Chapter 4 - Imperfections in Solids Flashcards
What is a point defect?
A defect that occurs with a singular atom
What is a linear defect?
A defect that occurs within a 1d space in the material
What is a interfacial defect?
A defect that occurs within a 2d space in the material
What is a vacancy?
A point defect where an atom is missing from where it should normally be
What is a interstitial?
An point defect where an atom places itself into a spot where normally nothing should be.
What type of metal has no defects?
None, all solids will have some type of defect, including pure metals
What is another name for a metal that is in greater amount in a solid solution?
Solvent
What is a solute in reference to alloys and solid solutions?
The metal in lesser concentration
What solid solutions are created by impurity point defects?
Substitutional and Interstitial
What do the Hume-Rothery rules describe?
The favorability of a solutes tendency to dissolve into a solvent
What is the maximum difference of atomic radius a solute and solvent can have according to Hume-Rothery, and what happens if the range is surpassed?
+-15% radius, lattice distortions form along with a new phase
What happens if the two metals have different crystal structures?
The solid solubility is non-appreciable
What is the relationship between electronegativity and solid solutions?
The more electronegative two metals are with each other, the less likely a solid solution is to form
Which metal is more likely to dissolve in another, one with higher or lower valency?
The metal with higher valency
How does a solute in an interstitial solid solution dissolve?
The impurity/solute fill the interstices between the host atoms.
What is the maximum allowable concentration of interstitial atoms in a solid solution?
10%
How much interstitial carbon can an iron-carbon alloy have?
2%
How are compositions of alloys usually expressed as?
Mass percent and Atom percent
What is the main form of linear defect?
Dislocations
What is an edge dislocation?
An extra half plane terminates within the structure
What is a screw dislocation?
When atoms on a plane partially shift due to shear stress
What is Burger’s Vector?
A vector that represents the extent of distortion
What is the direction of Burger’s vector within an edge dislocation?
Perpendicular to the dislocation
What is the direction of Burger’s vector within a screw dislocation?
Parallel to the dislocation
What is a mixed dislocation?
A dislocation that exhibits components of both edge and screw dislocations
What is a dislocation line?
The line of which the dislocation is centered on
Why do materials tend to minimize at the surface?
The surface atoms have extra energy due to not being bonded on the external layer, so minimization is necessary
What are some types of interfacial defects?
External surfaces, grain boundaries, phase boundaries, twin boundaries, and stacking faults
What are grain boundaries?
A defect that occurs when two different grains are misaligned with each other
What is a tilt boundary?
A special grain boundary where edge defects align
What can you call an array of screw dislocations?
A twist boundary
What is a twin boundary?
A grain boundary where the two sides are mirror images
What is a stacking fault?
Usually found in FCC, an interruption in the usual pattern of ABC planar stacking
What are some features of a microstructure?
Grain size, and shape
How is the microstructure revealed?
Etching
How does the transmission electron microscope work?
An electron beam passes through the specimen
How does the scanning probe microscope work?
The microscope generates a topographical map on an atomic scale
How does the scanning electron microscope work?
The specimen is scanned with an electron beam and the reflected beam is collected and displayed
What does ASTM stand for
American Society for Testing and Materials
