chap6_8

chap6_8 - 材材材材材材 材材材材材材 Fundamental...

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Unformatted text preview: 材材材材材材 材材材材材材 Fundamental of Materials Fundamental of Materials Prof: Prof: Tian Min Bo Tian Min Bo Tel: Tel: 62795426 62795426 材 62772851 62772851 E-mail: E-mail: [email protected] [email protected] Department of Material Science and Engineering Department of Material Science and Engineering Tsinghua University. Beijing 100084 Tsinghua University. Beijing 100084 Lesson thirty Lesson thirty §6.8 Diffusion Mechanism §6.8 Diffusion Mechanism Ⅰ Ⅰ .Flick's law in microscopic form .Flick's law in microscopic form 1. 1. One dimensional diffusion. One dimensional diffusion. Γ : probability of atom jumping to nearest position τ Γ 1 = : jump frequency period τ Γ Γ 2 21 1 12 2 1 2 1 n J n J = = δ ⋅ ⋅ = 1 1 n C 2 2 2 1 2 1 a D Γ δ Γ = = ∴ ) ( 2 1 2 1 21 12 1 n n J J J- =- = Γ x C C C C C J d d 2 1 ) ( 2 1 ) ( 2 1 2 2 1 2 2 1 1 δ Γ δ δ Γ δ Γ - =- =- = ∴ simple cubic: simple cubic: 2. 2. Two dimensional diffusion. Two dimensional diffusion. 3. 3. Three dimensional diffusion. Three dimensional diffusion. 2 4 1 a D Γ = FCC( ): Fe- α 2 2 12 1 ) 2 ( 12 4 a a D Γ Γ = = 1 2 2 6 1 a D Γ = 4....
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This note was uploaded on 10/15/2011 for the course ENG 242 taught by Professor Mingjiezhao during the Spring '11 term at BYU.

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chap6_8 - 材材材材材材 材材材材材材 Fundamental...

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