Quiz 2

Question 1

Solidification:

Answer 1

a phase transition in which a liquid turns into a

solid when its temperature is lowered below its freezing point

Question 2

Point Defects include

Answer 2

Vacancy, Interstitial, Frenkel defect, Schottky defect

Question 3

Line defects include

Answer 3

Edge and Screw Dislocation

Question 4

Surface defects include

Answer 4

Grain boundary, Twin boundary, Stacking faults

Question 5

Volume defects include

Answer 5

Dispersant, Precipitate, Inclusion, Void/Cracks

Question 6

Can grains be equiaxed?

Answer 6

Yes

Question 7

—–? a lattice irregularity on one or

more of its dimensions on the order of an atomic diameter

Answer 7

Crystalline defect

Question 8

Can there be a perfect crystal?

Answer 8

No

Question 9

The reason behind alloying?

Answer 9

To improve mechanical strength and corrosion resistance

Question 10

Is it difficult to refine metals to 99.99%?

Answer 10

Yes, and impurities will always be present

Question 11

Are most metals highly pure?

Answer 11

No, rather they are alloys

Question 12

Vacancy and Interstitial defects are in —– crystals

Answer 12

Non-ionic

Question 13

Schottky defect increases or decreases density?

Answer 13

Decreases

Question 14

Frenkel defect increases or decreases density?

Answer 14

Stays the same

Question 15

Does low temperature mean high vacancy?

Answer 15

False, High temperature and then diffusion can happen easily

Question 16

A closed burgers circuit is an

Answer 16

Ideal crystal

Question 17

An edge dislocation line is parallel or perpendicular to the plane of the page?

Answer 17

Perpendicular

Question 18

Is it an edge dislocation if b perpendicular to t?

Answer 18

Yes

Question 19

Is it a screw dislocation if b perpendicular to t?

Answer 19

No

Question 20

Screw dislocation is formed by

Answer 20

Shear stress

Question 21

Most dislocations found in crystalline materials are probably neither a pure edge nor pure screw, but exhibit components of
both types?

Answer 21

True

Question 22

Surface defects occur during

Answer 22

Solidification, mechanical or thermal treatment

Question 23

Void?

Answer 23

Trapped gases and they decrease mechanical strength

Question 24

Inclusions?

Answer 24

Foreign particles or large precipitate particles; undesirable ;
harmful

Question 25

Impurity point defects are found in solid solutions, of which there are two types:

Answer 25

substitutional and interstitial.

Question 26

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

Answer 26

15%

Question 27

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.

Answer 27

True

Question 28

For appreciable solid solubility the crystal structures for metals. the crystal structures of the
two elements must be different or the same?

Answer 28

The same

Question 29

Conditions for substitutional solid solution: Electronegativity should be different or similar?

Answer 29

Similar, otherwise they will form an intermetallic compound

Question 30

metal will have more of a tendency to dissolve another metal of

Answer 30

higher valency than one of a lower valency

Question 31

The microstructure is revealed by a surface treatment using an appropriate chemical agent termed —-?

Answer 31

Etching

Question 32

Transmission Electron Microscopy (TEM) approached magnification of —— times

Answer 32

x1,000,000 while optical microscopy reaches x2000

Question 33

Boltzmann’s Constant (k) =

Answer 33

8.62 x 10^-5