Chapter 1 L04 Flashcards
How are the structures of a crystalline and a non-crystalline material?
- Crystalline Material: Highly ordereded and structured molecules (All metals and many ceramins)
- Non-Crystalline Material: Lack of order in the structure of molecules
On what do properties of crystalline solids depend?
On the Lattice (crystalline structure)
In what is the Lattice subdivided?
Unit cell. They represent 3D colocation of points (ex: center of atom, ion, etc)
Image in notes
Characteristics of metallic lattice
- All points in the unit cell are same size
- Properties change depending on the lattice
Image in notes
Name the 3 common lattice for metals.
- Body centered cubic (BCC)
- Face centered cubic (FCC)
- Hexagonal closed packed (HCP)
Characteristics of ceramic lattice.
- Composed of at least 2 elements
- Ions instead of atoms
- Ceramic lattice are stable when the cation(+) is in contact with all the anions(-)
What is a Lattice defect. Name the 4 types.
Omnipresent defects and deformations in the solids which determine many material properties.
- 0 dimensional : Point defect
-1 dimensional : Linear defect
-2 dimensional : Interfacial defect
-3 dimensional : Bulk defect
Images in Notes
Point defect types
“Notes”
Linear defects.
“Notes”
Interfacial defects
Separate regions with different Lattice or Lattice orentation + “Notes”
What is alloying?
Dissolving foreign solid into an inicial solid in a homogeneous way. One of them must be a metal
Name 2 types of mechanical deformations. Describe them.
- Elastic Deformations: Deformation that dissapears when the stress is released
- Plastic Deformation: Deformation that remains when the stress is released.
What is a Slip?
A plastic deformation caused by dislocation
What is a Slip Plane?
Plane that appears after the slip
What is a Slip system?
Slip Plane + Slip direction
Which type of Lattice is the most ductile? How many slip systems do they have respectively?
FCC (12) > BCC (12) > HCP (3)
Name 2 characteristics of Dislocations (linear defect)
- Tense and compressed regions will appear, imposed in the atoms that are in contact
- This will cause repulsion or attraction. Attraction create perfect cristals
Recap: What is the Yield Point and the Maximum Tensile Strength?
Y.P : Point from which the material will start deforming plastically
T.S : Maximum stress that a material can take
Name 3 strengthening methods
- Solid solution strength.
- Strength by grain size reduction
- Strain hardening
Images in notes
Describe Solid Solution Strength.
Foreign atoms are dissolved in the crystal, restricting dislocations.
Describe Grain Size Reduction
Reduce grain size to create more grain boundaries, restricting dislocations.
Describe Strain Hardening
Create plastic deformation at low temperature, so that atoms can not rearenge themselves to decrease the movility of dislocations
