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In order to obtain the good match between yield strength and low-temperature toughness, the short-time partial austenitization (SPA) process was employed for V/Mo-bearing 0.22C–5.24Mn steel. The initial microstructure after intercritical tempering was dual-phase ferrite and reversed austenite (RA), while the final microstructure consisted of ferrite, RA, and secondary martensite (SM) after being subjected to the SPA process. (V, Mo)C with disclike morphology mainly precipitated during intercritical tempering, and the aspect ratio of particles decreased, leading to the appearance of near-spherical morphology. After being subjected to SPA process, the resultant multiphase hierarchical microstructure (three layers: outer layer of ferrite, interlayer of SM, and inner layer of RA) enabled a high yield strength of 1097 MPa, a total elongation of 14%, and an impressive impact energy of 33.3 J at −20 °C. The strengthening contribution of (V, Mo)C precipitation was estimated to be about 108 MPa. [ABSTRACT FROM AUTHOR]

Controlling the grain growth of ceramic powders is an interesting technological development. Due to the large aspect ratio, the packing of ceramic nanoplates during sintering may significantly improve the microstructure, which induces higher mechanical performance. In the present work, we successfully fabricated the Al 2 O 3 nanoplates by colloidal processing using graphene oxide (GO) as a template. Al 2 (SO 4) 3.18H 2 O was used as raw materials to deposit amorphous alumina on the GO surface. The phase transformation behavior of Al 2 O 3 nanoplates was evaluated at different temperatures. The thermally stable α ˗Al 2 O 3 nanoplates showed limited grain growth after spark plasma sintering (SPS) compared to Al 2 O 3 nanoparticles. The refined microstructure of α ˗Al 2 O 3 nanoplates derived alumina ceramic induced higher flexural strength and toughness. [ABSTRACT FROM AUTHOR]

24CrNiMoY alloy steel with high strength and toughness was prepared by selective laser melting (SLM) technology. The microstructure and mechanical properties of alloy steel samples prepared by SLM using different laser energies were studied. The results showed that with increasing energy density, the internal defects of the sample first decreased and then increased, and the hardness and tensile properties also showed a trend of increasing at first but decreasing afterwards. When the energy density was 100.7 J/mm3, the alloy steel sample has the fewest defects and the highest hardness (391.2 HV0.2). The tensile strength and impact toughness also reached the best state: the tensile strength was 1252.83 MPa, the yield strength was 1041.62 MPa, the elongation to fracture was 12.89%, and the impact toughness was 65.7 J. The microstructure of 24CrNiMoY alloy steel prepared by SLM is mainly composed of fine lath martensite, which has good strength and toughness. [ABSTRACT FROM AUTHOR]

Ti 3 AlC 2 as a typical MAX phase has attracted extensive attention due to its advantages of both metals and ceramics. However, the decomposition of Ti 3 AlC 2 during pressureless sintering leads to a low density, which restricts its application in complex-shaped components. To address this challenge, MgO, CeO 2 , Y 2 O 3 , and La 2 O 3 were employed as additives to fabricate Ti 3 AlC 2 ceramics with minimal decomposition via pressureless sintering. It was observed that these oxide additives reacted with aluminum and oxygen, forming MgAl 2 O 4 , CeAlO 3 , YAlO 3 , and LaAlO 3 , respectively. These in-situ generated aluminate particles effectively impeded the outward diffusion of aluminum and the inward diffusion of oxygen, thereby inhibiting the decomposition of Ti 3 AlC 2. Furthermore, the thermal expansion mismatch between the in-situ generated particles and the matrix induced beneficial residual stresses. These combined effects contributed to the synchronized enhancement of both strength and toughness. Among the four additives, CeO 2 displayed the best efficiency. Ti 3 AlC 2 -1.0 wt%CeO 2 reached a flexural strength of 680.74 MPa and fracture toughness of 7.82 MPa m1/2, equivalent to those by pressure assisted sintering. The calculated toughness considering the residual stress was approximately 7.71 MPa m1/2, in good agreement with the measured value. [ABSTRACT FROM AUTHOR]

The bone plate of turtle shell carapace is formed by several individual ribs through the suture structure of bone teeth. Based on the tensile and bending experiments as well as finite element analysis, the influence of bone teeth at the suture on the strength and toughness of the bone plate of turtle shell carapace is studied in this paper. Precisely morphological characterization shows that the bone teeth at the suture of bone plate are mainly formed by triangle and quadrilateral grooved cones instead of the perfect cone that is often assumed. Similar to the bone plate, 3D printed samples with suture structures formed by triangle or quadrilateral grooved conical teeth are then prepared. Based on the natural and printed samples, the tensile tests combined with the finite element calculations find that the peak-to-valley ratio of bone teeth is a key factor that can explain the strength and toughness of the sutured bone plate varying with the shape of bone teeth, instead of the supposedly lateral surface area or the project area of bone teeth. For bone teeth with a given shape, the larger the peak-to-valley ratio, the larger the strength and toughness of the bone plate are. Comparison of the bending experimental result of 3D printed suture structures with grooved conical bone teeth and that of the natural sutured bone plate of turtle shell carapace further verifies the finding that the peak-to-valley ratio is a decisive parameter on the strength and toughness of suture structure of bone teeth. The results of this paper should be of significance to the biomimetic design of suture structures with high strength and toughness. [ABSTRACT FROM AUTHOR]

It is still extremely challenging to endow epoxy resins (EPs) with excellent flame retardancy and high toughness. In this work, we propose a facile strategy of combining rigid–flexible groups, promoting groups and polar phosphorus groups with the vanillin compound, which implements a dual functional modification for EPs. With only 0.22% phosphorus loading, the modified EPs obtain a limiting oxygen index (LOI) value of 31.5% and reach V-0 grade in UL-94 vertical burning tests. Particularly, the introduction of P/N/Si-containing vanillin-based flame retardant (DPBSi) improves the mechanical properties of EPs, including toughness and strength. Compared with EPs, the storage modulus and impact strength of EP composites can increase by 61.1% and 240%, respectively. Therefore, this work introduces a novel molecular design strategy for constructing an epoxy system with high-efficiency fire safety and excellent mechanical properties, giving it immense potential for broadening the application fields of EPs. [ABSTRACT FROM AUTHOR]

To solve the problem of easy delamination of the interface of Al/CFRP/Al laminate (CFRP, carbon fiber composite; Al, aluminum), a method of constructing high strength and toughness at the interface is proposed. The effects of adding resin and carbon nanotubes at the interface on the shear, flexural strength and impact resistance of Al/CFRP/Al laminates are studied. Experimental results show that gullies and micropores can be formed on the surface of aluminum after pretreatment, and the contact area between aluminum and matrix can be increased. After resin is added to the Al/CFRP interface, the shear strength between layers and the bending strength and impact resistance of laminates are improved. Mixing carbon nanotubes into the added resin will further improve the mechanical properties of laminates. On the basis of strengthening and toughening the Al/CFRP interface, the carbon nanotubes added between the CFRP layers can strengthen and toughen the resin at the interface, which enhances the bending strength and impact resistance of the laminates. When the resin between the layers breaks, the carbon nanotubes will be pulled off and pulled out to resist the damage of the resin, and the carbon nanotubes at the end of the crack can hinder the propagation of the cracks. [ABSTRACT FROM AUTHOR]

The toughening mechanism of the nacre was widely investigated in recent decades, which presents a great prospect for designing high performance composite materials and engineering structures with bioinspired structures. To further elucidate which structural parameters and which kinds of morphology of the nacre-inspired structure are the best for improving tensile strength without sacrificing too much toughness is extremely significant for composite materials and engineering structures. The "brick-and-mortar" structure is a classical nacre-inspired bionic structure. Three characteristic structural parameters, including the aspect ratio ρ of the brick length and width, the thickness ratio β between the thickness of brick and mortar, and the spacing ratio τ between the width of brick and mortar, were used as variables to study their effect on tensile strength and toughness. It was found that ρ was the most prominent factor in determining the strength and toughness, and τ could improve the strength and toughness almost simultaneously. Racked and wedged morphology of the structural unit were established based on the structural parameters of the regular staggered unit, and were used to compare tensile behavior. It was found that the model with the wedged unit possessed the highest strength and toughness, and could absorb more strain energy during fracture crack growing. The crack propagation path further illustrated that the crack resisting ability of the wedged unit was the best. Our simulation results presented the connection between three characteristic structural parameters with the strength and toughness, and proved that the wedged staggered unit was the best in improving the strength and toughness. [ABSTRACT FROM AUTHOR]

Despite substantial advancements in optimizing structural designs for stiffness, the field of design against fracture is still in its early stages. This paper introduces a fundamental and standardized paradigm for structural design against brittle fracture, achieved through the minimization of the energy release rate G within the framework of linear elastic fracture mechanics (LEFM). By leveraging the Griffith criterion expression and the total potential energy in LEFM, we propose an efficient approach for structural optimization that enhances the toughness of architected materials. The energy release rate G is evaluated a synergistic application of finite element analysis and finite difference methods, yielding a precision of 0.6% compared to benchmarks in published handbooks. We demonstrate significantly reduced G values compared to standard stiffness and stress-oriented topology optimization, which directly contributes to increased toughness. To comprehensively analyze the fracture process encompassing damage, crack initiation, propagation, and failure, we employ post-processing phase field fracture modeling on the optimally designed architected materials. By performing multi-objective optimization of the stiffness and energy release rate G , the toughness and extreme load-bearing capacity can be simultaneously improved. The resulting perforated architecture effectively outperforms homogeneous structures in both toughness and peak load. Additionally, we extend our analysis to various configurations, such as non-center cracks, pure shear loading, and adherence to the standard 3D compact tension ASTM E-399-72. The designed structures are additively manufactured and experimentally validated, demonstrating a toughness increase of over 10 times compared to stress-based design. These contributions offer promising prospects for advancing the design of future engineering structures and materials with a favorable balance of critical fracture resistance characteristics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Supramolecular elastomer with high strength and toughness and low smoke toxicity. • SPU elastomer has a tensile strength of 53.77 Ma and a elongation at break of 715.26 %. • Fractional Effective Dose was used to evaluate the flue gas toxicity of elastomer composites. Elastomer with high strength and toughness, temperature resistance and low smoke toxicity have shown great application prospects in the field of safety protection. In order to meet the needs of high strength, high toughness and smoke toxicity safety, a high-strength structural elastomer is formed by introducing the integration of hard skeleton and soft elastomer, that is, two-dimensional black phosphorus with high flame retardant efficiency and bimetallic hydroxide with catalytic detoxification (BP-MA-LDH) as the hard skeleton, based on the special combination of internal hydrogen bonds. High strength supramolecular poly(Urethane) (SPU) elastomer was manufactured by molecular design. The high strength and toughness SPU elastomer also has a tensile strength of 53.77 Ma and a elongation at break of 715.26 %. The addition of 2.0 wt% BP-MA-LDH reduces the heat release rate of SPU by 58.84 % and the smoke production release by 61.54 %. In terms of flue gas toxicity inhibition, Fractional Effective Dose was used to evaluate the flue gas toxicity of elastomer composites, and the release of CO, HCN, oxynitride and other toxic gases were greatly reduced. The synthetic performance of SPU elastomer composites in strengthening and toughening, smoke suppression and toxicity reduction is much better than that reported by peers. [ABSTRACT FROM AUTHOR]

The effects of long-term tempering (2h, 4h and 8h) on microstructure and mechanical property of rack steel A514 GrQ for offshore platforms were studied. It is found that during the tempering process, the quenched martensite lath structure recovered, C, Cr, Mo and V elements diffused, and MC, M2C, and M23C6 type carbides were precipitated in the martensite matrix. After tempering for 2h, the carbides tended to be stable and the Ostwald ripening occurred. With the increase of tempering time from 0h to 8h, tensile strength of the tested steel decreased from 1100MPa to 813MPa and yield strength decreased from 931MPa to 725MPa. The impact energy at -60℃ increased from 187J of the as-quenched steel to 238J after 2h tempering and then it tended to be stable with a value about 245J for further tempering. The elongation increased from 15.2% of the as-quenched steel to 16.7% after 2h tempering and further increased up to 19.5% for 8h tempering. These results indicate that in the process of tempering at 600℃ for 2-8h, the experimental steel A514 GrQ can perform the good tempering stability and the excellent combination of strength and toughness, associated with the best tempering time of 2h. [ABSTRACT FROM AUTHOR]

A two-stage aging, involving initial low-temperature treatment followed by high-temperature treatment, was employed to induce a high number density M 2 C and inhibit the occurrence of chemical ordering and formation of large ellipsoidal particles at grain boundaries. The ultimate tensile strength, yield strength and Charpy impact energy increase by 233 MPa, 191 MPa and 3.3 J, respectively. [ABSTRACT FROM AUTHOR]

A thermal protection material (TPM) was prepared using Al 2 O 3 -phosphate, expanded aluminosilicate, and phenolics through compression molding and the gradient heating reaction technique, and the effect of the high-temperature treatment on the properties of the composites were investigated. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used to analyze the structures and compositions of the composites. After the high-temperature treatment, the composites exhibited increased porosity, decreased density, and generated SiC particles with high strength and temperature resistance. The prepared composites have high compressive strength and compression deformation ability of the bending point. Thermogravimetric analysis, coefficient of thermal conductivity measurements, and expansion analysis were carried out to evaluate the thermal properties of the composites, and the effects of the preparation conditions on the thermal properties of the composites were investigated. The results showed that the prepared composites exhibited complete morphology, excellent high-temperature resistance, high compressive strength and toughness, and low thermal conductivity before and after the high-temperature treatment at 1000 °C, and hence showed great potential for future thermal protection applications. [ABSTRACT FROM AUTHOR]

In this study, the effect of the silicon carbide (SiC) matrix content on the mechanical behaviour of a three-dimensional needled carbon fibre-reinforced SiC matrix composite (C/SiC) was investigated. The SiC matrix content was controlled by the infiltration time, and it can be divided into two stages for the evolution of matrix densification, leading to different mechanical responses. In the first stage, with an increase in the SiC matrix content from 12 to 39 vol%, the matrix was filled into a non-woven cloth, leading to an improvement in the loading efficiency of the fibre bundles. Thus, flexural strength and fracture toughness increased sharply from 54 to 218 MPa and 1.3–13.0 MPa m1/2, respectively. As the SiC matrix content increases to 59 vol% in the second stage, the flexural strength and fracture toughness increased to 256 MPa and 15.4 MPa m1/2, respectively. The infiltration ability of the SiC matrix into the non-woven cloth reached the threshold in this stage, and the SiC matrix filled the short-cut web layer, resulting in a slightly increasing tendency of strength and toughness. [ABSTRACT FROM AUTHOR]

Herein, the microstructural evolution and mechanical properties of a low‐carbon Nb–Ti–Mo‐bearing steel subjected to hot rolling followed by four different processing schedules (air cooling, direct quenching, low‐temperature tempering, and high‐temperature tempering) are studied to elucidate the significance of structural refinement and nanoscale precipitates for obtaining the optimized combination of strength and toughness. The microstructure of air‐cooled steel composed of coarse polygonal ferrite and granular bainite, and minimum yield strength of 473 MPa and lowest impact energy at −40 °C of 40 J are obtained. The microstructure of steel direct quenched and tempered at 520 °C consists of sub‐micron tempered martensitic and bainitic laths with a high relative fraction of high misorientation boundaries and high density of 3–5 nm (Nb, Ti, Mo)C precipitates, and maximum yield strength of 726 MPa and highest impact energy at −40 °C of 213 J are obtained. The formation of nanoscale precipitates coupled with fine tempered martensitic and bainitic blocks contributes to 253 MPa improvement of yield strength and more than five times enhancement of impact energy. The small blocks of tempered martensite and bainite can deviate and finally arrest the crack propagation, whereas the coarse polygonal ferrite and bainite provide inadequate resistance for crack propagation. [ABSTRACT FROM AUTHOR]

Polycarbonate (PC) has a very low environmental stress crack resistance (ESCR). This work aims at increasing its ESCR as well as its tensile strength and toughness via a hybrid ternary blend (HTB) which is composed of PC, hydroxyl-rich polyvinyl butyral (PVB) and hydroxyl-rich silica (SiO 2). Selective distribution and fine dispersion of SiO 2 in the dispersed phase (PVB) through hydrogen bonding between the PVB and SiO 2 endows the HTB with high ESCR, tensile strength and toughness. Two processes are compared to develop the HTB. One is composed of two steps: the SiO 2 is dispersed in the PVB dissolved in anhydrous ethanol; after the removal of the ethanol, the resulting (PVB/SiO 2) is then blended with the PC in the molten state. The other process is composed of a single step: PVB, SiO 2 and PC are directly blended in the molten state. The two-step process yields better properties: The PC/(PVB-10/SiO 2 -2) containing 10 wt% of PVB and 2 wt% of SiO 2 shows higher melt flow index, tensile strength and toughness. More importantly, its ESCR in carbon tetrachloride is 5 times that of the PC. We envision that this work provides a new perspective to the theory of HTB, and opens a promising route to prepare high-performance PC with excellent practicality. Polycarbonate-based hybrid ternary blends (HTBs) with high environmental stress crack resistance, high strength and high toughness are controllably fabricated by manipulating the distribution and fine dispersion of silica in polyvinyl butyral dispersion phase. This work provides a new perspective to the theory of HTB, and opens a promising route to prepare high-performance PC with better practicality. [Display omitted] • HTBs composed of PC, hydroxyl-rich PVB and hydroxyl-rich SiO 2 are prepared. • The HBTs exhibit high ESCR, high tensile strength and high toughness. • The two-step process with premixed PVB/SiO 2 yields better properties than the one-step process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The outstanding nanostructure of nacre was truly duplicated with planar orientation on the fiber along the strain direction. • It is the first time to introduce cation-π interaction into carbon fiber composites and induce the fabrication of interface. • The composites which equipped with the "brick-and-mortar" well-designed interface displayed dramatic high strength and toughness. • This work offers a new sight for the interface modification of fiber-based composites. The realization of carbon fiber composites with both high strength and toughness has been frustrated by the unfavorable interphase. Duplicating the nanostructure of nacre into the interface design of carbon fiber is an ideal route. However, truly constructing a nacre-like interphase on the carbon fiber surface is still one of the key challenges due to the unique nanostructure of the carbon fiber surface. Particularly, an important question is lack of proper and strong adhesion forces to guide the "brick" assembly, and hence the ordered arrangement of the brick phase on the carbon fiber surface is hindered. Therefore, we introduced a novel self-designed "mortar" to trigger the oriented assembly of "brick" (graphene oxide, GO) on the carbon fiber surface for the introduction of a truly bio-inspired interface. Owning to rich π conjugated electron density, GO was promising to align with cation-containing "mortar" along the longitudinal direction. The main driving force was the cation-π interaction, which could afford strong interaction along in-plane direction than other binding forces. Due to the carefully designed interface, the interlaminar shear strength (ILSS), and the toughness of upgraded composites achieved 108 MPa and 46.6 MJm−3. This work provided a new inspiration for designing high-performance carbon-based composites. [ABSTRACT FROM AUTHOR]

The strategies for nanosol from metal alkoxide have enabled production of ultratransparent and mechanically robust polymer nanocomposites at extremely high loading. Herein, a simple approach to fabricate high‐performance polyurethane‐based nanocomposites via unmodified boehmite nanoparticles is reported. Evaluating their physical properties, the uniform dispersion of boehmite in the matrix caused nanocomposites retains ultrahigh transparency. Hydrogen bonding and intermolecular entanglement between boehmite and polyurethane brings about the mechanical properties of the nanocomposites material enhanced, i.e., strength, stiffness, and toughness. Optimized strength, stiffness, and toughness of Boehmite/Cationic waterborne polyurethane at 40 wt% (BNC40) are up to 58.1 MPa, 1096.7 MPa, 249.5 MJ m−3, respectively. Furthermore, the feasibility and mechanism of polymer strengthening and toughening by inorganic rigid nanoparticles is explored from the aspects of crystallinity and micromorphology. [ABSTRACT FROM AUTHOR]

Bio-sourced nanocellulosic materials are promising candidates for spinning high-performance sustainable macrofibers for advanced applications. Various strategies have been pursued to gain nanocellulose-based macrofibers with improved strength. However, nearly all of them have been achieved at the expense of their elongation and toughness. Inspired by the widely existed hierarchical helical and nanocomposite structural features in biosynthesized fibers exhibiting exceptional combinations of strength and toughness, we report a design strategy to make nanocellulose-based macrofibers with similar characteristics. By combining a facile wet-spinning process with a subsequent multiple wet-twisting procedure, we successfully obtain biomimetic hierarchical helical nanocomposite macrofibers based on bacterial cellulose nanofibers, realizing impressive improvement in their tensile strength, elongation and toughness simultaneously. The achievement certifies the validity of the bioinspired hierarchical helical and nanocomposite structural design proposed here. This bioinspired design strategy provides a potential platform for further optimizing or creating many more strong and tough nanocomposite fiber materials for diverse applications. [ABSTRACT FROM AUTHOR]

Effects of QT (quenching + tempering) treatment on the proportion of grain boundary, grain size, carbide precipitation, strength and toughness of the tested steels were studied by room-temperature tensile test, pendulum impact test, optical and scanning electron microscopy, and the distribution and combination of the variants were also analyzed. The results show that when the tempering temperature increases, the strength of the tested steels gradually decreases with an increase of plasticity. The fracture modes of 450T and 500T steels are quasi-cleavage fracture, where the impact toughness becomes worse due to the carbides precipitated from bainite laths and the smaller proportion of high-angle grain boundary. The fracture modes of 600T and 650T steels are dimple fracture, where the increased proportion of the high-angle grain boundary hinders the crack propagation more effectively. The variant analysis shows that the variant combination mode of 450T steel is between Bain group and CP (close-packed) group, while that of 600T one tends to be a CP combination mode. The larger misorientation between the variants in the same CP group can deflect the path of crack propagation, which improves the low-temperature toughness. [ABSTRACT FROM AUTHOR]

In this work, a new dual-phase high-entropy alloy (HEA) coating is successfully synthesized by laser cladding. XRD, SEM, TEM, EBSD, and TG-DSC are employed to investigate the microstructures and high-temperature stabilities. Simultaneously, under high-temperature friction and universal mechanical tester, the wear properties at 25 °C, 400 °C, and 800 °C and the mechanical properties at the compression speeds of 1 %, 2 %, and 3 % are explored. As indicated by the results, the FeCoNiAlCu HEA coating is composed of FCC phase with small angle grain boundaries and small size grains and BCC phase with HAGBs and large size grains. In terms of mechanical properties, FeCoNiAlCu HEA coating has good strength and toughness. When considering the fracture mechanism, it transfers gradually from a ductile fracture to a brittle fracture with increased compression speed. Besides, FeCoNiAlCu HEA coating maintains good stability at a high temperature of 764.2 °C. Meanwhile, the wear resistance and friction reduction of HEA coating are improved obviously at 800 °C. With the rise of temperature, the friction coefficient decreases gradually, the wear rate reduces, and the antifriction and wear resistance are enhanced. • The FeCoNiAlCu HEA is composed of FCC phase (LAGBs and small size grains) and BCC phase (HAGBs and large size grains). • The yield strengths of FeCoNiAlCu HEA are 1516.2 MPa, 1189.1 MPa and 929.8 MPa at the compression speeds of 1%, 2% and 3%. • With the increase of compression speed, the fracture gradually changes from ductile fracture to brittle fracture. • The FeCoNiAlCu HEA has good high temperature stability from 25°C to 764.2°C. • The frictional performance of HEA are improved obviously at 800°C. [ABSTRACT FROM AUTHOR]

In the pursuit of high performance development of alloy materials, it is a long-standing problem to enhance strength and toughness simultaneously. In this study, by selecting heterogeneous high-entropy alloy (HEA) materials and conducting structural design and laser process optimization, an external-hard internal-tough HEA composite coating with an in-situ dual-phase interface layer was successfully prepared. For the microstructure, the phase structures at the top, middle, and bottom of the coating are single-phase body-centered cubic (BCC), dual-phase BCC/face-centered cubic (FCC), and single-phase FCC, respectively. Among them, the dual-phase interface layer gives priority to the FCC phase (79.4 %), supplemented by the BCC phase (16.7 %). In terms of mechanical properties, the hardness of the coating from the top to the bottom is 9.85 GPa, 5.53 GPa, and 4.86 GPa, respectively. As demonstrated by employing the three methods of K, H/E, and H3/E2, the HEA composite coating has favorable integrated characteristics of strength and toughness. Meanwhile, due to the in-situ generated dual-phase interface layer, the structural and performance differences between the high-hardness layer and the high-toughness layer are effectively alleviated, and the stress concentration is reduced, thus stabilizing the overall structure of the coating. Hence, the HEA composite coating designed and prepared in this study possesses better erosion resistance (mass erosion rate = 0.141 × 10−3 g.cm−2 s−1), tribological properties (wear rate = 0.30 × 10−6 mm3/(N · m)), and impact resistance (AKU = 103.5 ± 2.8 J). The study results can provide new methods and new theories for new HEA composite coatings with integrated strength and toughness, and can be used in guiding the development and design of similar HEA composite coating structures. [Display omitted] • The FCC/FCC + BCC/BCC HEA composite coating with gradient structure is successfully prepared. • The FeCoCrNiAl interface layer is formed in situ by FeCoCrNi and FeCoCrAl. • The interface layer alleviates the structural and performance differences between the surface and bottom layers. • The HEA composite coating possesses good strength and toughness. • The HEA composite coating has better erosion resistance, preferable tribological properties, and superior impact resistance. [ABSTRACT FROM AUTHOR]

Controlled rolling and direct quenching followed by intercritical annealing was adopted to process Ti microalloyed low-C medium Mn heavy steel plates. Furthermore, the effect of Ti content on the microstructure evolution and mechanical properties was elucidated. The submicro-laminar microstructure of reverted austenite and lath-shaped ferrite was obtained after intercritical annealing at 630 °C. Increase in Ti content from 0.014% to 0.032% increased the amount of nano-scale TiC precipitates, leading to refinement of both the prior austenite grains and the subsequent laminar structure. Ultra-high yield strength of 790 MPa, elongation of 27.4%, and high toughness of 158 J at 0 °C was obtained. Further increase of Ti content to 0.053%, the mechanical stability of reverted austenite was significantly decreased, and the work-hardening behavior was changed to three-stage because a large amount of reverted austenite transformed to martensite prematurely. As a result, the elongation and impact energy were decreased due to the insufficient TRIP effect. Ti remarkably influenced the precipitation behavior, transformation process, and the mechanical properties of low C medium Mn steel in terms of structural refinement and austenite stability. Ti remarkably influenced the precipitation behavior, transformation process, and the mechanical properties of low C medium Mn steel in terms of structural refinement and austenite stability. Ultra-high yield strength of 790 MPa, elongation of 27.4%, and high toughness of 158 J at 0 °C was obtained. Unlabelled Image • Ti affected precipitation behavior and austenite stability of low C medium Mn steel. • Amount of nano-scale TiC precipitates increased with increasing Ti content. • Increasing Ti content refined both prior austenite grains and laminar structure. • Medium Ti addition led to a high combination of strength, ductility and toughness. • High Ti decreased the ductility and toughness due to reduced austenite stability. [ABSTRACT FROM AUTHOR]

Abstract Conductive hydrogels have received great attention owing to their promising applications in electrodes, supercapacitors, actuators, fuel cells, biosensors and biomedical devices and so on. However, it is still a challenge to achieve conductive hydrogels with integrated high performances, including high strength, large stretchability, high toughness, rapid self-recovery and good self-healing. In the present work, multiple physically cross-linked conductive hydrogels with integrated high performances were fabricated by in situ doping conductive PEDOT:PSS during the formation of dual physically cross-linked poly(N-hydroxyethyl acrylamide)/Laponite hydrogels. At the optimal condition, the conductive gels exhibit high tensile strength, high extensibility, high tearing energy, rapid self-recovery property without any external stimuli, high conductivity, good self-healing property, as well as sensitive strain sensing for monitoring human activities (e.g. the movements of the finger and wrist, and tiny breathing movements). Considering easy preparation and integrated high performances, our conductive gels have potential applications in wearable electronic sensors and bioelectronics. Highlights • Multiple physically cross-linked PHEA/Laponite/PEDOT:PSS (PLE) conductive hydrogels were prepared. • The PLE conductive gel showed high mechanical properties with tensile strength of 0.43 MPa and tearing energies of 1025 J/m2. • The PLE conductive gel exhibited large dissipated energy and rapid self-recovery propert. • The PLE conductive gel demonstrated high conductivity and good self-healing property. • The PLE conductive gel could be used as strain sensor to monitor human activities. [ABSTRACT FROM AUTHOR]

Fused filament fabrication (FFF) or fused deposition modeling is an additive manufacturing (AM) process commonly used for geometric modeling and rapid prototyping of parts called three-dimensional (3-D) printing. Commonly used thermoplastic materials in FFF 3-D printing AM are acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and polybutylene terephthalate (PBT). However, these materials exhibit relatively low strength and toughness. Therefore, it is desirable to improve various properties of thermoplastics in 3-D printing AM by employing nanotechnology. The combination of 3-D printing and nanotechnology opens new venues for the manufacture of 3-D engineered materials with optimized properties and multifunctionality (e.g. mechanical, electrical, and thermal properties). Hence, in this work, the multifunctional property improvement effects of graphene oxide (GO) on thermoplastic materials suitable for 3-D printing AM are investigated. Low loading of GO with carboxyl and hydroxyl surface functional groups is incorporated into thermoplastic materials suitable for 3-D printing AM by a special mixing technique. ABS is chosen in this study due to its availability. Graphene nanosheets are employed to improve the properties of the developed nanocomposites by 3-D printing AM. GO is chosen to improve the dispersion of graphene nanosheets into the thermoplastic system to increase their interfacial adhesion. A multifunctional property improvement is observed in the developed nanocomposite with less than 0.1 wt% GO. Employing ASTM standard tests, it was found that at a very small loading of 0.06% by weight, GO could improve the properties of the thermoplastic in terms of strength, strain-to-failure, and toughness, while maintaining the stiffness, rendering the developed nanocomposites suitable for various applications of static and dynamic loading. GOs are now commercially available at low prices. At such low loadings, these graphene-type materials become economically feasible components of nanocomposites. [ABSTRACT FROM AUTHOR]

The strength and toughness of 1000 MPa grade steel plate for hydropower station treated by different reheated quenching temperatures were investigated. With the increasing of reheated quenching temperature, the yield strength and tensile strength increase sharply, whereas the value of impact toughness decreases slowly. The lath martensite with high density dislocations enhances dislocation strengthening. On the contrary, the acicular or block ferrite (soft phase) produced by intercritical quenching reduces the phase transformation strengthening. Moreover, the ferrite has a low solubility of interstitial carbon due to the body‐centered‐cubic lattice structure. The bar‐shaped precipitates occur during the isothermal holding at the intercritical temperature and it will reduce the precipitation strengthening. The ferrite phase and high misorientation boundaries are the main factors that contribute to the toughening of the experimental steel. The lower the reheated quenching temperature is, the higher proportion of ferrite and high misorientation boundaries becomes. Considering the requirements for mechanical properties of 1000 MPa grade steel plate for hydropower station, the optimal temperature of reheated quenching is ∼920 °C. [ABSTRACT FROM AUTHOR]

To clarify the effect of peak temperature on the Cu-rich nanoscale re-precipitation behavior and strength-toughness for welding heat affected zones (HAZs), Gleeble-3500 was utilized to simulate the HAZs for Cu-bearing high strength steel with the peak temperature of 780–1350 °C. 9R-Cu with the size of 5 nm precipitated in FGHAZ. Multi-structured Cu-rich particles precipitated in ICHAZ, including 9R-Cu with the size of 4 nm and 3R-Cu with the size of 12 nm. Phase field simulation showed that the re-precipitation behavior of Cu-rich particles was related to α-Fe transformation temperature. When the peak temperature was above A c3 , the increment of peak temperature decreased the α-Fe transformation temperature and inhibited the re-precipitation of Cu-rich particles. When the peak temperature was between A c1 and A c3 , the increase of peak temperature promoted the re-precipitation of 9R-Cu and suppressed the coarsening of 3R-Cu in ICHAZ. Re -precipitation of Cu-rich particles provided precipitation strengthening of 132 MPa and 237 MPa for ICHAZ and FGHAZ, respectively. The high cooling rate during welding increased the grain boundary density of HAZs, which improved the strength of matrix and crack propagation energy. Therefore, the strength and toughness of HAZs for Cu-bearing steel were both higher than base metal. • Phase field simulation showed that the re-precipitation behavior of Cu-rich particles was related to α-Fe transformation temperature. • The high cooling rate during welding increased the grain boundary density of HAZs, which improved the strength of matrix and crack propagation energy. [ABSTRACT FROM AUTHOR]

Medium-Mn steel was innovatively designed in terms of alloying elements for medium to heavy steel plates to obtain combination of high strength, good ductility, and excellent low temperature toughness. Martensite was the dominant microstructure in the directly quenched steel plate because of high hardenability obtained by the addition of 5.6 wt% Mn. Three intercritical annealing processes were adopted to ensure transformation-induced-plasticity (TRIP) effect through optimization of the volume fraction, morphology, and C and Mn-enriched reversed austenite. On annealing, the dislocation density of martensite plate was decreased because of recovery and recrystallization, and metastable austenite film nucleated at the interface. Both thermal and mechanical stability of austenite decreased with increase in annealing temperature. The high yield strength of 840 MPa, good elongation after fracture of 24.3%, and excellent toughness at − 60 °C of 130.3 J was obtained at intermediate annealing temperature of 650 °C, and the volume fraction of reversed austenite at room temperature and − 80 °C was 22% and 17%, respectively. The reversed austenite exhibited different stability with increased tensile strain, leading to improved ductility and delayed necking. Moreover, the crack initiation energy and crack propagation energy were increased via dynamic stress partitioning and relaxation together with the transformation of metastable austenite. Thus, significant degree of TRIP effect induced by moderate stability of austenite played an important role in governing mechanical properties. [ABSTRACT FROM AUTHOR]

A new maraging stainless steel with superior strength-toughness-corrosion synergy has been developed based on an innovative concept of alloy design. The high strength-toughness combination is achieved by forming dispersive nano-sized intermetallic compounds in the soft lath martensitic matrix with a slight amount of residual austenite. The good corrosion resistance is guaranteed by exactly controlling the Co content based on understanding the synergistic effect between Co and Cr. The fine structure characteristics of two dominant strengthening precipitations including Ni3Ti and Mo-rich phases were finely characterized associated with transmission electron microscope (TEM) and atom probe tomography (APT) analyses. The relationship among microstructure, strength and toughness is discussed. The precipitation mechanism of different precipitates in the new maraging stainless steel is revealed based on the APT analysis. [ABSTRACT FROM AUTHOR]

The laser-welded Fe-19Ni-3Mo-1.5Ti maraging steel joints with high strength and toughness were successfully obtained using the approach of the combination of Cu and aging temperature. This study underscores that the element of Cu has a significant effect on precipitates and reverted austenite, by influencing the element diffusion and phase transformation. For the strength, the element of Cu in the weld metal brings a lot of ε-Cu precipitates during the aging period. The amount of ε-Cu precipitates increases gradually with the increase of the aging temperature, which is beneficial to the strength. For the toughness, the addition of Cu changes the diffusion kinetic condition to promote the diffusion of Ni, resulting in the decrease of segregation of elements. The reverted austenite in grain boundaries which has an adverse effect on the toughness is correspondingly reduced. Meanwhile, Cu makes the thermodynamic condition different, with a lower critical driving force of phase transformation. This causes the increase of reverted austenite in the matrix, which is advantageous to the toughness. An excellent combination of strength and toughness of laser-welded maraging steel joint can be optimized by the appropriate content of Cu and aging temperature. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on the strength and toughness of laser-welded T-250 maraging steel joint, aimed at elucidating the influence mechanism of aging temperature on microstructures and mechanical properties of the joints. The results showed that as the aging temperature increased, the ultimate tensile strength of welded joints increased, reaching a maximum of 1640.5 MPa at 520 °C, and then decreased. The static toughness of welded joints decreased at first and increased later with the aging temperature increasing. The minimum of 38.8 MJ m −3 for the static toughness was obtained at 560 °C. There were two types of reverted austenite respectively distributing in grain boundaries and in the matrix of martensite, due to the change of aging temperatures. This study underscores that the Ni 3 (Ti, Mo) precipitate and reverted austenite are the critical factors influencing the strength and toughness of welded joints. The Ni 3 (Ti, Mo) precipitate in the weld metal improves the strength of welded joints remarkably as its volume fraction increases. The reverted austenite in grain boundaries is harmful to the toughness of welded joints, while the reverted austenite in the matrix is beneficial to the toughness of welded joints because of its finely dispersive distribution and its ability to prevent crack propagation. Increasing the amount of reverted austenite in the matrix is an effective way to improve mechanical properties of laser-welded maraging steel joints. [ABSTRACT FROM AUTHOR]

Mussel byssus is an elegant example with high strength and high toughness, inspiring the design of multiphase network structure. At present, many works focus on the design of noncovalent multiphase network. However, such noncovalent bonds (for example, hydrogen bonds) are sensitive to temperature and solvent, which limits the application in the engineering field. To overcome the shortcoming of noncovalent multiphase network, we construct the covalent multiphase network through thermodynamic incompatibility-driven covalent network in situ phase separation. Herein, this work increases the content of sulfur network in the polyolefin matrix. Due to the thermodynamics incompatibility between sulfur network and polyolefin chain, crosslinking network-rich domain and crosslinking network-poor domain appear in the matrix, forming the covalent multiphase network. The improvement in strength can be attributed to the increase in crosslinking density, while the improvement in toughness originates from the preferential rupture of crosslinking network-rich domain. Such covalent multiphase network opens up an innovative strategy for the design of robust materials. [Display omitted] • Polyolefin matrix and sulfur network are incompatible in thermodynamics. • With the increase of sulfur network content, sulfur network tends to aggregate in the matrix. • The covalent multiphase network is comprised of crosslinking network-rich domain and crosslinking network-poor domain. [ABSTRACT FROM AUTHOR]

• Li 2 Si 2 O 5 rods were firstly synthesized by a modified solid-state sintering method. • Li 2 Si 2 O 5 rods modified glass-ceramics indicated higher mechanical properties. • Li 2 Si 2 O 5 rods can be used to strengthen and toughen glass-ceramics. To achieve high performance of glass-ceramics, it is urgent to open a new path to enhance the mechanical properties. In this study, Li 2 Si 2 O 5 rods were successfully synthesized by a modified two-step solid-state reaction sintering method. The rod aspect ratio could be controlled by adjusting the second stage sintering time. The evolution process of such Li 2 Si 2 O 5 rods and their possible formation mechanism were put forward. For the first time, the Li 2 Si 2 O 5 rods were used to strengthen and toughen the homologous Li 2 Si 2 O 5 glass-ceramic in a typical quaternary Li 2 O-SiO 2 -K 2 O-La 2 O 3 system, which indicates a high flexural strength and toughness of 315±24 MPa and 2.42±0.6 MPa·m1/2, respectively. In this glass-ceramic, the microstructure features a densely stagger network formed by the elongated rods and smaller Li 2 Si 2 O 5 crystals in the glass matrix, contributing to the improvement of mechanical properties. The results demonstrate that Li 2 Si 2 O 5 rods could be an excellent candidate for strengthening and toughening glass-ceramics. [ABSTRACT FROM AUTHOR]

Medium Mn steels are promising candidates for the third-generation advanced high strength steels. However, it shows a distinct limit of mechanical property under conventional hot-rolling and intercritical annealing procedures. Aiming at improving the combination of strength, ductility and toughness, the present study proposed a multi-alloyed design principle together with a direct intercritical rolling process. The results show that the microstructure of the hot rolled steel consisted of wide delta ferrite, lath martensite, twinned-martensite and coarse retained austenite with a low stability, corresponding to a product of strength and elongation (PSE) of 24.0 GPa% and an impact toughness of 13.8 J/cm2 at −40 °C. In contrast, the intercritical rolling produced a laminated microstructure containing thin delta ferrite, submicron recrystallized ferrite and retained austenite. The PSE and impact toughness at −40 °C simultaneously increased to 46.1 GPa% and 46.7 J/cm2, respectively, which was also much higher than the hot rolled steel subjected to low temperature and high temperature annealing. The significant enhancement of mechanical property was mainly attributed to the highest content and optimal stability of retained austenite caused by the submicron grain size, high density of dislocations, granular morphology, and elemental enrichment. The optimized austenite stability provided persistent transformation-induced plasticity (TRIP) effect for work hardening and damage resistance. Moreover, the nano-sized VC precipitates in the intercritical rolled steel played a significant role in reaching an ultrahigh yield strength of ∼1 GPa. This study not only provides a very simple pathway to improve the mechanical property of medium Mn steel, but also sheds light on the design and development of high-performance materials. [ABSTRACT FROM AUTHOR]

Effect of Mo element on the precipitation behavior of nanoscale Cu-rich particles in Cu-bearing low carbon high strength steels was investigated in this work. The addition of 0.82 wt% Mo refined the size of grain interior Cu-rich particles (ICRPs) from 12 nm to 8 nm, accompanied by the structure changed from 3R-Cu to 9R-Cu. Mo also inhibited the formation of grain boundary Cu-rich particles (BCRPs) with the size of ∼30 nm. The calculation of phase field method indicated that Mo was repelled from Cu-rich particles and enriched in α-Fe matrix, which suppressed the diffusion of Cu atoms and merger of Cu-rich particles. The measured yield strength of CuMo-bearing steel increased by 87 MPa, mainly due to the refinement of ICRPs. The reduction of BCRPs suppressed the crack initiation and propagation at grain boundaries, which contributed to the increment of absorbed energy at −40 °C by 41J. [ABSTRACT FROM AUTHOR]

This paper elucidates here the strength and toughness behavior of T-250 maraging steel welded by laser beam under different approaches of three post-weld heat treatments, i.e. aging (A), solutionizing+aging (SA) and homogenizing+solutionizing+aging (HSA). The microstructures of the weld metals with A and SA processes both comprised of finely dispersive Ni 3 (Ti, Mo) precipitates, small martensite lath and reverted austenite along the grain boundary. However, in the weld metal with HSA process, it exhibited the same Ni 3 (Ti, Mo) precipitate with the large martensite lath and the absence of reverted austenite. The ultimate tensile strength and static toughness of the welded joint with HSA process were 1350.6 MPa and 63.8 MJ m −3 , respectively. The static toughness has been remarkably improved from 71% to 91% of the applied parent metal compared with that of the welded joint with A process. The present study underscores that the Ni 3 (Ti, Mo) precipitate and martensite are significant to ensure the high strength of welded joints. Due to its inconsistent deformation with the matrix of martensite, the reverted austenite has a notable influence on the toughness of welded joints. It shows that the post-weld heat treatments of HSA process can influence the mechanical behavior of welded joints by eliminating the reverted austenite. [ABSTRACT FROM AUTHOR]

The effects of homogenizing annealing and forging on the microstructure， strength and toughness of the dual-phase wear-resistant steel were investigated. The results showed that the microstructure of the steel contained mainly lath martensite， acicular bainite and a little retained austenite under 980℃ homogenizing annealing for 4 and 8hrs respectively and 1150℃ forging. The minimum grain size of the steel is No.7.0~7.5 grade after forging while the maximum grain size of the steel homogenized is No.6.5~7.0 grade. The holding time of the homogenizing annealing is the main factor that affects the mechanical properties of dual-phase wear resistant steels， and the impact toughness and elongation values of the test steels holding for 4hrs are higher than that of the test steels holding for 8hrs. Forging deformation improves the strength and toughness of dual-phase wear resistant steels more significantly than that under homogenizing annealing， and the optimized process parameters were as follow with initial forging temperature of 1150℃， final forging temperature of 800℃ and forging ratio of 2. [ABSTRACT FROM AUTHOR]

The present paper reports on the strength and toughness improvement in carbon-fiber reinforced silicon carbide (C/SiC) composites as a result of slurry-prone SiC whisker presence at varying concentrations. For whisker contents of 5 and 15wt%, the SiC w -C/SiC composite flexural strength was found to increase by 98.5% and 64.3%, respectively, from the whisker-free case while work of fracture increased by 209.8% and 179.0%, respectively. For the same respective whisker concentrations, porosity was found to decrease by 4.9% and increase by 19.4% compared to plain samples. The composites' interlaminar shear strength exhibited similar non-monotonic response with the property value for 5wt% whisker-reinforced composites being higher by 12.5MPa than the plain specimens and higher by 14.9MPa than the composites with 15wt% whisker content. Fiber pullout in SiC w -C/SiC composites was considerably more prominent than in the whisker-free material and the corresponding mean pullout lengths were significantly longer than in plain specimens. The improvements in strength and toughness were attributed to the energy dissipation mechanisms of crack deflection, whisker bridging and pullout coupled with conventional fiber pullout. [ABSTRACT FROM AUTHOR]

• Size effect in silica particle filled silicone rubber elastomers is investigated. • Reinforcing mechanisms of differently-sized silica particles are clarified. • Micro-damage mechanisms in composites with differently-sized particles are revealed. • The superior enhancing effect of nanoparticles over micro-particles is explained. Particle reinforced elastomer matrix composites always show a size-dependently mechanical behavior when the particle size shrinks down to micro- or even nano-scale. A systematic investigation on microscopic mechanisms of such a size effect is carried out in this paper based on tensile and tear experiments of silicone rubber elastomer filled with surface modified silica particles, in which the particle size ranges from tens of to several hundreds of nanometers. It is found that, when the particle content is fixed, the ultimate strength, fracture toughness and fracture tensile strain of the composite exhibit monotonic increase with the decrease of particle size. In the composite filled with monodispersed submicro-particles, the improved strength is due to the hindering effect of particles on the crack propagation and the strong interface bonding between particles and matrix, while the improved toughness is mainly resulted from the crack-pinning around particles. In the composite filled with nano-sized particles, both the filler-hindering effect and the strong interface still contribute to the strength of the composite, while not only the crack pinning but also the interface debonding around nanoparticle aggregates will toughen the composite. Furthermore, a hierarchical network structure consisting of differently-sized aggregates and bounded rubbers endows the composite with a better load bearing capacity than the one filled with separately distributed fillers. As a result, the composite filled with small nano-nanoparticles shows remarkably improved mechanical properties in comparison with the composite filled with submicro-particles. The present work should provide insights for optimally designing a flexible composite with both desirable strength and toughness. [ABSTRACT FROM AUTHOR]

A carbide-free bainite steel of 0.29C–2.50Si-1.50Mn-1.0Mo-0.97Cr (wt.%) with no voids and cracks was fabricated via laser powder deposition (LPD). Different post-treatment plans were conducted and then microstructures and properties of the steel were studied through optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), hardness meter and tensile test machines. Obtained results show that the microstructure of the deposited specimen consisted of granular pearlite and retained austenite (RA). The yield strength, tensile strength and elongation were 662 ± 71 MPa, 1051 ± 65 MPa and 13.03 ± 1.33 %, respectively. After austempering at 578 K, the microstructure of the specimen changed to bainite ferrite (BF) and RA. Moreover, it was found that the yield strength and tensile strength significantly increased to 1156 ± 60 MPa and 1289 ± 110 MPa, respectively. However, it had poor strain hardening capacity and elongation remained unchanged. After hot rolling and austempering, the RA content of the specimen significantly increased and the strain hardening capacity improved. However, when the isothermal temperature was less than the M s temperature (i.e. 553 K), the corresponding microstructure consisted of martensite, BF and 13.6 vol% of RA. In this case, the yield strength, tensile strength and elongation were 895 ± 74 MPa, 1157 ± 92 MPa and 14.59 ± 1.13 %, respectively, indicating slight improvement. Meanwhile, it was found that when the isothermal temperature exceeded M s temperature, the mechanical properties improved significantly. The present study demonstrated that specimens with an isothermal temperature of 578 K had the best mechanical properties. In particular, the yield strength, tensile strength and elongation of the optimized alloy were 1177 ± 44 MPa, 1398 ± 57 MPa and 19.80 ± 0.79 %, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Many refractory materials that are not readily available in fiber form, including ultra-high temperature ceramics (UHTC), are attractive candidates for use in high temperature structural components. This work explores the possibility of using non-conventional fiber forms that can be fabricated by “fibrous monolith” techniques to design composites with high strength and toughness along with 2D isotropy. The use of low-aspect ratio bone-shaped short fibers (BSSF) to improve fracture toughness and the use of composition tailoring to increase fiber strength were analyzed and it was found that both concepts need to be used in combination to achieve significant toughening. Computational models using UHTC as model materials indicate, for example, that significant improvements in fracture toughness can be realized with an aspect ratio of just 15, but only if the fiber strengths can be raised to 1.5GPa. The use of a single outer layer of lower thermal expansivity composition is predicted to increase low temperature strength by a factor of 2, while multilayers of reasonable thickness (10μm) result in strengthening by a factor of 3. For UHTCs, processing improvements that reduce flaw sizes will be necessary to take advantage of these results, but considerable improvement in properties can result from such progress. [Copyright &y& Elsevier]

Based on the idea of fracture caused by the statistical nucleation, growth and propagation of microcracks in the materials, the statistical distribution functions of brittle strength, fracture toughness and crack extension force of metals are derived from the solved statistical distribution function of microcracks. The forms of these three statistical distribution functions are similar, and the latter two can be derived from the former. The further approximation of these statistical distribution functions is not the Weibull distribution function but the Duxbury–Leath distribution function. The statistical distribution characteristics of fracture probability have been compared with experiment data. [Copyright &y& Elsevier]

This work focused on ultra-high strength steel strengthened by Cu-rich multistructured precipitates and toughened by bainite. A Cr–Mo bearing bainitic steel was designed and contrasted with a ferritic steel to examine the effects of Cr and Mo on microstructural transformation and precipitation evolution as well as the corresponding mechanical properties. By adding Cr and Mo elements, bainitic steel was obtained by an air cooling process after hot rolling, thus omitting controlled cooling and off-line quenching. Cr and Mo decreased the γ/α transformation temperature, such that the ferritic matrix was modified to fine bainite. Cu-rich multistructured particles and (Nb,Ti)C particles were found to be the two main precipitation phases in this bainitic steel. Cu-rich multistructured particles contained B2-ordered structure and transition-state structure between B2-ordered and 9R structure. Notably, this Cr–Mo bearing bainitic steel had better strength and toughness compared with ferritic steel. Its yield strength reached 1155 MPa, owing to precipitation and grain boundary strengthening, which were estimated to be 596 and 311 MPa, respectively. The impact absorbed energy of this steel at −40 °C was ~55.3 J and its fracture mode a brittle-ductile mixed mode, compared with the cleavage fracture mode of ferritic steel. The small grain size of this steel compensated for toughness deterioration caused by precipitation and contributed to high impact toughness. [ABSTRACT FROM AUTHOR]

• The effect of microwave sintering temperature on microstructure and mechanical behavior of HEAp/Al composites is investigated. • Ferromagnetic FeCoNi1.5CrCu particles improve the microwave absorption capacity of composites and reinforce the composites under microwave conditions. • The evolution mechanism of interface bonding in the preparation of ferromagnetic HEAp/Al composites under the condition of microwave assisted sintering is elucidated. The preparation of metal particle reinforced aluminum matrix composites by powder metallurgy has been widely studied in recent years. In this work, the effect of microwave sintering temperature on the microstructure and mechanical behavior of high-entropy alloys (HEAs) reinforced aluminum matrix composites prepared by powder metallurgy was investigated. Due to the outstanding microwave absorbing property of ferromagnetic HEAs particles, the composites sintering proceeded efficiently. At 480 °C, the aluminum matrix in the composite material is more compact, and the HEAs particles in the composite material are more evenly distributed, and the interface between HEAs particles and aluminum matrix is smooth. At 500 °C, the intensity of HEAs diffraction peak in the composite material changes significantly. At 520 °C, AlNi solid solution phase with BCC structure appears in the HEAs region, and the HEAs structure changes from FCC to FCC + BCC, and Al 5 Cr 8 , Al 5 Co 2 and Al 2 Cu phases precipitate. At 480 °C, the nanohardness and elastic modulus at the interface reaches 1245.31 MPa and 72.45 GPa, respectively, showing relatively excellent interfacial bonding strength. The elastic modulus of both HEAs reinforcement and aluminum matrix decrease at a sintering temperature above 480 °C, and the composites have hard and brittle characteristics. At 480 °C, the macroscopic compression and yield strengths of composites are ~ 421.2 MPa and ~ 289.5 MPa, and the maximum shrinkage rate is ~65.3%, exhibiting excellent strength and toughness. [ABSTRACT FROM AUTHOR]

The present work aims to unravel the effect of Ti microalloying on the refinement of co-precipitated nanoscale Cu and M 2 C carbides, and thereby the improvement of both strength and toughness of an ultrahigh-strength Fe-0.05C-1.3Cu steel. The co-precipitated Cu and M 2 C carbides in Ti-free and Ti-containing steels was characterized after quenching and aging treatment via atom probe tomography (APT), and their contribution to the yield strength was quantified. APT results show that after being aged at 550 °C for 1 h, nanoscale Cu particles and M 2 C carbides co-precipitated. And, the density of finer Cu was found to be higher in the Ti-containing steel than that in the Ti-free steel which can produce more nucleation sites for M 2 C carbides precipitation. After being aged at 550 °C for 1 h, the Ti-containing steel had a yield strength as high as 1055 MPa, and an impact toughness of 132 J at −40 °C, which was an improvement of 61 MPa and 27 J, respectively, in comparison to the Ti-free steel. The higher-density M 2 C carbides were found to contribute to precipitation strengthening enhancement. The co-precipitation strengthening contribution from the Cu-M 2 C precipitates of the Ti-containing steel was calculated to be 69 MPa higher than that of the Ti-free steel. This is similar to the difference of 61 MPa from the experiment. The high toughness of Ti-containing steel is attributed to a higher density of high angle grain boundaries and a smaller prior austenite grain size by deflecting crack propagation. [ABSTRACT FROM AUTHOR]

• The anisotropic alginate hydrogels were achieved by a self-reinforcing strategy. • Distinctive anisotropic materials were used to reinforce congeneric hydrogels. • The metal-ligand coordination served as self-generating interfacial binders. • The strategy overcame the weak interface in the composite hydrogels. • Super strong and tough hydrogels extended their applications as structural materials. Natural-derived hydrogels are expected as promising structural biomaterials, but the soft character severely limits their applications. Here, a facile yet effective strategy was developed to fabricate super-strong and tough alginate composite hydrogels via a self-reinforcing method. The strategy was based on the incorporation of alginate materials with distinctive anisotropic features (fibers, fabrics and aerogels) into the precursor solution of congeneric hydrogels, followed by the in situ ionic-crosslinking. Interestingly, triggered by the concentration difference, the cations-Ca2+ in reinforcing phase could diffuse into the interface and simultaneously chelate with alginate chains of both reinforcing phase and hydrogel matrix, acting as self-generating interfacial binders. Contributed by the intimate interface, the load was effectively transferred into the rigid reinforcing phase, and the hydrogels integrated them into a mechanical network. This research offers a new path to design the interface of polysaccharide composites without extra coupling agents. [ABSTRACT FROM AUTHOR]

This experimental laboratory study examines the potential use of tire-derived aggregate (TDA) products as an additive to alleviate the inferior geotechnical properties of a subgrade deposit of clay soil with high expansivity. A total of ten mix designs—the unamended soil and nine soil–TDA blends prepared at 5%, 10% and 20% TDA contents (by dry mass) using three different TDA gradations/sizes—were examined. The experiments included standard Proctor compaction, oedometer swell and unconfined compression tests. The TDA materials' lower specific gravity, hydrophobic character and higher energy absorption capacity compared with the soil solids led to notable reductions in the soil compaction characteristics. The amendment of the soil with TDA resulted in notable decreases in the rate and magnitude of swelling—the observed reductions were in favor of higher TDA contents, with larger TDA particle size being a secondary factor. Further, for any given TDA size, the variations of strength and toughness with respect to TDA content exhibited rise–fall relationships, peaking at 5% TDA and then decreasing for higher TDA contents. The stiffness and ductility parameters, however, were found to monotonically decrease and increase with the TDA content, respectively. Finally, TDA contents of up to 10%, with gradations equivalent to those of medium and coarse sands, were found to reduce the soil's swelling potential from high to moderate expansivity, while simultaneously improving its strength-related features, and thus can be deemed as optimum mix design choices from a geotechnical perspective. [ABSTRACT FROM AUTHOR]

• Microstructural damage effects in silicone rubber nanocomposites are investigated. • Reinforcing mechanisms of surface unmodified/modified nano-silica are clarified. • Strengthening and toughening mechanisms in rubber nanocomposites are disclosed. • Damage mechanisms governing the main crack formation in composites are revealed. Many experiments have apparently shown that hard nanoparticle-reinforced elastomer matrix composites have not only an improved loading bearing capacity but also a good flexibility. The microscopic damage mechanism and its effect on the mechanical properties of such composites are systematically investigated in this paper by both tensile and tear experiments on nano-silica-particle reinforced silicone rubber composites, in which not only the case of surface unmodified nano-silica particles but also that of surface modified nano-silica particles is considered. It is found that both the ultimate strength and toughness of both composites increase monotonically with an increasing weight fraction of nanoparticles. The improved strength and toughness of silicone rubber composites reinforced by surface unmodified nanoparticles are attributed to the blocking effect of micro-sized agglomerations on crack propagation and the weak interface debonding between agglomerations and matrix, respectively. As for the composites with surface modified nanoparticles, not only the filler-blocking effect but also the strong interface between fillers and matrix is responsible for the remarkable strengthening, while the improved toughness is attributed to the crack-pinning and interface debonding around fillers. Another interesting finding is that, with the increase of nanoparticle fractions, formation of the main crack in both composites is firstly inhibited by the filler-blocking effect, and then re-activated by micro-crack coalescences. As a result, the final fracture elongation changes from increase to decrease when the nanoparticle fraction is beyond a critical value. The results in the present paper disclose different microscopic mechanisms that influence the strength and toughness of silicone rubber-based composites reinforced by surface unmodified and modified nanoparticles, which is helpful not only for the understanding of mechanical performance of nanoparticle-reinforced flexible elastomer composites, but also for the design of novel flexible composites with matching strength and toughness. [ABSTRACT FROM AUTHOR]

• Cellulose nanofiber-templated hyperbranched nanohybrids was prepared. • Abundant active sites and architecture enabled high mechanical properties. • The stress and toughness of the film increased by 362.1 % and 718.8 %, respectively. • Integrated enhancement of strength and conductivity of composite were achieved. Smart conductive soft materials prepared from natural polymers are arousing ever-increasing attention in numerous advanced applications. However, achieving the synergistic properties of high biocompatibility, mechanical performance, and conductivity remains a key challenge. Herein, a novel and green strategy is proposed to fabricate a soy protein (SP)-based composite by the incorporation of hyperbranched poly(amino ester)-pyrrole (HPPy) via in situ polymerization into a bio template of cellulose nanofibril (CNF). The formed HPPy@CNF nanohybrids not only serve as dynamic cross-linking sites to construct a strong and stable network, but also impart a remarkable conductive ability to biopolymer materials. The tensile stress and toughness of the modified SP-based film increased by 362.1 % and 718.8 %, respectively superior to those of previously reported reinforcing approaches. Moreover, this biopolymer film exhibited significantly improved electrochemical properties, water resistance, and thermal stability. This synthesis strategy is facile and eco-friendly and can be easily extended to other material systems. [ABSTRACT FROM AUTHOR]

Freeze casting is a versatile approach for the design of lamellar metal−ceramic composites with unique combination of strength and toughness. However, previous studies mainly focused on ceramic factors such as content and lamellae structure, seldom concerning the effects of metal property and interfacial structures, which, in practice, are key factors in determining the mechanical performances of the composites. In this work, we prepared three kinds of Al/TiC lamellar-interpenetrated composites with different matrix compositions (pure Al, 6061Al (Al−0.4Cu−1.0Mg−0.6Si) and ZL107 (Al–7Si–5Cu)) via freeze casting and pressure infiltration, aiming at clarifying the roles of matrix property and interfacial reaction on the mechanical properties and fracture mechanisms of the composites. The flexural strengths of pure Al/TiC, 6061Al/TiC and ZL107/TiC composites reached 355 ± 10, 415 ± 15 and 459 ± 18 MPa, while the toughness values (characterized by crack-growth toughness) were 81.0 ± 2.0, 57.6 ± 1.2 and 43.4 ± 1.5 MPa m1/2, respectively. The exceptional damage tolerance of these lamellar composites was attributed to multiple toughening mechanisms such as crack deflection, uncracked-ligament bridging of ductile layers and plastic deformation of the metal matrix. However, the presence of Si in the 6061Al and ZL107 alloys weakened the stability of TiC and promoted interfacial reaction, leading to the formation of a certain number of (Al 1-m , Si m) 3 Ti and Al 4 C 3 , which greatly weakened the toughness of the composites. Due to the combined effects of alloy plasticity, lamellar-interpenetrated structure and interfacial reaction, the fracture of the materials changed from a multiple cracking mode in the Al/TiC composite to a single crack propagating mode in the 6061Al/TiC and ZL107/TiC composites. [ABSTRACT FROM AUTHOR]