Dislocations and materials classesmaecourses.ucsd.edu/~jmckittr/mae20-wi11/C7 - Strengthening.pdf · Chapter 7 Dislocations and strengthening mechanisms 13 Solid solution strengthening
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1Chapter 7 Dislocations and strengthening mechanisms
Dislocations and materials classes
+ + + +
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+ + + +
- - -
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- - -
++
++
++++++++ + + + + +
+++++++
2Chapter 7 Dislocations and strengthening mechanisms
Dislocation Motion
2
3Chapter 7 Dislocations and strengthening mechanisms
Stress around dislocations
⊥ ⊥
⊥ ⊥
4Chapter 7 Dislocations and strengthening mechanisms
Slip systems in FCC
3
5Chapter 7 Dislocations and strengthening mechanisms
Slip system in FCC
6Chapter 7 Dislocations and strengthening mechanisms
Slip in HCP
4
7Chapter 7 Dislocations and strengthening mechanisms
Slip in single crystals
Ao
P
slipdirection
slip plane normal
slip planeAslip
8Chapter 7 Dislocations and strengthening mechanisms
Critical Resolved Shear Stress
σ σ σ
5
9Chapter 7 Dislocations and strengthening mechanisms
Deformation of single crystal
10Chapter 7 Dislocations and strengthening mechanisms
1. Reduction in grain size
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11Chapter 7 Dislocations and strengthening mechanisms
2. Solid solution strengthening
A
B
C
D
r = 0.143 nm
r = 0.155 nm
r = 0.133 nm
12Chapter 7 Dislocations and strengthening mechanisms
Strengthening
7
13Chapter 7 Dislocations and strengthening mechanisms
Solid solution strengthening in Cu
Tens
ile s
treng
th (M
Pa)
wt.% Ni, (Concentration C)
200
300
400
0 10 20 30 40 50 Yiel
d st
reng
th (M
Pa)
60
120
180
0 10 20 30 40 50
wt.%Ni, (Concentration C)El
onga
tion
(%)
14Chapter 7 Dislocations and strengthening mechanisms
3. Precipitation strengthening
Side View
precipitate
Top View
Slipped part of slip plane
Unslipped part of slip plane
S
8
15Chapter 7 Dislocations and strengthening mechanisms
• Internal wing structure on Boeing 767
• Aluminum is strengthened with precipitates formed by alloying.
1.5µm
3. Precipitation strengthening
16Chapter 7 Dislocations and strengthening mechanisms
Effect of heating after cold work
tens
ile s
treng
th (M
Pa)
duct
ility
(%EL
)tensile strength
ductility
600
300
400
500
60
50
40
30
20
annealing temperature (ºC)200100 300 400 500 600 700
9
17Chapter 7 Dislocations and strengthening mechanisms
Recovery
τR
Grain growth
18Chapter 7 Dislocations and strengthening mechanisms
TR
º
º
10
19Chapter 7 Dislocations and strengthening mechanisms
20Chapter 7 Dislocations and strengthening mechanisms
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