Podcast
Questions and Answers
What two elements comprise a crystal structure?
What two elements comprise a crystal structure?
- Spherulites and lamellae
- Polymers and elastomers
- Lattice and basis (correct)
- Amorphous and semi-crystalline
Which term refers to the unique minimal spacings between lattice points?
Which term refers to the unique minimal spacings between lattice points?
- Polymer density
- Crystal parameters (correct)
- Spherulites
- Lamella density
What type of materials do not have a crystal structure at all?
What type of materials do not have a crystal structure at all?
- Semi-crystalline materials
- Spherulites
- Polymer crystallites
- Amorphous materials (correct)
What do organic polymers form that greatly increases density, opaqueness, and strength?
What do organic polymers form that greatly increases density, opaqueness, and strength?
How are crystals usually described in terms of repeat elements?
How are crystals usually described in terms of repeat elements?
What determines the yield strength of a material?
What determines the yield strength of a material?
What do crystallographic planes use to determine their indices?
What do crystallographic planes use to determine their indices?
Which type of crystallographic defect is a location where the periodicity in a crystal is disrupted?
Which type of crystallographic defect is a location where the periodicity in a crystal is disrupted?
In an FCC crystal, how many unique close-packed {111}-type planes exist?
In an FCC crystal, how many unique close-packed {111}-type planes exist?
What are defects that involve impurity atoms called?
What are defects that involve impurity atoms called?
What type of directions link the lattice sites along slip planes in FCC crystals?
What type of directions link the lattice sites along slip planes in FCC crystals?
What type of forces can arise due to stress fields around dislocations?
What type of forces can arise due to stress fields around dislocations?
Which type of doping is used to increase the number of free charge carriers in semiconductors?
Which type of doping is used to increase the number of free charge carriers in semiconductors?
What happens when an edge dislocation is created in a crystal?
What happens when an edge dislocation is created in a crystal?
What happens when unloading the material after yielding?
What happens when unloading the material after yielding?
What is the main consequence of strengthening a material through retained dislocations?
What is the main consequence of strengthening a material through retained dislocations?
What characterizes the incoherent inter-phase interface between dissimilar crystals?
What characterizes the incoherent inter-phase interface between dissimilar crystals?
How does solute strengthening impact the movement of dislocations?
How does solute strengthening impact the movement of dislocations?
What is the main effect of planar defects on the material?
What is the main effect of planar defects on the material?
What factor contributes to the increase in strength of aluminium when alloyed with magnesium?
What factor contributes to the increase in strength of aluminium when alloyed with magnesium?
Why does the presence of chemically ordered crystals in aluminium increase its strength?
Why does the presence of chemically ordered crystals in aluminium increase its strength?
In precipitation hardening, what role do fine particles with a stronger crystal structure play?
In precipitation hardening, what role do fine particles with a stronger crystal structure play?
What is the factor that determines whether dislocations must cut through particles or bypass them in precipitation hardening?
What is the factor that determines whether dislocations must cut through particles or bypass them in precipitation hardening?
What is the critical resolved shear stress increased by in the presence of chemically ordered crystals in aluminium?
What is the critical resolved shear stress increased by in the presence of chemically ordered crystals in aluminium?
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Study Notes
- The critical resolved shear stress due to a dissolved impurity is determined by factors such as the shear strength of the solute, the square of the atom/particle radius, solute concentration, and the shear modulus of the solute.
- Solution strengthening in aluminum alloys can be achieved by alloying aluminum with 5 weight % magnesium, significantly enhancing its strength compared to pure aluminum.
- Order strengthening can occur in a crystal with chemically ordered structures, creating antiphase boundaries that impede dislocation motion and increase material strength.
- Precipitation hardening involves forming fine particles within a crystal structure, which act as obstacles to dislocation glide, ultimately increasing material strength.
- A crystal consists of a lattice and a basis, where atoms or molecules are placed on lattice points, with unique lattice parameters defining the crystal structure.
- Polymer crystallites like spherulites in organic polymers increase density, opaqueness, and strength within the material.
- Crystallographic defects such as point defects, line defects, and planar defects can significantly impact material properties, both functionally and structurally.
- Solute strengthening occurs when a dissolved impurity atom with a different size from the host lattice atoms creates a stress field that inhibits dislocation glide, contributing to increased material strength.
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