Chapter 7: Dislocations And Strengthening Mechanisms Flashcards

1
Q

Plastic deformation as the result of dislocation motion; also, the shear displacement of two adjacent planes of atoms

A

Slip

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2
Q

The total dislocation length per unit volume of material; alternatively, the number of dislocations that intersect a unit area of a random surface section

A

Dislocation Density

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3
Q

The measured strength of a material is ——the theoretical strength.

  • greater than
  • equal to
  • less than
A

Less than

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4
Q

——is the process by which plastic deformation is produced.

-slip
-step
-screw

A

Slip

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5
Q

Dislocation motion is similar to the motion of a ——.

-snake
-caterpillar
-fish

A

Caterpillar

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6
Q

The majority of the deformation energy is——when metals are plastically deformed.

  • retained internally
  • dissipated as heat
  • stored as strain energy
A

Dissipated as heat

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7
Q

The extra half-plane of atoms in an edge dislocation causes a——lattice strain below the half-plane.

-compressive
-tensile
-shear

A

Tensile

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8
Q

The magnitude of the strains around a dislocation line——with radical distance from the dislocation.

  • remains constant
  • increases
  • decreases
A

Decreases

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9
Q

Two edge dislocations of the same sign and lying on the same slip plane will exert——on each other.

  • an attractive force
  • a repulsive force
  • no force
A

A repulsive force

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10
Q

Two edge dislocations of opposite sign and lying on the same slip plane will exert——on each other.

  • an attractive force
  • a repulsive force
  • no force
A

An attractive force

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11
Q

The number of dislocations in a metal——during plastic deformation.

  • increases dramatically
  • decreases dramatically
  • remains constant
A

Increases dramatically

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12
Q

Slightly displacements of atoms relative to their normal lattice positions, normally imposed by crystalline defects such as dislocations, and interstitial and impurity atoms.

A

Lattice Strain

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13
Q

Molybdenum (Mo) has a slip plane——and slip direction——.

  • {110}, (111)
  • {211}, (111)
  • {321}, (111)
A

{110}, (111)

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14
Q

Potassium (K) has——slip systems.

  • 6
    -12
    -24
A

24

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15
Q

The Burgers vector for BCC unit cells in terms of the unit cell edge length is——.

  • a/2 (110)
  • a/2 (111)
  • a/3 (1120)
A

A/2 (111)

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16
Q

The combination of a crystallographic plane and, within that plane, a crystallographic direction along which slip (i.e. dislocation motion) occurs.

A

Slip System

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17
Q

A material with——grains is hardest and strongest.

  • small
  • medium
  • large
18
Q

The grain size can be modified by——.

  • elastic deformation
  • plastic deformation
  • plastic deformation with heat treatment
A

Plastic deformation with heat treatment

19
Q

Grain size reduction improves——.

  • strength only
  • toughness only
  • strength and toughness
A

Strength and toughness

20
Q

Increasing the concentration of impurity atoms in an alloy will——the alloy’s strength.

  • not change
  • decrease
  • increase
21
Q

A substitutional atom larger than the host atoms exerts a——strain on the surrounding crystal lattice.

  • tensile
  • compressive
  • shear
A

Compressive

22
Q

A substitutional atom smaller than the host atoms will tend to move to a position——the slip plane near an edge dislocation.

  • below
  • above
  • on
23
Q

Hardening and strength in of metals that result from alloying in which a solid solution is formed. The presence of impurity atoms restricts dislocation mobility.

A

Solid-Solution Strengthing

24
Q

Cold working——the yield strength of 1040 steel.

  • increases
  • decreases
  • doesn’t change
25
Cold working——the tensile strength of brass - increases - decreases - does not change
Increases
26
Cold working——the ductility of copper - increases - decreases - doesn’t change
Decreases
27
The increase in hardness and strength of a ductile metal as it is plastically deformed below its recrystallization temperature.
Strain Hardening
28
The plastic deformation of a metal at a temperature below that at which it recrystallizes
Cold Working
29
——is the relief of some internal strain energy of a previously cold-worked metal. - grain growth - recrystallization - recovery
Recovery
30
Recovery of a cold-worked metal involves dislocation motion due to——. - external applied stress - enhanced atomic diffusion - stored internal strain energy
Enhanced atomic diffusion
31
Physical properties such as electrical and thermal conductivities——during recovery. - remain unchanged - return to a pre cold-worked state - are only slightly affected
Pre cold-worked state
32
The relief of some of the internal strain energy of a previously cold-worked metal, usually by heat treatment.
Recovery
33
The amount of recrystallization depends on——. -temperature -time -both time and temperature
Both time and temperature
34
The recrystallization temperature of a metal alloy is typically——the absolute melting temperature. -greater than -equal to -less than
Less than
35
For metals and metal alloys there is a critical degree of cold work——which recrystallization cannot occur. -below -at -above
Below
36
The formation of a new set of strain-free grains within a previously cold-worked material; normally, an annealing heat treatment is necessary.
Recrystallization
37
for a particular alloy, the minimum temperature at which complete recrystallization occurs within approximately 1 hour
Recrystallization Temperature
38
Grain growth can occur in——. -metals only -ceramics only -both metals and ceramics
Both metals and ceramics
39
During grain growth, ——grains can enlarge. -small -large -all
Large
40
Grain growth——the strength and toughness of a metal. -increases -decreases -doesn’t change
Decreases
41
The increase in average grain size of a polycrystalline material; for most materials, an elevated-temperature heat treatment is necessary
Grain Growth