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Unformatted text preview: Problem 1 Since creep is a diffusion-assisted process, metallurgical factors that can slow down the diffusion will be beneficial to creep resistance. This is achieved by 1) Increasing the diffusion distance , e.g. Using coarse-grained structures or single crystals 2) Choosing materials with low diffusion rate or high diffusion activation energy 3) Increase melting temperature 4) Preserving hardening mechanisms that are effective at temperatures less than 0.3 Tm The hardening of metallic materials at T < 0.3 Tm is achieved by various mechanisms that act to impede the dislocation slip. These mechanisms include: 1) Solid solution hardening where the strain fields associated with the solute atoms interact with the dislocation or solute atoms form an atmosphere surrounding the dislocation. The mechanism is not effective at high temperature because the stress\strain fields of solutes will be relaxed or solute atmosphere around the dislocation will diffuse away from dislocations and, therefore, cannot be used to induce high creep resistance....
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This note was uploaded on 12/14/2009 for the course MSE 113 taught by Professor Ritchie during the Spring '09 term at University of California, Berkeley.
- Spring '09