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Unformatted text preview: ME 382 Lecture 13 1 E FFECTS OF ALLOYING ON YIELD STRENGTH 1. Solid-solution hardening • Occurs with interstitial solid solutions or with substitutional solid solutions • Local compressive stress field around interstitial solute atoms • Local stress field when substitutional solute atom is different size from solvent atoms • Example: Bronze consists of Sn dissolved in Cu • Sn atoms larger than Cu • Stress field interacts with stress field of dislocation • Dislocation line distorts to minimize energy (at cost of extra length) ME 382 Lecture 13 2 • This is minimum energy position ∴ Extra work is needed to move the line from this configuration • Shear strength is given by: k shear strength ∝ ε m 3/ 2 misfit strain × c concentration • Increase concentration above equilibrium (supersaturated solution) for enhanced σ Y 2. Precipitation hardening Coherent or semi-coherent precipitates • If small precipitates develop they will generally have a mismatch strain with matrix (Coherent or semi-coherent pttes. have some lattice alignment with host) • Strengthening mechanism similar to solid-solution hardening...
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This note was uploaded on 09/08/2011 for the course MECHENG 382 taught by Professor Thouless during the Fall '08 term at University of Michigan.
- Fall '08