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MM: Fachverband Metall- und Materialphysik

MM 14: Topical Session Bulk Nanostrucured Materials III - Microstructure and Characterization I

MM 14.4: Vortrag

Montag, 26. März 2012, 16:30–16:45, H 0107

DSC investigations on lattice defects in hydrogenated Pd processed by High Pressure Torsion — •Daria Setman, Maciej Krystian, Matthias Bönisch, Gerhard Krexner, and Michael Zehetbauer — Faculty of Physics, University Vienna, Austria

Disk-shaped Pd (99.95%) samples (diameter 6mm, thickness 0.8mm) were loaded with hydrogen in a Sieverts-type apparatus up to a hydrogen content [H]/[Pd]~0.78. HPT-processing was performed at 195 K and 8 GPa hydrostatic pressure. DSC and TEM measurements revealed - for the first time - evidence of vacancy-hydrogen (Vac-H) clusters being formed during HPT. The vacancy densities from clusters reach atom concentrations as high as of order 10-3, and are thermally stable till 483 K (i.e. by 110 K higher than for undeformed Pd). Hydrogen desorption was monitored by microhardness and density measurements confirming effects typical of defect clusters on the mechanical properties. Results also demonstrate that hydrogen-assisted thermal stabilization not only occurs with vacancy-type defects but also with dislocations and grain boundaries, thus suggesting this effect for stabilization of nanocrystalline materials in general. However, prompt-gamma activation analysis showed that during annealing at RT for one year, the hydrogen desorbs completely, also including the part which had been trapped in the Vac-H-clusters.

[1] M. Krystian, D. Setman, B. Mingler, G. Krexner, M. J. Zehetbauer, Scripta Mater. 62, (2010) 49-52

Work supported by the Austrian Science Fund, Project S 10403