Part IB

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Part IB Materials Science and Metallurgy Course
A Metals Alloys
Professor Harry Bhadeshia
Lecture 2 Atomic Diffusion
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Revision of Lecture 1
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Revision of Lecture 1
Steady state diffusion Ficks first law
Cylinder containing gas under pressure
Atmosphere
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Revision of Lecture 1
Non-steady state diffusion Ficks second law
Constant concentration at surface, CS
Average concentration far from surface, C0
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• Interdiffusion
• Structure sensitive diffusion
• Thermodynamics of diffusion
• Uphill diffusion

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Moreno D, Embury JD, SCRIPTA MATERIALIA 40 (7)
821-824 MAR 5 1999
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Structure sensitive diffusion
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Thermodynamics of diffusion Flux proportional to
solute-concentration gradient? Flux
proportional to solute-free energy gradient?
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Binary A-B solution in which A is the solute
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o
m
B
o
m
Gibbs free energy per mole
A
Gx
A
B
x
Composition
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