Prof. Dr.

Gumbsch, Peter

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  • Publication
    Wear-resistant CoCrNi multi-principal element alloy at cryogenic temperature
    ( 2024)
    Ren, Yue
    ;
    Zhou, Qing
    ;
    Hua, Dongpeng
    ;
    Huang, Zhuobin
    ;
    Yulong, Li
    ;
    Qian, Jia
    ;
    Gumbsch, Peter
    ;
    Greiner, Christian
    ;
    Wang, Haifeng
    ;
    Liu, Weimin
    Traditional high strength engineering alloys suffer from serious surface brittleness and inferior wear performance when servicing under sliding contact at cryogenic temperature. Here, we report that the recently emerging CoCrNi multi-principal element alloy defies this trend and presents dramatically enhanced wear resistance when temperature decreases from 273 to 153 K, surpassing those of cryogenic austenitic steels. The temperature-dependent structure characteristics and deformation mechanisms influencing the cryogenic wear resistance of CoCrNi are clarified through microscopic observation and atomistic simulation. It is found that sliding-induced subsurface structures show distinct scenarios at different deformation temperatures. At cryogenic condition, significant grain refinement and a deep plastic zone give rise to an extended microstructural gradient below the surface, which can accommodate massive sliding deformation, in direct contrast to the strain localization and delamination at 273 K. Meanwhile, the temperature-dependent cryogenic deformation mechanisms (stacking fault networks and phase transformation) also provide additional strengthening and toughening of the subsurface material. These features make the CoCrNi alloy particularly wear resistant at cryogenic conditions and an excellent candidate for safety-critical applications.
  • Publication
    A Review on 3D Architected Pyrolytic Carbon Produced by Additive Micro/Nanomanufacturing
    ( 2023)
    Eggeler, Yolita M.
    ;
    Chan, Ka Chun
    ;
    Sun, Qing
    ;
    Lantada, Andrés Díaz
    ;
    Mager, Dario
    ;
    Schwaiger, Ruth
    ;
    Gumbsch, Peter
    ;
    Schröder, Rasmus R.
    ;
    Wenzel, Wolfgang
    ;
    Korvink, Jan G.
    ;
    Islam, Monsur
    Additive micro/nano-manufacturing of polymeric precursors combining with a subsequent pyrolysis step enables the design-controlled fabrication of micro/nano-architected 3D pyrolytic carbon structures with complex architectural details. Pyrolysis results in a significant geometrical shrinkage of the pyrolytic carbon structure, leading to a structural dimension significantly smaller than the resolution limit of the involved additive manufacturing technology. Combining with the material properties of carbon and 3D architectures, architected 3D pyrolytic carbon exhibits exceptional properties, which are significantly superior to that of bulk carbon materials. This article presents a comprehensive review of the manufacturing processes of micro/nano-architected pyrolytic carbon materials, their properties, and corresponding demonstrated applications. Acknowledging the “young” age of the field of micro/nano-architected carbon, this article also addresses the current challenges and paints the future research directions of this field.
  • Publication
    Electrical Conductivity and Photodetection in 3D-Printed Nanoporous Structures via Solution-Processed Functional Materials
    ( 2023)
    Xia, Kai
    ;
    Dong, Zheqin Qing
    ;
    Sun, Qing
    ;
    Debastiani, Rafaela
    ;
    Liu, Sida
    ;
    Jin, Qihao
    ;
    Li, Yang
    ;
    Paetzold, Ulrich W.
    ;
    Gumbsch, Peter
    ;
    Lemmer, Uli
    ;
    Eggeler, Yolita M.
    ;
    Levkin, Pavel A.
    ;
    Hernandez-Sosa, Gerardo
    3D-printed conductive structures are highly attractive due to their great potential for customizable electronic devices. While the traditional 3D printing of metal requires high temperatures to sinter metal powders or polymer/metal composites, low or room temperature processes will be advantageous to enable multi-material deposition and integration of optoelectronic applications. Herein, digital light processing technology and inkjet printing are combined as an effective strategy to fabricate customized 3D conductive structures. In this approach, a 3D-printed nanoporous (NPo) polymeric material is used as a substrate onto which a nanoparticle-based Ag ink is printed. SEM and X-ray nano computed tomography (nanoCT) measurements show that the porous morphology of the pristine NPo is retained after deposition and annealing of the Ag ink. By optimizing the deposition conditions, conductive structures with sheet resistance <2 Ω sq-1 are achieved when annealing at temperatures as low as 100 °C. Finally, the integration of an inkjet-printed photodetector is investigated based on an organic semiconductor active layer onto the NPo substrate. Thus, the potential of this approach is demonstrated for the additive manufacturing of functional 3D-printed optoelectronic devices.
  • Publication
    Classification of slip system interaction in microwires under torsion
    ( 2023)
    Zoller, Kolja
    ;
    Gruber, Patric
    ;
    Ziemann, Michael
    ;
    Görtz, Alexander
    ;
    Gumbsch, Peter
    ;
    Kraffert, Katrin
    Microwires have become of increasing interest for the miniaturization of structural components. A profound understanding of the deformation behavior of microwires is important for the assessment of their applicability and lifetime in specific components. In particular, the deformation behavior under torsional loading and the associated microstructure evolution are of interest. The exact involvement of individual slip systems and their activities in the complex stress field under torsional loading are mostly unknown. In this paper, the microstructure evolution of single crystalline gold microwires under torsion have been analyzed for the high-symmetry crystal orientations 〈100〉, 〈110〉, and 111〉using simulation and experimental results. It is shown that a classification of the slip systems can be derived a priori by theoretical considerations. It is found, that the slip system activity, stress relaxation mechanism, as well as screw and edge composition of the piled-up dislocation density depends on specific slip system groups. Furthermore, the misorientation and its rotational axes including the identification of the slip system activities are discussed.
  • Publication
    In Situ Pyrolysis of 3D Printed Building Blocks for Functional Nanoscale Metamaterials
    ( 2023)
    Sun, Qing
    ;
    Dolle, Christian
    ;
    Kurpiers, Chantal Miriam
    ;
    Kraft, Kristian
    ;
    Islam, Monsur
    ;
    Schwaiger, Ruth
    ;
    Gumbsch, Peter
    ;
    Eggeler, Yolita M.
    This study presents a novel approach for investigating the shrinkage dynamics of 3D-printed nanoarchitectures during isothermal pyrolysis, utilizing in situ electron microscopy. For the first time, the temporal evolution of 3D structures is tracked continuously until a quasi-stationary state is reached. By subjecting the 3D objects to different temperatures and atmospheric conditions, significant changes in the resulting kinetic parameters and morphological textures of the 3D objects are observed, particularly those possessing varying surface-to-volume ratios. Its results reveal that the effective activation energy required for pyrolysis-induced morphological shrinkage is approximately four times larger under vacuum conditions than in a nitrogen atmosphere (2.6 eV vs. 0.5-0.9 eV, respectively). Additionally, a subtle enrichment of oxygen on the surfaces of the structures for pyrolysis in nitrogen is found through a postmortem electron energy loss spectroscopy study, differentiating the vacuum pyrolysis. These findings are examined in the context of the underlying process parameters, and a mechanistic model is proposed. As a result, understanding and controlling pyrolysis in 3D structures of different geometrical dimensions not only enables precise modification of shrinkage and the creation of tensegrity structures, but also promotes pyrolytic carbon development with custom architectures and properties, especially in the field of carbon micro- and nano-electromechanical systems.
  • Publication
    Materials fatigue prediction using graph neural networks on microstructure representations
    ( 2023)
    Thomas, Akhil
    ;
    Durmaz, Ali Riza
    ;
    Alam, Mehwish
    ;
    Gumbsch, Peter
    ;
    Sack, Harald
    ;
    Eberl, Christoph
    The local prediction of fatigue damage within polycrystals in a high-cycle fatigue setting is a long-lasting and challenging task. It requires identifying grains tending to accumulate plastic deformation under cyclic loading. We address this task by transcribing ferritic steel microtexture and damage maps from experiments into a microstructure graph. Here, grains constitute graph nodes connected by edges whenever grains share a common boundary. Fatigue loading causes some grains to develop slip markings, which can evolve into microcracks and lead to failure. This data set enables applying graph neural network variants on the task of binary grain-wise damage classification. The objective is to identify suitable data representations and models with an appropriate inductive bias to learn the underlying damage formation causes. Here, graph convolutional networks yielded the best performance with a balanced accuracy of 0.72 and a F1-score of 0.34, outperforming phenomenological crystal plasticity (+ 68%) and conventional machine learning (+ 17%) models by large margins. Further, we present an interpretability analysis that highlights the grains along with features that are considered important by the graph model for the prediction of fatigue damage initiation, thus demonstrating the potential of such techniques to reveal underlying mechanisms and microstructural driving forces in critical grain ensembles.
  • Publication
    Confinement-induced diffusive sound transport in nanoscale fluidic fhannels
    ( 2023)
    Holey, Hannes
    ;
    Gumbsch, Peter
    ;
    Pastewka, Lars
    Molecular dynamics (MD) simulations have been widely used to study flow at molecular scales. Most of this work is devoted to study the departure from continuum fluid mechanics as the confining dimension decreases. Here, we present MD results under conditions where hydrodynamic descriptions typically apply, but focus on the influence of in-plane wavelengths. Probing the long wavelength limit in thermodynamic equilibrium, we observed anomalous relaxation of the density and longitudinal momentum fluctuations. The limiting behavior can be described by an effective continuum theory that describes a transition to overdamped sound relaxation for compressible fluids.
  • Publication
    Influence of casting defects on the low cycle fatigue performance of MAR-M247 - A path towards a probabilistic model
    ( 2023)
    Radners, Jan
    ;
    Schweizer, Christoph
    ;
    Eckmann, Stefan
    ;
    Al-Ameri, Malek
    ;
    Amann, Christian
    ;
    Gumbsch, Peter
    ;
    Kadau, Kai
    Intermittent renewable energy sources are becoming increasingly important. This creates a demand for more flexible gas turbine operation conditions, to fill supply gaps and manage peak loads. As a result, the number of startup and shutdown cycles - the low cycle fatigue (LCF) loading of a gas turbine component - increases substantially. This work investigates the LCF performance of a common rotor blade material, to support the future transition towards more flexible power plant operation. One of the goals of this multi-year government funded project is the development of a probabilistic life model of cast material including defects such as porosity. The focus of this work is the investigation of the influence of casting defects on the LCF performance of cast MAR-M247. A comprehensive test program on defective and defect-free specimens at realistic engine conditions, i.e., temperature and stress was conducted. A first deterministic fatigue life model that accounts for material defects is proposed.
  • Publication
    Correlated study of material interaction between capillary printed eutectic gallium alloys and gold electrodes
    ( 2023)
    Hussain, Navid
    ;
    Scherer, Torsten
    ;
    Das, Chittaranjan
    ;
    Heuer, Janis
    ;
    Debastiani, Rafaela
    ;
    Gumbsch, Peter
    ;
    Aghassi-Hagmann, Jasmin
    ;
    Hirtz, Michael
    The Supporting Information file was updated on the 16th of December, after initial article online publication on the 8th of September 2022. https://doi.org/10.1002/smll.202202987
  • Publication
    Author Correction: Materials fatigue prediction using graph neural networks on microstructure representations
    ( 2023)
    Thomas, Akhil
    ;
    Durmaz, Ali Riza
    ;
    Alam, Mehwish
    ;
    Gumbsch, Peter
    ;
    Sack, Harald
    ;
    Eberl, Christoph
    Correction to: Scientific Reports https://doi.org/10.1038/s41598-023-39400-2, published online 02 August 2023. In the original version of this Article the figure legend of Figure 3 was incomplete, where the color codes used in panels c, d and e were not defined.