EMCH 371 - Lecture 7_spring 2010 (1)

EMCH 371 - Lecture 7_spring 2010 (1) - Chapter 5 Diffusion...

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1 Chapter 5 Diffusion in Solids Issues to address… Why is it an important process? How does diffusion occur? How can the rate of diffusion be predicted for some simple cases? How does diffusion depend on structure and temperature?
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2 Case Hardened Gear Distortion of planes! Figure 4-4, Shackelford C: 0.077nm Fe: 0.124nm 37.9% difference in atomic radii
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3 Arrhenius Equation Figure 5-1 RT Q Ce rate / - = T R Q C rate 1 ln ) ln( - =
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4 Activation Energy
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5 Diffusion in Solids Figure 5-6 Diffusion by an interstitialcy mechanism Figure 5-5 Atomic migration
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6 Interdiffusion Figures 5-7 and 5-8
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7 Fick’s First Law Figures 5-9
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8 Diffusivity is Temperature Dependant Figure 5-13 RT Q o e D D / - =
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9 Relation between Diffusivity and Structure Figure 5-14
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Example The diffusion result described by can apply to the carburization process. The carbon environment is used to set the surface-carbon content (c s ) at 1.0 wt%. The initial carbon content of the steel (c 0 ) is 0.2 wt%. Using the error-function table, calculate how
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EMCH 371 - Lecture 7_spring 2010 (1) - Chapter 5 Diffusion...

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