YouTube: SEM study of slip in deformed cadmium single crystal

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Predicted by Theory YouTube Slip by movement of
whole lattice planes
Reduced Strength due to DislocationsYouTube
Model of slip by the movement of an edge
dislocationDislocation processes in
precipitation-hardened metals during in situ
deformation in an HVEM YouTube 3D atom
dislocation
YouTube Dislocation motion along grain
boundary.avi YouTube Dislocations in motion
YouTube SEM study of slip in deformed cadmium
single crystal
Young Modulus and Yield Strength
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Materials Moments Aaron LFiber-reinforced
plastics Troy/MicahErasers
Materials Moments
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Plastic Deformation
YouTube 3D atom dislocation
YouTube Model of slip by the movement of an edge
dislocation

• YouTube Brass Tension Test

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Real DislocationsDislocation processes in
precipitation-hardened metals during in situ
deformation in an HVEM YouTube Dislocation
motion along grain boundary.avi YouTube
Dislocations in motion YouTube Copy of particle
disl inter high t.avi
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Dislocation Densities Range 103 mm-2 1010
mm-2
Many opportunities to accommodate slip
Carefully solidified Metals
Highly deformed Metals
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SEM 100 planes

• SEM single crystal of cadmium deforming by
  dislocation slip on 100 planes.

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Slip in a single zinc crystal
YouTube SEM study of slip in deformed cadmium
single crystal
Fig. 7.9
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Slip Systems x y z lt a b c gt
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FCC Slip Systems
Fig. 7.6
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Table 7.1
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(0 1 1 0)
(1 0 1 0)
(1 1 0 0)
(0 1 1 0)
(1 1 0 0)
(1 0 1 0)


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Plastic Deformation
Section 7.5 Single Crystals
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Max. shear stress is on a plane 45º from
the tensile stress
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Slip in a single crystal Free to move at
critical SS
Fig. 7.8
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Table 7.1
Table 7.1
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Plastic Deformation
Section 7.6 Polycrystalline Materials
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• Plastic Deformation
• Slip in
• Polycrystalline Copper

Fig. 7.1 (173x photomicrograph)
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Plastic DeformationPolycrystalline Cold-worked
Nickel
Fig. 7.11--170x photomicrograph
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Before deformation After deformation
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Strengthening Mechanisms
Sections 7.8 7.13 Strengthening Metals
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Underlying Principle for Strengthening Metals

• Dislocations facilitate plastic deformation
• Inhibiting (binding, stopping, slowing)
  dislocation motion makes metals stronger

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• Strengthening Metals
• Grain-size Reduction
• Polycrystalline metals

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Grain size reductionDislocation motion at a
grain boundary
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Fig. 7.14
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Grain-size reduction

• Dislocation Pile-ups at grain boundaries

Young Modulus and Yield Strength 211
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Strengthening metals

• How do we reduce grain size?

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Strengthening metals

• How are dislocations bound in
• Grain-size reduction?

Its difficult for dislocations to move past a
grain boundary The more grain boundaries, the
more difficult for dislocations to move ?metal is
strengthened
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The key to strengthening metals
Bind Dislocations!
Sorry, I cant move right now. Im kinda tied up
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• Strengthening Metals
• (Ways to restrict dislocation motion)
• Grain-size reduction
• Solid-solution strengthening (Diffusion)
• Case hardening
• Alloying

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Case Hardening Hard Case w/ tough core
Low-C Steels (gt 0.30 C) Carburizing, Nitriding
, Carbonitriding Carburized depth of 0.030 to
0.050 in 4 hours _at_ 1700F
City Steel Heat Treating Co.
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Alloy
Cu-Ni Alloy
http//tankiialloy.en.made-in-china.com/offer/AqCn
WidOrYcV/Sell-Copper-Nickel-Alloy-Strip.html
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Atoms diffuse to a location that reduces strain
energy
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Solid-Solution StrengtheningSmaller
Substitutional Impurity
Tensile strains
Fig. 7.17
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Solid-Solution StrengtheningLarger
Substitutional Impurity
Compressive strains
Fig. 7.18
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2. Solid-Solution Strengthening Interstital
Impurity
Fits in interstitial sites
Compressive strains
Fig. 7.18
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2. Solid-Solution Strengthening Interstital
Impurity
Fits in interstitial sites
Compressive strains
Fig. 7.18
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Strengthening metals

• How are dislocations bound in
• Solid-solution strengthening?

They seek sites near dislocations to reduce
lattice strains. This stabilizes the lattice and
discourages plastic deformation.
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YouTube Dislocation motion is analogous to the
movement of caterpillar

• How Solid-Solution strengthening
• binds dislocations

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Cu-Ni alloy Strength Elongation Variation with
Ni content
Fig. 7.16
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The SECRET to strengthening metals
Bind Dislocations!