MTL200 Chapter 4: Impurities {Key Concepts, Formulas, Facts, and Important
Definitions} | Questions & Answers (100 %Score) Latest Updated 2024/2025
Comprehensive Questions A+ Graded Answers | With Expert Solutions
point defects - defects associated with one or two atomic positions
Linear Defects - one-dimensional defects or a row around which atoms are misaligned
crystalline defect - a lattice irregularity having one or more of its dimensions on the order of an atomic
diameter
Imperfections in solids - all crystals contain a considerable amount of defects that contribute to the
mechanical properties of metals
vacancy - unfilled position in which an atom is missing
Boltzmann's constant - 1.38 x 10^-23 J/K
equilibrium number of vacancies - Nv = no of vacancies
N = number of atomic sites
Qv = activation energy
T = Absolute Temperature (K)
k= boltzmann's constant
= 1.38 x 10^-23 J/atom-K or = 8.62 x 10^-5 eV/atom-K
R= Gas Constant
= 8.31 J/mol-K
=1.987 calories/mol-K
self-interstitial - same type of atom moves into an interstitial site, that under normal circumstances
normally isn't occupied.
, alloy - a combination; a mixture of two or more metals
solid solution - a homogenous mixture of two different kinds of atoms in solid state and have a single
crystal structure, where both substitutional and interstitial solid solutions are possible.
substitutional solid solution - A solid solution in which the solute atoms replace or substitute for the
host atoms, while maintaining the crystal structure, having no new structures formed.
interstitial solid solution - -a solid solution wherein relatively small solute atoms occupy interstitial
positions between the solvent or host atoms; filles voids/ interstices
-High APF = small interstitial positions (atomic diameter is very small)
-max allowable concentration < 10%
-small impurities distort lattice/lattice strains
4 rules: hume + rothery - rules for complete miscibility of different types of atoms on the same lattice.
1. Atomic size factor
2. Crystal Structure
3. Electronegative Factor
4. Valences
Atomic Size Factor (15% Rule) - quantities of solute may be accommodated in type of solid solution only
when atomic radii between two atom types is less than +- 15%. Otherwise, solute atoms create
substantial lattice distortions and new phase forms.
crystal structure - For appreciable solid solubility, the crystal structures for metals of both atom types
must be the same.
electronegativity factor - The more electropositive one element and the more electronegative the other,
the greater the likelihood that they will form an intermetallic compound instead of a substitutional solid
solution.
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