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IE 301 > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

How to increase strength in materials by 5-30% ?

A

Solution Hardening

Alloying & Grain Size Control

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2
Q

How to increase strength in materials by 50-300% ?

A

Strain Hardening

Heat Treatment

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3
Q

When a material is plastically deformed by
Strain Hardening / Work Hardening
Yield, Tensile, Hardness strength ________ but Ductility ________

A

increases

decreases

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4
Q

Fully strain-hardened material yield strengths increase from ______ and tensile strengths increase _______

A

100-500%

50-100%

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5
Q

Dislocations and brittleness can be removed with new strain-free grains by _______ the material.

A

heating

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6
Q

___________ can be induced by rolling a polycrystalline metal

A

Anisotropy

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7
Q

In isotropic materials. _____________

A

grains are equiaxed & randomly oriented

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8
Q

Rolling in anisotropic materials affects ______

A

grain orientation and shape

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9
Q

Stronger material have more _____________

A

dislocations

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10
Q

Too many dislocations may lead to ___________

A

cracking

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11
Q

For Strain Hardening, Strength is higher at the _______ than the ________

A

surface

center

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12
Q

Why is Strain Hardening desirable?

A

Wear and high stresses at surface

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13
Q

How is metal cold worked?

A

by forging, stamping or rolling

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14
Q

Cold working does what to metal?

A

permanently changes its shape, (DEFORMED)

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15
Q

What allows for the overall change in shape of the metal?

A

dislocations or slips in the grain structure

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16
Q

How is warm working done?

A

same cold working process performed below recrystallization temperature but above room temperature

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17
Q

What does warm working accomplish?

A

Reduces the mechanical energy to deform

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18
Q

What is cold working?

A

working of material below its recrystallization temperature

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19
Q

What is Annealing?

A

used to remove effects of cold working (heat and then slow cooling to soften materials)

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20
Q

What is hot working?

A

working of material above its recrystallization temperature

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21
Q

During hot working, _________

A

material recrystallizes immediately – no strain hardening builds up

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22
Q

What is the advantage of hot working?

A

less forces required to deform material

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23
Q

What are the disadvantages of hot working?

A

High temp may oxidize surface
Dimensions harder to control
Tolerances harder to control

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24
Q

What happens during Recrystallization?

A

• New grains form that:

- - have low dislocation densities
- - are small in size
- - consume and replace parent cold-worked grains
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25
Q

All grains in cold-worked material have been _________

A

consumed/replaced

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26
Q

What are the effects of cold working?

A 
Yield strength       (YS) increases.
Tensile strength    (TS) increases.
Ductility (%EL or %AR) decreases.
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27
Q

Strength is _______ by making dislocation

motion difficult.

A

increased

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28
Q

How to strengthen materials?

A

Dislocations

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29
Q

The ability of a metal to plastically deform depends on _________

A

the ability of dislocations to move

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30
Q

Restricting dislocation motion leads to

A

harder & stronger material

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31
Q

Grain boundary:
Point defect:
Dislocation:
Second phase:

A

grain size reduction
solid solution strengthening
strain hardening (cold work)
precipitation hardening

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32
Q

In the Plastic Deformation of Polycrystalline Materials, Because of the random crystallographic orientations of the different grains

A

the direction of slip varies from one grain to another.

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33
Q

During deformation, mechanical integrity is maintained along the

A

grain boundaries

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34
Q

Each individual grain is _________ to some degree by its neighboring grains

A

constrained

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35
Q

solute or impurity atoms replace or substitute for the host atoms

A

Substitutional Solid Solution

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36
Q

impurity atoms fill the voids or interstitials among host atoms

A

Interstitial Solid Solution

  • Small interstitial positions
  • Atomic size of an interstitial impurity must be small (H, N, & C).
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37
Q

completely soluble in one another at all proportions

A

Cu-Ni (SSS)

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38
Q

Solid Solution Hardening is also

A

alloying

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39
Q

What is the Solid Solution Hardening Technique?

A

adding atoms of one element (the alloying element) to the crystalline lattice of another element (the base metal)

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40
Q

Solvent is defined as

A

the base substance, wherein the solute is being dissolved

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41
Q

A solute is a

A

substance that is dissolved into the solvent

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42
Q

When both elements exist in the same ________, both elements in their pure form “should” be of the same __________ (for complete solubility)

A

crystalline lattice

crystal structure

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43
Q

Solvent and solute atoms must differ in ________ by less than __%

A

atomic size

15%

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44
Q

Strength is Solid Solution Hardening is dependent on

A

on ease of achieving dislocations in crystal lattice

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45
Q

Dislocations create ________ within material

A

stress fields

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46
Q

What is the process of Solid Solution Hardening?

A

Solute atoms introduced, then local stress fields are formed that interact with the dislocations, impeding their motion and causing an increase in the yield stress - increase in strength

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47
Q

Solute and solvent atoms differ in

A

size, local stress fields created

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48
Q

If the Solute atom size larger than solvent then____

A

field is compressive

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49
Q

If the Solute atoms are smaller than solvent atoms_____

A

field is tensile

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50
Q

Alloying with impurities form _______ or _______ solid solution.

A

Interstitial

substitutional

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51
Q

Impurity atoms _______

A

distort the lattice & generate stress

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52
Q

______ can produce a barrier to dislocation motion

A

Stress

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53
Q

Small impurities tend to concentrate at ________

A

dislocations (regions of compressive strains)

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54
Q

partial cancellation of dislocation compressive strains and impurity atom tensile strains

A

regions of compressive strains

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55
Q

Solid Solution Alloying_________ of dislocations and _______ strength

A

reduces mobility

increase

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56
Q

Large impurities tend to concentrate at __________

A

dislocations (regions of tensile strains)

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57
Q

Substitutional Rules: Conditions for substitutional solid solution

A
  1. Δr (atomic radius) < 15%
  2. Same crystal structure for pure metals
  3. Proximity in periodic table
    i.e., similar electronegativities
  4. Valency – “should” be identical
    All else being equal, a (solvent) metal will have a greater tendency to dissolve a (solute) metal of higher valency than one of lower valency.
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58
Q

solute or impurity atoms replace or substitute for the host atoms

A

Substitutional Defects

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59
Q

Metals have a ___________

A

crystalline structure

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60
Q

When metal solidifies from the molten state

A

millions of tiny crystals start to grow

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61
Q

The longer metal takes to cool, _______

A

the larger the crystals grow

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62
Q

These crystals form the ______ in the solid metal

A

grains

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63
Q

Each grain is a distinct _____l with its own ________

A

crystal

orientation

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64
Q

adjacent grain planes at different orientations

A

Grain boundaries

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65
Q

Grain boundaries_________

A

prevent slip or makes slip more difficult

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66
Q

Slip occurs along a ______ of one atom

A

plane

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67
Q

Numerous grains ________

A

reduce amount of slip

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68
Q

When grain size decreases ______

A

strength increases

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69
Q

Strength is ________ related to grain area

A

inversely

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70
Q

Optical Microscopy is _________

A

Useful up to 2000X magnification

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71
Q

What is the Interception Method?

A

Draw a number of straight lines of same length so that the total interception of the lines with grain boundaries should be > 50

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72
Q

Atoms are bonded ________ along a grain boundary

A

less regularly

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73
Q

Energy is a function of the degree of _________, being ______for high-angle boundaries

A

misorientation

larger

74
Q

The atoms are bonded ________ along a grain boundary

A

less regularly

75
Q

Greater disorder leads to

A

grain boundary energy

76
Q

More reactive_______

A

makes etching possible

77
Q

Impurity segregation _________

A

affecting the materials properties

78
Q

As the metal solidifies, __________ start to form first

A

small crystal nuclei

79
Q

Upon completion of solidification, the colonies contact each other, forming _________

A

grain boundaries

80
Q

What are grain boundaries?

A

Boundaries between crystals in a polycrystalline material

81
Q

There is a change in __________ across grain boundaries

A

crystal orientation

82
Q

Grain boundary hinders the dislocation motion or acts as a barrier to _________ motion (slip)

A

dislocation

83
Q

A ___________ material is harder and stronger than one that is coarse grained, as more _______ are acting to block dislocation movement

A

finer-grained

barriers

84
Q

Grain size reduction improves not only ________, but also the ________ of many alloys

A

strength

toughness

85
Q

Defects affect _________

A

material properties

86
Q

A knowledge and understanding of phase diagrams is important to the engineer as they relate to the design and control of ________

A

heat treating processes

87
Q

What is the Solubility Limit?

A

Max concentration for which only a solution occurs

88
Q

Solubility limit ________ with Temperature

A

increases

89
Q

In SSS Atoms of the parent metal (or solvent metal) are _______ or ________ by atoms of the alloying metal (solute metal)

A

replaced

substituted

90
Q

In SSS The atoms of the two metals in the alloy are of _______ size

A

similar

91
Q

In ISS The atoms of the parent or solvent metal are _____ than the atoms of the alloying or solute metal

A

bigger

92
Q

In ISS The smaller solute atoms fit into _________ or spaces between the large atoms

A

interstitial sites

93
Q

For many alloy systems and at some specific temperature, there is a _________ of solute atoms that may dissolve in the solvent to form a _______

A

maximum concentration

solid solution

94
Q

a homogeneous portion of a system that has uniform physical and chemical characteristics

A

phase

95
Q

If more than one phase is present in a given system, each will have its own ________

A

distinct properties

96
Q

A boundary separating the _____ exists across which there will be a discontinuous and abrupt change in ________

A

phases

physical and/or chemical characteristics

97
Q

The physically and chemically distinct material regions that result

A

Phases in Materials

98
Q

Solid solutions are commonly designated by

A

lowercase Greek letters (a , b, g, etc.)

99
Q

Equilibrium conditions may be defined

A

as slow heating and/or cooling of the many materials to permit any phase change to occur

100
Q

The relationships between ________ and the _______ & the quantities of phases at equilibrium

A

temperature

compositions

101
Q

For a binary system of known composition (C0) & temperature (T) that is at equilibrium, the following information can be obtained from the phase diagram:

A

The phases that are present
The composition of each phase
The amount (or percentage) of each phase

102
Q

Line indicates the temperature at which the first solid appears upon cooling and the temperature at which the last solid disappears on heating. In few instances liquid separates into two liquids, the temperature at which the separation starts.

A

Liquidus Line

103
Q

Line indicates temperature at which the last liquid disappears upon cooling.

A

Solidus Line

104
Q

The line indicates the solubility limits

A

Solvus line

105
Q

Line connecting three phases that are in equilibrium at a specific temperature in a binary system. Appears as a horizontal line because at constant temperature.

A

Invariant Reaction Line

106
Q

connects the phases in equilibrium with each other – also sometimes called an isotherm

A

Tie line

107
Q

liquid transforms to two solid phases

A

Eutectic

108
Q

one solid phase transforms to two other solid phases

A

Eutectoid

109
Q

liquid and one solid phase transform to a second solid phase

A

Peritectic

110
Q

In a Eutectic Reaction, Upon cooling, _______ phase is transformed into the _______ phases (a and b) at the ______ temperature TE; upon heating, the opposite reaction occurs

A

one liquid
two solid
eutectic

111
Q

For alloy of composition

A

C0 = CE

112
Q

In a Eutectoid Reaction, Upon cooling, _____ phase is transformed into the ______ phases at the _____ temperature TE; upon heating, the opposite reaction occurs

A

one solid
two solid
eutectoid

113
Q

one liquid phase transforms into two solid phase at a constant temperature

A

Eutectic reaction

114
Q

one solid phase transforms into two solid phase at a constant temperature

A

Eutectoid reaction

115
Q

Both steels and cast irons, primary structural materials in every technologically advanced culture, are essentially

A

iron-carbon alloys

116
Q

the art and science of controlling thermal energy for the purpose of altering the properties of metals and alloys

A

Thermal processing or heat treating

117
Q

a-Fe

A

Ferrite

118
Q

y-Fe

A

Austenite

119
Q

iron carbide Fe3C

A

Cementite

120
Q

Pure Fe (room temperature to 912C), a single-phase BCC solid solution

A

Ferrite

121
Q

a single-phase FCC solid solution (a ferrite transforms from BCC to FCC at 912C)

A

Austenite

122
Q

The maximum solubility of carbon in austenite

A

2.14 wt% at 1147C.

123
Q

Austenite is not stable below ______

A

727 degrees

124
Q

intermediate phase with the chemical formula Fe3C

A

Cementite

125
Q

Cementite is

A

brittle and hard

126
Q

One eutectic reaction exists for the iron-iron carbide system,

A

at 4.30 wt% C and 1147C

127
Q

One eutectoid reaction exists for the iron-iron carbide system

A

at 0.76 wt% C and 727C

128
Q

The microstructure of the eutectoid steel that is slowly cooled consists of alternating layer or lamellae of the two phases (ferrite and cementite) that form simultaneously during the transformation

A

Pearlite

129
Q

The thick light layers are the ______ phase, and the ______ phase appears as thin lamellae most of which appear dark

A

ferrite

cementite

130
Q

Pure iron

A

From the phase diagram, it is composed almost exclusively of the ferrite phase at room temperature

131
Q

Steels

A

In most steels the microstructure consists of both a and Fe3C phases.
Carbon concentrations in commercial steels rarely exceed 1.0 wt%.

132
Q

Cast irons

A

Commercial cast irons normally contain less than 4.5 wt% C.

133
Q

Phase diagrams are useful tools to determine:

A

-the number and types of phases
-and the composition of each phase
for a given T and composition of the system

134
Q

one liquid phase transforms into two solid phase at a constant temperature

A

Eutectic reaction

135
Q

one solid phase transforms into two solid phase at a constant temperature

A

Eutectoid reaction

136
Q

Steels and cast irons are based on binary Fe-C system and offer a wide range of properties due to different microstructures

A

Hypoeutectoid & hypereutectoid steels

137
Q

What are the Four strengthening mechanisms?

A

Grain size refinement
Solid-solution strengthening
Strain hardening
Precipitation hardening

138
Q

The development of microstructure in both single- and two-phase alloys ordinarily involves some type of __________

A

phase transformation

139
Q

an alteration in the number and/or character of the phases

A

phase transformation

140
Q

The _________ is fundamental to the development of microstructures in steel alloys

A

eutectoid reaction

141
Q

_______ is the microstructural product of this transformation

A

Pearlite

142
Q

The percentage of the transformation product is related to the __________ and __________

A

holding temperature

holding time

143
Q

For Fe-C alloys with compositions other than eutectoid composition, a _________ phase (either ferrite or cementite) will coexist with ________

A

proeutectoid

pearlite

144
Q

Pearlite has mechanical properties between the soft, ductile ________ and the hard, brittle _______

A

ferrite

cementite

145
Q

a change in the number and/or character of the phases that constitute the microstructure of an alloy

A

Phase Transformation

146
Q

Nucleation

A

formation of very small particles, or nuclei, of the new phase

147
Q

favorable nucleation sites

A

imperfection sites,

e.g. grain boundaries)

148
Q

increase of the nuclei in size. Some volume of the parent phase disappears

A

Growth

149
Q

The thickness of the ferrite/cementite layers in pearlite depends on the ___________

A

temperature

150
Q

With decreasing temperature, the layers of pearlite become progressively __________

A

thinner

151
Q

At temperatures just below eutectoid __________

A

relatively thick layers → coarse pearlite

152
Q

In the vicinity of 540°C__________

A

relatively thin layers

→ fine pearlite

153
Q

Pearlite forms above the nose ________; bainite forms below the nose ________

A

(540 ~ 727°C)

(215 ~ 540°C)

154
Q

Bainite consists of ______ and _______ phases

A

ferrite

cementite

155
Q

Bainite forms as ________ or _______, depending on the temperature of the transformation

A

needles

plates

156
Q

Unlike pearlitic transformation, martensitic transformation is _____________

A

instantaneous

157
Q

The horizontal lines indicate that

A
  • The transformation is independent of time;

- It is a function only of the temperature to which the alloy is quenched or rapidly cooled.

158
Q

What is the beginning of this Martensite transformation?

A

M(start)

159
Q

Two other horizontal and dashed lines, labeled ______ and _____, indicate percentages of the austenite-to- martensite transformation.

A

M(50%)

M(90%)

160
Q

Martensite is formed when _______ Fe-C alloys are rapidly ________ (or quenched) to a relatively _____ temperature (in the vicinity of the ambient)

A

austenitized
cooled
low

161
Q

A transformation product that is competitive with pearlite

A

Martensite

162
Q

Martensite is a transformation of FCC to

A

BCT (body-centered tetragonal)

163
Q

Martensite occurs _______

A

instantaneously → time-independent

164
Q

The martensite grains ________ and grow at a very rapid rate

A

nucleate

165
Q

< 0.6 wt%C,

long/thin plates, side by side, aligned parallel to one another

A

Lath

166
Q

> 0.6 wt%C,
lenticular or
platelike appearance

A

Lenticular

167
Q

Cementite (Fe3C) is much ______ but more _____ than ferrite (α)

A

harder

brittle

168
Q

Fe3C ↑

A

⇒ strength↑, ductility↓

169
Q

Fine pearlite is ______ and ______ than coarse pearlite but less ______

A

harder
stronger
ductile

170
Q

Hardest and strongest, and most brittle

A

Martensite

171
Q

Volume change in Martensite

A

crack formation during quenching

172
Q

In the as-quenched state, martensite, in addition to being ______, is so _____ that it cannot be used for most applications

A

very hard

brittle

173
Q

Any internal stresses that may have been introduced during quenching have a _________ effect

A

weakening

174
Q

The ductility and toughness of martensite may be enhanced and internal stresses relieved by a heat treatment know as

A

Tempering

175
Q

Tempering is accomplished by

A

heating the martensitic steel to a temperature below the eutectoid (normally, between 200-650°C) for a specified time period to allow microstructure/ property change through diffusion

176
Q

By diffusional processes: Martensite (BCT, single phase)_______

A

→ Tempered Martensite (α + Fe3C)

177
Q

Tempered martensite may be nearly as hard and strong as martensite, but with substantially enhanced _______
& _________

A

ductility

toughness

178
Q

Tempered martensite consists of _________

A

extremely small cementite particles embedded within a ferrite matrix

179
Q

_________ is involved in the transformation

A

Carbon diffusion

180
Q

Heat treatment variables are _______

A

temperature and time

181
Q

most treatments are

A

constant- temperature processes

IE 301 (3 decks)

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