Quiz 2 Flashcards
Solidification:
a phase transition in which a liquid turns into a
solid when its temperature is lowered below its freezing point
Point Defects include
Vacancy, Interstitial, Frenkel defect, Schottky defect
Line defects include
Edge and Screw Dislocation
Surface defects include
Grain boundary, Twin boundary, Stacking faults
Volume defects include
Dispersant, Precipitate, Inclusion, Void/Cracks
Can grains be equiaxed?
Yes
—–? a lattice irregularity on one or
more of its dimensions on the order of an atomic diameter
Crystalline defect
Can there be a perfect crystal?
No
The reason behind alloying?
To improve mechanical strength and corrosion resistance
Is it difficult to refine metals to 99.99%?
Yes, and impurities will always be present
Are most metals highly pure?
No, rather they are alloys
Vacancy and Interstitial defects are in —– crystals
Non-ionic
Schottky defect increases or decreases density?
Decreases
Frenkel defect increases or decreases density?
Stays the same
Does low temperature mean high vacancy?
False, High temperature and then diffusion can happen easily
A closed burgers circuit is an
Ideal crystal
An edge dislocation line is parallel or perpendicular to the plane of the page?
Perpendicular
Is it an edge dislocation if b perpendicular to t?
Yes
Is it a screw dislocation if b perpendicular to t?
No
Screw dislocation is formed by
Shear stress
Most dislocations found in crystalline materials are probably neither a pure edge nor pure screw, but exhibit components of
both types?
True
Surface defects occur during
Solidification, mechanical or thermal treatment
Void?
Trapped gases and they decrease mechanical strength
Inclusions?
Foreign particles or large precipitate particles; undesirable ;
harmful
Impurity point defects are found in solid solutions, of which there are two types:
substitutional and interstitial.
Extensive substitutional solid solution occurs only if the relative difference between the atomic diameters (radii) of the two species(the solute and the solvent) is less than
15%
A solid solution forms when, as the solute atoms are added to the host material, the
crystal structure is maintained and no new structures are formed.
True
For appreciable solid solubility the crystal structures for metals. the crystal structures of the
two elements must be different or the same?
The same
Conditions for substitutional solid solution: Electronegativity should be different or similar?
Similar, otherwise they will form an intermetallic compound
metal will have more of a tendency to dissolve another metal of
higher valency than one of a lower valency
The microstructure is revealed by a surface treatment using an appropriate chemical agent termed —-?
Etching
Transmission Electron Microscopy (TEM) approached magnification of —— times
x1,000,000 while optical microscopy reaches x2000
Boltzmann’s Constant (k) =
8.62 x 10^-5
