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Stress perturbations and material defects can significantly affect the fracture initiation and propagation behaviors in brittle materials. In this work, we show that (110)[110] cleavage in silicon deflects onto (111) plane in the presence of contact stresses. The deflection is however not permanent as the crack returns to the (110) plane after a certain length of propagation, even in the case where the crack velocity is up to 78% of the Rayleigh wave speed. The recovery behavior indicates that the (110)[110] cleavage is invariably prevailing when perpendicular to the maximum stress. Following this indication, it can be concluded that the observed (110)[110]–(111) deflection in previous literature is more likely driven by the external disturbance rather than the crack velocity induced toughness evolution. We also highlight that the extra energy for the (110) recovery is minimized at the expense of a large propagation distance upon the plane switch. [ABSTRACT FROM AUTHOR]

In this article, we report special fracture initiation behavior of (110) cleavage in silicon single crystal. It is found that the static energy release rate always exceeds the material toughness upon crack initiation. According to high-speed imaging measurements and fractographies, it is found that the crack has an important initial velocity, i.e. up to 3000 m/s, and then reaches the steady-state propagation regime very quickly. The experimentally revealed initial crack velocity is in good agreement with estimation from the energy flux at crack initiation. [ABSTRACT FROM AUTHOR]

The rigidity and the strength of photovoltaic cells, particularly the centerpiece-embedded silicon plates, are of great importance from an economical point of view since their reliability impacts the overall cost based on production, transportation and in-service use. The present work focuses on the solar-grade multi-crystalline silicon used in PV wafers. The aim is to characterize the Young’s modulus and to analyze the fracture behavior at room temperature. The Si plates have been laser cut from two different manufacturing processes of silicon wafers, MCSi and RST. Due to the brittle behavior of Si at ambient temperature, 4-point bending tests have been performed. The beam hypothesis has been used to analyze bending tests for determining the Young’s modulus. A correction strategy has then been proposed with a numerical model in order to determine with a higher accuracy the mechanical data and the measurement uncertainty. For fracture investigation, high speed imaging technique and fractography have been used to identify the failure mode as well as the crack origin. The Young’s modulus is found to be 166 ± 5 GPa for MCSi wafers. The anisotropic stiffness of RST plates is also revealed and correlates well with the micro-structural texture. Both kinds of plates fracture in trans-granular manner from the edges, where some defects are located due to laser cutting. [ABSTRACT FROM AUTHOR]

Dynamic fracture of silicon multi-crystal merits a systematic investigation given the complexity induced by microstructure defects, in particular grain boundaries. How crack selects its path in the presence of substantial grain boundaries is an issue still under debate in literature. In this work, fracture behavior of multi-crystalline silicon is carefully examined through bending tests, bringing to light new crack propagation scenarios. In the case of multi-cracking, massive branching events emerge, and crack paths are heavily affected by burst waves. When a single crack propagates across grain boundaries, orientation mismatch between cleavage planes generates an important constraint effect, leading the crack to eventually propagate along (112) plane, i.e., a path scarcely seen in single crystal. Perfect crack propagation along coherent Σ 3 twin boundary can hardly be achieved, presumably due to the crack inertia effect. Moreover, crack is found to incessantly deviate at the two sides of high order grain boundaries, resulting in a zigzag crack path. The observations suggest that grain boundaries are not prone to break up but significantly affect crack path in silicon multi-crystals. • Cascading waves and branching break up the monopoly of (111) cleavage in silicon. • Fracture along coherent TB cannot be achieved presumably due to crack inertia effect. • Misorientation plays a vital role in fracture path selection upon crossing GB. • High order GB is revealed to be unfavorable crack path in silicon multicrystal. [ABSTRACT FROM AUTHOR]

Abstract: Many materials contain inhomogeneities or inclusions that may greatly affect their mechanical properties. Such inhomogeneities are for example encountered in the case of composite materials or materials containing precipitates. This paper presents an analysis of contact pressure and subsurface stress field for contact problems in the presence of anisotropic elastic inhomogeneities of ellipsoidal shape. Accounting for any orientation and material properties of the inhomogeneities are the major novelties of this work. The semi-analytical method proposed to solve the contact problem is based on Eshelby’s formalism and uses 2D and 3D Fast Fourier Transforms to speed up the computation. The time and memory necessary are greatly reduced in comparison with the classical finite element method. The model can be seen as an enrichment technique where the enrichment fields from the heterogeneous solution are superimposed to the homogeneous problem. The definition of complex geometries made by combination of inclusions can easily be achieved. A parametric analysis on the effect of elastic properties and geometrical features of the inhomogeneity (size, depth and orientation) is proposed. The model allows to obtain the contact pressure distribution – disturbed by the presence of inhomogeneities – as well as subsurface and matrix/inhomogeneity interface stresses. It is shown that the presence of an inclusion below the contact surface affects significantly the contact pressure and subsurfaces stress distributions when located at a depth lower than 0.7 times the contact radius. The anisotropy directions and material data are also key elements that strongly affect the elastic contact solution. In the case of normal contact between a spherical indenter and an elastic half space containing a single inhomogeneity whose center is located straight below the contact center, the normal stress at the inhomogeneity/matrix interface is mostly compressive. Finally when the axes of the ellipsoidal inclusion do not coincide with the contact problem axes, the pressure distribution is not symmetrical. [Copyright &y& Elsevier]

The heterogeneous precipitation of the η (MgZn 2) phase on the E (Al 18 Mg 3 Cr 2) dispersoids of the 7075 aluminum alloy was systematically investigated by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-ray spectrometry (EDX). It is found that coarse η particles are heterogeneously precipitated at the E particle interface after water quenching and isothermal aging at 120 °C. The incoherent E/Al interface is responsible for the high tendency of heterogeneous precipitation of the η phase. Two different orientation relationships (ORs) between the η, E and Al matrix are identified: OR1 [2 1 ¯ 1 ¯ 0] η //[011] E // 1 ¯ 12] Al , (01 1 ¯ 0) η //(13 3 ¯) E //(2 0 1) Al , OR2 1 ¯ 12] E //[0001] η //[011] Al , (01 1 ¯ 0) η //(220) E //(3 4 4 ¯ ) Al. The η phase is preferential to nucleate along the {111} E or the {220} E planes, depending on its OR. The heterogeneous nucleation of η phase on the E particle could stabilize the E/Al interface by introducing a coherent E/η interface, which increases the drive force of heterogeneous precipitation. The reorientation of η phase and mutual diffusion of solute atoms could assist the coherency of the E/η interface. The present results suggest that increasing the coherency of the E/Al interface is a promising method to suppress the heterogeneous precipitation of the η phase. Image 1 • The incoherent E/Al interface can promote heterogeneous precipitation. • The heterogeneous nucleation of η phase on the E particle could stabilize the E/Al interface. • The reorientation of η phase can assist coherency of the E/η interface. [ABSTRACT FROM AUTHOR]

Re doping is an essential way to improve the high temperature mechanical properties of nickel-based single crystal superalloy (NBSCS). However, how the doped Re affects the mechanical properties of NBSCS is still unclear, and a quantitative description is lacking. This paper attempts to study the influence of Re doping on plastic deformation mechanisms of NBSCS at atomic scale. First, the grand-canonical Monte Carlo method was employed to determine the distribution of Re atoms within the two-phase microstructure of NBSCS. Then, the molecular dynamics simulations were carried out to study the effect of Re doping on the dislocation motion and evolution during plastic deformation, with a focus on two important deformation mechanisms in NBSCS, i.e., dislocation gliding in the hairpin-like shape in the narrow γ matrix channel and dislocation cutting into the γ′ precipitation from the γ matrix. The results show that Re atoms prefer to segregate at the γ/γ′ interface. The increase of Re concentration in NBSCS can significantly improve both the critical stress of dislocations gliding in the γ matrix channel and the critical stress of dislocation cutting into the γ′ precipitation. These simulation results are qualitatively consistent with experimental observations. Based on these atomic scale simulations, two quantitative models for screw dislocation gliding in a hairpin-like shape in the γ matrix channel and dislocation cutting into the γ′ precipitation in the super-dislocation pair that take into account the Re doping effects have been proposed. The good agreement between the molecular dynamics simulation and the model prediction suggests that these quantitative models can be used for up-scale simulations of the dislocation movement and evolution in the presence of Re doping in NBSCS. • Re segregation near the γ/γ′ interface was obtained by GCMC calculation. • The critical stresses for leading dislocation cutting into the γ′ precipitation and dislocation gliding in a hairpin-like shape in γ matrix both increase with the increasing Re concentration. • Two theoretical models were proposed to describe the critical stresses of the dislocation mechanisms. [ABSTRACT FROM AUTHOR]

AlSi10Mg manufactured by laser powder bed fusion (or selective laser melting) benefits from a very fine microstructure that imparts significant mechanical strength to the material compared to the cast alloy. The build platform temperature stands out as a significant processing parameter influencing the microstructure as it affects the cooling rate and thermal gradient during manufacturing. Setting the build platform temperature to 200°C yields a negligible residual stress level. However, the strength is lower compared to that obtained using a build platform temperature of 35°C, with a similar fracture strain. A detailed 3D microstructural analysis involving focused ion beam/scanning electron microscopy tomography was performed to describe the connectivity and size of the Si-rich eutectic network and link it to the strength and fracture strain. The coarser microstructure of the 200°C build platform material is more prone to damage. The α-Al cells as well as the Si-rich precipitates present a larger size in the 200°C material, the latter thus having a lower strengthening effect. The Si-rich eutectic network is also less interconnected and has a larger thickness in the 200°C material. An analytical model is developed to exploit these microstructural features and predict the strength of the two materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In the effort of expanding the already existing applications of additively manufactured parts, improving mechanical performance is essential. Friction stir processing (FSP) is a promising post-treatment solution to tackle this issue. FSP of selective laser melted AlSi10Mg leads to the globularisation of the Si-rich eutectic network, microstructural homogenisation and porosity reduction. These features have been characterised using in and ex situ mechanical testing and different imaging techniques. A significant modification of the damage mechanism is reported with an increase of the fracture strain from 0.1 to 0.4 after FSP and an enhancement over two orders of magnitude in fatigue life. Unlabelled Image [ABSTRACT FROM AUTHOR]

• Revealed chain evolution via molecular dynamics simulation. • Primitive paths change linearly to principal stretches. • Competition between elongation and constraint due to entanglement effect. • Derived constitutive model to connect microstructures and hyperelasticity. • Achieved precise mechanical response depiction. Due to the complexities of microstructure of molecular chains and their interactions, it has been a great challenge to quantify the correlation between physicochemical components and hyperelastic behavior of polymers through constitutive model. In the present work, molecular dynamics (MD) simulations are first performed to capture the evolutions of cross-linked and free chains under various deformation states. Following MD results, the conformations of entangled free chains are studied from two perspectives, one is the passive elongation induced by entanglement points and the other is the change in topological constraint. These conformations are then incorporated into a revised three-chain model to capture the enhancement in modulus and stretchability of highly entangled hydrogels. Accordingly, the Helmholtz free energy of polymers due to entangled free chains is divided into two parts, accounting for passive elongation and topological constraint, respectively. Based on this free energy decomposition and the revised three-chain model, a physics-based hyperelastic constitutive model is developed. This model is demonstrated to present an excellent capability to depict the behavior of a wide range of polymers under different deformation states. It can be used to decipher new enhancement mechanisms and map physicochemical components to mechanical behavior of polymers. The present model holds significant potential for optimal design of future polymeric materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel hydrogen transport model is developed within the coupled framework of crystal plasticity and hydrogen balance, in which both the contributions of plastic strain and plastic strain gradient to hydrogen transport are considered. • The hydrogen transport flux driven by plastic strain gradient results in a significant dynamic hydrogen segregation at grain boundaries during deformation, which is expected to drive the hydrogen-induced intergranular cracking as observed in experiments. • The roles of grain refinement in hydrogen transport are clarified with the present model. Hydrogen transport by moving dislocations is one of the key mechanisms for hydrogen embrittlement, which is considered responsible for local hydrogen accumulation at preferential crack initiation sites. Although numerous experiments corroborate this mechanism, there are few theoretical models for it available. In the present work, a novel hydrogen transport model is developed within the coupled framework of crystal plasticity and hydrogen balance. The hydrogen transport flux in the present model is divided into two parts: the first-order hydrogen transport flux driven by plastic strain and the second-order hydrogen transport flux driven by plastic strain gradient. With the calibrated parameters by fitting experimental results, the first-order hydrogen transport flux is negligible even for nickel with a low hydrogen diffusivity. In polycrystals, due to the intrinsic plastic heterogeneity induced by grain orientation mismatch, the second-order hydrogen transport flux results in significant dynamic hydrogen segregation at grain boundaries during deformation, which is expected to drive the hydrogen-induced intergranular cracking as observed in experiments. This dynamic segregation behavior is related to the evolution rate of geometrically necessary dislocations, depending on the grain boundary characters. The roles of grain refinement in hydrogen transport are clarified with the present model. This study shows the vital role of plastic strain gradient induced by grain boundary constraint in hydrogen transport, which is essential in understanding hydrogen migration and accumulation in deformed polycrystalline metals. [Display omitted] [ABSTRACT FROM AUTHOR]

Apoptosis of alveolar epithelial cells has been implicated in the pathogenesis of acute lung injury. Phospholipid transfer protein (PLTP) may play a role in apoptosis. In the present study, the effect of the novel function of PLTP in cigarette smoke extract (CSE)-induced apoptosis of alveolar epithelial cells and the possible mechanism were examined. Male Wistar rats were exposed to air and cigarette smoke (n = 10/exposure) for 6 h/day on 3 consecutive days, then the lungs were sectioned and examined. To investigate effects on alveolar epithelial cells, rat alveolar epithelial cells (RLE-6TN) were treated with different concentrations of CSE for various times. siRNA for PLTP was transfected into cells and an inhibitor of the transforming growth factor-β1 (TGF-β1) type I receptor was administered prior to CSE exposure. Apoptosis was measured, and mRNA expression of PLTP and TGF-β1 and protein levels of PLTP, TGF-β1, p-Smad2 and cleaved caspase-3 were analyzed. The results showed that apoptosis, as well as expression of PLTP, TGF-β1, p-Smad2 and cleaved caspase-3 were all significantly increased after CSE stimulation ( P < 0.05). Furthermore, the expression of TGF-β1, p-Smad2 and cleaved caspase-3 induced by CSE could be partly abrogated by knockdown of PLTP. The expression of PLTP showed no significant change as a result of TGF-β1 receptor inhibition, while cleaved caspase-3 showed a remarkable reduction. PLTP may act as an upstream signal molecule of the TGF-β1/Smad2 pathway and is likely to be involved in CSE-induced apoptosis of alveolar epithelial cells. [ABSTRACT FROM AUTHOR]

• The proposed model captures matrix pyrolysis, fiber sublimation and interface failure. • Matrix pyrolysis zone is larger than nominal laser beam size under laser irradiation. • Interface damage is highly related to anisotropic properties of CFRP laminates. Developing an accurate predictive model for laser ablation of laminated carbon fiber reinforced polymer (CFRP) composites is an important and yet challenging task. In this paper, we studied the thermomechanical response of a CFRP laminate under both continuous-wave and pulsed laser irradiations with large spot size. A heat transfer/birth–death element model and a sequential temperature-displacement coupling framework were established to investigate the ablation and delamination phenomena, respectively. The simulation results were found to be quantitatively consistent with the experimental observations in terms of ablation area size and depth. Moreover, it is revealed that the thermal stress induced interface damage is highly dependent on the material anisotropy and layering orientation of the CFRP laminates. The proposed thermomechanical model can be used to decipher the interplay between temperature induced ablation and stress triggered interface cracking under given laser ablation parameters. [ABSTRACT FROM AUTHOR]

Friction stir processing improves both fatigue life in general and fatigue crack growth rate in particular due to its porosity reduction effect, not achieved by SRHT, delaying crack nucleation, and its marked impact on ductility. [Display omitted] • LPBF AlSi10Mg presents early fatigue crack nucleation due to the presence of porosity. • FSP reduces porosity and improves fatigue life, delaying fatigue crack nucleation. • Both 300°C for 2h and FSP induce ductilisation, reducing fatigue crack growth rate. Numerous efforts have been devoted to produce reliable additive manufactured (AM) materials for structural applications. However, the critical fatigue issue poses a significant hurdle in relation to the nature of this production method. Despite the relative flexibility of the laser powder bed fusion (LPBF) AM process, there exists a limitation in the possibility of tailoring parameters to obtain a satisfactory combination of porosity and surface roughness for adequate fatigue resistance. This quandary arises interest for post-treatments that could help overcome this limitation. Friction stir processing was proved to be a viable solution to improve fatigue behaviour of LPBF AlSi10Mg in the present work. Indeed, thanks to this post-process that reduces overall porosity and eliminates critical defects while keeping a satisfactory fine microstructure and static mechanical behaviour, fatigue resistance of the material was significantly enhanced. In contrast, the other studied post-process, stress relieve heat treatment, did not reduce porosity, which remained the main factor behind fatigue crack nucleation, cyclic life of the material being thus little affected with respect to the as built state. Furthermore, both post-treatments decreased fatigue crack growth rate by an order of magnitude. This is interpreted as being due to plasticity induced crack closure and crack branching. [ABSTRACT FROM AUTHOR]

Premature failure due to hydrogen has been widely observed in different metallic materials. How does hydrogen affect the competition between brittle cleavage and ductile fracture is an important scientific question to be addressed. The key to solve this problem is to quantitatively depict the interactions between hydrogen and various defects in metals. In the present work, four atomically-informed mesoscale models which depict quantitatively four widely used hydrogen embrittlement (HE) mechanisms are established by DFT or MD simulations, and then integrated into the XFEM-based DDD framework. By this multi-scale framework, hydrogen-induced intergranular fracture in FCC Al and Ni is investigated, with typical twin boundary (TB) and high angle grain boundary (HAGB) considered for comparison. Computational results show that the dominant HE mechanism in different metals depends on the GB type when multiple HE mechanisms coexist and interact with each other. Compared with the HAGB, the TB has better resistance to hydrogen embrittlemen. The adsorption-induced dislocation emission (AIDE) mechanism dominates the crack propagation along the TB in Al and Ni, while the hydrogen-enhanced decohesion (HEDE) mechanism dominates the crack propagation along the HAGB in Al and Ni. Compared with the HEDE and AIDE mechanisms, the other two mechanisms, i.e., the elastic shielding (ES) and the hydrogen-enhanced strain-induced vacancy (HESIV), have much weaker effect on the hydrogen-induced intergranular fracture, unless the hydrogen concentration is unusually high. These results are helpful for us to understand the complex physical mechanisms behind the hydrogen embrittlement phenomenon. [Display omitted] • Four atomically-informed models were integrated in XFEM-based DDD framework to depict hydrogen embrittlement mechanisms. • The twin boundary has better resistance to hydrogen embrittlemen than high angle GB. • The AIDE and HEDE mechanisms dominate the crack propagation of twin boundary and high-angle GB,respectively. • The ES and HESIV mechanisms have weaker effect on intergranular fracture, unless hydrogen concentration is unusually high. [ABSTRACT FROM AUTHOR]

[Display omitted] • Exact property prediction of Cu is derived for reaching threshold in using CS as AM. • Post-spray annealing to gain properties similar to that of bulk material was studied. • Macroscopic properties of CS Cu were correlated with micro-mechanics. • Crack growth behaviors of CS Cu were discussed in as-sprayed and annealed states. Low ductility of metallic deposits manufactured by cold spraying (CS) impedes potential mechanical performances in industrial applications. Through appropriate annealing treatment, the amount of both, non-bonded interfaces and work hardening promoted dislocations during CS can be significantly reduced. Consequently, the annealed samples exhibit higher strength and fracture strain than the as-deposited ones. Cu was selected as a reliable material for CS. To correlate Cu deposit strength with primary process parameters and material properties, the Cu powder strength was assessed. Crack characterization of Cu deposits was performed by in-situ microscopic observations during tensile testing. The direct observation of crack initiation, growth and final fracture allows revealing failure mechanisms. The in-situ tests allow distinguishing the effects of reduced initial defect sizes due to annealing and improved ductility in the vicinity of initial defects on possible crack growth and part failure. Considering the necessary compromise between strength, uniform elongation, ductility and microhardness, a post-spraying annealing process is desirable for CSed Cu deposits. The identification of macroscopic and micro-mechanical properties attained under respective process parameters and influences of annealing processes therefore allow identifying solutions for improvements of CSed deposits for load-carrying applications, which is a prerequisite for using CS as additive manufacturing technique. [ABSTRACT FROM AUTHOR]

Informed by the current understanding of hydrogen-dislocations/vacancies interactions, a coupled diffusional-mechanical model accounting for hydrogen-enhanced strain-induced dislocations and vacancies is developed. This model is applied to capture hydrogen diffusion and trapping in the uniaxially tensioned column and type-I loaded crack specimens of nickel alloy, with special attentions paid to the influence of hydrogen-vacancies interaction on them, which is seldom discussed in previous studies. The results show that the hydrogen-enhanced hardening rate and the hydrogen-promoted vacancy enrichment for the nickel alloys observed in experiments can be addressed well by the present model. The strain-induced vacancies rather than dislocations dominate the hydrogen trapping behavior, due to their higher hydrogen binding energies for the nickel alloy. The hydrogen-saturated state of vacancies can heavily impact hydrogen diffusion/trapping, which could be characterized by the effective trap concentration. The supersaturated vacancies caused by hydrogen-enhanced strain-induced vacancies can promote void growth through vacancy condensation, thus accelerating plastic localization or interface rupture. For the type-I loaded blunt crack specimen, the hydrogen-enhanced dislocation multiplication contributes to intergranular cracking in the pressure valley, while hydrogen-enhanced vacancy generation facilitates void growth in the plastic zone, both of which can exacerbate plastic localization ahead of crack tip. A quantitative model for plasticity localization that accounts for the influences of hydrogen-induced IG cracking and void growth would be helpful in physically based modeling of hydrogen embrittlement. [Display omitted] • A coupled diffusional-mechanical model accounting for hydrogen enhanced strain-induced dislocations and vacancies is developed. • The strain-induced vacancies rather than dislocations dominate the hydrogen trapping behavior in nickel alloys. • For type I loading blunt crack, the hydrogen-enhanced dislocation multiplication and vacancy generation exacerbate plastic localization ahead of the crack-tip. [ABSTRACT FROM AUTHOR]

[Display omitted] • The texture effect on void growth in heterogeneous polycrystals is investigated in a statistical manner. • The texture effect on void growth is strongly dependent on the loading mode. • The statistical void growth for Cube (resp. Brass) texture is always slower (resp. faster) than that for Random texture. • The void growth in textured polycrystals correlates with material flow stress. • A modified Rice-Tracey model is proposed to predict the void growth involving texture effect. Polycrystalline materials usually exhibit obvious preferred grain orientations (i.e., crystallographic texture) after rolling and heat treatments, leading to a certain crystalline anisotropy. However, most previous studies on microvoid growth generally treated the material as homogeneous isotropic matrix, ignoring the influence of crystallographic texture. In the present work, four typical crystallographic textures of face-centered cubic crystal are considered, including the Cube, Goss, Brass and Copper textures. Afterwards, the texture effect on microvoid growth is systematically studied by crystal plasticity finite element simulation, from a statistical point of view. In addition, the role of loading mode (i.e., uniaxial or biaxial tension) in the texture effect on microvoid growth has also been explored. The results indicate that the crystallographic texture evidently affects the statistical void growth in heterogeneous polycrystals, regardless of the loading mode. Meanwhile, it has been found that the statistical void growth of Cube (resp. Brass) texture is always slower (resp. faster) than that of random grain-orientation case. Furthermore, it is interestingly concluded that for the four considered textures, the trend of statistical void growth (from fast to slow) is well consistent with that of average flow stress (from high to low) at any given strain level, which cannot be captured by the classical Rice-Tracey model. Finally, based on the statistical characteristics of void growth for different textures, a statistical Rice-Tracey model incorporating the texture effect is established. It is demonstrated that this statistical model can well envelop all the dispersed void growth results of different textures for the uniaxial tensile loading. [ABSTRACT FROM AUTHOR]

Leucine-rich repeat (LRR)-only proteins are involved in the innate immune responses as they mediate protein-ligand interactions. In the present study, three novel LRR-only proteins, Cf LRRop-4, Cf LRRop-5 and Cf LRRop-6, were identified and characterized from Zhikong scallop Chlamys farreri . They all contained LRR motifs with consensus signature sequences of LxxLxLxxNxL or LxxLxLxxCxxL. All the mRNA transcripts of three Cf LRRops were high abundant in hepatopancreas, gills and gonads, and their mRNA transcripts in hemocytes could respond to the stimulations of different microbes, including Vibrio anguillarum , Micrococcus luteus and Pichia pastoris . These three Cf LRRops exhibited similar ligand binding and recognition characteristics as Toll-like receptors (TLRs) and NOD-like receptors (NLRs). The immune effectors, including tumor necrosis factor α, superoxide dismutase, catalase and lysozyme, varied significantly after the scallops were stimulated by recombinant LRR-only proteins. All these results indicated that LRR-only proteins are functionally differentiated and exhibit different immunomodulation activities on various downstream immune effectors. [ABSTRACT FROM AUTHOR]

• The size- and stress-dependent dislocation-DLs interactions are investigated by MS and MD, with the emphasis focused on its kinetic effect. • The dislocation tends to fully absorb/transform small DLs but only to partially absorb/transform large ones. • When the dislocation is accelerated to subsonic speed, abnormal "pull-forward" configurations can be formed after it bypasses the small DLs. • The kinetic effect decreases the CRSS of dislocation bypassing DLs evidently. • Both amended DBH and BKS hardening models are proposed to consider the above kinetic effect. In this paper, the interaction between an edge dislocation and irradiation <100> sessile self-interstitial atom (SIA) type dislocation loops (DLs) is studied by atomistic simulations in BCC Ta at 0 and 300 K. Both molecular dynamics (MD) and statics (MS) simulations are performed to highlight the dislocation kinetic effect (or dynamic effect) on the critical resolved shear stress (CRSS) for dislocation bypassing the DLs and on the dislocation-SIA DLs interaction mechanisms. The simulation results show that the dislocation-DLs interaction mechanisms are two-fold. When the DL size is lower than a critical value, the moving edge dislocation tends to completely absorb the DLs or fully transform the original DLs into other-type ones. However, when the DL size is higher than the critical value, the moving dislocation tends to absorb or transform the DLs partially or even marginally. Moreover, with increasing applied shear stress, the high-speed dislocation has no sufficient time to absorb SIAs from DLs, which also changes the dislocation-DLs interaction process remarkably. When the dislocation is accelerated to subsonic, an abnormal "pull forward" dislocation configuration may present upon the dislocation bypasses a small DL. More importantly, with the kinetic effect considered, the CRSS for dislocation overcoming the barriers of DLs decreases significantly for the dislocation-DLs interaction mechanisms. In order to appropriately describe the kinetic effect on the CRSS, amended dispersed barrier hardening (DBH) and Bacon-Kocks-Scattergood (BKS) hardening models for the latter dislocation-DLs interaction mechanism are proposed. [Display omitted] [ABSTRACT FROM AUTHOR]

Nickel-based superalloys (NBSAs) serve as hot-end component materials of aero engines. NBSAs generally consist of γ and γ′ phases, the γ′ phase (i.e. Ni 3 Al) presents anomalous yield strength and non-Schmid effect, influencing the mechanical behaviors of NBSAs significantly. These phenomena are closely related to the ⟨ 110 ⟩ { 111 } superdislocations. In the present work, based on the quasiharmonic density functional theory (DFT), the improved semi-discrete variational Peierls-Nabarro (SVPN) model is employed to systematically investigate the properties of such superdislocations, in terms of dislocation density distribution, splitting distance (i.e., anti-phase boundary APB, super-lattice intrinsic stacking fault SISF and complex stacking fault width CSF), total energy, Peierls stress and so on. It is found that the predicted superdislocation characters, especially the Peierls stress, are in good agreement with previous experimental results, considering the lattice discreteness effect. This implies that the lattice discreteness plays an important role in the total dislocation energy and Peierls stress, which has however been ignored in previous studies. Although such superdislocation may have several possible core configurations, the dissociation of four 1 / 6 ⟨ 112 ⟩ Shockley partials separated by two CSFs and an APB may be more energetically favorable at both 300 K and 1200 K. In addition, the superdislocation properties with such the core structure may be easily affected by applied stress. The present work provides an improved SVPN model with consideration of lattice discreteness to describe the superdislocation properties in Ni 3 Al, which may be helpful for understanding the plastic deformation behavior of the γ′ phase and NBSAs. • The DFT-informed SVPN model is developed to investigate superdislocations in Ni 3 Al. • The effect of lattice discreteness plays an important role in both the total superdislocation energy and Peierls stress. • The predicted APB-width and Peierls stress by present SVPN model are well consistent with experimental results. • The formation of the type I′ configuration is the most energetically favorable at the considering temperatures. • The core structure of type I′ superdislocations is very sensitive to the externally applied stress. [ABSTRACT FROM AUTHOR]

• The growth of both intragranular and intergranular voids and their competition are first investigated systematically. • The void-growth mechanisms for single crystals (resp. bi-crystals) are not preserved in intragranular (resp. intergranular) cases. • The strong orientation effects observed in single crystals are weakened in polycrystals. • The statistical void growth distribution is closely related to the void-GB relative position. In polycrystalline materials, void growth is strongly dependent on its surrounding microstructural environment such as grain morphologies, crystallographic orientations and void-grain boundary (GB) relative position. In this study, two kinds of void-GB relative positions are considered to investigate the orientation effect on void growth in FCC polycrystals: intragranular type, i.e., void located in interior of a grain; and intergranular type, i.e., void located at boundary of two adjacent grains. The analysis of orientation effect in intragranular (resp. intergranular) cases is conducted through a comparative study with single-crystal (resp. bi-crystal) counterparts. Moreover, the competition between the intragranular and intergranular void growth behaviors is statistically investigated for the first time. To this end, the representative volume element (RVE) of polycrystalline aggregates containing either intragranular or intergranular void is created by 3D Voronoi tessellation. Multiple realizations with different grain morphologies and crystallographic orientation permutations are implemented using crystal plasticity finite element (CPFE) simulations. We show that the mechanism for orientation effect on void growth in single crystals (resp. bi-crystals) is not preserved in intragranular (resp. intergranular) cases. According to the statistical analysis, both the intragranular and intergranular void growth follows a Gaussian distribution, whose profile is affected by both macroscopic stress triaxiality and Lode parameter. It is revealed that the statistical void growth distribution induced by random grain morphologies and crystallographic orientations is closely associated with the void-GB relative position (intragranular or intergranular). The present study may provide much richer insights into the mechanism of damage evolution in polycrystalline metals. [ABSTRACT FROM AUTHOR]

Vacancies can easily capture H atoms in metals, forming hydrogen-vacancy complexes/clusters. In this work, the hydrogen-vacancy interactions in CoCrFeMnNi high-entropy alloy (HEA) were studied with first-principles calculations based on the density functional theory (DFT). The special quasi-random structure (SQS) method was used to construct a chemically disordered HEA, and the effects of solute H atoms on the formation energy of monovacancy, the formation energy and binding energy of multi-vacancy cluster were calculated. It is found that an H atom prefers to occupy an octahedral interstitial site neighboring a vacancy and attracts the charge from the surrounding first-nearest neighbor atoms (e.g. Co, Ni, Fe or Mn atom, excluding Cr atom), weakening the stability of the atoms around the vacancy and reducing the vacancy formation energy in CoCrFeMnNi HEA. After introducing H atoms, the formation energies of both vacancy and vacancy cluster decrease in CoCrFeMnNi HEA, but they are still higher than those in pure Fe and Ni. In addition, the reduction of the binding energy of vacancies in CoCrFeMnNi HEA is much lower than that in pure Fe and Ni, and the binding energy of vacancies even increases in some cases. The results of the first-principles calculations indicate that the solute hydrogen atoms, although promoting vacancies, unfavorably combining vacancies into clusters to form micro-voids. This provides a good explanation for the good resistance to hydrogen embrittlement of CoCrFeMnNi HEA observed in experiments. [Display omitted] • The vacancy formation energy reduction in HEA was revealed by the preferred site and electronic structure of a trapped H atom. • The effect of trapped H on the formation and growth process of multi-vacancy clusters in HEA was found. • The experimental phenomenon of HE in HEA was explained by first-principles calculations on H-vacancy interactions. [ABSTRACT FROM AUTHOR]

• The size-dependent microvoid growth in heterogeneous polycrystals is studied by local/non-local (MSG) CPFEM. • The first kind of void-growth size effect by void-grain size ratio is investigated. • The second kind of void-growth size effect by absolute microvoid size is studied. • Stress triaxiality T has a significant influence on the void-growth size effect, while Lode parameter L exhibits a negligible effect. • The void-growth size effect in polycrystalline environments should be understood from a statistical point of view. Microvoid growth involves a strong size effect, i.e., smaller microvoid presents a lower growth rate. In polycrystalline materials, the size ratio between microvoids and grains may also affect microvoid growth behavior. However, most previous studies treated material matrix surrounding microvoids as homogeneous. It turned out that such treatment cannot effectively depict the influence of the abovementioned void-grain size ratio on damage evolution. In the present study, both classical local and non-local strain-gradient crystal plasticity finite element simulations are performed to study size-dependent microvoid growth in heterogeneous polycrystals. The results indicate that both void-grain size ratio and absolute microvoid size influence microvoid growth significantly, referred to as first (induced by grain-scale heterogeneous deformation) and second kinds of (induced by plastic strain gradient) size effects, respectively. Besides, macroscopic stress triaxiality T has a significant influence on the size effect of microvoid growth, while Lode parameter L exhibits a negligible effect. Due to random grain-orientation distribution and grain-geometric characteristic, a smaller microvoid within polycrystalline environments may even grow faster than a larger one, implying that the size effect of microvoid growth should be understood from a statistical point of view in polycrystalline environments. The present study provides a fundamental understanding on the intrinsic mechanism of the size-dependent microvoid growth in heterogeneous polycrystals. [Display omitted] [ABSTRACT FROM AUTHOR]

The effects of hydrogen on dislocation mobility and operation of the Frank-Read source are evaluated using our recently developed phase-field model. This is achieved by accounting for long-range elastic hydrogen-dislocation interaction (i.e., hydrogen shielding effect) and short-range inelastic hydrogen-dislocation core interaction through atomically informed generalized stacking fault energy (GSFE, or γ -surface). The results show that, due to the short-range interaction, hydrogen impedes the dislocation motion, which is contrary to the long-range hydrogen shielding effect. The bow-out configurations of the Frank-Read source obtained by the phase-field model can agree well with that from the atomic simulations. Hydrogen can decrease the critical nucleation stress of the Frank-Read source and thus enhance the hydrogen-induced plasticity. Moreover, the hydrogen-induced dislocation core energy reduction prevails over the hydrogen-induced elastic shielding, especially when the hydrogen concentration is low. Our results suggest that the modification of the dislocation core structure due to the short-range interaction plays an important role in understanding the hydrogen-enhanced localized plasticity mechanism. Finally, quantitative influences of hydrogen on dislocation mobility and critical nucleation stress of the Frank-Read source are obtained, which can further serve upscaled dislocation dynamics simulation and dislocation-density based crystal plasticity modelling. [Display omitted] • Hydrogen can reduce rather than enhance the dislocation mobility, which is contrary to the hydrogen shielding effect. • Hydrogen can promote the dislocation multiplication, providing a viable interpretation of the HELP mechanism. • Quantitative influences of hydrogen on dislocation mobility and multiplication are obtained. [ABSTRACT FROM AUTHOR]

Self-healing strategies aim at avoiding part repair or even replacement, which is time consuming, expensive and generates waste. However, strategies for metallic systems are still under-developed and solid-state solutions for room temperature service are limited to nano-scale damage repair. Here we propose a new healing strategy of micron-sized damage requiring only short and low temperature heating. This new strategy is based on damage localization particles, which can be healed by fast diffusing atoms of the matrix activated during heat treatment. The healing concept was successfully validated with a commercial aluminum alloy and manufactured by Friction Stir Processing (FSP). Damage was demonstrated to initiate on particles that were added to the matrix during material processing. In situ 2D and 3D nano-imaging confirmed healing of the damaged material and showed that heating this material for 10 min at 400°C is sufficient to heal incipient damage with complete filling of 70% of all damage (and up to 90% when their initial size is below 0.2 µm). Furthermore, strength is retained and the work of fracture of the alloy is improved by about 40% after healing. The proposed Programmed Damage and Repair healing strategy could be extended to other metal based systems presenting precipitation. [Display omitted] [ABSTRACT FROM AUTHOR]