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Properties of Materials: Chapter 4 Imperfections in Solids (Interfacial…
Properties of Materials: Chapter 4 Imperfections in Solids
Vacancies and Self Interstitials
Vacancy: site where atom should be is empty
N can also be calculated using density and atomic weight
Where NA is avogadros number: 6.02*10^23. p is the density and A is the atomic weight.
k is the boltzmann constant
Or
Impurities in Solids
Two types of Impurity point defects
Substitutional
Interstitial
How to determine whether one or the other?
How to determine which is which?
Four factors
Atomic Size Factor
Difference in atomic radii should be less than or equal to 15 %.
Crystal Structure
Structures of both metals should be the same
Electronegativity
Closer electronegativities will dissolve in each other
Valence
All else equal, metals dissolve in higher valence than lower
Specification of Composition
Express an alloy in terms of its constituents
Atom Percent
number of moles divided by total moles
Weight Percent
Weight of each substituent divided by total
Specification of Composition
Two different ways to measure composition
Mass Percent
Simply Proportion of mass to total mass * 100
Go from weight to atom percent
Atom percent
Number of moles to total moles * 100
Interfacial defects
External Surfaces
Grain Boundaries
Twin Boundaries
Volume defects
Atomic Vibrations
Microscopic Examination
Microstructure
Photomicrograph
microscopy
Grain Size Determination
Use Equation
For any magnification other than 100, use this formula
