In situ nuclear magnetic resonance study of defect dynamics during deformation of materials

Autor: G Peters, O. Kanert, Korukonda L. Murty, K. Detemple, J.T.M. de Hosson
Přispěvatelé: Zernike Institute for Advanced Materials
Rok vydání: 1996
Předmět:
Zdroj: Journal of Materials Science, 31(12), 3289-3297. SPRINGER
ISSN: 1573-4803
0022-2461
Popis: Nuclear magnetic resonance techniques can be used to monitor in situ the dynamical behaviour of point and line defects in materials during deformation. These techniques are non-destructive and non-invasive. We report here the atomic transport, in particular the enhanced diffusion during deformation by evaluating the spin lattice relaxation time in the rotating frame, T-1p, in pure NaCl single crystals as a function of temperature (from ambient to about 900 K) and strain-rate (to approximate to 1.0s(-1)) in situ during deformation. The strain-induced excess vacancy concentration increased with the strain-rate while in situ annealing of these excess defects is noted at high temperatures. Contributions due to phonons or paramagnetic impurities dominated at lower temperatures in the undeformed material. During deformation, however, the dislocation contribution became predominant at these low temperatures. The dislocation jump distances were noted to decrease with increase in temperature leading to a reduced contribution to the overall spin relaxation as temperature is increased. Similar tests with an improved pulse sequence (CUT-sequence), performed on ultra-pure NaCl and NaF single crystals revealed slightly different results; however, strain-enhanced vacancy concentrations were observed. The applicability of these techniques to metallic systems will be outlined taking thin aluminium foils as an example.
Databáze: OpenAIRE
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