Defects & Diffusion Flashcards
What dimension are point defects found?
0D
What dimension are line defects found?
1D
What dimension are planar defects found?
2D
What dimension are volume defects found?
3D
True or false: vacancy only occurs in a few materials
False. Vacancy is found in all materials
What causes array expansion, atomic mobility & holes?
Vibrational energies due to temperature and the structure of crystal
What are the 3 main line defects?
edge dislocation, screw dislocation, mixed dislocation
What type of dislocation is caused by perpendicular Burgers vector?
Edge dislocation
What type of dislocation is caused by parallel Burgers vector?
Screw dislocation
What type of dislocation is caused by the Burgers vector always in the same direction?
mixed dislocation
What are some types of 2D (planar) defects?
external surfaces
grain boundaries
phase boundaries
twin boundaries
stacking faults
domain walls
How many grain boundaries would you expect for a polycrystalline structure?
MANY
What are some examples of 3D defects?
pores, cracks, foreign inclusions, other phases
What is a Frenkel defect?
paired set of cation vacancy + cation interstitial
What is a Shottky defect?
paired set of cation + anion vacancies
What are the characteristics of perfect metal crystals?
Higher electrical conductivity, higher thermal conductivity (more efficient metallic bonds). lower strength, higher ductility (more mobile dislocations)
What are the 2 ways to express alloy composition?
Weight %
Atomic %
What is ionic diffusion?
moving charges yield electrical conduction
What is flux?
mass flow per unit area
what is interdiffusion?
atoms migrate from high to low concentration
What is diffusion via substitution?
through vacancies
What is diffusion by interstitial motion?
small atoms can pass through matrix
True or false: substitution diffusion is faster than interstitial motion
False. Interstitial diffusion is faster
