A cold-worked nickel sample has

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Condensed Matter, Materials & Soft Matter · Crystal structure, bonding and diffraction

Solid State Physics, Ch Point defects, dislocations and alloys

Problem

A cold-worked nickel sample has G=76 GPaG = 76\,\mathrm{GPa}, conventional lattice constant a=3.52 A˚a = 3.52\,\text{\AA} (fcc, so b=a/2b=a/\sqrt2), a dislocation density ρd=5×1012 m−2\rho_d = 5\times10^{12}\,\mathrm{m^{-2}}, and a Taylor-law constant α=0.4\alpha = 0.4. ((a)) Calculate the flow stress τf=αGbρd\tau_{\rm f} = \alpha Gb\sqrt{\rho_d}. ((b)) Of the four obstacles to dislocation motion (work hardening, solid-solution hardening, precipitation hardening, grain-size hardening), which one does this calculation describe?

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