic and Peritectic Phase Diagrams
- Eutectic reaction: a reaction where the liquid freezes at a single temperature
- Peritectic reaction: a reaction where the liquid reacts with a solid to produce another solid
- Characteristics of eutectic and peritectic reactions:
- Complete liquid solubility
- Limited solid solubility
- Formation of a new solid phase
Allotropic Transformations
- Allotropic transformations: changes in crystal structure of a metal with temperature
- Examples:
- Iron: B.C.C. to F.C.C. structure
- Tin: diamond cubic to tetragonal structure
TTT Diagrams
- Time-Temperature-Transformation (TTT) diagrams: diagrams that show the kinetics of isothermal transformations
- Determination of TTT diagrams: using molten salt bath techniques combined with metallography and hardness measurements
- Utility of TTT diagrams: predicting microstructures and kinetics of phase transformations
Composite Materials
- Composite materials: engineered materials made from two or more constituent materials with different physical or chemical properties
- Advantages of composite materials:
- High strength-to-weight ratio
- Tailored properties
- Corrosion resistance### Benefits of Composites
- Offer designers greater flexibility in creating complex shapes and structures that would be difficult or impossible to achieve with traditional materials like metals
- Exhibit excellent fatigue resistance, making them suitable for applications subjected to cyclic loading
- Have good electrical insulation properties, making them suitable for electrical and electronic applications
Applications of Composite Materials
Aerospace Industry
- Extensively used due to high strength-to-weight ratio
- Components made from composites include aircraft fuselages, wings, and engine components
Automotive Industry
- Used to manufacture body panels, chassis components, and interior parts
- Contribute to weight reduction and improved fuel efficiency
Marine Industry
- Widely used for boat hulls, decks, and other structural components
- Chosen for corrosion resistance and high strength
Construction
- Used in bridges, buildings, and infrastructure components
- Valued for durability, corrosion resistance, and design flexibility
Sports and Recreation
- Prevalent in sports equipment such as tennis rackets, golf clubs, bicycles, and skis
- Lightweight nature and ability to enhance performance make them ideal
Wind Energy
- Wind turbine blades are often made from composite materials
- High strength and fatigue resistance enable efficient energy generation
Medical Industry
- Used in medical applications such as prosthetics, orthopaedic implants, and dental materials
- Biocompatibility and tailored mechanical properties make them suitable
Electronics
- Composite materials with excellent electrical insulation properties are used in electronic components, circuit boards, and insulation materials
Learn about phase diagrams, graphical representations of equilibrium relationships between phases in a system, and the components of a system, including independent chemical species.
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