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Advanced Study Group

Diffusion and Microstructure Analysis

The Advanced Study Group (ASG) Diffusion and Microstructure Analysis (DMA) is located at the Chair for Materials Physics of the Institute of Materials Physics at the Westphalian Wilhelms University Münster.

Members
  • Prof. Dr. Gerhard Wilde
  • Prof. Dr. Sergiy Divinski
  • Dr. Harald Rösner

Research

The ASG employs a range of complementing experimental analyses methods concerning the underlying physical mechanisms and microstructural origins of macroscopic materials behavior. Specific emphasis is on the coupled analysis of grain boundary diffusion, detailed characterization of the atomic structure of these internal interfaces, and microstructure evolution in deformed materials.

Other focus points are related to the analysis of defects and defect interactions by combining electron microscopy on different length scales with calorimetry and atomic mobility analyses. Moreover, nucleation and growth phenomena as well as phase transformations are in the center of interest.

Illustration of the atomic cluster expansion..
Microstructure of ECAP-processed Ni in the as-prepared state (a) and after annealing at 700 K for 17 hours (b); the Arrhenius plot for the measured self-diffusion coefficients D of 63Ni in ECAP-Ni (c). The Ni diffusion rates in ECAP-processed 99.6wt% pure Ni (symbols and solid lines) are shown against Ni grain boundary diffusion coefficients in coarse-grained Ni of 99.6wt% (dashed line) and 99.999 wt% (dashed-dotted line) purities.
WWU Münster

Our experimental analyses serve to generate input data for the modeling work on different length scales at ICAMS. Furthermore, it serves for in-depth comparison with and critical verification of the results obtained by computational analyses. Examples for collaboratively addressed topics are:

  • Defect dynamics at precipitates in severely deformed Al-based alloys
  • Grain boundary diffusion in ferromagnetic steels
  • Oxidation and nitridation kinetics of ODS steel
  • Recrystallization and grain growth in severely deformed Ni

Illustration of the atomic cluster expansion..
High-resolution TEM image of a 3-3-9 triple junction in nanocrystalline Pd (insert) and the atomistic strain field analysis. Shear components of the two-dimensional strain distortions near the triple junctions determined via the Geometric Phase Analysis (GPA) are shown. On the right, the strain profile measured along the 9-grain boundary is shown, indicating the presence of disclination-type defects along the distorted boundary.
WWU Münster

Institute of Materials Physics

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