1. Diffusion videos YouTube: Diffusion posted by smcblackburn
YouTube: Slide Puzzle Physics, Leiden University

2. Materials Moments: Abdelrhman A. – Paper
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3. Principles of Materials
Are everywhere
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4. Section , Diffusion

5. posted by smcblackburn
YouTube: Diffusion
posted by smcblackburn
0:16-1:10
View the rest of this video if you have trouble understanding the concept of diffusion.

6. Diffusion
Gases
Liquids
Solids

7. Diffusion Connect 2 gas tanks: Ar & He Assume equal T & P
Gasses diffusereach uniform comp.

8. Diffusion 2 gases: Ar & He 2 liquids: water & alcohol
Diffuse until uniform composition

9. Diffusion 2 gases: Ar & He 2 liquids: water & alcohol
2 solids: Blocks of Cu & Ni
Heat at elevated T (below Tm)
Leave for days
Eventually reaches uniform composition

10. Diffusion 2 gases: Ar & He Fastest 2 liquids: water & alcohol
In all cases, diffusion rate increases as T increases.
Rate
2 gases: Ar & He Fastest
2 liquids: water & alcohol
2 solids: Blocks of Cu & Ni Slowest

11. Diffusion Mechanisms f03_05_pg112 Vacancy Diffusion Interstitial
f03_05_pg112.jpg
Interstitial
Diffusion
Fig. 5.3

12. Diffusion Mechanisms f03_05_pg112 Vacancy Diffusion Interstitial
f03_05_pg112.jpg
Interstitial
Diffusion
Fig. 5.3

13. Interdiffusion f03_05_pg112 Example: Cu, Ni
Vacancy diffusion or interstitial diffusion?
f03_05_pg112
f03_05_pg112.jpg 13

14. Metallic xl Structures
Face-Centered Cubic (FCC)
Cu, Al, Ag, Au, Pb, Ni, Pt
Body-Centered Cubic (BCC)
Na, Fe, Cr, Mo, W
Hexagonal Close-Packed (HCP)
Ti, Zn, Cd, Co, Mg

15. Example: Cu, Ni
Thermocouples and resistors whose resistance is stable across changes in temperature contain the 55% copper-45% nickel alloy (constantan).
Monel metal is a nickel-copper alloy, containing a minimum of 63% nickel.
Cupronickel or copper-nickel or "cupernickel" is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese.

16. Example: Cu, Ni Vacancy diffusion f03_05_pg112 Interdiffusion
f03_05_pg112.jpg 16

17. Interdiffusion
Initially
After some time
See Figs. 5.1 and 5.2 17

18. YouTube: Slide Puzzle Physics, Leiden University

19. http://www. yale. edu/yaleche/chemeng/eia/eia. htm Eric I
Eric I. Altman “Vacancy diffusion in a layer of adsorbed Br atoms on Cu(100)”
What’s Cu(100)?

20. Interdiffusion f03_05_pg112 Vacancy diffusion Interstitial diffusion
Other paths
Dislocations
Grain boundaries
Free surfaces
f03_05_pg112.jpg 20

21. Two conditions for diffusion f03_05_pg112
Empty site near the diffusing atom
Diffusing atom needs enough energy to break existing bonds.
f03_05_pg112
f03_05_pg112.jpg 21

22. Fick’s First Law:
Steady-State Diffusion

23. Fick’s First Law—Steady-state diffusion

24. Factors affecting diffusion rates
Diffusing species & host material
Temperature
Concentration Gradient

25. t02_05_pg119
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Table 5.2

26. t02_05_pg119 Which diffuses faster? Fe through a-Fe at 500oC
Diffusing Host Metal T(oC) D (m2/s)
species
Fe a-Fe (BCC) x 10-21
Fe a-Fe (BCC) x 10-15
Fe g-Fe (FCC) x 10-17
Fe g-Fe (FCC) x 10-16
t02_05_pg119
Which diffuses faster?
Fe through a-Fe at 500oC
Fe through a-Fe at 900oC
Fe through g-Fe at 500oC
Fe through g-Fe at 900oC
t02_05_pg119.jpg

27. The question that’s kept you up
late at night:

28. How does diffusion affect material properties?
It strengthens

29. City Steel Heat Treating Co.
Case Hardening – Hard Case w/ tough core
f16_07_pg190
Low-C Steels
(> 0.30% C):
Carburizing,
Nitriding,
Carbonitriding
Carburized depth of 0.030” to 0.050”
in °F
f16_07_pg190.jpg
City Steel Heat Treating Co. 29

30. Steel = C + Fe Interstitial C imposes lattice strains in Fe
Strains near dislocations can bind atoms and reduce deformation

31. Carburizing—Solid Diffusion process
Composition & processing affect material properties
YouTube: Vacuum Carburizing and Heat treating
Begin at 1:35–2:40

32. Section 6.1-6.3 Mechanical Properties of Metals: Elastic Deformation: Stress-Strain behavior
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33. Mechanical Properties
Material Properties:
Mechanical Properties
t02_05_pg119
Stiffness
Ductility
Strength
Toughness
Hardness
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34. Tensile Test
t02_05_pg119
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35. Tensile Test
t02_05_pg119
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36. Tensile Test
t02_05_pg119
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37. Strain gages t02_05_pg119 Metal-foil gage
Bond to testing material using epoxy
Variations in electrical resistance converted to strain measurements.
Grid shape maximizes resistance while keeping gage small
t02_05_pg119.jpg

38. fig_06_11
Brittle Failure: Tensile test of Nodular Graphite Cast Iron

39. Tensile Test t02_05_pg119 AlMgSi alloy ductile fracture
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AlMgSi alloy ductile fracture

40. Principles of Stress and Strain