Berlin 2018 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 39: Topical session (Symposium EPS and MM): Mechanical Properties at Small Scales

MM 39.2: Vortrag

Mittwoch, 14. März 2018, 15:30–15:45, H 0107

Grain Boundary Effects in a High Entropy Alloys: Insights from Atomistic Computer Simulations — •Daniel Utt, Alexander Stukowski, and Karsten Albe — FB Materialwissenschaft FG Materialmodellierung, Technische Universität Darmstadt, Deutschland

High entropy alloys (HEAs) contain principle elements in concentrations between 5 and 35 at.%. Here we investigate the equimolar model alloy CuNiCoFe using atomistic simulations. We employs the embedded atom method potential by Zhou et al. (PRB 69, 2004), which has been used for HEA simulations before, but was not characterized further. We systematically determine thermodynamic properties of all binary subsystems, with a focus on mixing enthalpies of random solid solutions, and confirm its validity. [Koch et al. (JAP 122, 2017)]. We investigate the grain boundary (GB) segregation behavior in bicrystalline Cu_x(NiCoFe)_1−x samples using a hybrid Monte Carlo / Molecular Dynamics algorithm. We discover significant Cu segregation at these GBs and show that the McLean model is not capable of describing GB segregation in this psudobinary system. Opposite to that, we find, that there is no segregation to planar defects like stacking and twinning faults. Further, we investigate nanocrystalline samples and discover that the HEA is much more resilient against thermal and stress-driven grain growth than elemental elemental nanocrystalline Cu or Ni. Comparing the grain growth and yield strength of a Cu segregated and truly random nanocrystalline CuNiCoFe HEA sample shows no significant influence of the Cu enrichment.