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Materials Science & Engineering > Final Exam > Flashcards

Final Exam Flashcards

1
Q

Equation

true stress and true strain (plastic region to point of necking)

A
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2
Q

What is a crystal structure

A

The manner in which atoms, ions, or molecules are spatially arranged

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3
Q

2

A

2 engineering strain

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4
Q

Phase diagram

A

a graph representing the states of a material by composition and temperature

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5
Q

Equation

Interplanar spacing for crystals having cubic symmetry

A

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6
Q

mechanisms of diffusion for gases, liquids, and solids

A

gases & liquids - random (Brownian) motion

solids - vacancy diffusion or instititial diffusion

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7
Q

What is a crystal lattice?

A

A three dimensional array of points coinciding with atom positions or sphere centers

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8
Q

types of imperfections

A

point defects

  • vacancy atoms
  • interstitial atoms
  • substitutional atoms

line defects

  • dislocations

area defects

  • grain boundaries
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9
Q
A
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10
Q

Equation

Fick’s first law

A

steady-state diffusion independent of time

flux proportional to concentration gradient

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11
Q

6

A

6 yield point

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12
Q

Eutectic reaction

A

liquid is transformed into two solids

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13
Q

Equation

engineering stress

A
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14
Q

solubility limit

A

maximum concentration for which only a single phase solution exists

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15
Q

8

A

8 elastic deformation / elastic region

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16
Q

5

A

5 proportionality limit

point at which there is deviation from linearity

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17
Q

What types of materials form crystalline structures

A

All metals, many ceramic materials, and certain polymers under normal solidification conditions

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18
Q

grain boundaries

A

regions between crystals where there is a transition from one lattice to that of another

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19
Q

11

A

11 necking

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20
Q

conditions for substitutional solid solutions

A
  1. difference in radius < 15%
  2. lowest difference in EN
  3. same or higher no. of valent electrons
  4. same crystal structure
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21
Q

Which is faster Dinterstitial or Dsubstitutional and why?

A

Dinterstitial >> Dsubstitutional

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22
Q

Name the correlations between bonding type and material

A

Polymers – covalent

Metals – metallic

Ceramics - ionic/mixed ionic-covalent

Molecular solids – van der Waals

Semi–metals – mixed covalent–metallic

Intermetallics – mixed metallic–ionic

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23
Q

isomorphous system

A

complete solubility of one component in another

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24
Q

7

A

7 yield strength

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25
Q

Equation

temperature dependece of diffusion coefficient

A
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26
Q

Phase

A

homogeneous state of matter that has uniform physical and chemical characteristics

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27
Q

What does tensile strength represent and what point is it on the engineering stress strain curve?

A

It represents the maximum tensile stress that can be sustained by a specimen

It is taken as the stress level at the maximum point on the engineering stress-strain curve

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28
Q

components

A

the elements or compounds which are present in the alloy

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29
Q

Material Science

A

Materials science involves investigating the relationships that exist between the structures and propterties of materials

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30
Q

Equation

atomic packing factor (APF)

A
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31
Q

Equation

true stress

A
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32
Q

Name the types of point defects

A

Vacancies

Interstitials

Substitutions

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33
Q

tie line (isotherm)

A

connects the phases in equilibrium with each other

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34
Q

Equation

engineering strain

A
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35
Q

4

A

4 ultimate strain or fracture point

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36
Q

Equation

Fick’s second law

A

non-steady state diffusion where the concentration of diffusing species is a function of both position and time

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37
Q

How is yield strength determined and what is it indicative of

A

From a stress-strain plot using the .002 strain offset technique

It is indicative of the stress at which plastic deformation begins

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38
Q

What is a crystalline material?

A

One in which atoms are situated in a repeating or periodic array over large atomic distances–that is, long-range order exist, such that upon solidification, the atoms will position themselves in a repetitive three-dimensional pattern, in which each atom is bonded with its nearest neighbor atoms

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39
Q

9

A

9 plastic deformation / plastic region

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40
Q

Equation

unit cell edge length for BCC

A
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41
Q

Materials engineering

A

Materials engineering involves, on the basis of these structure-property correlations, designing or engineering the structure of a material to produce a predetermined set of properties

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42
Q

types of dislocations (describe)

A

edge dislocation - extra half plane of atoms inserted in a crystal structure [perpendicular]

screw dislocation - spiral planar ramp resulting from shear deformation [parallel]

43
Q

Equation

number of atomic sites per unit volume

A
44
Q

Name the types of materials

A

Metals (metallic elements)

Ceramics (compounds between metallic and nonmetallic elements)

Polymers (compounds composed of carbon hydrogen and other non-metallic elements)

Composites (composed of at least two different types of materials)

45
Q

What types of point defects are not allowed in ceramic / ionic compounds and why?

A

Vacancies and substitutions. They lead to charge imbalances in the system.

46
Q

Equation

ductility, percent reduction in area

A
47
Q

Equation

Bragg’s law; wavelength-interplanar spacing-angle of diffracted beam

A
48
Q

What is ductility?

A

A measure of the degree to which a material plastically deforms by the time fracture occurs

49
Q

Name the point defects in ionic systems

A

Schottky (pair of vacancies) and Frankel (atom relocates to an interstitial site)

50
Q

Equation

ductility, percent elongation

A
51
Q

Equation

modulus of elasticity (Hooke’s law)

A
52
Q

peritectic reaction

A

solid transforms into a liquid and another solid

53
Q

Equation

diffusion flux

A
54
Q

1

A

1 engineering stress

55
Q

eutectoid reaction

A

solid transforms into two other solids

56
Q

10

A

10 ultimate strength

57
Q

Equation

unit cell edge length for FCC

A
58
Q

3

A

3 youngs modulus

59
Q

How is ductility measured?

A

In terms of percents elongation (%EL) and reduction in area (%RA)

60
Q

burger’s vector

A

b

a measure of lattice distortion

61
Q

What happens on an atomic level during plastic deformation

A

Atomic bonds stretch as they go through elastic deformation. Slipping along interatomic crystal planes occurs past the yield point, increasing overall elongation

62
Q

Equation

number of vacancies per unit volume

A
63
Q

What happens on an atomic level during elastic deformation?

A

Atomic bonds are stretching. Interatomic separation increases with increasing stress and returns to equilibrium when no longer under tension

64
Q

Why does D have exponential dependence on T

A

An increase in temperature increases the number of vacancies. An increase in vacancies increases the rate of diffusion and decreases activation energy.

65
Q

12

A

12 strength hardening

66
Q

Describe elastic deformation on an atomic level

A

Elastic deformation corresponds to the stretching of interatomic bonds and corresponding slight atomic displacements

67
Q

linear defects (dislocations)

A

one dimensional defects around which atoms are misaligned

68
Q

Equation

true strain

A
69
Q

unit cell

A

smallest repeating volume which has a complete crystal lattice pattern

70
Q

APF for a simple cubic structure

A

0.52

71
Q

APF for a body-centered cubic structure

A

0.68

72
Q

APF for a face-centered cubic structure

A

0.74

73
Q

Equation

density

A
74
Q

vacancy diffusion

A

atoms exchange with vacancies

applies to substitutional impurities atoms

rate depends on number of vacancies and activation energy to exchange

75
Q

interstitial diffusion

A

smaller atoms diffuse between attoms

76
Q

case hardening

A

diffusion of carbon atoms onto the surface of a host iron atom

77
Q

free energy

A

A thermodynamic quantity that is a function of both the internal energy and entropy (or randomness) of a system. At equilibrium, it is at a minimum.

78
Q

diffusion is faster for

_____ structures

materials w/_____ bonding

_____ diffusing atoms

_____ density materials

A

diffusion is faster for

open crystal structures

materials w/secondary bonding

smaller diffusing atoms

lower density materials

79
Q

diffusion is slower for

_____ structures

materials w/_____ bonding

_____ diffusing atoms

_____ density materials

A

diffusion is slower for

close-packed structures

materials w/covalent bonding

larger diffusing atoms

higher density materials

80
Q

microconstituent

A

An element of the microstructure that has an identifiable and characteristic structure. It may consist of more than one phase, such as with pearlite.

81
Q

interstitial solid solution

A

A solid solution in which relatively small solute atoms occupy interstitial positions between the solvent or host atoms.

82
Q

solute

A

One component or element of a solution present in a minor concentration. It is dissolved in the solvent.

83
Q

atomic number (Z)

A

the number of protons within the atomic nucleus

84
Q

Exhibiting different values of a property in different crystallographic directions.

A

anisotropy

85
Q

shear

A

A force applied that tends to cause two adjacent parts of the same body to slide relative to each other in a direction parallel to their plane of contact

86
Q

fracture toughness

A

the measure of a material’s resistance to fracture when a crack is present

87
Q

fatigue strength

A

The maximum stress level that a material can sustain without failing, for some specified number of cycles.

88
Q

equilibrium

A

The state of a system in which the phase characteristics remain constant over indefinite time periods. At equilibrium the free energy is a minimum.

89
Q

A dislocation that has both edge and screw components.

A

mixed dislocation

90
Q

Atomic migration in pure metals

A

self-diffusion

91
Q

one of the two phases found in the eutectic structure

A

eutectic phase

92
Q

Miller indices

A

A set of three integers (four for hexagonal) that designate crystallographic planes, as determined from reciprocals of fractional axial intercepts

93
Q

creep

A

The time-dependent permanent deformation that occurs under stress; for most materials it is important only at elevated temperatures.

94
Q

The increase in hardness and strength of a ductile metal as it is plastically deformed below its recrystallization temperature.

A

strain hardening

95
Q

The combination of unit cell edge lengths and interaxial angles that defines the unit cell geometry.

A

lattice parameters

96
Q

polymorphism

A

The ability of a solid material to exist in more than one form or crystal structure.

97
Q

The increase in average grain size of a polycrystalline material; for most materials, an elevated-temperature heat treatment is necessary.

A

grain growth

98
Q

vacancy

A

A normally occupied lattice site from which an atom or ion is missing.

99
Q
A
100
Q

area defects

A

grain boundaries

twins

stacking faults

101
Q

Alloy

A

A metallic substance that is composed of two or more elements

102
Q

Interstitial solid solution

A

A solid solution in which relatively small solute atoms occupy interstitial positions between the solvent or host atoms.

103
Q

imperfection

A

A deviation from perfection; normally applied to crystalline materials in which there is a deviation from atomic/molecular order and/or continuity.

104
Q
A

The capacity of a material to absorb energy when it is elastically deformed.

Materials Science & Engineering (1 decks)

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