Effect Of Microstructure Research Articles

Internal erosion characteristics and microstructure effects of undisturbed loess

Internal erosion characteristics and microstructure effects of undisturbed loess

Data-Driven Surrogate Modeling with Microstructure-Sensitivity of Viscoplastic Creep in Grade 91 Steel

AbstractTo support the development of advanced steel alloys tailored to withstand extreme conditions, it is imperative to account for the mechanical performance of components, while considering the influence of local microstructure on the macroscopic response. To this end, this study focuses on the development of microstructure-sensitive constitutive models for the mechanical response of Grade 91 steel exposed to extreme thermo-mechanical environments. Polynomial chaos expansion (PCE) surrogates are used to emulate high-fidelity polycrystal simulations of the viscoplastic response of Grade 91 steel as a function of the microstructure fingerprint (e.g., dislocations and precipitates). To cover a wide temperature–stress domain, two separate PCE surrogates—one that captures softening and the other that captures hardening behavior—are combined using another (sparse) Gaussian process regression model. The resulting constitutive creep surrogate model is integrated within the MOOSE finite element framework to simulate the intricate effects of microstructure, in particular MX-phase precipitates, on a component with a graded microstructure. Surrogate sensitivity analysis is applied to quantify the relevant impact of spatially varying microstructure on the creep response in a test-case involving a Grade 91 alloy with a prototypical weld.

Subacute Toxicity Study of Alchornea cordifolia Ethanolic Leaf Extract on the Pituitary Gland of Wistar Rats

Introduction: Herbal medicines are plant-based products used to treat various illnesses and their uses have dramatically increased over the past years in many developed and developing nations. Alchornea cordifolia is one of these plants with reports of its use in health promotion. Some plants exhibit toxicity due to the presence of phytochemicals inherent in them, therefore further studies are necessary in evaluating their toxicity levels. In this study, the sub-acute toxicity of ethanolic extract of Alchornea cordifolia leaves was investigated on the pituitary gland of adult male Wistar rats. The objective was to determine its effect on the histology of the anterior pituitary gland. Methods: Twenty (20) adult male Wistar rats weighing 140-200 were used for the research and were randomly divided into four groups labelled A, B, C. and D. Each group consisted of five (5) rats. Group A (normal control) received normal saline, while group B, C and D received 500 mg/kg, 1,000 mg/kg and 1,500 mg/kg body weight of Alchornea cordifolia extract respectively with the aid of an oral gavage. This was done for a duration of 28 days after which the rats were sacrificed and the pituitary gland obtained for histological analysis using H&E and PAS Orange G staining methods. Results: Histological observations showed that the various doses of the extract used had no detrimental effect of the anterior pituitary gland microstructure in groups B, C, and D when compared to group A. Conclusion: The findings showed that the various doses of Alchornea cordifolia leaf extract used in this study are non-toxic to the anterior pituitary gland in Wistar rats.

Effect of Microstructure on Chemo-Mechanical Damage Evolution in Aluminum Foil Anodes for Lithium-Ion Batteries

Aluminum-based foil anodes could enable lithium-ion batteries with high energy density comparable to silicon and lithium metal. However, mechanical pulverization and lithium trapping within aluminum tend to cause capacity fading. The complex interplay between these damage modes is not well understood, as well as the role of microstructure on reaction front evolution. Here, we investigate aluminum foils with different compositions and processing conditions to understand how microstructure influences chemo-mechanical degradation. Backscattered electron imaging of ion-milled foil cross sections is used to visualize reaction front evolution and chemo-mechanical degradation. We find that the shape of the reaction front during lithiation is strongly affected by foil composition, defect distribution, and grain size, which, in turn, affects the evolution of chemo-mechanical damage within the foils. Furthermore, a key finding is that the extent of fracture upon delithiation is inversely related to lithium trapping, with foil compositions that exhibit uniform lithiation, and therefore, less fracturing showing greater lithium trapping. Nonreactive precipitate inclusions within alloy foils are also found to induce void formation. This work shows that material design strategies designed to overcome the inverse fracture-lithium trapping relationship could be useful for improving performance. Published by the American Physical Society 2024

Effect of microstructure on dynamic response of ferrite matrixed steel at high strain rates

Dynamic response of steels at high strain rates are of great practical significance for understanding mechanical structures under extreme load conditions. To explore the relationship between structure and stress during dynamic deformation at high strain rates, steel specimens were prepared with varied microstructures of ferrite, ferrite and pearlite, and ferrite and spherical carbide. It is revealed that different microstructured steels exhibit drastically different characteristic of waves excited by the instantaneous impact of a servo-hydraulic tensile testing. It is also observed that a beat frequency response exists under dynamic deformation at certain high strain rates. It is therefore proposed that dynamic plastic deformation starts with stress fluctuation with a dislocation damped vibration model, and two successively excited waves are superimposed to form the beat frequency response.

Effect of microstructure and texture gradient on the backscattered ultrasound amplitude of Ti-6Al-4V bars for aeroengine blade

Effect of microstructure and texture gradient on the backscattered ultrasound amplitude of Ti-6Al-4V bars for aeroengine blade

Low-velocity impact of castor oil-based rigid polyurethane foams: Experiments, microstructure effects and constitutive modelling

Low-velocity impact of castor oil-based rigid polyurethane foams: Experiments, microstructure effects and constitutive modelling

Effect of matrix microstructure on micro- and macro- mechanical properties of 2.5D woven oxide fiber reinforced oxide matrix composites

A comprehensive learning of the mechanical behavior change mechanism of oxide/oxide composites is of great significance as a guide for their industrial applications. This study focused on examining how matrix microstructure impacted the micro- and macro- mechanical properties of the composites mainly by nanoindentation tests, macro-mechanical tests and x-ray computed tomography. The results showed that the sintering phenomenon of matrix sintered at 1200 ºC was more obvious, and there were visible transverse and longitudinal cracks. The in-situ modulus of matrix and interfacial shear modulus of the composite increased by 61.1% and 36.4%, respectively, with the increase of matrix sintering densification. Combined with these micro-mechanical parameters of the composites, the He-Hutchinson model predicted the same crack propagation modes as those obtained from fracture toughness tests. Moreover, more matrix cracks directly led to a 45.4% reduction in the flexural strength of the composites sintered at 1200 ºC compared to that sintered at 1100 ºC. In addition, a comparison analysis was conducted on the evolution of microstructure, micro- and macro- mechanical properties of 2.5D and 2D composites with the same preparation parameters.

A distinct role of microstructure on hot corrosion behaviour of additively manufactured IN718

The effect of LPBF-IN718 microstructure on hot corrosion behavior was studied at 650 °C. H-IN718 with <001> oriented grains demonstrate more weight changes than V-IN718 with <110> oriented grains. Detailed characterization analysis corroborates that Rapp-Goto fluxing and sulphidation mechanisms are operating in LPBF-IN718 with 3SM. Further, GDOES confirms the sulphur gradient existence between Air/3SM and 3SM/H-IN718 interfaces. It suggests that <001> oriented grains serve as preferred sites for ion adsorption and reactions, which might facilitate the sulfur diffusion more effectively than other grain orientations. As a result, oxy-anions generated during sulfidation enhance the fluxing mechanism, increasing weight gain in H-IN718.

Adiabatic Shear Localization in Metallic Materials: Review

In advanced engineering applications, there has been an increasing demand for the service performance of materials under high-strain-rate conditions where a key phenomenon of adiabatic shear instability is inevitably involved. The presence of adiabatic shear instability is typically associated with large shear strains, high strain rates, and elevated temperatures. Significant plastic deformation that concentrates within a adiabatic shear band (ASB) often results in catastrophic failure, and it is necessary to avoid the occurrence of such a phenomenon in most areas. However, in certain areas, such as high-speed machining and self-sharpening projectile penetration, this phenomenon can be exploited. The thermal softening effect and microstructural softening effect are widely recognized as the foundational theories for the formation of ASB. Thus, elucidating various complex deformation mechanisms under thermomechanical coupling along with changes in temperatures in the shear instability process has become a focal point of research. This review highlights these two important aspects and examines the development of relevant theories and experimental results, identifying key challenges faced in this field of study. Furthermore, advancements in modern experimental characterization and computational technologies, which lead to a deeper understanding of the adiabatic shear instability phenomenon, have also been summarized.

Limitation and Potential of Lignin-Assisted Stabilisation of Oriented Liquid Crystalline Cellulosic Mesophase

This study aimed at progressing in the fundamental understanding of the lignin-assisted microstructural stabilisation observed in solution-processed materials based on the polymer blend of hydroxypropyl cellulose and hardwood organosolv lignin. Mechanical analysis, polarised infrared spectroscopy and wide-angle X-ray scattering of shear cast blend films revealed that the effect of lignin on the flow-oriented cellulosic mesophase is also valid for blends composed of ethyl cellulose as liquid crystalline matrix polymer and lignin derived oligomers from base-catalysed depolymerisation as dispersed “microstructural cementing agent”. The results underline the significant role of the solvent diffusion between the continuous cellulosic and the dispersed lignin phase, which is ascribed to polymer-/oligomer-solvent interactions. An abundance of the solvent within the lignin phase caused the disruption of the microstructural stabilisation effect. The concept of a balanced proton-donor activity was introduced linking the solvent diffusion with the lyotropic liquid crystalline phase formation, the macro- and microstructural blend morphology and aspects regarding the solution processing.

The effect of microstructure of an advanced duplex stainless steel on the pitting corrosion and chloride-induced stress corrosion cracking resistance

The effect of austenite morphology on the corrosion resistance of a newly-developed advanced duplex stainless steel (ADCS) was evaluated by electrochemical and chloride-induced stress corrosion cracking (CISCC) tests. By properly controlling heat treatment conditions, equiaxed (EQ) and elongated (EL) austenites were formed in ferrite matrix. ADCS-EQ exhibited higher pitting potential than ADCS-EL, primarily owing to less phase boundary. Meanwhile, ADCS-EL showed better CISCC resistance than ADCS-EQ, as the elongated austenite inhibited selective dissolution. Overall, the CISCC resistance of ADCS was more affected by austenite morphology and orientation, and would not be in accordance with pitting corrosion resistance.

Hierarchical Assembly of Ternary MOF-Derived Sandwich Composites for High-Efficiency Tunable Electromagnetic Wave Absorption.

The proliferation of electronic devices drives the adoption of electromagnetic wave (EMW) absorbing materials to mitigate electromagnetic pollution. Metal-organic frameworks (MOFs) reveal great potential in EMW absorption field due to their unique pore structure and outstanding physicochemical properties. However, single MOFs are difficult to achieve both efficient absorption and wide frequency coverage owing to the limited electromagnetic properties and structural composition. Herein, a sandwich-like ternary MOF composite is successfully synthesized through a hierarchical assembly strategy. Following high-temperature treatment, the materials are converted into nitrogen-doped porous carbon with magnetic metals, non-magnetic metal oxides, and carbon nanotubes on the surface (labeled as TiO2/C@Co/N/C@CNT). The unique sandwich structure of the resulting derivatives provides a multi-level microstructure and multi-component synergistic effects, significantly enhancing electromagnetic wave absorption capabilities and broadening the effective absorption bandwidth (EAB). At 1.8 mm matching thicknesses, the material achieves a reflection loss of -56.3 dB and a 6.6 GHz EAB. Adjusting the matching thicknesses to 2.3 and 3.1 mm extends the EAB to 6.1-18 GHz, with absorption peaks of -47.6 and -47.1 dB. This work offers a novel guidance for constructing advanced MOF-derived materials with ultra-broadband EAB and strong EMW absorption through meticulous structural design and multiple components combination.

Microstructural and Oxidation Effects of Nb Additions to U3Si2

U3Si2 is a long term, accident-tolerant nuclear fuel candidate for light-water reactors because of its superior thermal conductivity and increased uranium density when compared to traditional uranium dioxide (UO2). While reducing internal thermal stresses and increasing efficiency, U3Si2 exhibits energetic oxidation during certain off-normal and accident scenarios, which include coolant or steam exposure. To mitigate this, Nb is investigated as an alloy constituent to enhance corrosion resistance and increase mechanical strength. The work presented investigates the response of Nb-alloyed U3Si2 to steam atmospheres. A thermogravimetric analysis is conducted in flowing steam to T &gt; 1000 °C to assess oxidation resistance. The phase characterization of as-melted, thermally annealed and post-oxidation compositions with up to 12 vol% Nb by powder X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy is reported.

Microstructural and chemical effects of the argon cluster bombardment on a single crystal KGd(WO4)2 surface

Microstructural and chemical effects of the argon cluster bombardment on a single crystal KGd(WO4)2 surface

Interaction of propagating crack with microstructure in CGI: In situ tensile test and numerical simulation

Compacted graphite iron (CGI) is a double-phase material, in which complex graphite morphology greatly influences crack initiation and propagation. Despite its wide use and considerable past research on the fracture behaviour of CGI, the understanding of the interaction of propagating cracks with CGI's microstructure is still limited. In this study, a novel method is employed that integrates scanning electron microscopy (SEM) and an optical high-speed camera. This approach allows the clear visualisation of microstructures before and after fracture, as well as the calculation of crack-propagation rate during tensile tests. It is also revealed for the first time that in the case of graphite particles situated at a specific distance from the primary crack path, the initiation of secondary micro-cracks, near particles does not occur. A critical distance from the main crack path for crack initiation is analysed. Further, finite-element simulations are developed to study the effect of microstructure on the fracture behaviour of the tested microstructures. A Johnson-Cook (JC) damage model is calibrated and used in all simulations. The crack path and velocity of simulation results are in good agreement with the experimental data, demonstrating that the JC damage model can be used to predict the crack initiation and propagation of CGI. It is found that interface debonding and crack initiation always tend to appear near the tip of vermicular graphite. Thus, large vermicular graphite particles can affect negatively the toughness of CGI. Graphite particles situated farther from the primary crack significantly reduce the likelihood of crack initiation in that specific location. Furthermore, large nodular graphite particles absorb energy and generate secondary cracks, while small graphite particles have little effect on the crack-path direction. The newly discovered fracture mechanisms and simulation results provide new insights for the design and manufacture of metal-matrix composites (e.g., Al/SiC) with optimal mechanical properties.

Determination of the REV size for heterogeneous rocks with different grain sizes: Deep learning and numerical approaches

Accurate determination of the representative elementary volume (REV) size plays a pivotal role in analysing the mechanical properties and failure processes of heterogeneous rocks in complex engineering environments. In this study, a novel microstructure modelling strategy (NMMS) for determining the REV size is proposed by combining deep learning and an improved phase-field method (PFM). Micro- and macroscale experiments are systematically conducted to determine the real microstructural characteristics and mechanical properties of heterogeneous rocks with different grain sizes. On the basis of this experimental evidence, geometric models of different sizes were reconstructed through deep learning to avoid the limitations of human-based methods, and an improved PFM was used for numerical calculations. These models were then employed to perform numerical tests under uniaxial loading conditions, and the coefficient of variation was introduced to determine the REV size of heterogeneous rocks with different grain sizes. The research findings indicate that the final REV size is the maximum value of the REVs defined by the evaluation properties within an acceptable coefficient of variation. At a criterion of 5% for the coefficient of variation, the REV sizes are 60 mm×60 mm, 70 mm×70 mm, and 90 mm×90 mm for fine-medium-grained (FMG), medium-grained (MG), and coarse-grained (CG) rocks, respectively. Furthermore, the REV determined by the NMMS was applied to investigate the effects of microstructure on macromechanical properties and damage evolution under triaxial loading conditions. The numerical results show that the NMMS can accurately predict the macromechanical properties and microcracking patterns of heterogeneous rocks, especially the intracrystalline cracks in feldspar, the interfacial cracks in gravel, and the “voids” of cracks in biotite. This research can provide some basic references for the optimal choice of the REV size of heterogeneous rocks.

Effects of Initial Microstructure on Mechanical Properties of AA1050/AA2024 Laminated Metal Composite Fabricated by Accumulative Roll Bonding Process

Effects of Initial Microstructure on Mechanical Properties of AA1050/AA2024 Laminated Metal Composite Fabricated by Accumulative Roll Bonding Process

Modulating NFO@N‐MWCNTs/CC Interfaces to Construct Multilevel Synergistic Sites (Ni/Fe‐O‐N‐C) for Multi‐Heavy Metal Ions Sensing

AbstractA hierarchical heterogeneous composite electrode of NiFe2O4@nitrogen‐doped multi‐walled carbon nanotubes/carbon cloth (NFO@N‐MWCNTs/CC) is prepared via a dip‐coating method, followed by a hydrothermal process. The flexible carbon cloth (CC) substrate provides robust support and the cross‐linked nitrogen‐doped multi‐walled carbon nanotubes (N‐MWCNTs) on the CC form a highly porous network with a large specific area that facilitates electron‐transfer. The stable support strengthens the framework and prevents pore structure disorder within the porous network, that could lead to the structural instability of the active sites. The decorated NiFe2O4 nanoparticles offer abundant active sites for enhanced electrocatalytic activity. Benefiting from the synergistic effect of the 3D hierarchical heterogeneous microstructure and multilevel bimetallic oxide active site (Ni/Fe‐O‐N‐C) constructs, the NFO@N‐MWCNTs/CC electrode achieves stable detection of multiple heavy metal ions (HMIs) with high reproducibility. The modified electrode allowed stable detection of multiple heavy metal ions with high reproducibility. The sensitivities of the electrode for Cd(II), Pb(II), Bi(III), and Hg(II) are 344.98, 441.02, 176.484, and 371.099 µA µm−1, respectively. The assay recoveries ranged from 95.3% to 106.8%, highlighting its practical applicability. This study provides innovative composites and theoretical insights to facilitate further advances in the simultaneous high‐performance detection of heavy metal ions.

Thermal cycling performance of GYbZ/YSZ thermal barrier coatings with different microstructures based on finite element simulation

Three (Gd0.9Yb0.1)2Zr2O7/YSZ double ceramic layer (DCL) thermal barrier coatings (TBCs) with different microstructures were manufactured by electron-beam physical vapor deposition (EB-PVD). The thermal cycling behavior of the three TBCs was evaluated comparatively at 1150 ℃. The results showed that TBCs with small columnar grains exhibited the best thermal cycling performance among all the tested TBCs. The effect of microstructure on thermal cycling behavior, including crack evolution and failure mode was discussed. A finite element model tailored to the microstructural characteristics of the DCL coatings was established. Several in-plane stress concentration points appeared in the taller GYbZ column due to discontinuities in strain tolerance resulting from sudden structural or compositional changes. Analysis of the strain energy release rate variation for each concentration point suggested that the predicted delamination position and process aligned with experimental results.