Dresden 2020 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 18: Poster Session I
MM 18.9: Poster
Monday, March 16, 2020, 18:15–20:00, P4
Combining Atom Probe Tomography and Statistical Mechanics: Analysis of the Miscibility Gap in Copper-Nickel — •Marvin Poul, Rüya Duran, Sebastian Eich, and Guido Schmitz — Universität Stuttgart, Stuttgart, Deutschland
Although Copper-Nickel alloys are commonly used in technical applications, their alloying behavior at low temperatures is still controversial. Early theoretical and indirect experimental investigations indicated that the phase diagram may contain a miscibility gap. Nevertheless, direct experimental proof is missing due to the slow kinetics at low temperatures.
This work combines thin film Atom Probe Tomography measurements with a novel methodology based on statistical mechanics to extract Tc from histograms of thermodynamically inherent local concentration fluctuations annealed above Tc, i. e. in the region of complete miscibility, to side-step the slow kinetics. The same formalism allows access to relative chemical potential differences between samples with different mean concentration and the excess Gibbs free energy of mixing as a function of concentration, allowing direct approach to a Calphad parametrization.
The approach is showcased using Monte Carlo simulations and Atom Probe Tomography measurements of Copper-Nickel, yielding a Tc appreciably lower than the expected 600 K from current Calphad parametrizations and too low to be practically accessed in experiment.