Article
Nanoscience & Nanotechnology
K. A. Darling, B. C. Hornbuckle, C. J. Marvel, V. H. Hammond, K. Solanki
Summary: The paper provides a critical assessment of the role of grain size in limiting strength gains in stable nanocrystalline metals. Using copper-tantalum binary alloys, the study explores the breakdown of classical Hall-Petch behavior and its underlying mechanisms. The results show that Cu-Ta alloys exceed traditional strength limits predicted by the Hall-Petch relationship for NC Cu.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Nanoscience & Nanotechnology
B. B. Wang, G. M. Xie, L. H. Wu, P. Xue, D. R. Ni, B. L. Xiao, Y. D. Liu, Z. Y. Ma
Summary: Grain refinement is an effective method to enhance the mechanical properties of materials, with the strengthening effect of high angle grain boundaries being almost three times that of low angle grain boundaries. The study classified the Hall-Petch relationships into three stages as the grain size decreased, showing a positive deviation in fine grain regime due to the increased specific surface area of HAGBs. Additionally, the positive deviation in ultrafine grained regime was influenced by an extra dislocation source limited strengthening mechanism up to 29 MPa.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Crystallography
Matti Lindroos, Tom Andersson, Jarkko Metsajoki, Anssi Laukkanen
Summary: The study focuses on the length-scale dependent deformation behavior of doped copper overpacks, with emphasis on plasticity accumulation over the operational period. Different microstructural aggregates exhibit varying hardening responses, highlighting the importance of size dependent regularization of strain localization networks as a desired characteristic of the model.
Article
Materials Science, Multidisciplinary
Xu Li, Xiaotao Li
Summary: The tensile yield strength of coarse-grained thin films and wires is size-dependent, showing a "smaller is weaker" phenomenon, leading to a deviation from the Hall-Petch relationship. To address this issue, a modified Hall-Petch relation is proposed by considering the influence of free-surface on lattice dislocation pileup. The modified relations, written as sigma f = sigma 0 + ck0d-1/2 for films and sigma f = sigma 0 + 2 - cck0d-1/2 for wires, where c = cos(pi d/2D) and D is the thickness or diameter of the samples, demonstrate good agreement with experimental results, with a relative error within 15%.
Article
Materials Science, Multidisciplinary
Fengxia Wei, Baisong Cheng, Li Tian Chew, Jing Jun Lee, Kok Heng Cheong, Jiang Wu, Qiang Zhu, Cheng Cheh Tan
Summary: The study compared EBSD and OM techniques, investigated the effects of different parameters on results, and proposed a modified Hall-Petch equation considering grain size distributions for almost all AM alloy systems with remarkable agreement between predicted strength and experimental values.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Nanoscience & Nanotechnology
Kai Yao, Xiaohua Min
Summary: This study investigated the effect of grain size on the tensile properties of Ti-15Mo alloy, revealing that the impact decreased with increasing strain and eventually became negative. A dynamic Hall-Petch relation was established based on effective grain size, showcasing twin activation, twin suppression, and various interactions.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Chemistry, Physical
Marta Slowik, Amanda Akram
Summary: This study investigated the effect of cylinder length on the tensile strength of concrete using the Brazilian method. The results showed that shorter cylinders had a slight increase in tensile splitting strength, but this length effect was not influenced by the strength of the cement matrix or the type of aggregate, but rather by the aggregate size.
Article
Chemistry, Physical
Elango Chandiran, Yukiko Ogawa, Rintaro Ueji, Hidetoshi Somekawa
Summary: The effect of grain size and strain rate on the room-temperature compression of pure magnesium was studied. It was found that the deformation mechanisms and grain-boundary sliding were significantly influenced by grain size and strain rate, and the Hall-Petch relationship broke down under certain conditions. Additionally, the deformation mode had a negligible impact on the dominant deformation mechanisms and the Hall-Petch breakdown.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Materials Science, Multidisciplinary
Quanfeng Han, Xin Yi
Summary: As the average grain size decreases, the reduction in intragranular dislocation storage ability is revealed as the underlying mechanism of the breakdown of Hall-Petch behavior in nanocrystalline (NC) metals. The prediction of the critical grain size for the HP-inverse HP transition of NC metals agrees well with experimental results, showing remarkable ductility enhancement in the inverse HP region dominated by harmonized deformation of grain boundaries and grain interior. Additionally, the increase in grain boundary strength leads to enhancement in yield strength and delay in occurrence of the inverse HP behavior in NC metals.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2021)
Article
Multidisciplinary Sciences
Chaogang Ding, Jie Xu, Debin Shan, Bin Guo, Terence G. Langdon
Summary: Heterostructured materials offer a new approach to enhancing mechanical properties, which are crucial in materials science and engineering. In this study, Cu/Nb multilayer composites with varying layer thicknesses were produced using accumulative roll bonding and their microstructure and mechanical properties were investigated. The yield strength and ultimate tensile strength of these composites increase as the layer thickness decreases. Additionally, the relationship between yield strength and (layer thickness)-1/2 approximately follows the conventional Hall-Petch equation, but with a reduction in the Hall-Petch slope for nanometer-scale layer thicknesses. The deformation microstructure of these Cu/Nb multilayer composites reveals dislocation glide within the layers, leading to a weakening of the strengthening effect at the Cu-Nb interface.
Article
Materials Science, Multidisciplinary
Wenjun Huang, Shaochun Yin, Xuejiao Wang, Ruipeng Guo, Yucheng Wu, Junwei Qiao
Summary: The influence of heat treatment on the mechanical characteristics of Ti37V15Nb22Hf23W3 high-entropy alloy was investigated. It was found that the alloy's tensile strength decreases with increasing annealing time, and there is a Hall-Petch relationship between grain size and yield strength.
JOURNAL OF MATERIALS RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
F. H. Duan, Y. Naunheim, C. A. Schuh, Y. Li
Summary: The study investigates the hardness and deformation behavior of body centered cubic Mo(O) alloys with grain sizes ranging from 120 to 4 nm, highlighting a peak hardness at 11 nm and a transition towards glass-like deformation behaviors as grain size decreases.
Article
Engineering, Mechanical
Xuefeng Lu, Wei Zhang, Xin Guo, Xu Yang, Junchen Li, Junqiang Ren, Hongtao Xue, Fuling Tang
Summary: Grain boundary plasticity dominates the mechanical behavior of materials, and the introduction of nanotwins can achieve coordination between strength and ductility in metals and alloys. In this study, nanotwins with different volume contents are introduced in NiCoAl alloys to explore the strengthening mechanism under the Hall-Petch effect. The results indicate that the introduction of nanotwins effectively inhibits grain boundary migration and grain combination, improves the strength of the alloy, and changes the strengthening mechanism from dislocation movement, grain boundary migration, and deformation twinning to the dual strengthening of local dislocation movement and Lomer-Cottrell locks.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Nanoscience & Nanotechnology
Nguyen Q. Chinh, Daniel Olasz, Anwar Q. Ahmed, Gyorgy Safran, Janos Lendvai, Terence G. Langdon
Summary: Experimental data show that the conventional Hall-Petch relationship is not applicable to metals with submicrometer structures. A new dislocation model is proposed to modify the Hall-Petch relationship and provide a uniform description of grain size strengthening in submicron-structured f.c.c. metals and solid solution alloys.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Materials Science, Multidisciplinary
A. Kardani, A. Montazeri, H. M. Urbassek
Summary: Nanostructured tantalum-based dental implants have superior biocompatibility and bioactivity compared to titanium-based implants. However, the plastic deformation mechanisms of these implants are not fully understood. In this study, molecular dynamics simulation is used to explore the microstructural evolution of pure polycrystalline tantalum samples under tensile loading, revealing different deformation mechanisms for samples with different grain sizes.
JOURNAL OF MATERIALS SCIENCE
(2022)
Article
Physics, Applied
N. G. Mathews, A. K. Saxena, N. Venkataramani, G. Dehm, B. N. Jaya
Summary: This study investigates the cracking behavior of barium titanate films deposited on flexible substrates and quantifies the fracture performance of these nanocrystalline films. The study finds that the fracture strength and interface properties of the barium titanate films are influenced by the film thickness and should be considered in the engineering design of devices.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Multidisciplinary Sciences
Daniel Utt, Subin Lee, Yaolong Xing, Hyejin Jeong, Alexander Stukowski, Sang Ho Oh, Gerhard Dehm, Karsten Albe
Summary: By experiments and simulations, this study investigates the reasons for dislocation pinning in high-entropy alloys. The research finds that the critical stress required for dislocation glide is proportional to the density of high local Peierls friction.
NATURE COMMUNICATIONS
(2022)
Article
Materials Science, Multidisciplinary
Saba Ahmad, Tobias Brink, Christian H. Liebscher, Gerhard Dehm
Summary: In the past few decades, it has been discovered that a single grain boundary can exist in different stable and metastable states with different atomic structures. However, experimental insights into the atomic structure are rarely reported. This study reports two different microstates of incoherent Sigma 3 [111] (11 (2) over bar) grain boundaries in an aluminum thin film grown on sapphire, which have slightly different structural units. Molecular statics simulations are used to understand the differences between these states and strain is found to potentially contribute to the stability of one state over the other.
Article
Materials Science, Multidisciplinary
Hanna Tsybenko, J. Manoj Prabhakar, Michael Rohwerder, Gerhard Dehm, Steffen Brinckmann
Summary: The development of wear-resistant steels requires understanding of deformation behavior and chemical evolution in cementite (Fe3C) under tribological loading. This study examines the elemental and phase distributions in bulk polycrystalline cementite with minor fractions of graphite, iron, and wustite after single-pass sliding wear. The results show that severe plastic deformation leads to partial decomposition and mechanical mixing of non-cementite inclusions and partial elemental homogenization in the outermost deformed region.
Article
Engineering, Multidisciplinary
Jonas Rauber, Christian Motz, Florian Schaefer
Summary: This study compares the results of two methods and assesses the measurement error of quantitative thermometry using finite element analysis.
INTERNATIONAL JOURNAL OF STRUCTURAL INTEGRITY
(2023)
Article
Materials Science, Multidisciplinary
Wenzhen Xia, Piyush Pramod Patil, Chang Liu, Gerhard Dehm, Steffen Brinckmann
Summary: The tribology induced microstructure plays a key role in determining the tribological properties of metals. Single nano-/microasperity sliding tests have enabled the investigation of plastic evolution during the initial stages of wear, but the formation mechanisms of sliding induced grain refinement are still largely unknown. In this study, a novel microwall sliding test was conducted to simplify the stress state and directly inspect the contact zone. The formation of a misorientation jump in the crystal orientation below the wear track was observed, leading to the formation of large angle grain boundaries.
Article
Materials Science, Multidisciplinary
Wenjun Lu, Wenqi Guo, Zhangwei Wang, Jianjun Li, Fengchao An, Gerhard Dehm, Dierk Raabe, Christian H. Liebscher, Zhiming Li
Summary: In this study, a novel strategy is developed to mitigate the embrittlement of sigma phase particles in high-entropy alloys (HEAs) by utilizing displacive transformation and heterogeneous structures. The deformation behavior study reveals that the displacive transformation from face-centered cubic (FCC) to hexagonal close packed (HCP) phase effectively suppresses the propagation of microcracks in brittle sigma particles and contributes to high work hardening behavior. The transformation induced stress-relaxation around the regions containing brittle sigma particles in heterogeneously structured HEAs results in ultimate tensile strengths as high as -1.2 GPa while maintaining a ductility up to -50%.
Article
Materials Science, Multidisciplinary
Markus Felten, Jakub Nowak, Oliver Beyss, Patrick Gruenewald, Christian Motz, Daniela Zander
Summary: The time dependent native oxide surface conditions of Mg and Mg-Al-Ca alloys under moderate atmospheric conditions were analyzed using in situ SKPFM, in situ XRR, and ex situ XPS measurements. The progressive hydration of the MgO layer was found to be the dominant surface reaction for all investigated alloys during the time period of up to 24 h. Subsequent electrochemical measurements showed a reduced corrosion resistance of all Mg alloys under short-term immersion conditions with a higher hydration degree of the native oxide.
Article
Nanoscience & Nanotechnology
Hanna Bishara, Lena Langenohl, Xuyang Zhou, Baptiste Gault, James P. Best, Gerhard Dehm
Summary: The study focuses on the effect of Fe-alloying on the resistivities of grains and grain boundaries in Cu thin films. Cu films with varying grain sizes and Fe compositions were prepared. The properties, morphology, and compositions of bulk and grain boundaries were analyzed using different methods. Both local electrical measurements and global resistivity characterization were performed to obtain specific resistivities and calculate the grain boundary reflection coefficient. It was found that alloying significantly increased the resistivity of grain boundaries while causing only minor influence on the grain interior.
SCRIPTA MATERIALIA
(2023)
Correction
Multidisciplinary Sciences
Lena Langenohl, Tobias Brink, Rodrigo Freitas, Timofey Frolov, Gerhard Dehm, Christian H. Liebscher
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Xuyang Zhou, Ali Ahmadian, Baptiste Gault, Colin Ophus, Christian H. Liebscher, Gerhard Dehm, Dierk Raabe
Summary: Grain boundaries, the defects between differently oriented crystals, play an important role in solute segregation and material properties. The interplay of structure and composition of grain boundaries at the atomic level remains unclear. Through charge-density imaging and atom probe tomography, the authors reveal that the atomic motifs control the chemical properties of grain boundaries and enable the targeted design and passivation for various applications.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Sung-Gyu Kang, Ramil Gainov, Daniel Heussen, Soeren Bieler, Zhongji Sun, Kerstin Weinberg, Gerhard Dehm, Rajaprakash Ramachandramoorthy
Summary: This study demonstrates the fabrication of copper lattice structures using green laser in laser-powder bed fusion, which have well-defined unit cells and dense microstructure. The deformation behavior of these structures under different strain rates is investigated and rationalized, suggesting their suitability for dynamic loading applications.
MATERIALS & DESIGN
(2023)
Article
Materials Science, Multidisciplinary
Lena Langenohl, Tobias Brink, Gunther Richter, Gerhard Dehm, Christian H. Liebscher
Summary: Alloying a material and segregating solutes to grain boundaries is an effective approach to tailor material properties. In this study, we used advanced microscopy and spectroscopy techniques to investigate the atomic structure of a high-angle grain boundary in pure copper and upon silver segregation. Combining experimental observations with atomistic modeling, we were able to quantify the local silver concentration and elucidate the underlying segregation mechanism.
Article
Materials Science, Multidisciplinary
Tobias Brink, Lena Langenohl, Hanna Bishara, Gerhard Dehm
Summary: Increasing evidence indicates that grain boundaries exhibit ordered atomic structures and can be treated as grain boundary phases thermodynamically. While atomic structures have been identified for specific materials at particular grain boundaries, it remains unclear whether these structures and their thermodynamic properties are material specific or generalizable. In this study, we used atomistic simulations to investigate high-angle [111] symmetric tilt grain boundaries in various fcc metals and found two families of grain boundary phases. We also examined the thermodynamic excess properties of the grain boundaries and compared the structures to electron microscopy images.
Article
Metallurgy & Metallurgical Engineering
M. Laub, B- Bachmann, E. Detemple, F. Scherff, T. Staudt, M. Mueller, D. Britz, F. Muecklich, C. Motz
Summary: The prior austenite grain size (PAGS) is a crucial microstructural parameter in steel research and process development, directly influencing mechanical properties of steel plates. This paper focuses on chemical etching methods for reliable measurement of PAGS and introduces a novel approach for automatically reconstructing prior austenite grain boundaries (PAGB) and determining PAGS. By utilizing modern machine learning methods, optical micrographs can be quantitatively analyzed to assess the distribution and morphological parameters of PAGS.
PRAKTISCHE METALLOGRAPHIE-PRACTICAL METALLOGRAPHY
(2022)
Article
Materials Science, Multidisciplinary
Nizar Lefi, Salem Neily, Roland Bonnet
Summary: This paper investigates the elastic field in a bi-material crystal with an angular dislocation line with one branch placed in the crystal and the other along a strongly bound or welded interface. The analysis formulates the elastic field of a closed dislocation loop and solves it using the knowledge of the Green's tensor of the bi-material. The study provides a faster calculation method and has important implications for solving interfacial angular dislocation problems.
PHILOSOPHICAL MAGAZINE
(2024)
