Get-together Dinner (at your own cost!)

Welcome Address

• Weimin Gan (Helmholtz-Zentrum Hereon)
• Heinz-Günter Brokmeier

Materials science studies at the neutron source FRM II of Heinz Maier-Leibnitz Zentrum (MLZ)

• habil. Ralph Gilles (Heinz Maier-Leibnitz Zentrum (MLZ), Technical University of Munich (TUM))

This talk gives an overview of the possibilities for material science investigations at the neutron source FRM II of the Heinz Maier-Leibnitz Zentrum (MLZ). In addition to an introduction to the FRM II reactor, examples of material science experiments performed at various neutron instruments are presented. Topics such as alloys, motors, batteries, computer chips, silicon doping and gas pipelines are introduced. Finally, some comments on beam time applications and industrial activities are given.

Microstructure and Texture Formation during Tensile Deformation of Polycrystalline CrMnFeCoNi High-Entropy Alloy

• Werner Skrotzki

Room: Microstructure and Texture Formation during Tensile Deformation of Polycrystalline CrMnFeCoNi High-Entropy Alloy W. Skrotzki1*, R. Chulist2, C. Gadelmeier3, U. Glatzel3, L.S. Toth4,5,6, E.P. George7, and D. Sathiaraj8 1 Institute of Solid State and Materials Physics, Technische Universität Dresden, D-01062 Dresden, Germany 2 Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, 30-059 Krakow, Poland 3 Metals and Alloys, University Bayreuth, 95447 Bayreuth, Germany 4 Institute of Physical Metallurgy, Metal Forming and Nanotechnology, University of Miskolc, 3515 Miskolc, Hungary 5 Laboratoire d'Étude des Microstructures et de Mécanique des Matériaux (LEM3), F-57045 Metz Cedex 01, France 6 Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine, F-57045 Metz, France 7 University of Tennessee, Materials Science and Engineering Department, Knoxville, TN 37996, USA 8 Discipline of Mechanical Engineering, Indian Institute of Technology, Simrol Indore 453552, India *werner.skrotzki@tu-dresden.de Abstract The polycrystalline face-centered cubic high-entropy alloy CrMnFeCoNi was deformed under tension at temperatures between 4 K and 973 K and a strain rate of 10-4 s-1. The microstructure was analyzed by electron backscatter diffraction. The texture was measured by diffraction of synchrotron radiation. Depending on the stress-strain behavior, microstructure and texture, different characteristic temperature ranges can be distinguished. While at all temperatures the deformation is dominated by dislocation slip, below 125 K mechanical twinning and above 775 K dynamic recrystallization contribute to the plastic deformation. Moreover, below 25 K serrated flow takes place. The texture represents a <111> <100> double fiber parallel to the tensile axis. It changes with respect to the volume fractions of the fibers in the characteristic temperature ranges. Accompanied by texture simulations, the texture changes are discussed with respect to mechanical twinning, non-octahedral slip, dislocation cross-slip and climb, and dynamic recrystallization.

Orientation Selection and Stored Energy Effects During the Incipient Stage of Recrystallization in Low-Carbon Steels

• Leo Kestens (Ghent University, Belgium)

Orientation Selection and Stored Energy Effects During the Incipient Stage of Recrystallization in Low-Carbon Steels Leo Kestens Department of Materials Science and Engineering, Faculty of Engineering, Ghent University, Belgium Abstract In the literature on texture formation during recrystallization of cold rolled low-carbon steels the difference between low and high-stored energy nucleation is well established. In a series of experiments added with model simulations the precise nature of orientation selection during the early stages of recrystallizations is revealed. A comprehensive and unified interpretation is presented that encompasses all the findings in one single theoretical concept. The incipient stage of recrystallization (aka the nucleation stage) is controlled by growth selection on the substructural scale, benefitting from short range misorientation gradients, reminiscent of stored energy of plastic deformation and enhancing the local boundary mobility. These concepts have been obtained through high-resolution EBSD scans on deformed structures of IF steels after rolling and torsion deformation, for various deformation temperatures.

Crystallographic orientation dependence of plastically stored energy in torsion-sheared samples of an IF steel grade

• Tuan Nguyen-Minh (Ghent University, Ghent, Belgium)

Crystallographic orientation dependence of plastically stored energy in torsion-sheared samples of an interstitial free (IF) steel grade Tuan Nguyen-Minh1, Estefania Sepulveda Hernandez1, Leo A.I. Kestens1,2 1 Department of Electromechanical, System and Metal Engineering, Ghent University, Ghent, Belgium 2 Department of Materials Science and Engineering, Delft University of Technology, Delft, The Netherlands Abstract Crystallographic orientation preference in metallic materials after plastic deformation is known as the result of dislocation glides and/or mechanical twinning. By applying crystal plasticity theory (i.e. fully constrained Taylor, visco-plastic self-consistent and advanced Lamel models), evolutions of deformation textures are predicted with reasonable accuracy. However, the formation of annealing textures in deformed materials has never been fully accounted for by any mean-field model calculations. One of the main reasons is that the driving force for recrystallization behaviors in materials has not yet been assessed exhaustively. In this study, plastically stored energy of deformed crystals in torsion-sheared samples of an interstitial-free (IF) steel grade is measured by EBSD and HE-XRD techniques. Experimental results have been analyzed and compared with the corresponding Taylor factor map of crystal plasticity theory. The study aims at a better understanding on the orientation dependence of stored energy in deformed crystals, as well as its influence on recrystallization behaviors of the materials after annealing.

Elastic Neutron Scattering for in situ characterization of high temperature alloys

• Cecilia Solís (Helmholtz-Zentrum Geesthacht)

Microstructures and Residual stress of AMed 316L (via zoom-meeting)

• Guichuan Li

Residual stresses in bronze matrix composite surface deposits manufactured via laser melt injection

• Erik Walz

Dislocation dissociation assisted formation mechanism of σ phase and its impact on producing heterogeneous lamella microstructure in CoCrV medium-entropy alloy

• Luda Wang

Dislocation dissociation assisted formation mechanism of σ phase and its impact on producing heterogeneous lamella microstructure in CoCrV medium-entropy alloy. Luda Wang1, 2, 4, Hai-Le Yan1, Yudong Zhang2, 4, Benoit Beausir2, 4, Weimin Gan3, Peltier Laurent2, Nathalie Siredey-Schwaller2, Claude Esling2, Xiang Zhao1, Liang Zuo1 1 Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819, China 2 Université de Lorraine, CNRS, Arts et Metiers ParisTech, LEM3, Metz, France 3 German Engineering Materials Science Center at MLZ. Helmholtz-Zentrum hereon, Garching, Germany 4 Laboratory of Excellence on Design of Alloys for low-mAss Structures (DAMAS), Université de Lorraine, Metz, France Abstract: Controlling the σ phase is crucial for balancing its strengthening effects while preventing embrittlement. However, the specific influence of dislocation activity on its formation remains unclear. In this work, an FCC-structured Co66.66Cr16.67V16.67 MEA prone to σ phase formation under non-equilibrium conditions. After cold rolling and heat treatment, in-situ and ex-situ diffraction techniques revealed ultra-rapid, spatially inhomogeneous precipitation of nano-sized σ particles, enriched in Cr and V but depleted in Co, mainly in severely deformed regions. This rapid formation was driven by defect-assisted atomic segregation and structural transformation via dislocation dissociation. The similarity of the atomic arrangement of the partial dislocations to that of the {001} sigma planes provides favorable structure transformation stimulus, enabling an FCC {111} to σ {001} orientation inheritance and a specific σ texture. Owing to the spatially inhomogeneous precipitation, a heterogeneous lamellar microstructure was formed, composed of alternatively distributed fine dual-phased layers and coarse single-phased layers. This work provides comprehensive information of dislocation-dissociation-assisted formation mechanism of σ phase.

High-temperature deformation induced β to γ phase transformation in TiAl alloy

• hail. Yudong Zhang

High-temperature deformation induced β to γ phase transformation in TiAl alloy M. Keïta1, 2, 3, C. Solís2, W.M. Gan2, J-F. Moulin2, Y.D. Zhang1, 3, E. Bouzy1, 3 1Université de Lorraine, CNRS, Arts et Metiers ParisTech, LEM3, Metz, France 2German Engineering Materials Science Centre (GEMS) at MLZ, Helmholtz-Zentrum hereon, Garching, Germany 3Laboratory of Excellence on Design of Alloys for low-mAss Structures (DAMAS), Université de Lorraine, Metz, France Keywords: TiAl alloys, Phase transformation, High-Temperature compression, EBSD, Blackburn orientation relationship. Abstract Titanium aluminide (TiAl) alloys are promising for aerospace and automotive applications due to their low density, high strength, and excellent oxidation and creep resistance. Among these, β-solidifying TNM (Ti-Al-Nb-Mo-B) alloys exhibit remarkable mechanical properties and thermal stability. Hot deformation is commonly used to shape these alloys, typically below the (α + β) phase region. In this study, hot compression at the temperature (1280 °C) within the (α + β) phase region was performed. Unexpectedly, the γ phase resurged from α despite its thermodynamic instability. The γ phase follows a Blackburn orientation relationship (Blackburn OR) and exhibits lamellar and nodular morphologies. Crystallographic analysis reveals that the activation of the basal slip of α triggered this transformation. The nodular γ is evolved from the early formed γ lamellae through fragmentation, spheroidization, and boundary sliding.

Closing Address

• Weimin Gan (Helmholtz-Zentrum Hereon)

Room: Main Entrance Building Seminar Room