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This paper presents laboratory test results on the mechanical properties and bond strength of new generation of carbon fibre reinforced polymer (CFRP) reinforcing bars used as nonprestressed reinforcement for concrete structures. Two types of CFRP reinforcing bars, namely, 9-mm-diameter CFRP ribbed bars and 9.5-mm-diameter CFRP sand-coated bars, were investigated. Tensile tests and pullout bond tests were conducted to evaluate the tensile properties and bond strength of the CFRP bars in comparison with that of the steel bar. Experimental results showed that the tensile stress-strain curves of the CFRP bars were linear up to failure. The ultimate tensile strength of the two types of CFRP bars was at least 1500 MPa, three times that of steel bars. The modulus of elasticity of two types of the CFRP bars was 128–145 GPa, about 65–75% that of steel. Furthermore, both types of the CFRP bars exhibited almost the same bond strength to concrete similar to steel bars. The minimum bond development length for the two types of CFRP bars seemed to be equal to about 20d[sub b] for the sand-coated bars and 30d[sub b] for the ribbed bars.Key words: fibre reinforced polymer (FRP), carbon FRP (CFRP), bar, mechanical properties, tensile strength, embedded length, pullout, bond strength, concrete structures.Cet article présente les résultats d'essais en laboratoire sur les propriétés mécaniques et la résistance à l'adhérence d'une nouvelle génération de barres d'armature en polymères renforcés de fibres de carbone (PRFC) utilisées comme renforcements de structures en béton armé non précontraint. Deux types de barres d'armature en PRFC de 9 mm de diamètre ont été utilisées: des barres crénelées et des barres recouvertes de sable. Des essais de traction et d'arrachement ont été réalisés pour évaluer les propriétés en traction et la résistance à l'adhérence des barres en PRFC, et les comparer à celles de l'acier. Les résultats expérimentaux montrent que les courbes contrainte de traction-déformation sont linéaires jusqu'à la rupture. La résistance ultime en traction des deux types de barres en PRFC est d'au moins 1500 MPa, soit trois fois celle de l'acier. Le module d'élasticité des deux types de barres en PRFC varie entre 128 et 145 GPa, soit 65 à 75% celui de l'acier. De plus, les deux types de barres en PRFC montrent une contrainte d'adhérence maximum analogue à celle de la barre d'armature en acier. La longueur minimale de développement d'ancrage pour les deux types de barres d'armature en PRFC semble être égale à environ 20d[sub b] pour les barres recouvertes de sable et 30d[sub b] pour les barres crénelées.Mots clés : polymères renforcés de fibres (PRF), PRF carbone (PRFC), barre, propriétés mécaniques, résistance à la traction, longueur d'ancrage, arrachement, résistance à l'adhérence, structures en béton. [ABSTRACT FROM AUTHOR]

• Al 2 O 3 /Al–Cu composite has been synthesized by promoting liquid–solid reactions in Al–10CuO system. • The in–situ prepared composite contains a heterogeneous structure. • The θ' precipitate–rich zone and Al 2 O 3 particle–rich zone were formed after T6 treatment. • The composite exhibits attractive mechanical properties. [Display omitted] In this paper, an Al–Cu based composite reinforced by nano α–Al 2 O 3 particles has been synthesized by promoting liquid–solid reactions of Al–10CuO, followed by hot extrusion process. The Al 2 O 3 /Al–Cu composite was found exhibiting a heterogeneous structure after extrusion, composing of alternately distributed Al 2 O 3 particle–rich zones and Al 2 O 3 particle–poor zones. In the Al 2 O 3 particle–rich zones, the in–situ formed Al 2 Cu and Al 2 O 3 particles exhibit similar distribution law, which is supposed relating to the composite synthesizing process. However, after T6 heat treatment, the precipitated θ' nano–particles were mainly found locating in the Al 2 O 3 particle–poor zones. The ultimate tensile strength and elongation of the T6 treated Al 2 O 3 /Al–Cu composite is 420 MPa and 5.7%, respectively. Differential scanning calorimetry analysis has been carried out to reveal the reaction procedure between Al and CuO. The microstructure evolution process of the composite was discussed. This work may provide new insights for designing Al composites strengthened by ceramic particles and intermetallic compounds simultaneously. [ABSTRACT FROM AUTHOR]

The present paper analyzed the microstructural characteristics and the mechanical properties of a Ti–Nb–Zr–Fe–O alloy of β-Ti type obtained by combining severe plastic deformation (SPD), for which the total reduction was of εtot = 90%, with two variants of super-transus solution treatment (ST). The objective was to obtain a low Young's modulus with sufficient high strength in purpose to use the alloy as a biomaterial for orthopedic implants. The microstructure analysis was conducted through X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) investigations. The analyzed mechanical properties reveal promising values for yield strength (YS) and ultimate tensile strength (UTS) of about 770 and 1100 MPa, respectively, with a low value of Young's modulus of about 48–49 GPa. The conclusion is that satisfactory mechanical properties for this type of alloy can be obtained if considering a proper combination of SPD + ST parameters and a suitable content of β-stabilizing alloying elements, especially the Zr/Nb ratio. [ABSTRACT FROM AUTHOR]

• High Mg-content AlSiMg1.4 alloy was fabricated by selective laser melting. • YS and UTS of SLMed AlSiMg1.4 alloy reached 341 ± 14 MPa and 518 ± 6 MPa, respectively. • The strength of alloy are much higher than most known SLM fabricated Al-Si-Mg alloys. • The new strengthening mechanism was mentioned in the paper. A high Mg-content AlSiMg1.4 alloy was designed for selective laser melting (SLM) processing. The SLMed AlSiMg1.4 alloy exhibits a high yield strength of 341±14 MPa and a high ultimate tensile strength of 518±6 MPa, along with a total elongation of 7.1±0.4%. The composition profile in the α -Al matrix of the alloy manifests in-phase concentration fluctuations of Mg and Si. The presence of high density Mg-Si atomic clusters as strong obstacles to dislocation gliding is suggested to provide an additional strengthening mechanism for the SLMed Al-Si-Mg alloy. [ABSTRACT FROM AUTHOR]

Al-Zn-Mg-Cu alloy, as an important lightweight structural material in the aerospace field, has ushered in a broader application space and proposed higher performance requirements. This paper presents the experimental investigation of the effect of Zr content on the microstructure refinement and performance improvement of cast Al-5.8Zn-2.3Mg-1.7Cu alloy, aiming to optimize the additional amount of Zr, refine the alloy grains, and improve the microstructure uniformity and mechanical properties. The chemical component, phase, and microstructure were observed by inductively coupled plasma, X-ray diffraction, optical microscope and scanning electron microscope; the hardness and mechanical properties were measured by Brinell hardness tester and tensile testing machine. The addition of different contents of Zr into the alloy can form fine dispersed or primary coarse Al 3 Zr phase, which has a significant effect on the microstructure and mechanical properties of the alloy. The results indicate that the addition of 0.05 wt% Zr does not significantly improve the grain refinement and mechanical properties, but the Brinell hardness reaches the maximum. As the Zr content rises, the grain refinement effect becomes more obvious, while the mechanical properties first increase and then decrease. The addition amount reaches 0.20 wt%, the second dendrite arm spacing is the smallest, the ultimate tensile strength, yield strength and elongation at room temperature reach the maximum of 296.74 MPa, 249.41 MPa and 8.26%, respectively. When the amount of Zr added exceeds 0.20 wt%, the existence of coarse and brittle primary Al 3 Zr phase reduces the mechanical properties, and the fracture morphology changes from ductile to brittle intergranular fracture. • Zr element can refine the alloy grains. The higher the amount of Zr added, the more obvious the grain refining effect. • With the increase of Zr content, the mechanical properties of the alloy will first increase and then decrease. • When Zr content is excessive, the Al 3 Zr phase is the reason for the decrease in toughness. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of multiwalled carbon nanotubes on the mechanical and electrical properties of epoxy resins and epoxy composites. The research concerns multiwalled carbon nanotubes obtained by catalytic chemical vapor deposition, subjected to purification processes and covalent functionalization by depositing functional groups on their surfaces. The study included the analysis of the change in DC resistivity, tensile strength, strain, and Young's modulus with the addition of carbon nanotubes in the range of 0 to 2.5 wt.%. The effect of agents intended to increase the affinity of the nanomaterial to the polymer on the aforementioned properties was also investigated. The addition of functionalized multiwalled carbon nanotubes allowed us to obtain electrically conductive materials. For all materials, the percolation threshold was obtained with 1% addition of multiwalled carbon nanotubes, and filling the polymer with a higher content of carbon nanotubes increased its conductivity. The use of carbon nanotubes as polymer reinforcement allows higher values of tensile strength and a higher strain percentage to be achieved. In contrast, Young's modulus values did not increase significantly, and higher nanofiller percentages resulted in a drastic decrease in the values of the abovementioned properties. [ABSTRACT FROM AUTHOR]

The paper presents the results of mechanical tests of models manufactured with two 3D printing technologies, FDM and CFF. Both technologies use PLA or PA-based materials reinforced with carbon fibers. The work includes both uniaxial tensile tests of the tested materials and metrological measurements of surfaces produced with two 3D printing technologies. The test results showed a significant influence of the type of technology on the strength of the models built and on the quality of the technological surface layer. After the analysis of the parameters of the primary profile, roughness and waviness, it can be clearly stated that the quality of the technological surface layer is much better for the models made with the CFF technology compared to the FDM technology. Furthermore, the tensile strength of the models manufactured of carbon fiber-enriched material is much higher for samples made with CFF technology compared to FDM. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quantified machine-powder induced variability in mechanical properties of LPBF 316L. • HIP reduced variability in tensile strength, porosity and impact toughness. • Lower impact toughness compared to wrought 316L was mainly due to oxide inclusions. Laser powder bed fusion additive manufacturing is used for demanding applications in industries such as aerospace. However, machine-specific, optimized process conditions and parameters are required to assure consistent part quality. In addition, differences in supplied powder can cause variation in the mechanical properties of the final parts. In this paper, the variability in mechanical properties of 316L stainless steel produced with two different laser powder bed fusion machines from two different powder batches was studied by producing an identical set of tensile and impact toughness test specimens. The samples were subjected to stress-relieving, solution annealing and hot isostatic pressing to assess the effectiveness of standardized heat-treatments in reducing variation in the mechanical properties of the built parts. Porosity, microstructure, tensile properties, and impact toughness of the specimens were measured to study the effect of changing the material, machine, and heat treatment. The maximum differences observed between the studied machine-powder combinations were approximately 7% for tensile properties and approximately 20% for impact toughness. HIP reduced the variability in all other studied properties except elongation. All the specimens fulfil the minimum requirements set in ASTM F3184-16 for AM 316L. [ABSTRACT FROM AUTHOR]

Chitosan is a versatile biopolymer with many interesting functionalities. Its effects on the barrier and mechanical properties of single- or double-coated fibre-based packaging papers in dependence on the applied drying regime were successfully tested. Our investigations revealed chitosan to be a highly robust biopolymer, since the different drying regimes did not alter its contribution to the development of strength and barrier properties of the coated packaging papers. These properties showed a stronger influence of the applied coat weights than of the different drying regimes. The effect of chitosan coatings were quantified by measuring tensile strength (TS), burst strength (BS) and tensile energy absorption (TEA). These revealed that TS, BS and TEA of the coated papers increased significantly. Moreover, the chitosan-coated papers were less permeable against water vapor and air. High grease resistance was observed for double-coated papers, irrespective of the drying regimes. The coated paper surface showed a more hydrophilic character, resulting in lower contact angles and higher water absorption properties. In this study, industrially produced chitosan has been proven to be a renewable, robust biopolymer that can be utilized as an additive to increase strength and the barrier properties of fibre-based materials. [ABSTRACT FROM AUTHOR]

• 52 tensile coupons of high-performance bolt material are tested. • Effects of test strain-rate on the elevated temperatures are clarified. • Elevated-temperature behaviour of the steel is elucidated at microstructure level. • Prediction equations are proposed for elevated-temperature performance. • Constitutive model of full-range stress-strain relation is developed. Mechanical properties of steel at elevated temperatures are critical to the fire-resistant analysis and the fire safety design of steel structures. Thus, one solution for improving the fire resistance is use of high-performance (HP) steel, such as fire-resistant (FR) steel. However, practical use of the FR steel in steel structures implies requirements of sufficient fire resistance for the high-strength (HS) bolts as well, so that the loading capacities of bolted connections commonly used in steel structures can be guaranteed in case of fire. In this paper, material properties of grade 10.9 HP bolts recently developed in China, possessing both fire resistance and corrosion resistance, are tested at various elevated temperatures. Their stress-strain curves, modulus of elasticity, yield strength, ultimate tensile strength (UTS), and elongation percentage after fracture are obtained. These results are compared with that of conventional HS bolts and with reduction factors given in national standards. Constitutive models and prediction equations of the HP bolts at elevated temperatures are proposed. Besides, the relationship between degradation in macro mechanical properties and change in microstructure is clarified. The research outcomes may provide essential bases for the fire response analysis of steel structures applying the FR steel and the HP bolts. [ABSTRACT FROM AUTHOR]

Nanotechnology has emerged as a field with promising applications in building materials. Nanotechnology-based mortars are examples of such building materials that have widespread applications in the construction industry. The main nanomaterials used in mortars include nano-silica, nano-magnesium oxide, nano-alumina, nano-titanium oxide, nano-zinc oxide, nano-clay, and nano-carbon. This review paper presents a summary of the properties and effects of these nanomaterials on cement mortar in terms of its fresh-state and hard-state properties. The fresh-state properties include the setting time, consistency, and workability, while the hard-state properties include mechanical properties such as compressive, flexural, tensile strengths, as well as the elasticity modulus, in addition to durability properties such as water absorption, shrinkage strain, strength loss due to freeze–thaw cycles, and chloride penetration, among others. Different nanomaterials cause different physical and chemical alterations within the microstructures of cement mortar. Therefore, the microstructural characterization and densification of mortar are discussed in detail at varying temperatures. In general, the involvement of nanomaterials in cement mortar influences the fresh-state properties, enhances the mechanical properties, and impacts the durability properties, while reducing the porosity present in the mortar matrix. Cementitious nanomaterials can create a pathway for the easy injection of binding materials into the internal microstructures of a hydration gel to impact the hydration process at different rates, whereas their non-cementitious counterparts can act as fillers. Furthermore, the research gaps and future outlook regarding the application of nanomaterials in mortar are discussed. [ABSTRACT FROM AUTHOR]

Large magnetostriction has been discovered in the FeCo binary alloys at the composition of Fe 30 Co 70. In this paper, a series of (Fe 30 Co 70) 100- x (NiMn) x cast alloys is developed. The mechanical properties and magnetostriction of these alloys are intimately related to the crystal structure and phase constituent. The (Fe 30 Co 70) 100- x (NiMn) x magnetostrictive alloys keep in the body-centered-cubic (bcc) phase region with the addition of NiMn to 5%, where the strength and ductility are intensively improved simultaneously. The enhancement of the mechanical behaviors is attributed to the generation of fine laminate structure after doping. The tensile strength and magnetostriction drop with increasing NiMn content when the face-centered-cubic (fcc) phase appears. In (Fe 30 Co 70) 95 (NiMn) 5 polycrystalline alloy, a magnetostriction of 114× 10−6 coupled with a yield strength of more than 1200 MPa and a tensile elongation of 5% is achieved. Image 1 • A series of (Fe 30 Co 70) 100- x (NiMn) x cast alloys are developed. • The strength and ductility are improved simultaneously in the Fe 30 Co 70 alloys with an addition of NiMn. • A magnetostriction of 114× 10−6 coupled with a yield strength of 1200 MPa and a tensile elongation of 5% is achieved. [ABSTRACT FROM AUTHOR]

Reinforcing agents and accelerators are the most important auxiliaries for rubber industry. In this paper, ceric ammonium nitrate (CAN), for the first time, worked as a catalyst for hydroxyl groups in silica to prepare silica grafted sodium xanthate (SSX), which was used as an in-situ modified multifunctional rubber additive in this work. Compared with sodium isobutyl xanthate (SIBX), SSX has enhanced the initial and final degradation temperatures, achieving the improvement of 103 °C and 277 °C, respectively. Notably, owing to the powerful interaction between each component, SSX can be homogeneously dispersed in the natural rubber (NR) matrix in contrast to the seriously aggregated silica. Meanwhile, NR/SSX composites exhibited superior curing properties and showed an increase of 29.1% and 33.4% in the tensile strength and tear strength, respectively, compared to that of traditional 2-mercaptobenzothiazole (MBT) system. Since high-performance rubber composites can be obtained by introducing SSX, we believe that this work can provide a novel and facile approach to prepare natural silicate minerals-based vulcanization accelerators. Image 1 • Compared with traditional accelerators, SSX is an eco-friendly accelerator. • SSX can be better dispersed in the rubber matrix and improve the thermal stability of the xanthate. • Due to the excellent vulcanization and reinforcement effect, the mechanical properties of NR/SSX composites are greatly improved. [ABSTRACT FROM AUTHOR]

Highly reinforcing and desirable antiwear performance poly(vinyl alcohol) (PVA) hydrogels based on 2D Ni-Fe MOF nanosheets The crucial challenge of 2D inorganic nanomaterials-filled composite hydrogel with outstanding mechanical properties was concentrated on the surface modification that was capable to access a better interface between 2D inorganic nanomaterials and hydrogel in past. In this paper, for the first time, we extensively studied the application of as-synthesized 2D Ni-Fe MOF nanosheets with natural organic interface and interlayer structure in PVA hydrogel. The morphology and structure of the as-prepared 2D Ni-Fe MOF/PVA composite hydrogels were determined by a series of characterizations. The results indicated that the as-prepared 2D Ni-Fe MOF/PVA composite hydrogel with porous structure exhibited a desirable dispersion due to the existence of the potential interfacial interaction. Furthermore, the swelling, mechanical and tribological properties of the composite hydrogel were intensively investigated. Dramatically, the tensile strength and compression modulus of the as-prepared 2D Ni-Fe MOF/PVA with 0.1 wt.% filling content were increased by 62.5 % and 113 % relative to pure PVA hydrogel, respectively. Owing to the presence of the interlayer structure of 2D Ni-Fe MOF nanosheets, the friction coefficient of the 2D Ni-Fe/PVA composite hydrogel with 0.15 wt.% filling content was reduced by 41 % compared to pure PVA hydrogel. [ABSTRACT FROM AUTHOR]

The proper process of preparing an adhesive composition has a significant impact on the degree of dispersion of the composition ingredients in the matrix, as well as on the degree of aeration of the resulting composition, which in turn directly affects the strength and functional properties of the obtained adhesive compositions. The paper presents the results of tensile strength tests and SEM microphotographs of the adhesive composition of Epidian 57 epoxy resin with Z-1 curing agent, which was modified using three fillers NanoBent ZR2 montmorillonite, CaCO3 calcium carbonate and CWZ-22 active carbon. For comparison purposes, samples made of unmodified composition were also tested. The compositions were prepared with the use of six mixing methods, with variable parameters such as type of mixer arm, deaeration and epoxy resin temperature. Then, three mixing speeds were applied: 460, 1170 and 2500 rpm. The analyses of the obtained results showed that the most effective tensile results were obtained in the case of mixing with the use of a dispersing disc mixer with preliminary heating of the epoxy resin to 50 °C and deaeration of the composition during mixing. The highest tensile strength of adhesive compositions was obtained at the highest mixing speed; however, the best repeatability of the results was observed at 1170 rpm mixing speed. Based on a comparison test of average values, it was observed that, in case of modified compositions, the values of average tensile strength obtained at mixing speeds at 1170 and 2500 rpm do not differ significantly with the assumed level of significance α = 0.05. [ABSTRACT FROM AUTHOR]

Carbon fibre composites have great potential for vehicle lightweighting but the high cost and environmental impact of their production tends to largely undermine the advantages in non-aerospace applications. Recycled fibre has the potential to significantly reduce both cost and environmental impact but has yet it has not been widely accepted by the composites industry due to reduced mechanical performance in components as well as the difficulties in handling and processing caused by the fluffy discontinuous form which is quite unlike any current material formats which suit existing processing methods. The developed alignment process allows discontinuous random recycled carbon fibre to be processed into tapes with a highly aligned orientation distribution. This allows composites with high fibre content to be manufactured at lower moulding pressures with the added benefit of keeping fibre length degradation to a minimum. To evaluate the effects of process factors on fibre orientation, a two-level full factorial experimental plan was designed. This represents the first time a systematic study of input parameters on final part performance has been published in the open literature. With further improvements to the process, it is shown that it is possible to manufacture a composite achieving high fibre volume content (46%) under 7 bar moulding pressure in an autoclave, exhibiting competitive mechanical properties with almost 100 GPa tensile modulus and over 800 MPa tensile strength. • Recycled carbon fibre composites have great potential for vehicle light-weighting. • High-performance materials have been produced through the developed process. • Processing factors influencing the alignment quality are addressed. • A highly aligned fibre orientation distribution is observed enhancing fibre packing. • The observed mechanical properties compete with metals for transport applications. [ABSTRACT FROM AUTHOR]

To further improve the mechanical properties of the as-cast 7.5 vol.% TiBw/Ti–6Al–2.5Sn–4Zr–0.7Mo–0.3Si composite, multi-directional forging (MDF) and subsequent heat treatments were carried out to adjust TiB whiskers (TiBw) and matrix characteristics. The effect of various microstructures on the tensile properties and fracture toughness of the composites was analyzed in this paper. After MDF, the TiBw are broken into short rods with a low aspect ratio and display a random distribution. Moreover, distinct microstructures were obtained after thermomechanical processing and different heat treatments. Both room-temperature and high-temperature tensile strength and ductility are improved after thermomechanical processing. By increasing the solution-treatment temperature, the microstructures transform from equiaxed to fully lamellar. A simultaneous improvement of the room-temperature and high-temperature properties is associated with the microstructural changes. In addition, the fracture toughness exhibits an increasing trend as the volume fraction of equiaxial α phases decreases. The lamellar microstructure demonstrates excellent fracture toughness due to deflection of the crack propagation path. [ABSTRACT FROM AUTHOR]

For the efficient and durable design of concrete, the role of fiber-reinforcements with mineral admixtures needs to be properly investigated considering various factors such as contents of fibers and potential supplementary cementitious material. Interactive effects of fibers and mineral admixtures are also needed to be appropriately studied. In this paper, properties of concrete were investigated with individual and combined incorporation of steel fiber (SF) and micro-silica (MS). SF was used at six different levels i.e., low fiber volume (0.05% and 0.1%), medium fiber volume (0.25% and 0.5%) and high fiber volume (1% and 2%). Each volume fraction of SF was investigated with 0%, 5% and 10% MS as by volume of binder. All concrete mixtures were assessed based on the results of important mechanical and permeability tests. The results revealed that varying fiber dosage showed mixed effects on the compressive (compressive strength and elastic modulus) and permeability (water absorption and chloride ion penetration) properties of concrete. Generally, low to medium volume fractions of fibers were useful in advancing the compressive strength and elastic modulus of concrete, whereas high fiber fractions showed detrimental effects on compressive strength and permeability resistance. The addition of MS with SF is not only beneficial to boost the strength properties, but it also improves the interaction between fibers and binder matrix. MS minimizes the negative effects of high fiber doses on the properties of concrete. [ABSTRACT FROM AUTHOR]

High-strength aluminum alloy (mainly refers to the 7xxx series) is the optimum material for lightweight military equipment. However, this type of aluminum alloy is a wrought aluminum alloy. If it is directly formed by traditional casting methods, there will inevitably be problems such as coarseness, unevenness, looseness, and hot cracking in the structure, which will greatly affect the final performance of the part. Based on the internal cooling with annular electromagnetic stirring (IC-AEMS) method, a new technology of rheological die forging is developed in this paper, and the scale-reduced parts of a brake hub of Al-6.54Zn-2.40Cu-2.35Mg-0.10Zr aluminum alloy were prepared. The influence of IC-AEMS and the addition of rare element Sc on the structure and mechanical properties of the parts was studied. An optical microscope and scanning electron microscope (SEM) were used to observe the microstructure evolution, energy dispersive spectroscopy (EDS) was used to analyze the phase distribution and composition, and the mechanical properties of the parts were tested by uniaxial tensile tests. The results show that the addition of Sc element can effectively refine the grains and improve the strength and elongation of the material; the application of IC-AEMS improves the cooling rate of the melt, increases the effective nucleation rate, and the grains are further refined. Through process optimization, scale-reduced parts of a brake hub with good formability and mechanical properties can be obtained, the ultimate tensile strength is 597.2 ± 3.1 MPa, the yield strength is 517.8 ± 4.3 MPa, and the elongation is 13.7 ± 1.3%. [ABSTRACT FROM AUTHOR]

Ultrafine-grained (UFG) materials produced by severe plastic deformation methods generally exhibit a higher strength, but a lower uniform ductility. In this paper, an UFG Al–Zn–Mg–Cu alloy was fabricated via cross accumulative extrusion bonding (CAEB) and subsequent aging to achieve high strength and moderate uniform elongation. The influences of CAEB and subsequent aging on microstructure and tensile properties of the alloy were investigated. After CAEB, TEM characterization revealed that the microstructure exhibited typically ED-elongated ultrafine grains (740 ± 20 nm). Post-CAEB aging led to the formation of many nano-sized particles with different morphologies. These particles precipitated in the grain interiors and at grain boundaries, among which the main strengthening phase was η′ phase. EBSD characterization showed that the fraction of high angle grain boundaries increased to 61.0% for the post-CAEB aged alloy. At the same time, microtexture was significantly weakened as the CAEB process was applied to the alloy. The main texture components were mainly composed of Cu and S as well as a small amount of Brass and Cube. In addition, the tensile test at room temperature demonstrated that the post-CAEB aged sample possessed a high ultimate tensile strength of 562 MPa while simultaneously maintaining a moderate uniform elongation of 21.5%. • UFG Al–Zn–Mg–Cu alloy (740 ± 20 nm) was produced by cross accumulative extrusion bonding (CAEB). • Post-CAEB aging made the GP zone, η′ and η phase appear on the Al matrix. • The SST+CAEB+aging alloy possessed a high strength of 562 MPa and moderate uniform elongation of 21.5%. [ABSTRACT FROM AUTHOR]

In ultra-high strength Al-Zn-Mg-Cu alloys, traditional heat treatments such as peak aging, two-stage aging and retrogression and re-aging cannot perfectly balance the relationship between mechanical properties and corrosion resistance and usually consume more time. Based on previous studies, the aim of this paper is to establish a suitable non-isothermal aging method for ultra-high strength Al-Zn-Mg-Cu alloys. In this study, after enhanced solution treatment and aging process with the heating rate of 20 °C/h, the alloy achieves excellent hardness and ultimate tensile strength of 195.7 HV and 680 MPA, respectively. When heating rate increases to 40 °C/h, non-isothermal aging can also ensure the alloy achieve the excellent mechanical properties (195.6 HV, 675 MPA). Similar to mechanical properties, the samples have outstanding resistance to intergranular and exfoliation corrosion, which is in accordance with the results of potentiodynamic polarization and electrochemical impedance spectroscopy tests. Evidences from high resolution transmission electron microscopy show that non-isothermal aging can promote the formation of a large number of smaller GP zones, η' precipitates and few η 2 precipitates inside grains, which greatly strengthens the mechanical properties. Furthermore, the grain boundaries precipitates transform from continuous to discontinuous and precipitate free zones form gradually, which greatly enhances the corrosion resistance. Because of these precipitates inside grains and grain boundaries, the samples with enhanced solution treatment +20 °C/h aging process and both solution treatments +40 °C/h aging process can achieve good mechanical properties closing to T6 state and corrosion resistance similar to T74 state simultaneously with much less aging time. Image 1 • The non-isothermal aging was designed as a novel route for heat treatments of ultra-high strength Al-Zn-Mg-Cu alloy. • An excellent combination of strength-ductility and corrosion resistance was achieved in the studied alloy. • The strengthening and corrosion mechanisms of non-isothermal aging on the studied alloy were discussed systematically. • Precipitation behavior of MgZn 2 strengthening phase was well studied. [ABSTRACT FROM AUTHOR]

Designing of Al based composites with enhanced high temperature strength is of great significance nowadays. In this paper, an (α–Al 2 O 3 +ZrB 2)/Al composite has been prepared utilizing the liquid–solid reaction of Al–ZrO 2 –B 2 O 3 system, while an (α–Al 2 O 3 +ZrAl 3)/Al composite was synthesized through Al–ZrO 2 for comparison. Nano–sized Al 2 O 3 and micron ZrAl 3 particles have been in–situ formed in the (5.5Al 2 O 3 +14ZrAl 3)/Al composite, in which the coarse ZrAl 3 particles are regarded harmful for the composite's properties. By promoting the reaction between ZrAl 3 and B 2 O 3 , nano–sized Al 2 O 3 and ZrB 2 particles have been synthesized in the (13.8Al 2 O 3 +9.2ZrB 2)/Al composite. Based on the results of X–ray diffraction and electron backscatter diffraction, the Al matrix of the two extruded composites both prefer to form fiber texture (<111> Al //ED) in the longitudinal section, while the small difference between them is regarded relating to the distributing orientation of D0 23 –ZrAl 3 particles. Compared with (Al 2 O 3 +ZrAl 3)/Al composite, the (Al 2 O 3 +ZrB 2)/Al composite exhibits more excellent properties. The ultimate tensile strength can reach 463 MPa at 25 °C and 188 MPa at 350 °C. • The (α–Al 2 O 3 +ZrAl 3)/Al and (α–Al 2 O 3 +ZrB 2)/Al composites were prepared in Al–ZrO 2 (–B 2 O 3) systems. • The <111> Al //ED fiber texture was formed in the extruded composites. • The (α–Al 2 O 3 +ZrB 2)/Al composite exhibits enhanced high temperature strength. [ABSTRACT FROM AUTHOR]

Recently, 3D concrete printing has progressed rapidly in the construction industry. However, this technique still contains several factors that influence the buildability and mechanical properties of the printed concrete. Therefore, this study investigated the effects of the nozzle speed, the interlayer interval time, the rotations per minute (RPMs) of the screw in the 3D printing device, and the presence of lateral supports on the buildability of 3D concrete printing. In addition, this paper presents the results of the mechanical properties, including the compressive, splitting tensile, and flexural tensile strengths of 3D printed concrete. The buildability of 3D printed structures was improved with an extended interlayer interval time of up to 300 s. The printing processes were interrupted because of tearing of concrete filaments, which was related to excessive RPMs of the mixing screw. The test results also showed that a lateral support with a wide contact surface could improve the resistance to buckling failure for 3D printed structures. The test results of the mechanical properties of the 3D printed concrete specimens indicated that the compressive, splitting tensile, and flexural tensile strengths significantly depended on the bonding behavior at the interlayers of the printed specimens. In addition, although metal laths were expected to improve the tensile strength of the printed specimens, they adversely affected the tensile performance due to weak bonding between the reinforcements and concrete filaments. [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets reinforced aluminum matrix (GNPs/Al) composites were successfully fabricated by high-energy ball milling and spark plasma sintering. The microstructure and mechanical properties of the GNPs/Al composites were investigated. Microstructure and distribution of GNPs were analyzed with a scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). Tensile properties and hardness were studied at room temperature. The GNPs/Al composites with the well-dispersed GNPs and good densification were fabricated, indicating this technology can effectively fabricate the GNPs/Al composites. The randomly distributed nano-rods Al 4 C 3 was found in the GNPs/Al composites fabricated at 600 °C. The ultimate tensile strength, yield strength, elongation, as well as Vickers hardness of GNPs/Al composites increase with the increase of fabrication temperature. The GNPs/Al composites with nano-Al 4 C 3 have a good balance between tensile strength and elongation, because the nano-sized Al 4 C 3 phase helps to improve the interfacial bonding and mechanical properties of GNPs/Al composites. The GNPs/Al composites exhibit a ductile mode of failure, and GNPs pull-out was detected at the fracture surface. The strengthening mechanism of GNPs/Al composites was discussed according to the load transfer strengthening, Orowan strengthening and dislocations strengthening, and the interfacial Al 4 C 3 phase plays a critical role in determining the load transfer efficiency of GNPs. This paper may render significant information for understanding the strengthening behaviors of GNPs reinforced metal matrix composites. • Al 4 C 3 phases take on short rod-like morphology. • Strengthening mechanisms in GNPs/Al composites are revealed. • Interfacial Al 4 C 3 phase plays a critical role in determining load transfer efficiency. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties, thermal stability, and transparency of ethylene–propylene copolymer (EPC) elastomer modified with various weight percentages (1, 3, and 5 wt.%) of SiO2 nanofillers have been studied. The nanocomposites were prepared via a simple melt mixing method. The morphological results revealed that the nanofillers were uniformly dispersed in the elastomer, where a low concentration of SiO2 (1 wt.%) had been added into the elastomer. The FTIR showed that there are interfacial interactions between EPC matrix and silanol groups of SiO2 nanoparticles. Moreover, by the addition of 1 wt.% of SiO2 in the EPC, the tensile strength and elongation at break of EPC increased by about 38% and 27%, respectively. Finally, all samples were optically transparent, and the transparency of the nanocomposites reduced by increasing the content of SiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

In this paper, a BN-Gr-BN planar heterojunction is established, and the BN-Gr-BN planar heterojunction is used as reinforcing materials for copper-based materials. The coupling effects of defects and temperature on mechanical properties of the graphene-h-BN/copper vertically-stacked heterostructures were investigated. The results show the BN-Gr-BN heterojunction layer exerts a strengthening influence on the Young' modulus as well as the load transfer ability, thereby enhancing the stability capacity and the plasticity of composite system under axial tension. the introduce of BN-Gr-BN heterojunction layer gives rise to geometrical imperfections at interface, which in turn causes a reduction in the ultimate tensile strength and the associated facture strain. The positive effects of BN-Gr-BN heterojunction layer overpower their negative effects on the mechanical behavior of composite system. The adverse and strengthening effects induced by the BN-Gr-BN heterojunction layer are also strongly dependent of temperature. The present results can serve as a guide for diversified structure design and defect control. [ABSTRACT FROM AUTHOR]

Additive manufacturing of Al alloys presents an opportunity to produce complex parts that leverage their high specific strength. This paper aims to study the effect of processing parameters on the fabrication of single tracks and thin walls using AlSi10Mg powder in L-DED. A processing window was identified to enable continuous single track deposition with a regular shape. Deposition of thin walls and single tracks were used as a guideline to deposit blocks. Blocks were deposited using L-DED, and the physical, microstructural, and mechanical properties of the samples were investigated. Results demonstrated that the morphology of the thin walls were a better indicator of the morphology of the block samples than single tracks were, and care must be taken when transitioning from depositing single tracks to bulk (thin walls and blocks) samples. Results from mechanical testing show slight inhomogeneity as a function of height within the build for elongation and ultimate tensile strength. Microhardness and yield strength, however, were mostly uniform throughout the build. Overall, the results of this study demonstrate that L-DED is suitable for depositing AlSi10Mg and obtaining mechanical properties superior to those achieved through casting. Unlabelled Image • Laser directed energy deposition (L-DED) is used to deposit AlSi10Mg. • Single tracks, thin walls, and block geometries were deposited. • A processing window is defined for successful single track and thin wall deposition. • Single track parameters have limited scalability to bulk geometries. • Slight inhomogeneity in the mechanical properties is observed due to the microstructure. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure and mechanical properties of two magnesium matrix composites—a hypoeutectic with 1.9 wt% Mg2Si phase and a hypereutectic with 19 wt% Mg2Si compound—were analyzed. The investigated materials were prepared using the gravity casting method. Microstructure analyses of the fabricated composites were carried out by XRD and light microscopy. The tensile and compression strength as well as yield strength of the composites were examined in both uniaxial tensile and compression tests. The microstructure of the hypoeutectic composite was in agreement with the phase diagram and composed of primary Mg dendrites and an Mg–Mg2Si eutectic mixture. For the hypereutectic composite, besides the primary Mg2Si phase and eutectic mixture, additional magnesium dendrites surrounding the Mg2Si compound were observed due to nonequilibrium solidification conditions. The composites exhibited a rise in the examined mechanical properties with an increase in the Mg2Si weight fraction and also a higher tensile and compression strength in comparison to the pure magnesium matrix (cast in the same conditions). Additionally, analyses of fracture surfaces of the composites carried out using scanning electron microscopy (SEM + EDX) are presented. [ABSTRACT FROM AUTHOR]

The combination of selective laser melting (SLM) and Cu-based alloys has attracted attention in recent years due to the increasing requirements for components characterized by complicated structures and high electrical and thermal conductivity. In this paper, to investigate the forming properties of a Cu–Cr–Zr alloy in SLM, a statistical model regarding the impacts of the processing parameters on the density was established via an experimental approach (response surface method and analysis of variance). Furthermore, based on the acquired optimal processing parameters, samples with nearly full density and standard tension specimens were fabricated, and their microstructures and mechanical properties were analyzed. X-ray diffraction results indicate that the phase composition of the as-built sample by SLM contains only α-Cu phase and the Bragg peaks of the α-Cu phase in SLMed sample distinctly differs from those of powders and of wrought copper alloy. Compared with wrought copper alloy, SLMed Cu–Cr–Zr shows a comparable ultimate tensile strength (∼321 MPa); however, its elongation at break (25%) is much higher than that of wrought sample (15%). In addition, according to electron back-scattered diffraction analysis, a strong texture with respect to the <110> direction parallel to the building direction arose during SLM process. • Near fully density Cu–Zr–Cr copper alloy was successfully fabricated by SLM. • Grain morphologies were different in parallel and perpendicular to building direction. • The SLMed samples showed much higher plasticity compared with the wrought ones. • A strong texture with <110> direction parallel to the building direction was found. [ABSTRACT FROM AUTHOR]

In this paper, cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC) was proposed as a novel severe plastic deformation process for fabricating bulk ultrafine-grained (UFG) metals. Increasing the size of the processed sample and introducing the shear strain by attaching an asymmetrical extrusion cavity are the core advantages of this technology. The CEE-AEC process was applied to Mg-13Gd-4Y–2Zn-0.4Zr alloys for four passes deformation with the decreasing temperature, and then the microstructure evolution, texture analysis, and mechanical properties were investigated. Microstructure results show that a dramatical grain refinement is achieved from initial value of 24 ± 0.3 μm to 1.4 ± 0.3 μm which is mainly led by continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) as well as the particle-stimulated nucleation (PSN) induced by interdendritic long-period stacking ordered (LPSO) phases. With increasing CEE-AEC passes, the intensities of basal texture are gradually weakened, and the basal plane tends to incline to transverse and normal directions with different degrees of different passes, leading to a remarkable increase in Schmid factor for the activation of basal slip system. Tensile tests at room temperature (RT) indicate that the samples after three-passes of CEE-AEC exhibit the best comprehensive mechanical properties with tensile yield strength (TYS) of 302 MPa, ultimate tensile strength (UTS) of 330 MPa, and fracture elongation of 6.1%, which are mainly ascribed to the grain refinement, broken of interdendritic block-shaped LPSO phases, and texture modification. • A novel SPD method entitled CEE-AEC was proposed. • The Mg-13Gd-4Y–2Zn-0.4Zr alloy was processed by CEE-AEC with consecutive four passes deformation. • A significant grain refinement from initial 24 ± 0.3 μm to 1.4 ± 0.3 μm was obtained. • Continuous and discontinuous dynamic recrystallizations took place during CEE-AEC. • The mechanical properties were contributed from the competitive of fine grains strengthening and texture modification. [ABSTRACT FROM AUTHOR]

Automotive and industrial design companies have profusely used commodity materials like glass fiber-reinforced polypropylene. These materials show advantageous ratios between cost and mechanical properties, but poor environmental yields. Natural fibers have been tested as replacements of glass fibers, obtaining noticeable tensile strengths, but being unable to reach the strength of glass fiber-reinforced composites. In this paper, polyamide 6 is proposed as a matrix for cellulosic fiber-based composites. A variety of fibers were tensile tested, in order to evaluate the creation of a strong interphase. The results show that, with a bleached hardwood fiber-reinforced polyamide 6 composite, it is possible to obtain tensile strengths higher than glass-fiber-reinforced polyolefin. The obtained composites show the existence of a strong interphase, allowing us to take advantage of the strengthening capabilities of such cellulosic reinforcements. These materials show advantageous mechanical properties, while being recyclable and partially renewable. [ABSTRACT FROM AUTHOR]

In this paper, a new kind of AlTiC–B master alloy, containing large amounts of nano‒sized TiC particles, has been applied in 7050 alloy. The influence of master alloy addition on the casting microstructures, extrusion behaviors and mechanical properties of 7050 has been investigated. It is found that 0.5 wt% addition of AlTiC–B master alloy exhibits the most attractive performance, resulting in much finer matrix grains and less casting defects. After hot extrusion, typical <100> and <111> fiber textures co‒exist in the microstructure of original 7050 alloy, whereas the alloys with AlTiC–B inoculation possess a higher intensity of <111> fiber texture. Besides, the inoculated alloys show better anti–recrystallization performance and larger local misorientation. It has been confirmed that a proper addition of AlTiC–B master alloy is beneficial for the mechanical properties of extruded 7050, which may be due to its refining effect on α–Al grains and its improvement for the precipitation of L1 2 –ZrAl 3. The Brinell hardness, ultimate tensile strength, yield strength and elongation of 7050 alloy with 0.5 wt% addition of AlTiC–B addition are 174 HBW, 665 MPa, 724 MPa and 9.8%, respectively. This work provides a promising prospect of AlTiC–B master alloy for applying in 7050 alloy in industries. • Research highlights: • A new AlTiC–B master alloy with B doped nano‒sized TiC particles was applied on 7050 alloy. • Improvement of casting quality and grain refining can be achieved with AlTiC–B inoculation. • Texture intensity and recrystallization fraction of as‒extruded 7050 vary with AlTiC–B addition. • Mechanical properties can be significantly improved. [ABSTRACT FROM AUTHOR]

In this paper, nanostructured multilayer with overall composition of Cu 53 Ni 47 was fabricated by means of accumulative roll bonding (ARB) of pure Cu and Ni metal strips. In the first four ARB cycles, the thickness reduction of the Cu layer was slow and twin boundaries were formed. Necking and fracture of the harder Ni layer happened and the Ni island-like areas were therefore formed. After four ARB cycles, the thickness of both Cu and Ni single layers became homogeneous and finally the single layer thickness less than 100 nm was formed after seven ARB cycles, corresponding to an equivalent strain of 11.11. 3DAP element concentration analysis confirmed that Cu–Ni solid solution was formed due to the inter-diffusion of the constituent elements across the interface, which increased the bonding strength of the adjacent layers. Tensile tests revealed that the ultimate tensile strength of the multilayer was up to 950 MPa, which is approximately five times higher than that of the initial pure Cu metal. For all the tensile specimens with various ARB cycles, debonding of the layer interface formed during the last ARB cycle was observed. The plastic strain first increased to a maximum value of 9.1% after four ARB cycles due to the homogenization of deformation between Cu and Ni single layer. Then the plastic strain decreased to about 4.6% after seven ARB cycles due to the formation of nanoscale microstructure. • Nanoscale Cu/Ni multilayer was fabricated by ARB up to seven cycles. • Cu–Ni solid solute was formed along the interface by mechanical alloying. • The nanoscale Cu/Ni multilayer showed maximum tensile strength of 950 MPa. • Debonding of the last formed interface occurred during tensile tests. [ABSTRACT FROM AUTHOR]

The performance of welded members and connections in fire-induced steel structures depends on the mechanical properties of welds at elevated temperatures. At present, the fire resistance of steel welds is estimated by considering the high-temperature strength to be the same as those of structural carbon steel. This is because of the lack of data on mechanical properties of steel welds at elevated temperatures. This paper presents results from an experimental investigation on high-temperature mechanical characteristic of steel welds made using shield metal arc welding (SMAW) process, and E6013 and E7018 electrodes. Steady-state tension tests were conducted on weld metal specimens at 20–800 °C temperature range. Results from these experiments were utilized to evaluate stress-strain response, tensile strength, ultimate strength and the modulus of elasticity as a function of temperature for steel welds. Furthermore, the influence of electrode type in welding process and test temperature on the failure mode and microstructure of steel welds was investigated. Data from the experiments indicate rapid reduction in strength of steel welds at temperatures greater than 400 °C reaching to 50% and 8% of its original ultimate strength at 600 and 800 °C, respectively. Test data also indicate that the yield stress of steel welds decreases faster than that of structural steel at 450–800 °C. Electrode type in the welding process is an important factor besides the exposure temperature, which has a great effect on strength characteristics of steel welds at elevated temperatures. • High-temperature mechanical properties of steel welds made using SMAW process were experimentally studied. • Beyond 400 °C up to 800 °C heating temperature, welds lose ultimate strength rapidly. • The yield stress of steel welds decreases faster than that of structural steel at 450–800 °C. • Electrode type has a great effect on strength characteristics, failure mode and microstructure of weld metals in fire. • The high-temperature strength of steel welds can be improved through the use of E7018 electrode in place of E6013. [ABSTRACT FROM AUTHOR]

As-Selective Laser Melted (as-SLMed) Ti6Al4V in horizontal direction possess poor ductility because of acicular α ' martensite and columnar β grains in microstructure. However, traditional ductility improvement methods including high-temperature preheating or heat treatment will decrease not only strength but also the efficiency of SLM fabrication to application. For a satisfactory mechanical property of as-SLMed Ti6Al4V alloy, some special temperature evolution conditions brought about from processing parameters such as layer thickness, hatch spacing, energy density and area ratios between support structure and part, were carried out in the paper. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the microstructure. The microstructure of as-SLMed specimens are found to be different extent decomposing of α ' martensite. Also, the formation mechanisms of such microstructural variables are proposed based on temperature evolution vs time during SLM process. Moreover, the tensile test presents high elongation (>8%) is achieved for horizontally as-SLMed Ti6Al4V specimens without lowering their strength (the ultimate tensile strength ∼ 1260 ± 30 MPa and yield strength ∼1160 ± 50 MPa), which markedly exceed ASTM standard for castings. The mechanical properties and fracture mechanisms of specimens are obviously affected by the width of α ' / α martensite and the content of β phase. This work marks an important step forward in the understanding of microstructural tailoring in SLM process for a high-performance Ti6Al4V alloy. • Three types microstructures that full α′ martensite, α'+(α+β) and (α+β) can be tailored by special SLM conditions. • Microstructural formation mechanism was studied to further understand mechanical properties. • The as-SLMed Ti6Al4V exhibits improved elongation without decreasing strength. [ABSTRACT FROM AUTHOR]

Tungsten inert gas (TIG) welding was considered as one of the candidate technologies to achieve the box structure of test blanket module (TBM). In this paper, the effects of heat input on the microstructure and mechanical properties of multilayer TIG butt-welded China Low Activation Martensitic (CLAM) steel were investigated by microstructure observations, Vickers hardness, tensile and Charpy impact tests. The results showed that the microstructure of the weld metal (WM) were coarse quenched martensite and residual delta-ferrite. When the heat input value increased from 1.73 kJ/mm to 2.41 kJ/mm, the width of martensite laths increased slightly and the delta-ferrite content decreased firstly then increased. Moreover, the increasing heat input resulted in remarkable tempering effect on the previous layer of the WM by the following deposited layers. The transverse hardness distribution of the joints showed that softening occurred in the heat-affected zone (HAZ), and the hardness of WM decreased slightly as the heat input increased. The ultimate tensile strength values of the joints with various heat input were all higher than 630 MPa, and the rupture position located at the HAZ. Charpy impact toughness of the as-welded joints met the toughness criteria for the welded joint (≥27 J) of creep resistant 9Cr steel according to the standard of ISO-3580. [ABSTRACT FROM AUTHOR]

High strength and excellent electrical conductivity of Al alloys are highly desired in the field of power transmission. However, these two factors are usually contradictory in metallic materials. A novel boron coupling nano-AlN particles (about 0.6 wt% nano-AlN p and 0.06 wt% B) reinforced A356 alloy is proposed in this paper, which obtains excellent electrical conductivity (σ: 46.2% IACS), high ultimate tensile strength (UTS: 300 MPa), superior yield strength (YS: 240 MPa) and good elongation (EL: 7.5%) synchronously. Contrasting with the general A356 alloy modified by Sr, the σ, UTS, YS, and EL increased by about 8.2%, 9.1%, 4.3% and 66.7% respectively. This strategy is mainly based on boron treatment and nano-AlN p inhibiting the lapped growth of eutectic Si to ensure high conductivity, and the modification of Si, the refinement of the SDAS of α-Al grains and the relative homogeneous distribution of the individual or small flocculent nano-AlN p in the matrix and at the Al/Si interface to ensure high mechanical properties. • A novel high performance conductive A356 alloy has been designed, which is promising in industrial manufacture. • This strategy realizes the synchronous improvement in conductivity and strength. • The electric conduction and strengthening mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Oriented structure, mainly controlled by processing conditions, is another efficient method of reinforcing polymer materials in addition to compounding with rigid inorganic fillers such as carbon nanotubes (CNTs). The mechanical properties of oriented polypropylene (PP)/multiwalled CNT (MWCNT) composites, which are vital to their application fields, are investigated extensively in this paper, with an aim to distinguish the contribution of MWCNTs contents from that of the oriented structure to the final performance of the composite. The results indicate that MWCNTs mainly increase the modulus of the composites by approximately 140%. The oriented structure formed during the die-drawing process contributes more to the enhancement of tensile strength, increasing up to 550%. The modulus and tensile strength can be further improved by increasing the drawing speed. Moreover, the tensile stress field in the die-drawing process can vastly improve the dispersion of the MWCNTs in the matrix, thus providing a new idea for improving the dispersion of nanofillers in the polymer matrix. • Die-drawing process contributes more to increase tensile strength. • MWCNTs mainly increase modulus rather than tensile strength. • Tensile strength and modulus can be further improved by increasing the drawing rate. • The die-drawing process can vastly improve the dispersion of MWCNTs in the PP matrix. • MWCNTs can hinder the molecular chain orientation. [ABSTRACT FROM AUTHOR]

In this paper, we study the mechanical behavior of surface nanoconnectors that are developed using two contacting sets of patterned copper (Cu) nanowire (NW) arrays. Specifically, comprehensive molecular dynamics (MD) simulations are conducted to establish the mechanics and the mechanisms involved at the atomic level that govern the mechanical integrity and ultimately the functionality of the formed bonds. All MD simulations were conducted using the embedded-atom and the Lennard-Jones potentials. Two aspects of the work were accordingly examined. The first considers the effect of temperature and diameter of an isolated Cu-NW on its tensile and fracture strength, as this determines the static strength and durability of the surface connector. The second considers the effect of NW diameter, separation distance between the NWs, overlapping depths, and temperature on the tensile strength of the nanoconnector. The results reveal that the formed surface joint between two interacting NWs can resist up to 70 nN in tension at an overlapping depth of 50 Å. It also reveals that increasing the nanowire diameter, the bonding failure becomes more surface dominated with insignificant plastic deformation outside the interface contacting region. These findings are useful in designing advanced conductive adhesives with tenable performance. Unlabelled Image • Surface nanoconnectors manufactured from patterned copper nanowire arrays are investigated using molecular dynamics simulations. • The fracture strength of copper nanowires decreases with increasing the nanowire diameter and temperature. • The overlap depth between the contacting nanowire determine the strength and failure mechanism of the interface region. • The interface strength reaches its maximum value when the NW diameter is 15 nm and slightly decreases when the diameter is increased. • The operating temperature of the nanoconnector leads to a major reduction in the load transmitted by the nanoconnector. [ABSTRACT FROM AUTHOR]

In this work, a novel approach combining liquid deposition with selective laser melting (SLM) is used for fabricating reduced graphene oxide (RGO)/S136 metal matrix composites (MMCs). The grain sizes, crystallographic textures, phase compositions and mechanical properties can be tailored by controlling the RGO content in the RGO/S136 MMCs. The results show that the average grain size reaches its smallest size of 0.75 μm when 0.1 wt% RGO was added to the RGO/S136 MMCs. As the RGO content is increased from 0 wt% to 0.5 wt%, a continuous transition of the grains from the (001) orientation to the (101) and (111) orientations is observed. In addition, the cellular dendritic grains transform into equiaxed fine grains with increasing RGO content. The SLM-prepared RGO/S136 MMCs are dominated by high-angle grain boundaries (˃15°) and the martensite (bcc) phase. The hardness, ultimate tensile strength and yield strength of the SLM RGO/S136 MMCs exhibit trends that initially increase and then decrease, with maximum values of 580.6 HV, 535.3 MPa and 515.8 MPa, respectively. This paper highlights the possibility of controlling the RGO content to achieve the desired microstructural characteristics and mechanical properties of RGO/S136 MMCs fabricated by the SLM process. Unlabelled Image • The fully dense RGO/S136 composites via molecular-level mixing were firstly fabricated by selective laser melting. • EBSD patterns revealed the refined grain and tailored microstructure for SLM RGO/S136 composites. • SLM RGO/S136 composites with 0.1 wt% RGO exhibited maximum tensile properties and hardness. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties of 36 aluminum alloy specimens subjected to repeated tensile loading were tested. The failure characteristics, stress-strain hysteresis curves and its corresponding skeleton curves, stress cycle characteristics, and hysteretic energy of specimens were analyzed in detail. Furthermore, the finite element model of aluminum alloy specimens under low-cycle fatigue loading was established and compared with the experimental results. The effects of specimen parallel length, parallel diameter, and repeated loading patterns on the mechanical properties of aluminum alloys were discussed. The results show that when the specimen is monotonously stretched to fracture, the failure result from shearing break. When the specimen is repeatedly stretched to failure, the fracture of the specimen is a result of the combined action of tensile stress and plastic fatigue damage. The AA6061, AA7075, and AA6063 aluminum alloys all show cyclic softening characteristics under repeated loading. When the initial stress amplitude of repeated loading is greater than 2.5%, the repeated tensile loading has a detrimental effect on the deformability of the aluminum alloy. Finally, based on experiment research as well as the results of the numerical analysis, the calculation method for the tensile strength of aluminum alloys under low-cycle fatigue loading was proposed. [ABSTRACT FROM AUTHOR]

The thermomechanical behavior of coal and sandstone during excavation using the freezing method is a new challenge for coal mining and geotechnical engineering. In this paper, the influence of temperature on the mechanical characteristics and fracture patterns of two types of saturated rocks (coal and sandstone) were investigated. A series of laboratory tests, including the Brazilian tensile strength (BTS), uniaxial compressive strength (UCS), and triaxial compressive strength (TCS), were conducted at temperatures of 20, −4, −10, and −15 °C. The results indicated a significant increase in their strength when the temperature was reduced from 20 to −15 °C, especially near the phase-transition point. Then, a theoretical model was proposed to predict rock strength change with temperature, based on the phase-transition theory. To evaluate this model, the predicted results were compared with experimental data, where a good correlation was identified. In addition, four failure patterns were observed in indirect tensile tests (i.e., layer activation, central fracture, noncentral fracture, and central and layer activation), and three types of failure modes in compression tests (i.e., axial splitting, shearing along a single plane, multiple fracturing). The evolution of the rock damage was divided into four stages: Crack closure, fracture initiation, critical energy release, and rupture. These results could be applied to evaluate and predict the mechanical behavior of saturated coal and sandstone during excavation using the freezing method. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT)-reinforced metal matrix composites (MMCs) face the problems of dispersion and interfacial wetting with regard to the matrix. A synergetic method of spray pyrolysis (SP) and flake powder metallurgy (FPM) is used in this paper to improve the dispersibility and interfacial bonding of CNTs in a Cu matrix. The results of the interface characterization show interface oxygen atoms (in the form of Cu2O) and a high density of dislocation areas, which is beneficial for interfacial bonding. The tensile results show that the tensile strength of the SP-CNT-Cu composites is much higher than that of the CNT-Cu composites when the mass fraction of the CNTs does not reach the critical value. This can be explained by the nanoparticles which are found on the surface of the CNTs during the SP process. These nanoparticles not only increase the tensile strength of the SP-CNT-Cu composites but also improve the dispersion of the CNTs in the Cu matrix. Thereby, uniform dispersion of CNTs, interfacial bonding between CNTs and the Cu matrix, and the enhancement of tensile strength are achieved simultaneously by the synergetic method. [ABSTRACT FROM AUTHOR]

Continuous carbon fiber (CF)-reinforced poly (ether ether ketone) (PEEK) composites have excellent mechanical properties, but their processing techniques are limited. Therefore, we promoted a braiding method based on the hybrid fiber method by hot-compacting CF/PEEK plain weave fabrics to solve the problem of difficult wetting between CF and PEEK. Four parameters—melting temperature, molding pressure, crystallization temperature and the resin contents—were investigated for optimized fabrication. After studying the melting range, thermal stability and the contact angle of PEEK under different temperatures, the melting temperature was set at 370 °C. An ultra-depth-of-field 3D microscope was adopted to investigate the effects of molding pressure in the melting stage. The tensile strength or modulus along and perpendicular to the carbon fiber direction and crystallinity under different crystallization temperatures were analyzed. As a result, the sample crystalized at 300 °C showed an excellent tensile properties and crystallinity. The increased mass ratio of PEEK ranging from 50.45% to 59.07% allowed for much stronger interfacial strength; however, the higher resin content can lead to the dispersion of CFs, loss of resin and the formation of defects during processing. Finally, the optimal resin mass content was 59.07%, with a tensile strength of 738.36 ± 14.49 MPa and a flexural strength of 659.68 ± 57.53 MPa. This paper studied the optimized processing parameters to obtain better properties from CF/PEEK plain weave fabrics and to further broaden the specific applications of CF/PEEK composites, demonstrating a new direction for its fabrication. [ABSTRACT FROM AUTHOR]

• Fracture analysis of hadfield scrap shredder hammer is carefully investigated. • CFB steel 1.6511is a suitable alternative for austenite manganese steels. • The use of CFB on a shredder machine increased the lifetime of the hammer by up to 40%. Shredders are widely used in metal scrap recycling. The Shredder device includes hammers joined to a massive rotor. Hammers are responsible for grinding, therefore, play a key role in the shredder. Most of the casted hammers are made from austenitic manganese steel. Austenitic manganese steels usually have good mechanical properties at impact and wear use but in field use as shredder hammer, they are faced to the different type of failures. Finding reasons for these failures could help increasing shredding efficiency and reducing cost. In this study, several factors, such as the lack of work hardening of the as quench hammer, low yield strength and tensile strength, carbide growth at the user's temperature and stopping the work hardening at temperatures between 200 and 300 °C have been defined as reasons of failure. Regarding these points, castable Nano bainitic steel suggested as an alternative to the austenitic manganese steels. In file test results proved that nano bainitic steel hammers has better performance than austenitic manganese steel hammers. [ABSTRACT FROM AUTHOR]

Foamed poly(lactic acid) films reinforced with micro-crystalline cellulose (MCC), were uniaxially stretched to different ratios. At 10% (weight) loading MCC particles gave an approximately 3.5 times improvement in stiffness over unreinforced foams. X-ray tomography and image analysis showed that most MCC particles had low aspect ratios, were randomly oriented and well distributed. Stretching did not change the orientation of the MCC particles. Increases in stiffness with stretching were due to the alignment of the foam cell walls. Electron microscopy and image analysis showed that the foam cells were elongated and the walls aligned in the stretch direction. There was a good fit between measured stiffness and micro-mechanical modelling based on a variation of the Mori-Tanaka model for reinforcing particles randomly oriented in 3 dimensions. [ABSTRACT FROM AUTHOR]

This study aims to understand the material properties and long-term indoor stability of a biocomposite based on pine wood flour and poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) modified by a nucleating agent, boron nitride (BN), and an inorganic filler, talc, and to develop knowledge of the linkage between the microscale-structure and mechanical properties. Both BN, at a loading of 1 wt% and talc, at 5 wt%, had a nucleating effect on polymer crystallisation, with BN being more effective as evidenced by Avrami kinetic analysis. The addition of 5 and 10 wt% of talc enhanced the tensile strength of the PHBV/wood flour (50/50 wt%) composite from 22.3 ± 1.3 MPa (mean ± 95% confidence interval) to 24.3 ± 0.6 MPa and 24.7 ± 0.9 MPa respectively. The tensile modulus was also improved from 5.6 ± 0.6 GPa to 6.9 ± 0.4 GPa and 8.1 ± 0.7 GPa respectively. The micron-sized talc may fill voids within the composite matrix and/or act as an alternate filler, altering the deformation mechanism. However, the level of improvement in modulus was reduced after 1 year of conditioned ageing under a controlled environment (20 °C, 50% humidity). It is proposed that the combined effects of the swelling of wood through moisture uptake, the shrinkage of PHBV through secondary crystallisation, and the localised stress around talc particles led to weakened talc-PHBV interfaces. [ABSTRACT FROM AUTHOR]

Mechanical properties were evaluated for pulp delignified by four deep eutectic solvents (DES). The DES systems were based on choline chloride and lactic acid (1:9), oxalic acid:dihydrate (1:1), malic acid (1:1), and the system alanine:lactic acid (1:9). The results indicated that the type of DES system used influenced the delignified pulp's mechanical properties including tensile, burst and tear indexes, tensile length, and stiffness. The most suitable DES systems were choline chloride:malic acid (1:1) and alanine:lactic acid (1:9), which achieved the best aforementioned mechanical properties compared to the other DES systems. The weakest performance in the process of pulp delignification was the system with choline chloride and oxalic acid dihydrate (1:1). [ABSTRACT FROM AUTHOR]

The goal of this work was to evaluate the technical feasibility of walnut shell flour (WSF) as substitute for wood in walnut shell flour/thermoplastic starch (WSF/TPS) composites. The effects of walnut shell flour (WSF), thermoplastic starch (TPS), and nanoclay on the physical and mechanical properties of WSF/TPS composites were investigated. The composite samples were formed in a Colin extruder with four-chamber heat with temperatures. Then, test samples were made using injection molding. The addition of up to 40% WSF greatly improved the tensile strength, flexural strength, and elasticity modulus of the composite. Also, the composites made with higher WSF contents had increased thickness swelling and water absorption. The incorporation of nanoclay (0% to 5%), greatly improved the tensile properties. Soil burial degradation experiments showed that biodegradation was accelerated by the increase of starch in the composite mixtures. The study showed that WSF can be successfully utilized for the manufacture of composites with useful physical and mechanical properties. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the use of the reed stem in manufacturing three-layer particleboard. Variable factors were mixing ratio of reed and industrial wood particles (0:100,25:75, 50:50, 75:25 and 100:0 in the surface and middle layers), press temperature (170, 180, 190 °C) and pressing cycle time (5, 6, 7 min). Other parameters such as resin content (8% in core and 10% in faces), hardener content (2%), press closing rate (4,5 mm/min), press pressure (30 kg/cmr), board thickness (15 mm), and target density (700 kg/m3) were held constant. The physical and mechanical properties of particleboard panels including modulus of rupture, modulus of elasticity, internal bonding, water absorption and thickness swelling were determined according to the procedures of European standards. The results showed that modulus of rupture, modulus of elasticity, internal bond, water absorption and thickness swelling increased with the increase of reed particles content. The positive influence of press temperature and press time can also be seen in terms of improved physical and mechanical properties. Based on the findings of this study, we can conclude that reed stem can be used to manufacture particleboard. [ABSTRACT FROM AUTHOR]