7-Chapter_05--Diffusion - 1 Chapter 5 - ISSUES TO...

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Unformatted text preview: 1 Chapter 5 - ISSUES TO ADDRESS... How does diffusion occur? Why is it an important part of processing? How can the rate of diffusion be predicted for some simple cases? How does diffusion depend on structure and temperature? CHAPTER 5: DIFFUSION IN SOLIDS 2 Chapter 5 - Take a Glass tube filled with water. At time t = 0, add some drops of ink to one end. Observe what happens as time passes. t o t 1 t 2 t 3 x o x 1 x 2 x 3 DIFFUSION: A Mass Transport Mechanism Energy Transport by --- Radiation, Convection, Conduction Mass Transport -- in Fluids by --- Convection, Diffusion in Solids by --- Diffusion 3 Chapter 5 - 100% Concentration Profiles Cu Ni In an alloy, atoms tend to migrate from regions of higher concentration to lower concentrations. Initially After some time 100% Concentration Profiles 4 Chapter 5 - applies to substitutional solutes atoms exchange with vacancies rate depends on:--number of vacancies--activation energy to exchange (i.e., frequency of jumping) . increasing elapsed time DIFFUSION MECHANISMS : Substitutional Diffusion 5 Chapter 5 - Applies to interstitial solutes. More rapid than vacancy diffusion Occurs by the jumping of an interstitial (smaller) atom from one interstitial site to another....
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This note was uploaded on 09/25/2011 for the course METE 227 taught by Professor Ali during the Spring '10 term at Middle East Technical University.

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7-Chapter_05--Diffusion - 1 Chapter 5 - ISSUES TO...

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