Regensburg 2019 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 14: Topical session (Symposium MM): High entropy and compositionally complex alloys

MM 14.6: Vortrag

Dienstag, 2. April 2019, 12:15–12:30, H43

Radiotracer diffusion in single crystalline CoCrFeNi and CoCrFeMnNihigh entropy alloys — •Daniel Gaertner¹, Josua Kottke¹, Yury Chumlyakov², Gerhard Wilde¹, and Sergiy V. Divinski¹ — ¹Institute of Materials Physics, University of Münster, Münster, Germany — ²Department of Physics of Metals, Tomsk State University, Tomsk, Russia.

High entropy alloys are multicomponent alloys, which consist of five or more elements in equiatomic or nearly equiatomic concentrations. These materials are hypothesized to show significantly decreased self-diffusivities. For the first time, diffusion of all constituent elements in equiatomic CoCrFeNi and CoCrFeMnNi single crystals and additionally solute diffusion of Mn in the quaternary alloy is investigated using the radiotracer technique, thereby the tracer diffusion coefficients of ⁵⁷Co, ⁵¹Cr, ⁵⁹Fe, ⁵⁴Mn and ⁶³Ni are determined in a temperature range between 923 K and 1373 K. The components are characterized by significantly different diffusion rates, with Mn being the fastest element and Ni and Co being the slowest ones in the quinary composition. In the quaternary composition Mn and Cr are the slowest elements at low temperatures and the situation is reversed with increasing temperature. Furthermore, solute diffusion of Cu in the CoCrFeNi single crystal is investigated in the temperature range of 973−1173 K using the ⁶⁴Cu isotope. In the quaternary alloy, Cu is found to be a fast diffuser at the moderate temperatures below 1273 K and its diffusion rate follows an Arrhenius law with an activation enthalpy of about 149 kJ/mol.