Imperfections in solids

Question 1

What are the three point defects?

Answer 1

Vacancy, Interstitial, Substitutional

Question 2

What are the two main line defects?

Answer 2

Edge and Screw Dislocation

Question 3

What are the 4 Hume-Rothery Rules for the formation of an alloy?

Answer 3

Atomic size factor, Crystal Structure, Electronegativity, Valences.

Question 4

What are the area Defects?

Answer 4

Grain boundaries.

Question 5

What is meant by a Self interstitial?

Answer 5

an atom that is crowded into an interstitial site (a small void that under ordinary circumstances is not occupied)

Question 6

what is alloying in metals used for in metals?

Answer 6

to improve mechanical strength and corrosion resistance.

Question 7

what does the addition of impurity atoms to a metal result in?

Answer 7

the formation if a solid solution and/or a new second phase.

Question 8

what is a solvent?

Answer 8

the element or compound that is present in the greatest amount. (Sometimes called host atoms)

Question 9

what is a solute?

Answer 9

element or compound present in minor concentration.

Question 10

What is a Substitutional atom?

Answer 10

an atom which causes bonds to tighten up, it is an atom which is not of the same size as its surrounding atoms.

Question 11

How do you express the composition of an alloy in terms of its constituent elements?

Answer 11

Weight % and Atom %

Question 12

What Letter and number are used for weight percent?

Answer 12

C1

Question 13

What Letter and number are used for atom percent?

Answer 13

C’1

Question 14

What is an edge dislocation?

Answer 14

it is a linear defect that centers on the line that is defined along the end of the extra half plane of atoms.

Question 15

What is a screw dislocation?

Answer 15

atoms are arranged in a helical pattern that is normal to the direction of the stress.

Question 16

How are grain sizes measured?

Answer 16

Area method and linear intercept method

Question 17

The bigger the grain size the

Answer 17

smaller the number

Question 18

how is the linear intercept method performed?

Answer 18

lines are drawn randomly through the grains. grain boundaries which are intercepted by the line segments are counted.

Question 19

what are the four other defects not studied in this course

Answer 19

Interfaces, Grain Boundaries, Phase boundaries, Twin Boundaries.

Question 20

A crack that progresses exclusively through grains results in a fracture called

Answer 20

transgranular fracture.

Question 21

for an internal crack, the smaller the radius of the crack tip, the lower the magnification of the applied stress

Answer 21

False