Regensburg 2010 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 5: Diffusion and Point Defects I

MM 5.1: Vortrag

Montag, 22. März 2010, 10:15–10:30, H6

A Novel Approach to Identify the Mechanism of Gold Diffusion in Lead — •Nico Stolwijk and Dirk Böckmann — Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster

Fast impurity diffusion in metals has been extensively studied in the 1960s and 1970s, with Pb:Au serving as a prototype system. In particular, it was concluded from measurements of self-diffusion enhancement factors in Pb(Au) alloys that the high Au diffusivity cannot be reconciled with the vacancy mechanism. Alternative models interpreted Au transport in terms of fast moving interstitial-type defects including conventional interstitials Aui, Aui-vacancy pairs, or Au-Au diplons (dumbbells), however, without providing convincing evidence. Specifically, the role of substitutional Aus was not sufficiently clarified. Our experiments aim at identifying the Au diffusion mechanism by closely looking at the evolution of the Au penetration profiles in a regime of short-term isothermal annealing. To this aim, we utilise the suitability of the Pb:Au system for neutron activation analysis, which allows for the detection of diffusion profiles on an absolute concentration scale. The results are evaluated within the framework of the dissociative mechanism involving Aui-Aus exchange with the aid of vacancies.