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What is toughness?
The ability of material to absorb energy without fracturing. Area under stress-strain graph.
What is stiffness?
Higher elastic modulus.
What is ultimate tensile strength?
Maximum stress.
What are the three types of lattice structures?
FCC, BCC, HCP
Rate lattice structures in terms of atomic packing factor.
HCP=FCC>BCC
What are the 0-dimensional defects?
Point defects
What are the 1-dimensional defects?
linear defects, dislocations
What are the 2-dimensional defects?
Interfacial defects, stacking faults, grain boundaries
What are the 3-dimensional defects?
Precipitates, Impurities, Voids
What are dislocations?
Dislocations are line defects in metals and ceramics. They are generated by deforming a crystalline
material.
What is ductility?
Ductility is the ability to undergo substantial plastic deformation before failure.
Rate the lattice structures in terms of ductility.
FCC > BCC > HCP
What are the three strengthening mechanisms for metals and ceramics?
- Solid Solution Strengthening
- Grain Size Reduction
- Strain Hardening
How do strengthening mechanisms strengthen a material?
They hinder the movement of dislocations.
What is solid solution strengthening?
Foreign atoms dissolved in material.
What is grain size rediction?
Increasing number of grain boundaries.
What is strain hardening?
Introducing new dislocations.
What is a single crystal?
Perfect periodic arrangement of atoms throughout specimen with same orientation.
What is a polycrystalline material?
Many crystals separated by grain boundaries.
What are the advantages of larger grain size? (3)
- Higher melting temperature
- Higher elastic modulus
- Higher creep resistance
What are advantages of smaller grain size? (2)
- Higher creep
- Better toughness and strength
What is a phase diagram?
Phase diagrams in metals represent the physical states (microstructure) and transformation as a function of its alloy and temperature.
Draw the Iron-Iron Carbide Phase Diagram.
check with lecture
What carbon content defines iron?
C < 0.008%