Regensburg 2022 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 21: Transport in Materials: Thermal transport
MM 21.8: Talk
Wednesday, September 7, 2022, 12:15–12:30, H45
grain boundary melting phase transition in Ni-Bi system — •Baixue Bian1, Boris Straumal2, Sergiy Divinski1, and Gerhard Wilde1 — 1Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Gemany — 2Chernogolovka
Grain boundary segregation may drastically decrease the strength of structural materials. The intermediate temperature embrittlement of Ni-based alloys is a classical example of a catastrophic matrix degradation caused by solute segregation, in particular by Bi. In this work, the impact of grain boundary segregation of Bi in dilute polycrystalline Ni-Bi alloys on Ni grain boundary diffusion was systematically studied as function of temperature and composition. The radiotracer technique was used applying the 63Ni radioisotope and measuring grain boundary diffusion in both B- and C-type kinetic regimes after Harrison*s classification. An abrupt increase of the grain boundary diffusivities by about two orders of magnitude was observed at certain Bi contents which are unequivocally in the single-phase region of the corresponding bulk phase diagram. The present results unambiguously prove the occurrence of a pre-melting grain boundary phase transition in the Ni-Bi system.