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This study investigated the inclusion of magnesium silicate monohydrate (MSMH) crystal in MgO–SiO 2 mixes designed for extrusion-based 3D printing. Considering the adjustment and optimization of rheological properties are fundamental for the printability of cement pastes, the dynamic rheology, thixotropy and strength development of the prepared mixes were analyzed to characterize their fresh properties, workability, buildability, and mechanical performance. Furthermore, isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TG/DTG), and scanning electron microscopy (SEM) were employed to investigate the phase composition and microstructural evolution of the pastes, with and without the presence of MSMH. Addition of MSMH at 2 % of the binder component significantly enhanced the plastic viscosity, dynamic yield stress and thixotropy. Pastes incorporating 2 % MSMH exhibited excellent structural build-up without affecting extrudability, with a minimal strain deformation in the printed structure. The compressive strength of all pastes exceeded 20 MPa after 3 days, reaching ∼50 MPa at 28 days with 2 % MSMH inclusion. The introduction of MSMH improved the peak heat flow measured by isothermal calorimetry and enhanced the formation and growth of hydration products after 7 days of curing, resulting in a more compact microstructure. [ABSTRACT FROM AUTHOR]

The thermo-mechanical stress, which was a combination of thermal stress from rapid temperature changed and dynamic mechanical stress from scrap impact, accelerated the damage to MgO–C refractories during service. The influence of graphite content (8 wt% and 16 wt%), heat treatment temperature, and oxidation level (partially oxidized or not) on dynamic mechanical stress damage behavior was investigated using the Split-Hopkinson pressure bar test at various loading velocities. The results indicated the SHPB test could form dynamic stress, and the parameters obtained post-test could characterize the dynamic mechanical properties of MgO–C refractories. Furthermore, all of the specimens' dynamic compressive strength clearly demonstrated the strain rate hardening effect; this phenomenon was particularly evident in the low-graphite specimens. Additionally, the thermally treated specimens dissipated impact energy by destroying the whole volume, whereas the oxidized specimens suffered damage layer by layer, and the specimens' dynamic mechanical characteristics were weakened by oxidization or heat treatment. [ABSTRACT FROM AUTHOR]

This study presents a method to characterize anisotropic microcracks and discontinuous bedding in rock using the discrete element method (DEM). We focus on the influence of microstructure on P-wave velocity anisotropy under both isotropic and anisotropic stress states. The methodology is applied to three experimentally calibrated models: a homogeneous model, a bedding model, and a crack model. Thomsen's parameters are utilized for analyzing P-wave velocity anisotropy. The results indicate that the response of particle motion to seismic waves, cracks, and bedding structures are key inducers of anisotropy in sedimentary rocks. Under isotropic stress, particle motion patterns being different in diverse directions lead to a weak anisotropy. Interestingly, in a homogeneous model, horizontal P-wave velocity slightly exceeds the perpendicular direction velocity because of that motion. Preset crack closure modifies the anisotropy, with bedding direction influencing the final orientation of the symmetry axis. Consistency between preexisting crack and bedding directions leads to a decrease in the anisotropy coefficient with increased confining stress, while an initial decrease followed by an increase occurs otherwise. Under anisotropic stress, bedding and cracks aligned perpendicular to the loading direction more effectively increase anisotropy compared to other orientations. A consistent increase in anisotropy is observed when induced cracks exceed 40% of the total crack number at peak stress due to anisotropic cracks enlarging the difference of P-wave velocity. An anisotropy reversal is noted when bedding orientation does not align with principal stress. Additionally, increased lateral compression reduces the anisotropy parameter ε in sedimentary rock with perpendicular bedding. Highlights: A DEM method to characterize anisotropic microcracks and discontinuous bedding in sedimentary rocks is developed. Under isotropic stress, a homogeneous rock model still presents a weak anisotropy due to particle motion pattern in diverse directions. Under anisotropic stress, bedding and cracks aligned perpendicular to the loading direction more effectively increase anisotropy compared to other orientations. A consistent increase in anisotropy is observed when induced cracks exceed 40% of the total crack number at peak stress. [ABSTRACT FROM AUTHOR]

For this article, hot compression tests were carried out on homogenized 2050 Al-Cu-Li alloys under different deformation temperatures and strain rates, and an Arrhenius-type constitutive model with strain compensation was established to accurately describe the alloy flow behavior. Furthermore, thermal processing maps were created and the deformation mechanisms in different working regions were revealed by microstructural characterization. The results showed that most of the deformed grains orientated toward <101>//CD (CD: compression direction) during the hot compression process, and, together with some dynamic recovery (DRV), dynamic recrystallization (DRX) occurred. The appearance of large-scale DRX grains at low temperatures rather than in high-temperature conditions is related to the particle-stimulated nucleation mechanism, due to the dynamic precipitation that occurs during the deformation process. The hot-working diagrams with a true strain of 0.8 indicated that the high strain-rate regions C (300 °C–400 °C, 0.1–1 s−1) and D (440 °C–500 °C, 0.1–1 s−1) are unfavorable for the processing of 2050 Al-Li alloys, owing to the flow instability caused by local deformation banding, microcracks, and micro-voids. The optimum processing region was considered to be 430 °C–500 °C and 0.1 s−1–0.001 s−1, with a dissipation efficiency of more than 30%, dominated by DRV and DRX; the DRX mechanisms are DDRX and CDRX. [ABSTRACT FROM AUTHOR]

Due to its exceptional mechanical and chemical properties at high temperatures, Inconel 718 is extensively utilized in industries such as aerospace, aviation, and marine. Investigating the flow behavior of Inconel 718 under high strain rates and high temperatures is vital for comprehending the dynamic characteristics of the material in manufacturing processes. This paper introduces a physics-based constitutive model that accounts for dislocation motion and its density evolution, capable of simulating the plastic behavior of Inconel 718 during large strain deformations caused by machining processes. Utilizing a microstructure-based flow stress model, the machinability of Inconel 718 in terms of cutting forces and temperatures is quantitatively predicted and compared with results from orthogonal cutting experiments. The model's predictive precision, with a margin of error between 5 and 8%, ensures reliable consistency and enhances our comprehension of the high-speed machining dynamics of Inconel 718 components. [ABSTRACT FROM AUTHOR]

Lightweight thin-walled parts are widely used in the aviation and aerospace industries, and with the further increase in the complexity of their features, the traditional manufacturing process can no longer fully meet the high requirements of industrial component manufacturing. In this work, thin-walled parts are processed by Laser based powder bed fusion of metals (PBF-LB/M), and the effects of process parameters on residual stress, hardness, mechanical properties and microstructure of thin-walled parts are systematically investigated. The simulation results show that the maximum equivalent residual stresses are distributed in the combination of the solid and the substrate, and the minimum equivalent residual stresses are mainly distributed in the top two ends and the middle part of the solid, and the stress distribution is symmetrical. In addition, the maximum equivalent residual stress increases with the increase of laser power, and decreases with the increase of scanning spacing or scanning speed. The experimental results show that with the increase of laser energy density, the tensile strength and yield strength of thin-walled parts show a tendency of increasing first and then decreasing. Finally, high-quality thin-walled parts were successfully fabricated by the optimized process parameters, and their tensile and yield strengths were increased by 6.1% and 15.9%, respectively. [ABSTRACT FROM AUTHOR]

As the size of a layered structure scales down, the adhesive layer thickness correspondingly decreases from macro- to micro-scale. The influence of the material microstructure of the adhesive becomes more pronounced, and possible size effect phenomena can appear. This paper describes the mechanical behaviour of composites made of two solids, bonded together by a thin layer, in the framework of strain gradient and micropolar elasticity. The adhesive layer is assumed to have the same stiffness properties as the adherents. By means of the asymptotic methods, the contact laws are derived at order 0 and order 1. These conditions represent a formal generalization of the hard elastic interface conditions. A simple benchmark equilibrium problem (a three-layer composite micro-bar subjected to an axial load) is developed to numerically assess the asymptotic model. Size effects and non-local phenomena, owing to high strain concentrations at the edges, are highlighted. The example proves the efficiency of the proposed approach in designing micro-scale-layered devices. This article is part of the theme issue 'Non-smooth variational problems with applications in mechanics'. [ABSTRACT FROM AUTHOR]

Graphene/copper composites are promising in electronic and energy fields due to their superior conductivity, but microstructure control during thermal mechanical processing (TMP) remains a crucial issue for the manufacturing of high-performance graphene/copper composites. In this study, the hot deformation behavior of graphene/copper composites was investigated by isothermal compression tests at deformation temperatures of 700~850 °C and strain rates of 0.01~10 s−1, and a constitutive equation based on the Arrhenius model and hot processing map was established. Results demonstrate that the deformation mechanism of the graphene/copper composites mainly involves dynamic recrystallization (DRX), and such DRX-mediated deformation behavior can be accurately described by the established Arrhenius model. In addition, it was found that the strain rate has a stronger impact on the DRX grain size than the deformation temperature. The optimum deformation temperature and strain rate were determined to be 800 °C and 1 s−1, respectively, with which a uniform microstructure with fine grains can be obtained. [ABSTRACT FROM AUTHOR]

Flexoelectricity is the universal electric polarization of dielectrics upon exertion of a non‐uniform strain gradient. With the advancement of nano‐technology and miniaturization of electronic devices, flexoelectricity holds the promise to address the power requirements for such device operation. The direct flexoelectric effect in liquid crystal (LC) embedded poly(vinylidene fluoride) (PVDF) polymer films is examined for the first time by the application of external strain on the films. Physical characterizations such as Differential Scanning Calorimetry (DSC), dielectric spectroscopy, X‐ray diffraction, and field emission scanning electron microscopy (FESEM) are carried out to study the composite films' intrinsic and extrinsic properties like dielectric, crystallinity, and morphologies. The value of the flexoelectric coefficient (μ12) increases with the concentration of LC incorporation. At 3 wt%, μ12 attains a maximum value of 68 nC m−1, which is more than a threefold increase compared to that of the pure PVDF film. The role of Maxwell–Wagner–Sillars (MWS) polarization in determining flexoelectric polarization in polymer composites is also discussed. Moreover, the influence of the microstructure and domain size formation in determining the flexoelectric response are discussed in detail to infer the behavior of the flexoelectric coefficients of the films. Potential device applications based on this phenomenon have been proposed for future research in sensing and actuation. [ABSTRACT FROM AUTHOR]

Antigorite occurs at seismogenic depth along plate boundary shear zones, particularly in subduction and oceanic transform settings, and has been suggested to control a low‐strength bulk rheology. To constrain dominant deformation mechanisms, we perform hydrothermal ring‐shear experiments on antigorite and antigorite‐quartz mixtures at temperatures between 20 and 500°C at 150 MPa effective normal stress. Pure antigorite is strain hardening, with frictional coefficient (μ) > 0.5, and developed cataclastic microstructures. In contrast, antigorite‐quartz mixtures (10% quartz) are strain weakening with μ decreasing with temperature from 0.36 at 200°C to 0.22 at 500°C. Antigorite‐quartz mixtures developed foliation similar to natural serpentinite shear zones. Although antigorite‐quartz reactions may form mechanically weak talc, we only find small, localized amounts of talc in our deformed samples, and room temperature friction is higher than expected for talc. Instead, we propose that the observed weakening at temperatures ≥200°C primarily results from silica dissolution leading to a lowered pore‐fluid pH that increases antigorite solubility and dissolution rate and thus the rate of dissolution‐precipitation creep. We suggest that under our experimental conditions, efficient dissolution‐precipitation creep coupled to grain boundary sliding results in a mechanically weak frictional‐viscous rheology. Antigorite with this rheology is much weaker than antigorite deforming frictionally, and strength is sensitive to effective normal stress and strain rate. The activation of dissolution‐precipitation in antigorite may allow steady or transient creep at low driving stress where antigorite solubility and dissolution rate are high relative to strain rate, for example, in faults juxtaposing serpentinite with quartz‐bearing rocks. Plain Language Summary: Some major, plate‐boundary fault zones are very weak, and in some places this is thought to be because they contain the mineral serpentine. Antigorite is a common form of serpentine at depth, but in many rock deformation experiments, antigorite is found to be relatively strong. In natural fault zones, however, antigorite can be highly deformed at seemingly low stress. The motivation for this study was to explore whether antigorite can be weak also in the laboratory. Because laboratory experiments occur relatively fast, the mechanism of deformation may be different from in nature. To address this, we mixed antigorite with quartz, which changes the pH and promotes dissolution of antigorite. We found that when deforming antigorite mixed with quartz, the experimental fault was very weak, because the dissolution of antigorite removed sticking points ‐ a process that is also documented in natural faults. The experiments also produced minor talc, from the reaction of antigorite with quartz, but too little to affect strength. We suggest that it is the activation of dissolution and precipitation of antigorite which allows deformation of major serpentine‐bearing faults at low stress at temperatures of several hundred degrees Celsius. Key Points: At 20°C and 500°C antigorite is strain‐hardening, develops cataclastic microstructures and has a frictional coefficient of ∼0.5Samples of antigorite mixed with quartz are strain‐weakening, and the friction coefficient decreases from 0.36 at 200°C to 0.22 at 500°CThe weakness of quartz‐antigorite is associated with activation of dissolution‐precipitation creep [ABSTRACT FROM AUTHOR]

By employing the strain gradient elasticity theory, we investigate the propagation of in-plane surface waves in a coated half-space with microstructures. We first investigate the general case of the present problem, that is, both the surface layer and the half-space are described by the strain-gradient elasticity theory. We formulate the boundary and continuity conditions of the general case and derive the dispersion relations of the surface waves. Then we investigate two special cases: (1) the surface layer is described by the strain-gradient elasticity theory, while the half-space by the classical elasticity theory; (2) the surface layer is described by the classical elasticity theory while the half-space by the strain-gradient elasticity theory. We examine the effects of strain-gradient characteristic lengths on the dispersion curves of surface waves in all cases. This study helps to further understand the propagation characteristics of elastic waves in materials with microstructures. [ABSTRACT FROM AUTHOR]

Crack-free Al–Zn–Mg–Cu alloy, processed by laser powder bed fusion, displays a characteristic microstructure comprising fine equiaxed grains (EGs) and coarse columnar grains (CGs). Notably, the CGs show a high hardness compared to EGs due to the high density of in-situ precipitates. Analysis of mechanical properties takes into account the precipitates in the grain and hierarchical differences in grain morphologies near the melt pool boundary. Strengthening mechanisms are elucidated through synergistic hetero-deformation-induced strengthening, where multi-modal-sized EGs induce significant strain gradients within EG regions. Our findings demonstrate the potential to enhance strength of Al–Zn–Mg–Cu-based alloy in as-built state through architecting microstructures. The Al–Zn–Mg–Cu alloy, fabricated by laser powder bed fusion, exhibiting hierarchical microstructure consisting of hard coarse and soft fine grains shows synergistic in-situ precipitation and hetero-deformation-induced strengthening. [ABSTRACT FROM AUTHOR]

Continuous dynamic recrystallization (CDRX) forms a new recrystallized microstructure through the progressive increase in low-angle boundary misorientations (LAGBs) during the hot forming of metallic materials with high stacking fault energy (SFE), such as aluminum alloys. The present work investigates the effect of deformation parameters on the evolution of the dynamic recrystallization microstructures of an AA1050 aluminum alloy during compression at elevated temperatures. The alloy microstructure is investigated at deformation temperatures and strain rates in the range of 300 °C to 500 °C and 0.001 to 0.8 s−1. A well-defined substructure and subsequent DRX grains provide indication that recrystallization can proceed with continued strain under high-temperature compression. At a strain rate of 0.1 s−1, the DRX fraction is observed to be 0.25 at a temperature of 300 °C. This fraction increases to 0.32 as the temperature rises to 400 °C. The recrystallization mechanism is identified by analyzing the flow stress, the evolution of the subgrain misorientation angle, and the distribution of recrystallized grains. The observations of discontinuous dynamic recrystallization (DDRX) and CDRX under various deformation parameters are discussed. Moreover, the main substructure evolution laws observed from the high-temperature compression of an AA1050 Al alloy are summarized. [ABSTRACT FROM AUTHOR]

Compared with conventional isothermal creep aging (ICA), non‐ICA (NICA) does not involve a prolonged holding stage, but only has heating and cooling stages. During the NICA process, the precipitates nucleate and grow up in the early part of heating stage, resulting in fluctuations in creep rate and an increase in strength. The coarsening of precipitates in the later part of the heating stage can lead to significant increase of creep rate. Upon approaching the peak temperature, the dissolution of the precipitates occurs in conjunction with a partial coarsening of the remaining precipitates, causing a reduction in strength. However, the secondary precipitation during the cooling stage facilitates a significant strength enhancement in a relatively shorter period. In contrast to the ICA, the targeted NICA treatment gives an increase in ultimate strength while improves the stress corrosion cracking resistance. Moreover, the time required for NICA to obtain ultimate strength is only 13.9% of that of the ICA treatment. A large amount of creep strain can be generated during the NICA process, which is equivalent to 630% of that of creep age forming treatment. [ABSTRACT FROM AUTHOR]

Hexagonal close-packed (HCP) metals, particularly Zirconium (Zr), Titanium (Ti), and Magnesium (Mg) alloys, have attracted significant attention due to their unique properties and wide-ranging applications in the aerospace, biomedical, and energy industries. This review paper provides a comprehensive analysis of the microstructural and textural evolution in these HCP materials under various conditions, including rolling, extrusion, drawing, and annealing. The focus of the present work lies on the deformed microstructure and texture development in HCP metals, thus elucidating the fundamental mechanisms that govern their response to mechanical stress. The interaction between dislocation movements, twinning, and slip systems is discussed in detail, illustrating how these factors contribute to the anisotropic behavior characteristic of low-symmetry HCP structures. Unlike high-symmetry metals, deformation in Zr alloys depends on the activation of various slips and twin deformation modes, which are sensitive to crystallographic orientation and strain. Like Zr, Ti alloys present a more complex deformation behavior, heavily influenced by their crystallographic orientation. The most common deformation textures in Ti alloys include split-transverse direction (split-TD), split-rolling direction (split-RD), and normal direction (ND) symmetric basal fiber textures. These textures emerge due to the activation of multiple slip systems and twinning, which are dependent on external factors such as temperature, strain rate, and alloy composition. For Mg alloys, the poor formability and brittleness associated with the dominance of the basal slip system under ambient conditions is a critical material development challenge. The activation of non-basal slip systems introduces complexities in controlling texture and microstructure. However, their activation is crucial for optimizing mechanical properties such as strength and fatigue resistance. The tendency for twinning in Mg alloys further complicates their deformation behavior, leading to challenges in ensuring uniform mechanical performance. Modifying the alloy composition, grain size, and texture can additionally influence the activation of these deformation mechanisms. This review further explores the roles of dynamic recrystallization and grain growth in tailoring mechanical properties, with a particular focus on microstructure and texture evolution during annealing. Through this detailed review, we aim to present a thorough understanding of the microstructural and textural evolution in HCP materials, thereby guiding future research and industrial applications. [ABSTRACT FROM AUTHOR]

Additive friction stir deposition (AFSD) is an emerging solid-state additive manufacturing process with a high deposition rate. Being a non-fusion additive manufacturing (AM) process, it significantly eliminates problems related to melting such as cracking or high residual stresses. Therefore, it is possible to process reactive materials or high-strength alloys with high susceptibility to cracking. Although the residual stresses are lower in this process than with the other AM processes, depending on the deposition path, geometry, and boundary conditions, residual stresses may lead to undesired deformations and deteriorate the dimensional accuracy. Thermal cycling during layer deposition, which also depends on the geometry of the manufactured component, is expected to affect mechanical properties. To this day, the influence of the deposit geometry on the residual stresses and mechanical properties is not well understood, which presents a barrier for industry uptake of this process for large-scale part manufacturing. In this study, a stepped structure with 4, 7, and 10 passes manufactured via AFSD is used to investigate changes in microstructure, residual stress, and mechanical property as a function of the number of passes. The microstructure and defects are assessed using scanning electron microscopy and electron backscatter diffraction. Hardness maps for each step are created. The residual stress distributions at the centreline of each step are acquired via non-destructive neutron diffraction. The valuable insights presented here are essential for the successful utilisation of AFSD in industrial applications. [ABSTRACT FROM AUTHOR]

Ni‐rich layered oxide cathode material with Ni contents greater than 90% is considered as a highly promising candidate for lithium‐ion batteries (LIBs) owing to its remarkable specific capacity and cost‐efficiency. However, severe capacity degradation caused by the structural collapse and interfacial instability with electrolyte under high voltage greatly hinders the practical application. Here, an antimony (Sb)‐doped LiNi0.91Co0.06Al0.03O2 (Sb‐NCA91) cathode is proposed, where the Sb doping modifies the morphology of primary particles and enables the radially aligned microstructure. This unique microstructure can disperse the anisotropic mechanical stress caused by the H2‐H3 phase transformation, and mitigate the shrinkage and expansion of the primary particles during high‐voltage and low‐temperature cycling, thus inhibiting the formation of microcracks and structural deterioration. Meanwhile, the closely arranged radial spokes allow fast ion transport in the secondary particles and effectively improve the rate performance and low‐temperature performance of the cathodes. As a result, the Sb modified cathode demonstrates superior capacity retention of ≈84% at 1 C after 200 cycles in 2.7–4.5 V at 25 °C, while the pristine NCA91 cathode only retains ≈79%. Additionally, the capacity retention at −20 °C is significantly increased from ≈61% (NCA91) to ≈88% (Sb‐NCA91) after 100 cycles. [ABSTRACT FROM AUTHOR]

The dispersion and reflection characteristics of coupled waves in the piezomagnetic solid with flexomagnetic microstructure effect are studied in this paper. The flexomagnetic effect, strain gradient effect and micro-inertia effect are introduced into the constitutive equation and the governing equation to establish the wave propagation theory in the piezomagnetic solid with flexomagnetic microstructure effect. The secular equation of wave propagation is derived, and the properties of five coupled waves are analyzed. The dispersion characteristics of coupled waves and the reflection properties of coupled waves at the free boundary are solved numerically and checked by the energy conservation law. The influences of the flexomagnetic effect, strain gradient effect and micro-inertia effect on the wave propagation are discussed. It is found that the flexomagnetic effect mainly enhances the mechanical-magnetic coupled property, strain gradient effect mainly enhances the elastic property, and micro-inertia effect not only enhances the inertia property, but also essentially changes the dispersion characteristics of coupled waves. [ABSTRACT FROM AUTHOR]

The cast IN 713 C alloy is extensively used in the aerospace and automobile industries. Even with improved casting methods, the inhomogeneity in the microstructure is still inevitable and causes strain localizations during cyclic loading. So far, the effect of microstructural variables on the low cycle fatigue (LCF) deformation behavior of IN 713 C alloy has rarely been studied. In this study, IN 713 C alloy is LCF tested at 650°C and 750°C for strain amplitudes of 0.35% to 0.6%. The results showed that the deformation heterogeneity resulted from carbides, γ′ precipitates, and γ–γ′ eutectics distribution, governing the LCF failure micro‐mechanisms. The principle fatigue cracks were seen to be initiated from the precipitate‐free zone and oxidized‐surface carbides. It is corroborated that the higher GNDs were observed at carbide/matrix, eutectic/matrix, γ′/matrix interfaces, and in the interdendritic areas where voids and cracks formed. The higher GNDs at these sites facilitate crack initiation and propagation. Highlights: The fatigue life of alloy IN 713 C is highly sensitive to the microstructure.Higher tendency for carbide cracking was observed at high Δε/2.Cracks are seen to be initiated in PFZ and at oxidized MC carbides.Higher GND density was observed near carbides and eutectics. [ABSTRACT FROM AUTHOR]

A dynamic impact test was performed on as-rolled AZ31 alloys with gradient microstructure under various strains. The microstructural evolution and mechanical properties were systematically investigated. As the strain rate gradually increased, an increasing number of twins were formed, facilitating dynamic recrystallization (DRX), and the mechanical properties were also gradually improved. The microstructure became heterogeneous at higher strain rates, but the peak stress decreased. The impact process resulted in a significantly higher performance due to microstructural refinement, work hardening by dislocations, and precipitates. In addition, both the adiabatic shear band and the adjacent crack experienced a temperature rise that exceeded the recrystallization temperature of the alloys. This observation also explains the presence of ultrafine recrystallized grains within the adiabatic shear band and the appearance of molten metal around the crack. [ABSTRACT FROM AUTHOR]

Extremely low cycle fatigue tests, up to a total axial strain amplitude of 10%, were conducted on Fe-15Mn-10Cr-8Ni-4Si bidirectional transformation-induced plasticity (B-TRIP) steel. The fatigue life was approximately five times longer than that of SUS316 when the total strain amplitude was 4% or higher. The improved fatigue life of Fe-15Mn-10Cr-8Ni-4Si was attributed to reversible bidirectional γ ↔ ε transformation during fatigue deformation, which might mitigate fatigue damage. In contrast, the fatigue life tended to decrease with increasing strain rate when the strain rate was varied from 0.1 to 2.5%/s with a total strain amplitude of 10%. Fractography revealed that the fracture surface varied significantly with strain rate. At low strain rates, crystallographic fracture surfaces characterized by facets and secondary cracks were observed, whereas these features were not observed at high strain rates. Electron backscatter diffraction measurements of the postmortem microstructure showed that frequent ε-martensite formation occurred at low strain rates, whereas martensitic transformation was suppressed at high strain rates. The change in the specimen surface temperature was evaluated in terms of the Gibbs free energy difference between γ-austenite and ε-martensite (i.e.,ΔGγ↔ε), and the effect of strain rate on the extremely low cycle fatigue was discussed from the viewpoint of the deformation mechanism. At a low strain rate, the condition for B-TRIP to work effectively, that is, ΔGγ↔ε is negative but close to zero, was maintained over the entire life span. At a high strain rate, the deformation mechanism changed to one in which γ-austenite was dominant because of the increase in ΔGγ↔ε caused by self-heating; the fatigue damage mitigation mechanism provided by B-TRIP was less likely to occur at high strain rates, which reduced the fatigue life. [ABSTRACT FROM AUTHOR]

Mg-0.8Si alloy plates were rolled at high strain rates of 15, 20, and 25 s−1, and the effects of the rolling strain rate on the microstructure, mechanical properties, and damping properties of the Mg-0.8Si alloy were studied. With the increasing strain rate, the area fraction of DRX in the HSRRed Mg-0.8Si alloy gradually increases, resulting in the decrease in dislocation density and dislocation tangles. A higher strain rate can enlarge the grain size of the Mg-0.8Si alloy, so the basal texture and tensile strength can both decrease because of the increased strain rate. The maximal elongation is 8.40% at 20 s−1. The damping properties of HSRRed Mg-0.8Si alloy increase with the strain rate and the critical strain amplitude gradually decreases. [ABSTRACT FROM AUTHOR]

Flexoelectricity is often studied at the macroscopic scale for energy conversion and harvesting. The fact that microstructural heterogeneities can have a profound impact on a material's flexoelectric response has been under-appreciated and largely unexplored. To capture the effects of microstructure on both the macroscopic flexoelectric behavior and the development of microscopic electric field that drives such microscale processes, we develop a computational framework that enables the quantification of how the microstructure can influence the flexoelectric behavior of heterogeneous materials. The specific material evaluated is a porous composite of tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride polymer and aluminum (Al) particles. The models explicitly resolve the Al particles and voids within the microstructure. The focus of the analysis is on assessing the physical mechanisms that enhance the macroscopic flexoelectric output and determining the effective flexoelectric coefficient of the inhomogeneous material. The approach also allows the contributions of individual strain gradient components to the effective flexoelectric coefficient to be delineated and offers a method of determining the flexoelectric coefficients associated with individual strain gradient components using measurements of the macroscopic flexoelectric responses of microstructures with different concentrations of Al particles and voids. It is concluded that the enhancement of local strain gradients near the Al particles and voids and the activation of contributions from multiple strain gradient components are the primary mechanisms for the increase in the macroscopic flexoelectric output of the composites. The macroscopic flexoelectric coefficient under cantilever beam bending is found to rise linearly with the Al content, consistent with the experimental measurements. [ABSTRACT FROM AUTHOR]

Graphene and its derivatives have garnered significant attention as novel nanomodifiers in the asphalt industry. Despite its vast potential, poor compatibility and dispersion between graphene and asphalt have been persistent challenges for researchers. To prepare well-dispersed graphene materials, polyvinylpyrrolidone (PVP) was grafted onto water-soluble graphene (WG), resulting in PVP-WG composites. This PVP-WG composite was introduced into matrix asphalt as a modifier to improve the compatibility and dispersion of graphene with asphalt. Various advanced techniques such as Fourier transform infrared spectroscopy, laser particle size analyzer, scanning electron microscopy, and X-ray diffraction confirmed the successful attachment of PVP to the surface of water-soluble graphene, thereby increasing the spacing between WG and promoting the intercalation of asphalt molecules. The loose structure of PVP facilitated the effective binding between WG and asphalt molecules. The multiple stress creep recovery and dynamic shear rheometer tests demonstrated that PVP-WG was effective in enhancing the elastic recovery performance, high temperature resistance to deformation, and viscoelastic properties of the asphalt binder. In addition, the results of the bending beam rheometer test showed that PVP-WG slightly reduces the low-temperature performance of asphalt, but PVP significantly improves the low-temperature cracking resistance of WG-modified asphalt. This study provides valuable insights into the potential application of graphene in asphalt pavement materials. [ABSTRACT FROM AUTHOR]

The transportation and disposal of tunnel muck have detrimental environmental impacts. For this reason, the practice of reusing such a resource in engineering materials has substantial environmental and economic benefits. Seasonal frozen regions are extensively distributed worldwide, and freeze–thaw (F-T) cycles can largely degrade the performance of engineering materials, underscoring the importance of knowledge on the F-T resistance of tunnel muck. This study investigates the impact of F-T cycles on the mechanical and microscopic behavior of slurry shield tunnel muck stabilized with basalt fiber (BF) and inorganic curing agent (ICA). The qualities of muck discharged from slurry shield tunneling were improved in the composite formation of fine sand and muddy silty clay. Then tests were conducted to obtain the stress-strain characteristics, uniaxial compressive strength (UCS), and microstructure of the improved tunnel muck with different numbers of F-T cycles (N) and BF contents. Based on the Weibull probability distribution function, the damage evolution model of ICA-BF stabilized tunnel muck was proposed. The results show that the UCS decreases parabolically when the F-T cycle increases, and the F-T damage degree is 24.5%–40.6% after 12 cycles. Increasing BF content can effectively improve tunnel muck's F-T resistance (an optimal ratio of 0.5%). The failure strain of the reinforced tunnel muck is linearly correlated to the BF content and has a weak correlation with the number of F-T cycles. The F-T damage to material strength can be divided into rapid (N=0–3), slow (N=3–9), and stable (N>9) stages. The established F-T damage model can accurately predict the evolution of the F-T damage degree. [ABSTRACT FROM AUTHOR]

Using the methods of transmission and scanning electron microscopy, the microstructure of a V–W–Cr–Zr alloy is studied as a function of its plastic deformation value under the condition of high-pressure torsion in the Bridgman anvils. The main stages of structure transformation and the respective mechanisms are identified. It is found out that the grain and defect structure transformation up to e ≈ 1.1 is provided by the dislocation and dislocation-disclination mechanisms, which when combined activate the processes of submicrocrystalline structure formation. The deformation impact in the strain interval from e ≈ 1.1 to e ≈ 3 is characterized by a significant increase in the grain-boundary length. A high strength state is achieved in the course of this deformation, where the dislocation modes of plastic deformation are suppressed. This is accompanied by the activated processes of formation of two-level nanostructured states, wherein the principal mechanism is a quasi-viscous re-orientation by the flows of non-equilibrium point defects. A further increase in the deformation to e ≈ 5.3 gives rise to refinement of the submicrocrystalline grains and formation of two-level nanostructured states in the entire material volume. The main contribution to the grain- and subgrain transformations comes from the disclination and quasi-viscous modes of plastic deformation. At higher strain degrees (e > 5.3), the size of submicrocrystalline grains does not virtually change, and the transformation of two-level nanostructured states makes itself evident in the rotations of some of the fragments of this structure with respect to the other by small angles from tens of fractions of a degree to several degrees. The formation of the submicrocrystalline state is followed by a multiple increase in the microhardness; its values are observed to saturate at e ≈ 3.3. [ABSTRACT FROM AUTHOR]

Both microstructure and stress affect the structure and kinematic properties of magnetic domains. In fact, microstructural and stress variations often coexist. However, the coupling of microstructure and stress on magnetic domains is seldom considered in the evaluation of microstructural characteristics. In this investigation, Magnetic incremental permeability (MIP) and magnetic Barkhausen noise (MBN) techniques are used to study the coupling effect of characteristic microstructure and stress on the reversible and irreversible motions of magnetic domains, and the quantitative relationship between microstructure and magnetic domain characteristics is established. Considering the coupling effect of microstructure and stress on magnetic domains, a patterned characterization method of microstructure and stress is innovatively proposed. Pattern recognition based on the Multi-layer Perceptron (MLP) model is realized for microstructure and stress with an accuracy rate higher than 97%. The results show that the pattern recognition accuracy of magnetic domain features and micro-magnetic features simultaneously as input parameters is higher than that of micro-magnetic features alone as input parameters. [ABSTRACT FROM AUTHOR]

In this article, the microstructure and mechanical properties of the Fe–0.31C–6.86Mn–3.53Al steel and DP980 and 22MnB5 steel dissimilar/similar joints by fiber laser welding are studied. Based on experimental results, fusion zone (FZ) of transformation‐induced plasticity (TRIP)‐welded joint mainly consists of 77 vol% martensite and 23 vol% ferrite. The FZ of TRIP‐DP980 and TRIP‐22MnB5 welds mainly consist of martensite. The hardness profile of weld cross‐section exhibits significant asymmetry, and softening zones hardness of TRIP‐DP980 and TRIP‐22MnB5 accounts for 82% and 64% of DP980 and 22MnB5 base materials (BM), respectively. However, no softening zone is observed on TRIP steel side, primarily due to the lack of martensite in TRIP BM. The tensile results showed that welding efficiency of TRIP‐TRIP reached 99%, but elongation of welded specimen is only 50% of TRIP BM due to the high hardness and brittleness of FZ region. TRIP‐DP980 and TRIP‐22MnB5 joints did not fail in softening zone, because the constraint stress is generated on both sides of softening zone to inhibit the plastic deformation in softening zone during tensile process. The tensile stress is distributed on the surface of tensile specimens and concentrated in BM on the side with low yield strength (YS), resulting in the final fracture. [ABSTRACT FROM AUTHOR]

To find the suitable deformation temperature range for the as‐cast Fe–5.5Cr–5.5Ni–3.0Al–0.27C high‐strength lightweight steel, the thermal mechanical behavior and the dependent microstructure characteristics are studied to investigate the high‐temperature mechanical response of the steel. In the results, it is shown that the microstructure of the steel owns a dendrite framework consisting of the martensite dendrite and the interdendritic austenite, among which precipitations of NiAl, Ni3Al, and δ‐Fe are induced by high‐temperature deformation. The flow stress dependence of deformation temperature shows two different variation tendencies, corresponding to the varied deformation mechanisms of strain‐induced precipitation of second phases and δ‐Fe nucleation, and then resulting in different variation of dislocation density. It is found that a periodical fluctuation of flow stress appears as the alternative occurrence of first rise and then drop followed by drop and rise, and the phenomenon is inferred to be caused by local dynamic recrystallization in the dendrites and the neighboring interdendritic spacings. [ABSTRACT FROM AUTHOR]

This study investigates the nonlinear dynamic response of an auxetic sandwich structure under impact load. The core is made of a micro-cellular auxetic structure. The main point of interest is studying the micro-cellular core properties' effects on the structure's nonlinear dynamic response. First, the mechanical properties of the micro-cellular auxetic core are introduced based on modified strain gradient theory (MSGT), followed by experimental and numerical validation. Then, Hamilton's principle is applied to derive the sandwich structure's nonlinear governing partial differential equations. Lastly, Galerkin's method paved the way to achieving the final solution. So as to perform frequency-response analysis, the four-dimensional averaged equations are obtained using the perturbation method. In order to carry out experimental validation, a nanosecond laser system is used for micro-cellular auxetic sample fabrication, and the tensile tests are carried out per ISO 6892 standard. The comparison between the experimental and the theoretical results indicates an excellent agreement among the results. It can be concluded that MSGT plays a significant role in the mechanical properties and the nonlinear dynamic response of the micro-cellular auxetic structures. The present study is applicable in the field of protective panels, sensors, and energy harvesters. [ABSTRACT FROM AUTHOR]

This research investigates the coupling effect of microstructure and temperature on the fatigue performance of an equiaxed Ni-base superalloy, EA, at design-significant temperatures (750–930°C) for different strain amplitudes (Δϵ/2). It is observed that distinguishing damage features (specific to the temperature and Δϵ/2) remarkably affect the extent and distribution of strain localisation, leading to the divergence in associated fatigue behaviour. The strain is uniformly distributed at lower Δϵ/2 for all temperatures. Compared to the 850 and 930°C, the strain localisations at 750°C are more effectively alleviated, accounting for the highest fatigue life. Moreover, this alloy exhibited a bilinear Coffin-Manson (C–M) relationship. It is ascertained that the strain localisation resulting from the dislocation and precipitates (γ′, Cr6C23, and γ-γ′ eutectic) interactions are mainly responsible for the dual-slope C–M behaviour. [ABSTRACT FROM AUTHOR]

In this study, the microstructure and thermal properties of the plasma-sprayed free-standing Lu 2 Si 2 O 7 coating before and after thermal aging at 1350 °C were investigated. The tri-layer Yb 2 SiO 5 /Lu 2 Si 2 O 7 /Si EBCs were designed and prepared onto SiC f /SiC substrates, and its thermal shocking behaviors were also explored. Results showed that the as-sprayed coating was mainly composed of Lu 2 Si 2 O 7 and amorphous phase, and significant microstructural evolution, such as grain growth and defects reduction, was observed after thermal aging. Plastic deformation and well damage tolerance including twinning and dislocation were confirmed by TEM analysis. The CTE of the coating before and after heat treatment were similar, while the thermal conductivity increased after thermal aging. After 100 thermal cycles, penetrating microcracks in the Yb 2 SiO 5 top layer were mostly stopped at the Yb 2 SiO 5 -Lu 2 Si 2 O 7 interface, implying the excellent crack propagation resistance of the tri-layer EBCs. The thermal shock behaviors were clarified based on microstructure combined with thermal stresses analysis. • Microstructure and thermal property of Lu 2 Si 2 O 7 coating were studied. • Lu 2 Si 2 O 7 exhibited microstructure and thermal property evolution after aging. • The Yb 2 SiO 5 /Lu 2 Si 2 O 7 /Si EBCs possessed excellent thermal shock resistance. • Lu 2 Si 2 O 7 could be a promising interlayer material for tri-layer EBCs. [ABSTRACT FROM AUTHOR]

High-temperature creep refers to the slow and continuous plastic deformation of materials under the effects of high temperatures and mechanical stress over extended periods, which can lead to the degradation or even failure of the components' functionality. AlxCr0.2NbTiV (x = 0.2, 0.5, or 0.8) refractory high-entropy alloys were fabricated by arc melting. The effects of Al content on the microstructure of AlxCr0.2NbTiV alloys were studied using X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction. The microhardness, compression properties, and nanoindentation creep properties of AlxCr0.2NbTiV alloys were also tested. The results show that the AlxCr0.2NbTiV series exhibits a BCC single-phase structure. As the Al content increases, the lattice constant of the alloys gradually decreases, and the intensity of the (110) crystal plane diffraction peak increases. Adding aluminum enhances the effect of solution strengthening; however, due to grain coarsening, the microhardness and room temperature compressive strength of the alloy are only slightly improved. Additionally, because the effect of solution strengthening is diminished at high temperatures, the compressive strength of the alloy at 1000 °C is significantly reduced. The creep mechanism of the alloys is predominantly governed by dislocation creep. Moreover, increasing the Al content helps to reduce the sensitivity of the alloy to the loading rate during the creep process. At a loading rate of 2.5 mN/s, the Al0.8Cr0.2NbTiV alloy exhibits the lowest creep strain rate sensitivity index (m), which is 0.0758. [ABSTRACT FROM AUTHOR]

The microstructure evolution of TC18 titanium alloy (Ti-5Al-5Mo-5V-1Cr-1Fe) after β solid solution plus aging (β-STA) and β annealing slow cooling plus aging (BASCA) heat treatments were investigated in this paper. The effects of microstructure on tensile properties and plastic deformation behavior were studied. The results suggested that α lamellar structures are formed after both STA and BASCA heat treatment. A multi-scale lamellar structure consisting of micro- and nano-scaled α platelets is formed during BASCA treatment, whereas β-STA treatment mainly generated conventional lamellar structure. In addition, the alloy after β-STA treatment displayed high strength but limited elongation, while the alloy after BASCA treatment exhibited good strength-ductility combination. A model considering α/β phase boundary strengthening, solid solution strengthening and dislocation strengthening is applied to analyze the strength of the alloy. Finally, the plastic strain partition and deformation behavior of the lamellar structure are discussed. [ABSTRACT FROM AUTHOR]

This work studies the evolution of microstructure, texture, and anisotropy of pure titanium foils by symmetric rolling (SR) and asymmetric rolling (ASR) and subsequent annealing. The as‐received material shows equiaxed alpha grains and strong transverse texture (S‐T texture), which leads to severe anisotropy. The index of plane anisotropy (IPA) of yield stress (YS) and ultimate tensile stress (UTS) of the as‐received material is 15.2% and 7.5%, respectively. With the increase of deformation, the S‐T texture is mainly transformed into a mixed texture of transverse texture (T texture) and rolling direction texture (R texture), which balances the start‐up of the slip system when loading in the rolling direction (RD) and transverse direction (TD), so that the mechanical stress along RD and TD are close to each other and the anisotropy is improved. Especially for the samples prepared by ASR and annealing, the appearance of more R texture or basal texture (B texture) at the same deformation makes them show lower anisotropy. Therefore, after the same annealing treatment, the IPA of titanium foil with a thickness of 0.2 mm prepared by ASR is the smallest, which is 6.6% and 0.03%, respectively, while the IPA prepared by SR is 10.5% and 2.5%. [ABSTRACT FROM AUTHOR]

SnPb solder was widely used in electronic packaging for aerospace devices due to its high reliability. However, its creep resistance is poor and can be improved by adding alloying elements. The effects of Sb content on the microstructure, tensile, and creep properties of eutectic SnPb solder were investigated. Sb addition effectively improved the mechanical properties of the SnPb solder. When Sb content exceeds 1.7 wt.%, SbSn intermetallic compounds (IMCs) occurred. And increasing the Sb content increased the tensile strength. Furthermore, Sb addition decreased the steady-state creep rate and increased the stress exponent n, suggesting that the creep resistance had been enhanced, which may be attributed to the hindrance of dislocation movement by SbSn IMCs, as well as the reduction in phase boundaries, which consequently reduced grain boundary sliding. [ABSTRACT FROM AUTHOR]

In this study, the influence of initial microstructure and deformation temperature on the flow stress behavior and microstructural evolution of TIMETAL®407 (Ti-407) alloy are investigated. For this purpose, compression cylinders were β-annealed at 940 °C and then cooled to room temperature using furnace cooling, static air, and water quenching to promote three initial microstructures with different α lath thicknesses. The annealed cylinders were compressed isothermally in the range of 750 °C to 910 °C at a constant crosshead speed of 0.05 mm/s up to an engineering strain of −0.8. The resulting stress–strain curves are discussed in terms of the morphology and distribution of the α and β phases. It was found that flow stress is inversely proportional to deformation temperature for all initial microstructures. At the lowest temperatures, compressive yield strength was higher in water-quenched and air-cooled samples than in furnace-cooled specimens, suggesting that the acicular α-phase morphology obtained by rapid cooling could enhance mechanical strength by hindering dislocation motion. Two high-temperature flow regimes were determined based on the shape of the flow stress curves, indicating microstructural changes occurring during deformation. At higher temperatures, the effect of the initial microstructure is negligible as the primary α phase is transformed to the β phase at around 850 °C irrespective of the initial α-lath thickness. [ABSTRACT FROM AUTHOR]

Deep cryogenic aging (DCA) is a newly developed heat treatment technique for additive-manufactured metallic materials to reduce residual stress and improve their mechanical properties. In this study, AlSi10Mg alloy samples fabricated by selective laser melting were deep-cryogenic-treated at −160 °C and subsequently aged at 160 °C. Phase and microstructural analyses were conducted using X-ray diffraction, optical microscopy, scanning electron microscopy, and transmission electron microscopy, while the mechanical properties were evaluated through microhardness and tensile testing at room temperature. The results indicated that the DCA treatment did not have an effect on the morphology of the melt pools. However, it facilitated the formation of atomic clusters and nanoscale Si and β′ phases, as well as accelerating the coarsening of grains and the ripening of the eutectic Si phase. After DCA treatment, the mass fraction of the Si phase experienced an increase from 4.4% to 7.2%. Concurrently, the volume fraction of the precipitated secondary phases elevated to 5.1%. The microhardness was enhanced to 147 HV, and the ultimate tensile strength and yield strength achieved 495 MPa and 345 MPa, respectively, with an elongation of 7.5%. In comparison to the as-built specimen, the microhardness, ultimate tensile strength, and yield strength increased by 11.4%, 3.1%, and 19.0%, respectively. The improvement in mechanical properties is primarily attributed to the Orowan strengthening mechanism induced by the secondary phases. [ABSTRACT FROM AUTHOR]

Duplex stainless steels are materials with high performance under mechanical stress and stress corrosion in chloride ion environments. Despite being used in many new applications such as components for offshore drilling platforms as well as in the chemical and petrochemical industry, the automotive industry, etc., they face issues of wear and hardness that limit current applications and prevent the creation of new use opportunities. To address these shortcomings, it is proposed to develop a hardfacing process by a special welding technique using a universal TIG source adapted for manual welding with a pulsed current, and a manganese austenitic alloy electrode as filler material. The opportunity to deposit layers of manganese austenitic steel through welding creates advantages related to the possibility of achieving high mechanical characteristics of this steel exclusively in the working area of the part, while the substrate material will not undergo significant changes in chemical composition. As a result of the high strain hardening rate, assisted mainly by mechanical twinning, manganese austenitic alloys having a face-centered cubic crystal lattice (f.c.c) and low stacking fault energy (SFE = 20–40 mJ/m2) at room temperature, exhibit high wear resistance and exceptional toughness. Following cold deformation, the hardness of the deposited metal increases to 465 HV5–490 HV5. The microstructural characteristics were investigated through optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and Vickers hardness measurements (HV). The obtained results highlighted the feasibility of forming hard coatings on duplex stainless steel substrates. [ABSTRACT FROM AUTHOR]

Experimental laboratory equipment for friction stir welding (FSW) as a result of working out the optimal welding modes at different linear velocities allows producing high-quality butt joints from thin ductile metals. With the development of new mathematical methods for modeling thermodeformational processes, it became possible to analyze the stress-strain state and thermomechanical processes occurring in the FSW joint zone, which is necessary for predicting the operational properties, strength and service life of welded structures made of thin metal. Using mathematical models and finite element analysis, the temperature distributions from the volume heat source at FSW were visualized, and the residual deformations and stresses in the zone of butt-welded joints of thin sheets of magnesium alloys were numerically determined. In the future, it is advisable to determine the effective balance of the linear speed and the rotation speed of the FSW tool to obtain better homogeneity of the weld structure and reduce heat input into the metal during welding. [ABSTRACT FROM AUTHOR]

Improving the volume stability of cement paste is crucial for designing high-strength and high-durability cementitious materials. Therefore, this study proposes a novel approach using calcium carbonate whiskers (CW) with high aspect ratio and high modulus to control the autogenous shrinkage and drying shrinkage of cement paste, and reveals its regulation mechanism through microscopic experiments. The results showed that the addition of 3 vol.% CW in cement paste had the most significant effect on reducing autogenous shrinkage and drying shrinkage, which were reduced by 33.2% and 19.8%, respectively. One is that CW has a retarding effect, which reduced shrinkage cracking due to rapid hydration. Secondly, the water-locking effect of CW slowed down the rapid evaporation of water, thus reducing the mechanical stress in the capillary pores due to water loss, and at the same time reducing the low mass loss. In addition, CW constrained the shrinkage and deformation of capillary pores due to water loss by crossing the capillary pores, and CW also formed a three-dimensional network structure in the microstructure, which increased the overall volume stability of the paste. It is worth that CW as a micron-sized fiber also bridged microcracks due to shrinkage, exhibiting the reinforcement effect of CW. [ABSTRACT FROM AUTHOR]

Traditional physics-based mathematical models of viscoelastic (VE) damper often exhibit different degrees of prediction errors under complex working conditions, whereas data-driven approaches have shown significant potential for overcoming such problems, and have not been introduced into any study to describe the dynamic mechanical properties of VE damper. In this paper, the architecture of microsphere model is adopted to represent the spatial distribution of molecular chain structure of VE damping material, which is categorized into free chains and elastic chains. Then, the physics-informed neural network surrogates are introduced to describe the statistical stress–strain behaviors of free chains and elastic chains. Finally, by constructing the physics-constrained loss function based on the combination of physics-based model and data-driven model, a physics-constrained data-driven model is proposed to characterize the dynamic mechanical behaviors of VE damper used for structure vibration control. Based on the existing experimental data, the prediction ability and robustness of the proposed model are comparatively verified, the results reveal that the proposed model can accurately reflect the stiffness and energy dissipation of VE damper under different ambient temperatures, excitation frequencies, and deformation conditions. This study proves the potential of physics-informed neural network theory in characterizing the complex mechanical behaviors of VE damper. [ABSTRACT FROM AUTHOR]

Establishing the influence of sample preparation method on shear wave velocity or associated small-strain shear modulus (G0) of silty sands is a subject of considerable interest. This paper presents an attempt to address this topic through a comprehensive experimental programme covering four sample preparation methods. The experiments were conducted on clean Toyoura sand and its mixtures with two types of fines of different sizes. For each sample preparation method, a range of void ratio and confining stress was investigated to obtain a comprehensive view of the influence of sample preparation and its interplay with other factors. One of the notable findings is that, compared with clean sand, the difference of G0 induced by different sample reconstitution methods can be much enlarged for silty sand, and the influence is coupled with the size disparity ratio of the mixtures. The reduction of G0 due to the presence of fines also depends on sample preparation method and for smaller fines the reduction is more significant. A careful examination of the X-ray images of the specimens made by different methods suggests that the observed effects are mainly associated with the different contact conditions of coarse and fine grains. [ABSTRACT FROM AUTHOR]

Lutetium monosilicate (Lu2SiO5) has been considered as environmental barrier coatings (EBCs) materials for SiCf/SiC. Microstructural evolution and thermal properties changes of the Lu2SiO5 coating would occur in high temperature environment. In this study, Lu2SiO5 coating was fabricated by vacuum plasma spray technique. The microstructure, thermal stability, thermal conductivity, as well as thermal expansion behavior of the coating before and after thermal aging at 1350 °C were investigated. The tri-layer EBCs of Lu2SiO5/Yb2Si2O7/Si were designed and prepared onto SiCf/SiC substrates, and its thermal shocking behaviors were also explored. Results showed that the as-sprayed coating was mainly composed of Lu2SiO5, Lu2O3 and amorphous phases, and significant microstructural evolution, such as grain growth and defects reduction, was observed after thermal aging. The coating exhibited linear expansion, and the CTE of the coating before and after heat treatment were similar, while the thermal conductivity increased after thermal aging. Thermal shock results showed that the coating remained intact after 100 cycles, and penetrating microcracks in the Lu2SiO5 top layer were mostly stopped at the Lu2SiO5-Yb2Si2O7 interface, indicating that the tri-layer EBCs on the SiCf/SiC substrate had good thermal shock resistance. The thermal shock behaviors were explained based on microstructure combined with thermal stresses analysis. [ABSTRACT FROM AUTHOR]

Vibrational stress relief (VSR) treatment is a method of stress relief which is currently used for different alloys in different sizes. Since the effect of VSR has not been fully analyzed and compared versus thermal stress relief (TSR) process, its merits require wider investigations. In this paper VSR treatment has been performed with certain parameters to check and assure the advantages of the process in terms of mechanical and metallurgical improvements on AISI 1008 workpiece as a preparatory process. The chosen parameters consist frequency, time, and amplitude of vibration. Factorial design of the experiment using response surface methodology has been performed to obtain an optimal response in numerical and experimental tests. The testing coupons have been evaluated in terms of hardness, tensile strength, elasticity modulus, toughness, elongation before fracture, and micro-structure. Experimental results have been compared with finite element analysis (FEA) results and previous studies. FEA elastic-plastic model was used to extract mechanical properties, while hardening effect has been accounted for in the model. The study has demonstrated the influential performance of VSR on the mechanical properties of the samples i.e., yield strength, toughness, elongation, and elasticity modulus while hardness and microstructure have not been affected significantly. [ABSTRACT FROM AUTHOR]

In this study, the microstructural evolution of a Ti-15Mo medical alloy was investigated, when the in situ cyclic tensile strain had 2% amplitude and the tension–compression cyclic deformation had 1%, 2%, and 3% amplitude. The Vickers hardness and wear resistance of the alloy were also optimized due to the grain-refining effect after cyclic deformation and annealing. The twinning-induced plasticity (TWIP) was considered the main deformation mechanism of the Ti-15Mo alloy during the tensile–compressive cycle deformation with suitable strain amplitude. The {332}<113> twins and boundaries were the main contributors to the grain refinement. The optimal microstructure, hardness, and wear resistance were obtained in the alloy deformed by tension–compression cyclic strain with a 3% strain amplitude. The wear resistance of the annealed alloy in Hank's solution was excellent in contrast to the original Ti-15Mo alloy due to its reasonable microstructure and hardness. It is clear that abundant twins were formed and retained in the coarse grains of the original alloy after cyclic deformation and annealing, which provided the expected refined grains and performance. [ABSTRACT FROM AUTHOR]

The goal of the present research is an investigation of the smart control and wave propagation examination of a graphene nanoplatelets reinforced (GPLRC) cylindrical micro-shell covered with piezoelectric layers as the sensor and actuator (PLSA) in the framework of an analytical method. The stress and strain components are given based on the first-order shear deformable theory (FSDT), and for accessing the size effects, the nonlocal strain gradient theory is used for obtaining the correct results. The material properties of the GPLRC micro-shell are modeled via modified Halpin–Tsai and the rule of the mixture. The external voltage is applied to the sensor layer, and a Proportional-Derivative (PD) controller is used for sensor output control. The governing equations of the electrically micro-shell are derived via Hamilton's principle. This work concludes that the PD controller, wave number, applied voltage, and weight fraction of graphene nanoplatelets (GPL) have a significant influence on the wave propagation of the GPLRC cylindrical micro-shell. The remarkable result is that consideration of the PD controller leads to expand the stable area and improve the dynamic behaviors of the smart system. [ABSTRACT FROM AUTHOR]

The study investigated the microstructures, residual stress and mechanical properties of double carbides cermet coatings manufactured on AZ31 magnesium alloy substrate by high-velocity oxy-fuel spraying (HVOF). The HVOF spraying was carried out using a JP 5000 TAFA spray system and the commercially available powder WC-20Cr3C2-7Ni was used to manufacture coatings. The variable process parameter was spray distance (320, 360 and 400 mm). The top surfaces of the manufactured coatings are typical for HVOF coatings and is relatively smooth. Nevertheless, some irregularities and voids are observed. All coatings exhibit dense structure with relatively low porosity level (below 3 vol. %) as well as a robust mechanical binding to the substrate which indicates high adhesion. More deep microstructure analysis carried out by TEM microscopy revealed two types of precipitation: WC hexagonal phase in the space group P-6m2 with irregular shape and size as well as Cr7C3 orthorhombic one, in the space group P nma with a rounded shape and regular size. Phase composition after the spraying process indicates the hexagonal WC phase as the main one. Additionally, two chromium carbides phases, Cr3C2 and Cr3C7 have been identified. A small peak of hexagonal W2C carbide was found as well. Analysis of residual stress showed that both components of linear stress for all deposited coatings have a compressive nature. The increasing spray distance caused an increase of the linear stress values, from – 72.7 up to – 131.5 MPa for δ11 and from – 57.2 up to – 112.2 MPa for δ22. Such values could suggest that thermal stress generated during coating deposition was also low. In the case of the shear stress the values are much lower than linear one, but with the same tendency, increasing with longer spray distance: 14.2, 21.0 and 32.2 MPa for 320, 360 and 400 mm, respectively. The obtained results of HIT show a slight influence on the spray distance. With the increasing spraying distance, the value of hardness decreasing: 12.96, 12.53 and 11.76 GPa according to SD equal to 320, 360 and 400 mm, respectively. Similar was in the case of the EIT values: 315, 309 and 304 GPa for 320, 360 and 400 mm, respectively. All values of the fracture toughness were in the range between 3.5 and 4.0 MPa m1/2, with little influece of the spray distance. [ABSTRACT FROM AUTHOR]