Exam 2 notes - Chpt 7 mechanical properties Elastic...

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Chpt.6 Diffusion Inter diffusion/impurity diffusion- when atoms or one metal diffuse into the other and vice-versa Self diffusion- atoms exchanged positions in pure metals For an atom to diffuse there must be an empty adjacent site and sufficient energy Vacancy diffusion- normal diffusion to adjacent vacant site Interstitial diffusion- when atoms diffuse into interstitial spots, must be small atoms Steady state diffusion- when diffusion flux (J) doesn’t change with time, it is a constant slow of diffusion Concentration profile- the curve of concentration vs position within a solid, slope=concentration gradient In ionic diffusion, atoms have to obey electrical neutrality, vacancies etc. most ionic diffusion is a result of electrical/magnetic activity. Polymertic diffusion- diffusion similar to that of metals. Diffusion rates are greater in amorphous regions as opposed to crystalline regions. Smaller molecules defuse faster, and non-reactive molecules diffuse faster than ones that react with the polymer.
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Unformatted text preview: Chpt 7 mechanical properties Elastic deformation- when stress and strain are proportional, usually up to strains of 0.005 Anelasticity- the time dependent elastic behavior, how some stuff takes time to return to its original shape, for metals it is usually neglected. For some polymers its time takes longer and is called viscoelastic behavior Plastic deformation- permanent deformation. Called slip in crystalline materials Proportional limit- when the stress-strain curve becomes non-linear Yield strength- when the material breaks, where the parallel line intersects the curve. Tensile strength- maximum on the stress-strain curve. Ductility- the measure of the degree of plastic deformation sustained at fracture. Resilience- capacity of a material to absorb energy while being stretched then having that energy recovered when the force is let off Toughness- a materials resistance to fracture when a crack or other defect is present...
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