Strain hardening Mechanisms for Polycrystalline Molybdenum Alloys.pdf
Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on...
Transcript of Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on...
![Page 1: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/1.jpg)
Chapter 8 Strain hardening and
annealing
![Page 2: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/2.jpg)
Reading
All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening
exponent, strain-rate sensitivity and Bauschinger Effect.
![Page 3: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/3.jpg)
Homework No. 10
Problems 8-19, 8-22, 8-28, 8-54, 8-64
![Page 4: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/4.jpg)
Strengthening mechanisms in metals
A correlation exists between dislocation motion and mechanical behavior of metals.
Macroscopic plastic deformation motion of large #s of dislocations.
The ability of a metal to plastically deform depends on the ability of dislocations to move.
Limiting the dislocation motion hardness and strength increase greater mechanical forces required to initiate
plastic deformation.
![Page 5: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/5.jpg)
Strengthening mechanisms in metals
Strengthening principle: restricting or hindering dislocation motion renders a material harder and stronger.
Mechanisms for strengthening single phase metals:
grain size reduction
solid solution alloying
strain hardening
![Page 6: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/6.jpg)
Strengthening by grain size reduction
A grain boundary poses a barrier to dislocation motion for two reasons:
A dislocation moving in grain A to pass into grain B of different orientation will have to change its direction of motion. This is rather difficult.
Slip planes are discontinuous from one grain to the other.
![Page 7: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/7.jpg)
Strengthening by grain size reduction
Dislocation pile-up
![Page 8: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/8.jpg)
Strengthening by grain size reduction
A fine grain material is harder and stronger than one that is coarse grained.
Toughness also improves with finer grain.
Small-angle grain boundaries are not as effective as large-angle grain boundaries in interfering with dislocation motion.
![Page 9: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/9.jpg)
Solid-solution strengthening Alloys are almost always stronger than their pure metals,
because the solute atoms strain the solvent lattice.
These strain fields interact with those of the dislocations restricting the dislocation movement.
![Page 10: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/10.jpg)
Solid-solution strengthening Solute atom and its segregation
towards dislocations causes reduction of the strain fields.
As solute atoms are attached to the dislocations, the resistance to slip is greater since dislocations have to be torn away from them to move.
![Page 11: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/11.jpg)
![Page 12: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/12.jpg)
Solid-solution strengthening
Hardness and strength increase with increase of alloy concentration.
Ductility usually decreases.
![Page 13: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/13.jpg)
Solid-solution strengthening
![Page 14: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/14.jpg)
Solid-solution strengthening
![Page 15: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/15.jpg)
Solid-solution strengthening
![Page 16: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/16.jpg)
Strain hardening (Work hardening)
Cold Work: Mechanical deformation of a metal at relatively low
temperatures (below about 1/3 of the melting temperature in K).
% C.W. is defined relative to the reduction in cross sectional area of the material.
1000
A
AACW% do
![Page 17: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/17.jpg)
Strain hardening (Work hardening)
![Page 18: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/18.jpg)
The fibrous grain structure of a low carbon steel produced by cold working: (a) 10% cold work, (b) 30% cold work, (c) 60% cold work, and (d) 90% cold work (250). (Source: From ASM Handbook Vol. 9, Metallography and Microstructure, (1985) ASM International, Materials Park, OH 44073. Used with permission.)
![Page 19: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/19.jpg)
![Page 20: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/20.jpg)
![Page 21: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/21.jpg)
Common metal working methods
![Page 22: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/22.jpg)
Rolling
![Page 23: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/23.jpg)
Open die forging
![Page 24: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/24.jpg)
Closed die forging
![Page 25: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/25.jpg)
Direct extrusion
Indirect extrusion
![Page 26: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/26.jpg)
Wire drawing
![Page 27: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/27.jpg)
Stamping
![Page 28: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/28.jpg)
Strain hardening Process whereby a metal is plastically deformed, making it
harder and stronger. Stress-strain diagram & strain hardening.
![Page 29: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/29.jpg)
A material is stressed beyond the yield strength before the stress is removed.
![Page 30: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/30.jpg)
Now the material has a higher yield strength and tensile strength but lower ductility.
![Page 31: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/31.jpg)
By repeating the procedure, the strength continues to strength and the ductility continues to decrease until the material becomes very brittle.
![Page 32: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/32.jpg)
![Page 33: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/33.jpg)
![Page 34: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/34.jpg)
![Page 35: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/35.jpg)
Strain hardening
Dislocation multiplication and strain field interactions dislocation motion is hindered by the presence of other dislocations.
As the dislocation density increases, dislocation motion resistance by other dislocations becomes more pronounced.
![Page 36: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/36.jpg)
![Page 37: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/37.jpg)
Annealing
To make a material more ductile after cold working
![Page 38: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/38.jpg)
Stages of annealing
Thermal recovery - Stress relief
- Dislocation rearrangement
Recrystallization - Birth of new strain-free grains
Grain growth
![Page 39: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/39.jpg)
![Page 40: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/40.jpg)
![Page 41: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/41.jpg)
Effect of annealing time at a fixed annealing temperature
Brass
![Page 42: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/42.jpg)
Cold-worked brass
![Page 43: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/43.jpg)
After 3 s at 580°C, new grains appear.
![Page 44: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/44.jpg)
After 4 s at 580°C, many more grains appear.
![Page 45: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/45.jpg)
8 s at 580°C, complete recrystallization has occurred.
![Page 46: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/46.jpg)
1 h at 580°C, substantial grain growth has occurred.
![Page 47: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/47.jpg)
Effect of annealing temperature
Brass
![Page 48: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/48.jpg)
Annealed at 400°C Twin boundaries
![Page 49: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/49.jpg)
Annealed at 650°C
![Page 50: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/50.jpg)
Annealed at 800°C
![Page 51: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/51.jpg)
Recrystallization
![Page 52: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/52.jpg)
![Page 53: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/53.jpg)
![Page 54: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/54.jpg)
![Page 55: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/55.jpg)
![Page 56: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/56.jpg)
Effect of prior cold work on recrystallization temperature
![Page 57: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/57.jpg)
![Page 58: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/58.jpg)
![Page 59: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/59.jpg)
![Page 60: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/60.jpg)
![Page 61: Chapter 8 Strain hardening and annealing. Reading All of Ch. 8 except subsections in Sec. 8-1 on strain-hardening exponent, strain-rate sensitivity and.](https://reader034.fdocuments.us/reader034/viewer/2022052219/5697bfd81a28abf838caf389/html5/thumbnails/61.jpg)
©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
During hot working, the elongated anisotropic grains immediately recrystallize. If the hot-working temperature is properly controlled, the final hot-worked grain size can be very fine.
Hot working