Quantitative evaluation of strain enhanced vacancy concentration using NMR pulse techniques in-situ during deformation of materials

Deformation induced vacancy production is responsible for the observed critical strain to serrated flow. Nuclear magnetic resonance techniques can be used to monitor in-situ the dynamical behavior of point and line defects in materials during deformation, and these techniques are nondestructive and noninvasive. We used in-situ pulse NMR to determine the strain dependence of the deformation-induced vacancy concentration in alkali halide (NaCl and NaF) single crystals and polycrystalline aluminum. Experimental results correlated with models based on vacancy production through mechanical work (versus thermal jogs) while in-situ annealing of excess vacancies is noted at high temperatures.