MS115a Lect 17 11-02-2011

MS115a Lect 17 11-02-2011 - Defects in Solids 0-D or point...

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Unformatted text preview: Defects in Solids 0-D or point defects vacancies, interstitials, etc. control mass diffusion 1-D or linear defects dislocations control deformation processes 2-D or planar defects grain boundaries, surfaces, interfaces, heterophase boundaries 3-D or volume defects voids, secondary components (phases) (mechanical properties yield, metals) (mechanical props fracture, ceramics) Volume Defects / Heterophase Boundaries Composites Two or more distinct types of materials, phases Boundary between them is a heterophase interface A B At grain boundaries Second phase concentrated at triple contacts of host grain boundaries Typical when liquid phase forms at high temperature liquid / amorphous grain 1 grain 3 grain 2 Balance of forces interphase boundary SS LS LS SS = 2 SL cos( /2) Pores 2 nd phase is a void increases scattering thermal insulation white, not transparent Volume Defects and Mechanics A secondary (different) material: phase in metals: secondary phases tend to pin dislocations Pores in ceramics: tend to be source of failure = F/A = L/L ceramic metal Mechanical Behavior y frac Y Y Y from chemical bonds y due to dislocation glide y (obs) <<...
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This note was uploaded on 01/03/2012 for the course MS 115a taught by Professor List during the Fall '09 term at Caltech.

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MS115a Lect 17 11-02-2011 - Defects in Solids 0-D or point...

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