Dresden 2020 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 4: Microstructure and Phase Transformations - Characterization

MM 4.2: Talk

Monday, March 16, 2020, 10:30–10:45, IFW B

Analysis of the miscibility gap in Copper-Nickel with Atom Probe Tomography — •Rüya Duran and Guido Schmitz — University of Stuttgart, 70569 Stuttgart, Germany

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.

In this project, the miscibility gap is determined by a direct experimental method applying Atom Probe Tomography (APT) to thin film structures. The temperature and time dependence of the segregation in Cu/Ni thin films is investigated. The quantitative evaluation was made by a cluster analysis, which determines the local atomic fraction in coarse-grained analysis cells located around each detected atom. By plotting the abundances of the concentrations (histograms), the boundary concentrations of a miscibility gap for a certain temperature are given.

At temperatures of total miscibility, the cluster analysis show deviations from binomial distribution, which can be explained by statistical fluctuations in concentration. By using a recently developed model based on the probability distribution of the local concentration, important thermodynamic parameters can be extracted, like the Gibbs free energy and the chemical potential, which also can be used to predict the critical temperature of the miscibility gap.