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Critical to the growth of digital manufacturing is the development of rapid yet accurate quality control technologies to assess the microstructure of each metal part produced. Typical surface analysis methods are limited in measurement throughput and impose constraints on maximum area size and surface quality, which enforce the tedious practice of extracting and preparing flat, small-scale samples for microstructure analysis. Here, we propose a new approach based on directional reflectance microscopy (DRM) which can yield part-scale microstructure information nondestructively and on curved, complex surfaces. We demonstrate our approach on the airfoil of a turbine blade and carry out a rigorous error analysis using other samples with variable surface geometry. Our results highlight the potential for part-specific quality control in the context of digital manufacturing. [ABSTRACT FROM AUTHOR]

Energy absorption by matter is fundamental to natural and man-made processes. However, despite this ubiquity, developing materials capable of withstanding severe energy fluxes without degradation is a significant challenge in materials science and engineering. Despite recent advances in creating alloys resistant to energy fluxes, mitigating the damage caused by the absorption and transfer of mechanical energy remains a critical obstacle in both fundamental science and technological applications. This challenge is especially prominent when the mechanical energy is transferred to the material by shock loading. This study demonstrates a phenomenon in which microstructurally stabilized nanocrystalline Cu-Ta alloys can undergo reversal or nearly complete recovery of the dislocation structure after multiple shock-loading impacts, unlike any other known metallic material. The microstructure of these alloys can withstand repeated shock-wave interactions at pressures up to 12 GPa without any significant microstructural damage or deterioration, demonstrating an extraordinary capacity to be virtually immune to the detrimental effects of shock loading. This study reveals that under 12 GPa shock loading, stabilized nanocrystalline Cu-3Ta can generate and reabsorb dislocations, enabling near-complete recovery without microstructural deterioration. This behavior contrasts with other known metals. [ABSTRACT FROM AUTHOR]

While large language models learn sound statistical representations of the language and information therein, ontologies are symbolic knowledge representations that can complement the former ideally. Research at this critical intersection relies on datasets that intertwine ontologies and text corpora to enable training and comprehensive benchmarking of neurosymbolic models. We present the MaterioMiner dataset and the linked materials mechanics ontology where ontological concepts from the mechanics of materials domain are associated with textual entities within the literature corpus. Another distinctive feature of the dataset is its eminently fine-grained annotation. Specifically, 179 distinct classes are manually annotated by three raters within four publications, amounting to 2191 entities that were annotated and curated. Conceptual work is presented for the symbolic representation of causal composition-process-microstructure-property relationships. We explore the annotation consistency between the three raters and perform fine-tuning of pre-trained language models to showcase the feasibility of training named entity recognition models. Reusing the dataset can foster training and benchmarking of materials language models, automated ontology construction, and knowledge graph generation from textual data. [ABSTRACT FROM AUTHOR]

High-energy irradiation significantly increases the optical losses and noise coefficients of laser materials, leading to a substantial decrease in the slope efficiency or gain performance of laser output. To address this issue, we propose a strategy to enhance the radiation resistance of glasses/fibers by introducing phase interfaces. Based on the sol–gel method, through phase-separation techniques and high-temperature annealing treatments, silica-rich and phosphorus-rich phases were formed in erbium-ytterbium co-doped high-phosphorus silica glass, and nanoscale phase interfaces with specific densities, stability levels, and homogeneous distributions of doped elements were constructed between the phases. Using high-resolution transmission electron microscopy, nuclear magnetic resonance, and spectroscopic analyses, we tracked the evolution of the internal microstructure of the glasses at the atomic level. The findings confirmed that annealing effectively controlled the density of the phase interfaces formed. Under 1 kGy X-ray irradiation, glasses with effective phase interfaces exhibited significant reduction in radiation-induced attenuation (RIA) and improvement in photoluminescence intensity compared to pristine glasses. This indicated that effective phase interfaces could act as complex centers for irradiation-induced point defects, absorbing radiant energy and trapping these defects, thus mitigating high-energy radiation-induced damages. Furthermore, online irradiation tests on the Er3+/Yb3+ co-doped silica fibers supported this result. Compared to pristine fiber, fibers annealed for 3 h and annealed for 20 h with different phase interfacial densities showed 45% and 73% lower RIA at 1080 nm, respectively. Highlights: Erbium-ytterbium co-doped high-phosphorus silica glasses/fibers were synthesized via a modified sol–gel method, incorporating nanoscale phase-interface structures. Annealing treatment was utilized to increase the density of phase interfaces in the glasses/fibers. Strengthening the phase interfaces resulted in reduced radiation-induced attenuation and improved radiation resistance of glasses/fibers. [ABSTRACT FROM AUTHOR]

Phase-field modeling offers a powerful tool for investigating the electrical control of the domain structure in ferroelectrics. However, its broad application is constrained by demanding computational requirements, limiting its utility in inverse design scenarios. Here, we introduce a machine-learning surrogate to accelerate 3D phase-field modeling of tip-induced electrical switching. By dynamically handling the boundary conditions, the surrogate achieves accurate reproduction of switching trajectories under various tip locations and applied voltages. With stable predictions throughout entire morphological evolution pathways and a relative error inferior to 10% compared to direct solvers, the model efficiently emulates intricate switching sequences. By successfully replicating the boundary conditions, the presented framework strides towards a holistic surrogate for the ferroelectric phase field. With up to 2500-fold speed-ups over classical methods, our approach opens the path for the tractable design of the domain structure and the resolution of realistic inverse problems. [ABSTRACT FROM AUTHOR]

Grain boundaries (GBs) profoundly influence the properties and performance of materials, emphasizing the importance of understanding the GB structure and phase behavior. As recent computational studies have demonstrated the existence of multiple GB phases associated with varying the atomic density at the interface, we introduce a validated, open-source GRand canonical Interface Predictor (GRIP) tool that automates high-throughput, grand canonical optimization of GB structures. While previous studies of GB phases have almost exclusively focused on cubic systems, we demonstrate the utility of GRIP in an application to hexagonal close-packed titanium. We perform a systematic high-throughput exploration of tilt GBs in titanium and discover previously unreported structures and phase transitions. In low-angle boundaries, we demonstrate a coupling between point defect absorption and the change in the GB dislocation network topology due to GB phase transformations, which has important implications for the accommodation of radiation-induced defects. Grain boundaries strongly influence the properties of crystalline materials, but identifying their multiple phases remains difficult. Here, authors show a new tool for automated grain boundary structure prediction with an application to Ti. [ABSTRACT FROM AUTHOR]

Interdiffusion-based macromolecular transport across glassy interfaces is reportedly achieved at high temperatures in accordance with the classical model of reptation. Here, for the first time, we report a new mechanistic pathway for achieving solid-state glassy joining by triggering rapid macromolecular acceleration through mechanical deformation. Large-scale molecular simulations reveal that active plastic deformation in glassy polymers, at temperatures well below the bulk (and surface) glass transition temperatures T g b (and T g s ), causes segmental translations of macromolecules leading to interfacial interpenetrations, and the formation of new entanglements. The mechanistic basis for this new type of bonding is identified as molecular-scale dilatations and densifications during deformation-induced mobility. The reported insights open promising avenues for achieving quick, strong, and energetically less-intensive joining of polymeric glasses across various sectors. [ABSTRACT FROM AUTHOR]

Unraveling the effects of continuous dislocation interactions with interfaces, particularly at the nanometer length scales, is key to a broader understanding of plasticity, to material design and to material certification. To this end, this work proposes a novel discrete dislocation dynamics-based model for dislocation interface interactions tracking the fate of residual dislocation on interfaces. This new approach is used to predict the impact of dislocation/interface reactions on the overall mechanical behavior of accumulative roll bonded nanometallic laminates. The framework considers the dynamic evolution of the interface concurrent with a large network of dislocations, thus, accounting for the local short and long range effects of the dislocations under the external boundary conditions. Specifically, this study focuses on two-phase Fe/Cu nanometallic laminates, and investigates the role of the underlying elastic and plastic contrast of the Fe and the Cu layers on the composite response of the material. Moreover, the role of initial microstructures, resulting from processing is also investigated. Subsequently, the model is used to examine the effect of layer thickness and interface orientation relationship on the residual stresses of the relaxed microstructure. The associated mechanical response of these laminates are compared when loaded under normal direction compression, as well as shear compression. Finally, this work predicts a dominant effect of the layer thickness, as compared to the interface orientation relationship, on the macroscopic response and on the residual stresses of these nanolaminates, while the local dislocation transmission propensity through the interface is significantly influenced by the corresponding orientation relationship. [ABSTRACT FROM AUTHOR]

Some low-coordination materials, including water, silica, and silicon, exhibit polyamorphism, having multiple amorphous forms. However, the microscopic mechanism and kinetic pathway of amorphous-amorphous transition (AAT) remain largely unknown. Here, we use a state-of-the-art machine-learning potential and local structural analysis to investigate the microscopic kinetics of AAT in silicon after a rapid pressure change. We find that the transition from low-density-amorphous (LDA) to high-density-amorphous (HDA) occurs through nucleation and growth, resulting in non-spherical interfaces that underscore the mechanical nature of AAT. In contrast, the reverse transition occurs through spinodal decomposition. Further pressurisation transforms LDA into very-high-density amorphous (VHDA), with HDA serving as an intermediate state. Notably, the final amorphous states are inherently unstable, transitioning into crystals. Our findings demonstrate that AAT and crystallisation are driven by joint thermodynamic and mechanical instabilities, assisted by preordering, occurring without diffusion. This unique mechanical and diffusion-less nature distinguishes AAT from liquid-liquid transitions. The mechanism of amorphous-amorphous transitions is highly debated. Here, the authors use molecular dynamics simulations to reveal transitions via nucleation-growth or spinodal decomposition, resembling a thermodynamic phase transition but influenced by mechanics. [ABSTRACT FROM AUTHOR]

We use micro-computed tomography (µ-CT) to characterize the sizes, shapes, and locations of layer perforation (LP) defects in laminates of copper (Cu) and tantalum (Ta) processed by accumulative roll bonding (ARB). One—termed Cu/Ta—was processed from an initial stacking of seven alternating Cu and Ta sheets, with the exterior sheets being Cu. In the other—termed Ta/Cu—the exterior sheets are Ta. Cu/Ta remained intact during processing and exhibits an approximately uniform spatial distribution of LPs. By contrast, Ta/Cu fractured by longitudinal splitting. LPs in this latter sample are concentrated near the sample surfaces. Moreover, their density increases with decreasing distance to the fracture surface. These findings show that materials undergoing ARB may remain intact, despite profuse formation of LPs, provided that the LPs are uniformly distributed. However, a non-uniform distribution of LPs is correlated with longitudinal splitting. [ABSTRACT FROM AUTHOR]

Welded joints exhibit fatigue failure potential from weld geometry and characteristics of the heat affected zone. In order to counteract fatigue, structures and components require larger thicknesses resulting in heavier designs exhausting the finite natural resources. We hereby introduce a novel post-weld treatment, which postpones or even prevents fatigue failure of the welded connection. A Cu/Ni nanostructured metallic multilayer (NMM) is applied via electrodeposition and a 300–600% increase in usable lifetime compared to the untreated weld is observed. A FAT class 190 with a slope of k = 6 is proposed for the design of NMM treated butt welds. Material mechanisms responsible for the fatigue strength increase are introduced herein. A case study shows that the design of offshore wind turbine support structures applying NMM post-weld treatment enables a lifetime extension as well as a 28% weight reduction compared to the structure without post-weld treatment. [ABSTRACT FROM AUTHOR]

It is essential to discover an affordable electrode for the glucose detection application, which can be easily prepared. In this regard, we report a novel non-enzymatic glucose sensor that utilizes a free-standing electrode with a hybrid structure consisting of nanoporous CuZn/CuO nanoparticle (NPC/CuO). This electrode was fabricated through the process of dealloying the Zn80Cu20 precursor alloy and subsequent natural oxidation. We conducted a thorough investigation of the phase structure and morphology evolution. The results revealed that the NPC/CuO composite-based glucose biosensor displayed remarkable electrocatalytic activity toward glucose oxidation, exhibiting a high sensitivity of 2.33 mAcm−2 mM−1, wide linear range from 0 to 3.5 mM, low detection limit of 2.42 μM, excellent selectivity and suitable stability. These outstanding characteristics were attributed to the combined effect of the electroactive CuO and the nanoporous structure. These findings highlight that NPC/CuO composites have the potential to replace expensive noble metal biosensors in non-enzymatic glucose detection. By leveraging the cooperative effect of the nanostructure and copper oxide, these composites offer promising prospects for future development in this field. [ABSTRACT FROM AUTHOR]

The temperature-dependent [from room temperature (RT) to 500°C] nanoindentation behavior of a precipitation-strengthened Al0.3Ti0.2Co0.7CrFeNi1.7 high-entropy alloy (HEA) processed via two different additive manufacturing (AM) techniques was investigated in the as-deposited and annealed conditions. The hierarchically heterogeneous microstructures were achieved via simple one-step annealing treatments, exploiting the residual stresses in the AM-processed HEA to partially recrystallize the microstructure, performed remarkably better than the nearly homogeneous microstructures in the as-deposited state. The one-step annealed conditions revealed < 6.6% reduction in hardness values at 500°C compared to RT, while the as-deposited conditions showed a > 18% reduction in the hardness. The one-step annealed conditions also exhibited significantly higher hardness than the as-deposited conditions owing to their L12-strengthened FCC microstructures. Furthermore, serrated yielding or the Portevin-Le Chatlier effect indicative of microstructural instability was observed during nanoindentation deformation (at 500°C) for the as-deposited conditions but not for the one-step annealed conditions. This, therefore, signifies the robustness of the hierarchically heterogeneous microstructures at elevated temperatures presenting a strong avenue for tuning the HEAs for future nuclear reactor applications. [ABSTRACT FROM AUTHOR]

Recently, Ta/Cu nanocomposites have been widely used in therapeutic medical devices due to their excellent bioactivity and biocompatibility, antimicrobial property, and outstanding corrosion and wear resistance. Since mechanical yielding and any other deformation in the patient's body during treatment are unacceptable in medicine, the characterization of the mechanical behavior of these nanomaterials is of great importance. We focus on the microstructural evolution of Ta/Cu nanocomposite samples under uniaxial tensile loading conditions at different strain rates using a series of molecular dynamics simulations and compare to the reference case of pure Ta. The results show that the increase in dislocation density at lower strain rates leads to the significant weakening of the mechanical properties. The strain rate-dependent plastic deformation mechanism of the samples can be divided into three main categories: phase transitions at the extreme strain rates, dislocation slip/twinning at lower strain rates for coarse-grained samples, and grain-boundary based activities for the finer-grained samples. Finally, we demonstrate that the load transfer from the Ta matrix to the Cu nanoparticles via the interfacial region can significantly affect the plastic deformation of the matrix in all nanocomposite samples. These results will prove useful for the design of therapeutic implants based on Ta/Cu nanocomposites. [ABSTRACT FROM AUTHOR]

Compression of a magnetic material leads to a change in its magnetic properties. We examine this effect using spin-lattice dynamics for the special case of bcc-Fe, using both single- and poly-crystalline Fe and a bicontinuous nanofoam structure. We find that during the elastic phase of compression, the magnetization increases due to a higher population of the nearest-neighbor shell of atoms and the resulting higher exchange interaction of neighboring spins. In contrast, in the plastic phase of compression, the magnetization sinks, as defects are created, increasing the disorder and typically decreasing the average atom coordination number. The effects are more pronounced in single crystals than in polycrystals, since the presence of defects in the form of grain boundaries counteracts the increase in magnetization during the elastic phase of compression. Also, the effects are more pronounced at temperatures close to the Curie temperature than at room temperature. In nanofoams, the effect of compression is minor since compression proceeds more by void reduction and filament bending—with negligible effect on magnetization—than by strain within the ligaments. These findings will prove useful for tailoring magnetization under strain by introducing plasticity. [ABSTRACT FROM AUTHOR]

In this article we shed light on newly emerging perspectives to characterize and understand the interplay of diffusive mass transport and surface catalytic processes in pores of gas phase metal catalysts. As a case study, nanoporous gold, as an interesting example exhibiting a well-defined pore structure and a high activity for total and partial oxidation reactions is considered. PFG NMR (pulsed field gradient nuclear magnetic resonance) measurements allowed here for a quantitative evaluation of gas diffusivities within the material. STEM (scanning transmission electron microscopy) tomography furthermore provided additional insight into the structural details of the pore system, helping to judge which of its features are most decisive for slowing down mass transport. Based on the quantitative knowledge about the diffusion coefficients inside a porous catalyst, it becomes possible to disentangle mass transport contributions form the measured reaction kinetics and to determine the kinetic rate constant of the underlying catalytic surface reaction. In addition, predictions can be made for an improved effectiveness of the catalyst, i.e., optimized conversion rates. This approach will be discussed at the example of low-temperature CO oxidation, efficiently catalysed by npAu at 30 °C. The case study shall reveal that novel porous materials exhibiting well-defined micro- and mesoscopic features and sufficient catalytic activity, in combination with modern techniques to evaluate diffusive transport, offer interesting new opportunities for an integral understanding of catalytic processes. [ABSTRACT FROM AUTHOR]

Recently, Ta/Cu nanocomposites have been widely used in therapeutic medical devices due to their excellent bioactivity and biocompatibility, antimicrobial property, and outstanding corrosion and wear resistance. Since mechanical yielding and any other deformation in the patient's body during treatment are unacceptable in medicine, the characterization of the mechanical behavior of these nanomaterials is of great importance. We focus on the microstructural evolution of Ta/Cu nanocomposite samples under uniaxial tensile loading conditions at different strain rates using a series of molecular dynamics simulations and compare to the reference case of pure Ta. The results show that the increase in dislocation density at lower strain rates leads to the significant weakening of the mechanical properties. The strain rate-dependent plastic deformation mechanism of the samples can be divided into three main categories: phase transitions at the extreme strain rates, dislocation slip/twinning at lower strain rates for coarse-grained samples, and grain-boundary based activities for the finer-grained samples. Finally, we demonstrate that the load transfer from the Ta matrix to the Cu nanoparticles via the interfacial region can significantly affect the plastic deformation of the matrix in all nanocomposite samples. These results will prove useful for the design of therapeutic implants based on Ta/Cu nanocomposites. [ABSTRACT FROM AUTHOR]

Compression of a magnetic material leads to a change in its magnetic properties. We examine this effect using spin-lattice dynamics for the special case of bcc-Fe, using both single- and poly-crystalline Fe and a bicontinuous nanofoam structure. We find that during the elastic phase of compression, the magnetization increases due to a higher population of the nearest-neighbor shell of atoms and the resulting higher exchange interaction of neighboring spins. In contrast, in the plastic phase of compression, the magnetization sinks, as defects are created, increasing the disorder and typically decreasing the average atom coordination number. The effects are more pronounced in single crystals than in polycrystals, since the presence of defects in the form of grain boundaries counteracts the increase in magnetization during the elastic phase of compression. Also, the effects are more pronounced at temperatures close to the Curie temperature than at room temperature. In nanofoams, the effect of compression is minor since compression proceeds more by void reduction and filament bending—with negligible effect on magnetization—than by strain within the ligaments. These findings will prove useful for tailoring magnetization under strain by introducing plasticity. [ABSTRACT FROM AUTHOR]

Nanoporous metals can serve in unique functional applications due to their high surface area, and they are often made through dealloying, which removes a sacrificial element through chemical etching and leaves a nanoporous matrix of the remaining element(s). Several variations on this technique allow for a wider variety of metals and alloys to be processed, but simple, scalable, and reliable production of nanoporous devices is still not a reality using the majority of techniques and alloy systems. Oxide reduction may provide a suitable alternative, and in this work, nanoporous Cu was produced via oxide reduction in the Cu–CuO system. This method uses mechanical milling to create a metal matrix composite powder primarily composed of CuO that is reduced under hydrogen to leave pure Cu behind. It requires no harsh chemicals, and it uses modest temperatures and short reaction times. Furthermore, it is fully compatible with traditional powder metallurgy, making it readily scalable. Powder compacts were also processed to track the geometric changes associated with each composition and demonstrate that device creation is feasible, even with the basic process applied here. This work reveals important parameters associated with these materials by incorporating a wide range of milling times and compositions, with shorter milling times and higher oxide concentrations providing the finest pore sizes, the highest porosity, and the greatest simplicity. [ABSTRACT FROM AUTHOR]

Fatigue in metals involves gradual failure through incremental propagation of cracks under repetitive mechanical load. In structural applications, fatigue accounts for up to 90% of in-service failure1,2. Prevention of fatigue relies on implementation of large safety factors and inefficient overdesign3. In traditional metallurgical design for fatigue resistance, microstructures are developed to either arrest or slow the progression of cracks. Crack growth is assumed to be irreversible. By contrast, in other material classes, there is a compelling alternative based on latent healing mechanisms and damage reversal4–9. Here, we report that fatigue cracks in pure metals can undergo intrinsic self-healing. We directly observe the early progression of nanoscale fatigue cracks, and as expected, the cracks advance, deflect and arrest at local microstructural barriers. However, unexpectedly, cracks were also observed to heal by a process that can be described as crack flank cold welding induced by a combination of local stress state and grain boundary migration. The premise that fatigue cracks can autonomously heal in metals through local interaction with microstructural features challenges the most fundamental theories on how engineers design and evaluate fatigue life in structural materials. We discuss the implications for fatigue in a variety of service environments.We report that fatigue cracks in pure metals can undergo intrinsic self-healing; they were observed to heal by crack flank cold welding induced by local stress state and grain boundary migration. [ABSTRACT FROM AUTHOR]

UO2-BeO is an important composite nuclear fuel with high thermal conductivity. The impact of grain boundaries between UO2-UO2 and phase boundaries between UO2-BeO on the bubble evolution and the thermal conductivity in nuclear fuels is significant. In this study, we utilize a 3D phase field model to examine the influence of these boundaries on the nucleation and growth of bubbles in a bicrystalline UO2-BeO. Our simulations reveal that the diffusion of vacancies and gas atoms towards the phase boundaries results in bubbles preferentially forming at the phase boundaries. Intergranular bubbles possess an asymmetrical lectical shape due to the long-range diffusion-controlled boundary migration and the different defect production rate on the both sides. Spherical intragranular bubbles appear after the intergranular bubbles with high defects production rates and large grain size. The effective thermal conductivity decreases with the irradiation time and shows three distinct stages for systems that have both inter- and intragranular bubbles. [ABSTRACT FROM AUTHOR]

Structural metallic materials with interfaces of immiscible materials provide opportunities to design and tailor the microstructures for desired mechanical behavior. Metallic microstructures with plasticity contributors of the FCC and BCC phases show significant promise for damage-tolerant applications due to their enhanced strengths and thermal stability. A fundamental understanding of the dynamic failure behavior is needed to design and tailor these microstructures with desired mechanical responses under extreme environments. This study uses molecular dynamics (MD) simulations to characterize plasticity contributors for various interface microstructures and the damage evolution behavior of FCC/BCC laminate microstructures. This study uses six model Cu/Ta interface systems with different orientation relationships that are as- created, and pre-deformed to understand the modifications in the plasticity contributions and the void nucleation/evolution behavior. The results suggest that pre-existing misfit dislocations and loading orientations (perpendicular to and parallel to the interface) affect the activation of primary and secondary slip systems. The dynamic strengths are observed to correlate with the energy of the interfaces, with the strengths being highest for low-energy interfaces and lowest for high-energy interfaces. However, the presence of pre-deformation of these interface microstructures affects not only the dynamic strength of the microstructures but also the correlation with interface energy. [ABSTRACT FROM AUTHOR]

The deformation mechanism, crack initiation, propagation and fracture behavior of a new near-α titanium alloy Ti80 (Ti-6Al-3Nb-2Zr-1Mo) with a bimodal microstructure consisting of primary α (αp) grains and transformed β (βtrans) matrix is systematically investigated by in situ tensile testing in SEM. The results show that αp preferentially undergoes plastic deformation (single slip) in the early stage of deformation. As the deformation continues, the crack nucleates in the hard-to-deform region near the U-shaped notch, and then advances through αp to form small cracks, which tend to initiate at the αp/βtrans interface and slip bands region. However, slip transfer occurs between some αp and adjacent βtrans, and multi-slip or cross-slip is generated in αp, which plays a role in coordinating the inhomogeneity of local plastic deformation and delaying crack initiation. In the crack propagation stage, the main crack and microcracks are connected to promote crack growth. The crack tends to propagate along the αp/βtrans interface or slip bands inside αp. The αp boundaries play the role of deflecting the crack propagation direction. However, a relatively flat crack path is formed from a macroscopic point of view due to the small particle size of αp. [ABSTRACT FROM AUTHOR]

The purpose of the paper is to study the efficiency of modification with CeO2 nanoparticles (average particle size — 20–30 nm) in a concentration range from 0.1 to 10 wt.% aimed at improving the optical features and radiation stability of micron-sized ZnO powders. The optimal concentration of CeO2 nanoparticles, 3 wt.%, was determined. The change of the solar absorptance in a range of 0.2 to 2.2 µm after electron irradiation of the modified powder (E = 30 keV, F = 2·1016 cm−2) is 1.41 less compared to the unmodified powder. The paper demonstrates that the increase in radiation stability of zinc oxide powders modified with cerium dioxide nanoparticles is provided by two mechanisms: relaxation of primary defects on nanoparticles and capture of formed free electrons by cations of a rare-earth element. [ABSTRACT FROM AUTHOR]

Hetero-boundary-affected regions (HBARs) are widely observed in metallic materials and believed to play important roles in heterostructured materials that are currently attracting broad attention due to their superior mechanical properties which defy the conventional rule-of-mixtures. Here, we perform a series of discrete dislocation dynamics (DDD) simulations to confirm the existence of HBARs and investigate the mechanisms of their formation, growth, and evolution during plastic deformation. Our DDD simulations reveal that the HBARs are well characterized by a heterogeneous dislocation microstructure with distinct stress/strain gradients that depend on interface penetrability and applied strain. Furthermore, it is shown that the HBARs can significantly affect the mechanical responses of materials. This study aimed to provide a mechanistic basis to understand the formation mechanism of HBARs, which is critical for physics-based modeling of the mechanical behavior of heterostructured materials. [ABSTRACT FROM AUTHOR]

The leading theory of primary radiation damage in materials, by Norgett, Robinson, and Torrens (NRT), assumes that materials are homogeneous. This is inadequate for most engineering materials, which have rich microstructures. The lack of alternative theories has led to the widespread assumption that the microstructure only affects defect recombination and not defect production. We extend the NRT formalism to account for microstructural variations and explicitly include the damage caused in a phase by primary knock-on atoms that are produced in another nearby phase. Our approach reveals new insight on the interplay between radiation damage and microstructure, and converges to conventional NRT at suitably large length-scales. Applying it to real two-phase nuclear alloys we discover a reversal of primary radiation damage localisation when grain size is < 1 μm: in some fine-grained superalloys more damage is produced in the matrix than the precipitates, and the opposite is true for coarse-grained superalloys of same composition. [ABSTRACT FROM AUTHOR]

The rhenium element and grain boundaries have an essential effect on the dislocation slip generated during the grinding process of Ni-based superalloys. To study the impact of rhenium and grain boundaries on the grinding surface quality of Ni-based superalloys, the experiments were conducted with Ni-based polycrystalline superalloy GH4169 and Ni-based single-crystal superalloy DD5 (containing rhenium element) and DD98 (without rhenium element) as the research objects. The experiments with flat groove grinding as a machining method were conducted to explore the changes in surface roughness, grinding force, and surface morphology of the three Ni-based superalloys under different grinding parameters. The experiments show that the rhenium element significantly improves the high-temperature durability of Ni-based superalloys. In the relatively low-temperature condition (low grinding speed, considerable grinding depth, and high feed rate), the machining quality of DD5 is better than that of DD98, while in the relatively high-temperature condition, the machining quality of DD5 is lower than that of DD98. In the range of grinding parameters, the distortion of the subsurface microstructure of DD5 is lower than that of DD98. However, there is little difference between the two superalloys in chip morphology and serration. In high-temperature environments, grain boundaries become the weak link in Ni-based superalloys. The surface quality of GH4169 with grain boundaries is better than DD5, and its chip morphology differs significantly from DD5. [ABSTRACT FROM AUTHOR]

In this study, a unique SiOCN ceramic coating with exceptional compliance has been developed using perhydropolysilazane and polysiloxane preceramic polymers. The coating layers are defect-free and smooth with < 42 nm average surface roughness. The inter-diffusion of Si, C, and N further enhances the coating integration. The SiOCN coating has a hardness of 6.3 ± 0.7 GPa and shows plastic deformation. With repeated thermal quenching, the SiOCN hybrid coating stays intact and demonstrates a compliant deformation behavior, which has never been observed for polymer-derived ceramic coatings. This coating has great potential in corrosion prevention of steel substrates in different harsh environments, especially for nuclear waste storage canisters. [ABSTRACT FROM AUTHOR]

The microstructural evolution and variations in the dislocation properties and the dislocation density of drawn ultralow-carbon (ULC) steel wires, which exhibited an ultimate tensile strength of over 1500 MPa at ε = 5.3, were investigated through scanning electron microscopy/electron backscatter diffraction (SEM/EBSD) analysis and synchrotron radiation X-ray diffraction (SR-XRD), respectively. The wire drawing did not cause systematic changes in the dislocation properties of the drawn ULC steel wire. Dislocation strengthening and the grain size effect, such as the Bailey–Hirsch relationship and the Langford–Cohen relationship, were found to be dominant in the early and subsequent stages of drawing, respectively. Moreover, tensile strength of the drawn ultralow-carbon steel wires at ε > ~ 4 showed a positive deviation from the extrapolated Langford–Cohen relationship in the early stages of drawing, which was found to be caused by changes in the character of grain boundaries during drawing, that is, an increase in the fraction of grains surrounded by boundaries with misorientation angles of 15 deg or greater and a relative decrease in the fraction of low-angle boundaries with misorientation angles of less than 5 deg contributed to the excessive strengthening in the drawn ULC steel wires. [ABSTRACT FROM AUTHOR]

The mechanical and microstructural evolution of Alloy 2205 during severe plastic deformation is examined in this study. A combination of accumulative roll bonding (ARB) and cold rolling results in the successful formation of a nanograined dual-phase microstructure of austenite and ferrite with some transformed martensite. Severe deformation to cumulative reductions of 80.5, 92.5, 95, and 97 pct were performed. Microscopy indicates that grain dimensions in the sheet normal direction is less than 100 nm for reductions ≥ 92.5 pct. Shear banding is observed at reductions ≥ 95 pct while twinning is only observed at reductions < 92.5 pct. Neutron diffraction measurements indicated the presence of martensite for reductions ≥ 95 pct at ~ 8 pct volume fraction. Taken in conjunction, it appears that during initial ARB processing, both slip and twinning are active plastic mechanisms. As twinning becomes exhausted, martensitic transformation, slip, and intermittent shear banding account for the active plasticity mechanisms. Material hardness saturates at 92.5 pct reduction, with a maximum hardness of 45 HRC. Sub-sized tensile testing confirms this approximate hardness with measurements indicating a UTS of ~ 1440 MPa. Texture analysis of crystal orientation distributions in the plate normal direction suggest an approximate Kurdjumov–Sachs orientation relationship at all reductions above 80 pct indicating stability of the orientation relationship at high strains. The intragranular structure develops a fine scale sub-grain content with increasing deformation, resulting in a continual evolution of texture up to and including 97 pct reduction. The final structure presents strong components of Goss and rotated cube texture in both the austenite and ferrite. This body of work aims to compare ARB of an industrially relevant FCC/BCC system (Alloy 2205) to historical model FCC/BCC systems such as Cu/Nb. [ABSTRACT FROM AUTHOR]

Accumulative roll-bonded(ARB) Cu/Nb multilayer composites were cryorolled and room-temperature rolled. The ultimate tensile stress of ARB composite increased from 575 to 683 MPa after cryorolling. The cryorolled composites show better thermal stability. The cryorolling promotes the formation of deformation twins in the Cu layer, thereby increasing the strength of the composite. The zigzag interface with {112} <111> Cu||{112} <110> Nb orientation in ARB sample is transformed into a smooth interface with {110} <111> Cu||{001} <110> Nb orientation in cryorolled sample, improving thermal stability. [ABSTRACT FROM AUTHOR]

Porous materials with high specific surface area, high porosity, and high electrical conductivity are promising materials for functional applications, including catalysis, sensing, and energy storage. Molten salt dealloying was recently demonstrated in microwires as an alternative method to fabricate porous structures. The method takes advantage of the selective dissolution process introduced by impurities often observed in molten salt corrosion. This work further investigates molten salt dealloying in bulk Ni–20Cr alloy in both KCl–MgCl2 and KCl–NaCl salts at 700 ℃, using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction (XRD), as well as synchrotron X-ray nano-tomography. Micro-sized pores with irregular shapes and sizes ranging from sub-micron to several microns and ligaments formed during the process, while the molten salt dealloying was found to progress several microns into the bulk materials within 1–16 h, a relatively short reaction time, enhancing the practicality of using the method for synthesis. The ligament size increased from ~ 0.7 μm to ~ 1.3 μm in KCl–MgCl2 from 1 to 16 h due to coarsening, while remaining ~ 0.4 μm in KCl–NaCl during 16 h of exposure. The XRD analysis shows that the corrosion occurred primarily near the surface of the bulk sample, and Cr2O3 was identified as a corrosion product when the reaction was conducted in an air environment (controlled amount sealed in capillaries); thus surface oxides are likely to slow the morphological coarsening rate by hindering the surface diffusion in the dealloyed structure. 3D-connected pores and grain boundary corrosion were visualized by synchrotron X-ray nano-tomography. This study provides insights into the morphological and chemical evolution of molten salt dealloying in bulk materials, with a connection to molten salt corrosion concerns in the design of next-generation nuclear and solar energy power plants. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) display outstanding mechanical properties which make possible new technological applications. There are many studies of bulk HEAs, but here we focus on FeCrNiCuCo single-crystal face-centered cubic (FCC) samples with 40% and 50% nanoscale porosity, where the pores constrain plasticity. In order to disentangle the role of chemical complexity during deformation, we compare HEA samples to Average Atom (AA) samples with the same average properties as the HEA, but where all atoms are equivalent. Elastic modulus and plastic yielding are much higher than expected from Au nanofoam scaling predictions. We find that HEA and AA materials behave similarly to each other and to other FCC nanoporous samples until the point where failure begins. Deformation produces mostly partial dislocations that move and leave behind stacking faults crossing filaments, with sessile dislocations and some dislocation tangles forming due to the large plastic strain. Differences in sample failure modify the evolution of void and ligament size distributions. The AA sample presents ductile necking and ductile fracture of a few filaments, as in other single element FCC nanoporous samples. Failure in the HEA sample not only includes some ductile filaments fracture, but also brittle fracture of the filaments due to localized shear, which causes plane slippage, as identified by machine learning methods. Therefore, chemical complexity diminishes ductility in nanoporous FCC HEA samples. [ABSTRACT FROM AUTHOR]

Radiation damage in the nuclear structural components is a stochastic phenomenon in both length and time scales. In this work, molecular dynamics-based numerical simulations were employed to model and investigate the primary radiation damage within irradiated Cu specimens. Here, a single-crystal Cu specimen and two nanocrystalline specimens: hexagonal columnar grain Cu specimen with ∑3 and ∑9 GBs (CG Cu) and Cu specimen randomly oriented grain boundary (GBs) (RG Cu), were irradiated at 600 K at primary knock-on atom (PKA) energy magnitudes, EPKA = 10 keV, 20 keV, 30 keV, respectively. The equilibrium part of the long-range Finnis–Sinclair (FS)-type interatomic potential was smoothly conjoined with the universal short-range repulsive Ziegler–Biersack–Littmark potential to account for simulations of high-energy collisions. By investigating the evolution of point defects, defect cluster distribution, and dislocation analysis, it was observed that the irradiated nanostructured Cu specimens survived with comparatively lower defects at the end of cascade simulations. GB serves as the effective radiation sink junctions for the generated Frenkel pair defects. Secondly, the population of point defects increases with the increase in PKA energy magnitude and the annihilation rate. Therefore, polycrystalline irradiated Cu specimens can be favoured for potential radiation immune candidate in the next-generation nuclear reactor structural materials. [ABSTRACT FROM AUTHOR]

The objective of this study is to determine the effects of coupled deformation and irradiation extremes on Ta phase evolution in Cu-10at.%Ta nanocomposite. Heterophase nanocomposites with positive heat of mixing offer exceptional mechanical properties, high temperature performance, and irradiation tolerance. Here, we consider cooperative effects of irradiation and deformation on phase stability using transmission electron microscopy phase mapping during interrupted in situ indentation. Following irradiation-induced dissolution of Ta nanoparticles, deformation-induced Ta nanoparticle nucleation and growth occur along grain boundaries. This result shows promise that irradiation and deformation may be coupled to stabilize or rejuvenate Ta nanoparticles in extreme environments. [ABSTRACT FROM AUTHOR]

In many applications involving functional oxides, composite structures consisting of multiple oxides and interfaces between the two are of particular interest, as they provide enhanced properties over the individual phases. Often, materials intended for radioisotope immobilization are composite structures, consisting of multiple chemistries and structures. In this work, two pyrochlore materials, Gd 2 Zr 2 O 7 (GZO) and Gd 2 Ti 2 O 7 (GTO) are interfaced in a bilayer structure and irradiated to test the composite's capacity to accommodate lattice point defects and the potential for cation transport across the interface. Using x-ray energy dispersive spectroscopy after the pristine bilayer was irradiated to damage levels of 0.2–0.8 dpa using a 12 MeV Cu 4 + ion beam, significant cation intermixing was observed by the highest dose. While, as might be expected, the bulk of the GTO layer easily amorphized, surprisingly, the GZO layer also amorphized with arelatively small dose. More interestingly, the structure maintained a crystalline layer at the original interface between the two pyrochlores, even though the interface moved significantly during the irradiation. These results are explained through a physical model for ballistic mixing in pyrochlore. These results highlight the complex structural response of oxide heterostructures under extreme conditions. [ABSTRACT FROM AUTHOR]

Copper is under consideration as the optimum material for both high heat flux applications and high-frequency pulsed magnets. One challenge is that copper has low strength which is problematic to deployment in these applications. One solution is to alloy copper with body center cubic (BCC) elements to improve its mechanical properties. However, the limited solubility of the BCC elements in copper requires high deformation processes to be used in order to manufacture these 3D composites. In this work high-energy ball milling combined with high-pressure torsion was used to manufacture 3D Cu-Nb composites. After the consolidation, the mechanical properties of the composites were measured using micro-and nano-hardness testing at room and elevated temperatures. The results indicated that after 10 turns during the high-pressure torsion consolidation, the mechanical properties of the composites were completely saturated, displaying uniform properties across the manufactured disk. Performing the high-pressure torsion at elevated temperature further improved the consolidation of the disk. The high-temperature nanoindentation also indicated a change in the deformation mechanism between 200°C and 500°C. [ABSTRACT FROM AUTHOR]

This study examined the improvement of microscopy segmentation intersection over union accuracy by transfer learning from a large dataset of microscopy images called MicroNet. Many neural network encoder architectures were trained on over 100,000 labeled microscopy images from 54 material classes. These pre-trained encoders were then embedded into multiple segmentation architectures including UNet and DeepLabV3+ to evaluate segmentation performance on created benchmark microscopy datasets. Compared to ImageNet pre-training, models pre-trained on MicroNet generalized better to out-of-distribution micrographs taken under different imaging and sample conditions and were more accurate with less training data. When training with only a single Ni-superalloy image, pre-training on MicroNet produced a 72.2% reduction in relative intersection over union error. These results suggest that transfer learning from large in-domain datasets generate models with learned feature representations that are more useful for downstream tasks and will likely improve any microscopy image analysis technique that can leverage pre-trained encoders. [ABSTRACT FROM AUTHOR]

TiAl alloys are regarded as ideal lightweight structural materials above 600 °C and show remarkable application prospects in the field of aerospace materials. However, many potential TiAl alloy engineering applications have been limited by their low room-temperature tensile plasticity and insufficient high-temperature capability. Composite technology is an effective method for enhancing the comprehensive properties of TiAl alloys. In this paper, recent research progress in TiAl matrix composites is reviewed to highlight the scientific and technological investigation of TiAl matrix composites with excellent properties. The content includes four aspects of TiAl matrix composites: reinforcement selection, configuration design, interfacial microstructure, and processing technology. The aim of this work is to provide a reference for the preparation and research of TiAl matrix composites and open up a novel design direction for TiAl matrix composites with excellent comprehensive properties. [ABSTRACT FROM AUTHOR]

Irradiation using Fe ion at 300 °C up to 100 dpa was carried out on three variants of Grade 91 (G91) steel samples with different grain size ranges: fine-grained (FG, with blocky grains of a few micrometers long and a few hundred nanometers wide), ultrafine-grained (UFG, grain size of ~ 400 nm) and nanocrystalline (NC, lath grains of ~ 200 nm long and ~ 80 nm wide). Electron microscopy investigations indicate that NC G91 exhibit higher resistance to irradiation-induced defect formation than FG and UFG G91. In addition, nano-indentation studies reveal that irradiation-induced hardening is significantly lower in NC G91 than that in FG and UFG G91. Effective mitigation of irradiation damage was achieved in NC G91 steel in the current irradiation condition. [ABSTRACT FROM AUTHOR]

This work elucidates the effect of interface orientation, loading mode, and crystallography on the deformation mechanisms of Cu-Nb–multilayered nanocomposites. Molecular dynamics simulations of deformation behavior of accumulative roll-bonded Cu-Nb–multilayered nanocomposites (MNCs) were performed at room temperature conditions and at a constant strain rate under iso-stress and iso-strain conditions. Interface deformation mechanisms involving nucleation of partial dislocation at the interface and gliding in the Cu layer were observed under iso-stress and iso-strain conditions. Uniaxial stress–strain curves were analyzed for tension and compression under iso-stress and iso-strain loading conditions. The stress–strain plots were explored to understand the elastic, yield, and post-yielding behavior of Cu-Nb MNCs. Under compression with interface orientation normal to the loading direction, twin nucleated via gliding of partial dislocations. Under tension in the iso-stress case, only slip-assisted deformation was observed. Conversely, the deformation behavior under compression and tension was via slip and twinning, respectively, for iso-strain conditions. [ABSTRACT FROM AUTHOR]