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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 m 3/ 2 misfit strain c concentration Increase concentration above equilibrium (supersaturated solution) for enhanced 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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- Fall '08