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We previously used a grinder to prepare cellulose nanofibers (CNFs) that were then added to pulp to improve the wet strength of paper, with subsequent alkali treatment further improving its wet tensile strength. However, mass production of CNF using ultra-fine grinders is not feasible; moreover, fabricating paper sheets by first preparing CNFs and adding them to pulp is a complex process. Therefore, in this study, we directly fibrillated pulp using a refiner instead separately preparing CNFs, with the refined pulp used to make paper sheets, thereby simplifying the process. The resulting dried sheets were subsequently treated with 8 and 16 wt% NaOH, after which the co-reinforcing effect of the refiner and NaOH treatments on the wet tensile strength of paper was examined. Unexpectedly, wet tensile strength of 39 and 45 MPa was achieved. These values are higher than values obtained using the CNFs and NaOH treatment, and comparable to the dry strength of untreated and unrefined pulp sheet. Moreover, the dewatering time of the refiner-treated pulp was significantly shorter than that of the CNF-mixed pulp, which reduces the time required to prepare paper. This study demonstrated that refiner-treated pulp is more suitable than CNF-mixed pulp for improving paper wet strength. [ABSTRACT FROM AUTHOR]

Because of excellent insulation properties and thermal stability, meta-aramid paper can be commonly applied to a vast number of fields, like power systems. But poriferous and relatively lax structure of meta-aramid paper would limit its applications in high-voltage environment. This paper proposes a sandwich structure design to combine PDA@BNNS/PMIA film and meta-aramid paper with high breakdown strength. After coating with 6 wt% PDA@BNNS/PMIA solution, this kind of paper became more compact, so there were few pores in the paper and it further enhanced the mechanical and dielectric performances of specimens. The tensile strength in the cross direction increased from 31.3 to 40.5 MPa, and the performance in the machine direction was from 75.5 to 78.9 MPa. Furthermore, the breakdown strength of compound-coated paper achieved 55 kV/mm, which is much higher than meta-aramid paper. Additionally, compound-coated paper still remained outstanding thermal stability. Overall, our fabricated PDA@BNNS/PMIA compound-coated paper has excellent comprehensive properties, which provides a broad prospect for the applications in high-temperature and high-voltage transformers. [ABSTRACT FROM AUTHOR]

The small punch (SP) test has been widely used in applications where conventional mechanical tests cannot be performed; this paper predicts the material strength from the SP test results by empirical correlations method. The yield strength (YS) and ultimate tensile strength (UTS) models serve to associate the load–displacement (LD) curves of SP tests with the stress–strain data of uniaxial tensile tests, and then, the feasibility of these models at different temperatures is investigated. Using the Pearson's correlation coefficient (PCC) method, the ideal strength equations are accessed from past studies for the cast superalloys, including ZG15Cr2Mo1, P91, 316H, and Hastelloy X, whereas the validation results of the additively manufactured (AM) GH4169 alloy are not satisfactory. As a result, considering the unique manufacturing process of AM GH4169, this paper develops a YS model with correlation coefficients higher than 90% between the calculated and actual values and proposes a UTS formula with estimation errors less than 3.5%. Furthermore, with the purpose of superior strength prediction results, the discussion of the SP test velocity reveals that 0.50 mm min−1 had wide adaptability to various strength models and operating temperatures. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) is a pure biopolymer with abundant sources. BC has been used in wound dressings, artificial blood vessels, bone tissue engineering, and other applications because of its microporosity, superior water retention, thermal stability, and biocompatibility. The tensile strength of pure BC in wet state is weak, and the water holding capacity is above 90%, which limits its application. However, the mechanical properties of dehydrated BC are excellent at the expense of toughness, which is not enough to meet the demand of high additional-value materials, such as high strength flexible electronic device substrate, wearable electronic devices, vibration film for microphone and earphone, and others. Therefore, it is of great importance to systematically investigate the strategies to improve the mechanical properties of BC. Herein, this paper demonstrates the intrinsic factors affecting the mechanical properties of BC, along with the strategies to enhance the mechanical properties. Compared with the well-known adhesion reinforcement and chemical modification, six strategies to enhance the mechanical properties were discussed thoroughly in this paper. In addition, layer-by-layer self-assembly and orderly arrangement of fibrils are proposed in this paper to improve the mechanical properties of BC, which have not been described in detail in previous literature. [ABSTRACT FROM AUTHOR]

The current study suggested that nano-scale twins in magnesium alloys can significantly affect the elastic limit, ultimate strength and corrosion performance. However, the complicated process of nano-scale twins preparation limits its industrial application. In this paper, the microstructure with submicron twins and precipitates of ZK60 magnesium alloy was designed by room temperature multi-directional forging (MDF) process, aiming to improve the enhancement effect of submicron twins by compensating the denseness of coherent interfaces with diffusely distributed precipitates. The results show that the MDFed ZK60 alloy can obtain high strength (yield stress (YS): 248.5 MPa, ultimate tensile strengths (UTS): 371.4 MPa). Good comprehensive mechanical properties can be finally achieved after heat treatment at 150 °C (YS: 226.5 MPa, UTS: 352.6 MPa, elongation: 17.1%). Submicron lamellar {10–12} twins were formed within the alloy due to the small strains in multi-passes of forging. During heat treatment at 150 °C, a large amount of β1' phase was diffusely precipitated within the matrix and twins. The presence of precipitates effectively increases the denseness of dislocation motion barriers in submicron twins, which enables twin-boundary enhancement of ZK60 magnesium alloy. This work provides a new idea for the design of low-cost magnesium alloy forgings in industry. [ABSTRACT FROM AUTHOR]

Due to the machining-induced residual stress while processing, the machining distortion of thin-walled 7050 aluminum alloy parts occurs easily, which greatly affects the pass rate of the products. Herein, electromagnetic coupling treatment (EMCT) was proposed to relieve the residual stress of 7050 aluminum alloy. It was found that EMCT had a significant effect on residual stress relief (13.3–89.7%). The energy input by EMCT promoted the movement of dislocation, resulting in the uniform distribution of microplastic strain, the release of stored elastic strain energy, and the residual stress relief, ultimately. A numerical simulation method to visualize the evolution of the electromagnetic field, the stress, and the strain in the materials was proposed to explain the causes of microplastic strain. Specimen #5 with the optimal EMCT processing parameter (1.5 T, 1.5 V) was considered to be the most effective for both residual stress relief and mechanical property enhancement, in which the residual stress decreased by 85.1% and the tensile strength increased by 8.3%. In this paper, it is proposed that EMCT can be used as an effective method to reduce the residual stress of 7050 aluminum alloy. Moreover, it has certain technical reference value for the study of residual stress relief of other thin-walled part materials. [ABSTRACT FROM AUTHOR]

Acylhydrazone bonds can participate in dynamic exchange reactions under acid-stimulated conditions, and disulfide bonds can participate in dynamic exchange reactions under thermally stimulated conditions. It is of great significance to prepare epoxy vitrimer that can rapidly self-repair under acid and thermal stimulation conditions. In this paper, vanillin was used as raw material, and monomer (VAN-AD) containing acylhydrazone bond was synthesized by reaction with adipic dihydrazide. Then, VAN-AD and 4-aminophenyl disulfide (SS) were cured together with glycerol triglycidyl ether to prepare an epoxy vitrimer with acylhydrazone and disulfide dual dynamic covalent bonds. Where VAN-AD provides some of the flexible chain segments and acylhydrazone bonds and SS provides the aromatic phenyl and disulfide bonds. The material was prepared in a simple process and under mild condition, and the properties of the material were optimized by changing the ratio of VAN-AD to SS. The Tg of the material was 50 °C when the ratio of SS was the highest, the thermal stability was enhanced with the increase of the ratio of SS, and the maximum tensile strength up to 50.9 MPa, and the material can be completely degraded by DMF with 5% HCl. It is worth noting that the material shows rapid self-healing properties under acid-heat conditions, self-healing rates up to 97.37%, and the tensile strength can reach 26 MPa after repair. The material can be successfully remodeled by hot pressing for 1 h at 140 °C and 10 MPa. [ABSTRACT FROM AUTHOR]

The mechanisms of microstructure transformation and mechanical anisotropy of laser-MIG hybrid additive manufacturing TC11 titanium alloy after solution aging treatment are investigated. In this paper, different solution temperatures and cooling modes are applied to tailor the microstructure and improve high-temperature properties and anisotropy. The result shows the microstructure of the samples in the as-deposited state is dominated by a widmanstatten structure composed of lamellar α clusters. Following solution aging treatment, a large area of basket-weave structure is obtained in the samples. A major influence of spheroidization of lamellar α clusters and dynamic recrystallization on mechanical anisotropy is revealed. The heat-treated samples exhibit more superior combined strength, elongation, impact toughness. The hardness difference between the layers and mechanical anisotropy decreases. During high-temperature tensile tests, the tensile strength increases with rising solution temperature; while, the elongation shows the opposite trend. The tensile fracture exhibits abundant uniform equiaxed dimples, and the fracture mode changes from intergranular fracture to transgranular fracture. Solution treatment at 990 °C for 2 h followed by air cooling is considered to be the optimal heat treatment process. Consequently, it results in a high tensile strength of 811 MPa and an excellent impact toughness of 50 J, representing improvements of 16.08% and 71.08%. [ABSTRACT FROM AUTHOR]

The alloy composition and sensitization behavior are crucial factors that cannot be overlooked in Al–Mg alloys. The effect of Zn addition on mechanical properties and sensitization behavior of 5083 alloy was investigated by tensile tests, weight loss experiments, and first-principles calculation in this paper. The results show that Zn can significantly improve the strength and sensitization behavior of the alloy. The tensile strength of the cold-rolled alloy increased from 459 to 498 MPa with the addition of 1.5%Zn. Furthermore, by incorporating 2.0% Zn, the mass loss of the cold-rolled alloy after sensitization at 170℃/1 h decreased from 49.3 mg·cm−2 to 19.5 mg·cm−2. First-principles calculations indicate that Mg clusters can only exist stably near grain boundaries, while Mg–Zn clusters can exist stably both within and at grain boundaries. This reduces the number of corrosive media at grain boundaries and weakens their continuity. Moreover, the energy barrier that T-phase precipitation needs to overcome during precipitation is lower than β-phase, which transforms the stabilization schedule of the alloy from 240℃/12 h without Zn to that 210℃/4 h with 2.0% Zn-containing. The synergistic effects of Zn content and sensitization on the properties of the alloy were revealed, which sheds some light for the design of the composition and processing method according to application scenarios. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) composites are expected to serve as reinforcement materials for coastal and island infrastructure due to their high strength, lightweight, and good corrosion resistance. However, the performance of FRP bars as reinforcement materials in long-term service in the marine environment is also subject to deterioration. Therefore, for improving the durability performance of FRP bars, it seems necessary to understand their degradation behavior. This paper first analyzes the deterioration mechanisms of the fibers, resins, and fiber–resin interfaces that make up the FRP bars under the action of seawater/salt solution, seawater sea-sand concrete pore solution/alkali solution, and stress-marine corrosive environment coupling, respectively, and further investigated the mechanical property degradation of FRP bars under the action of various factors, including interlaminar shear strength, tensile strength, and bond strength with concrete. The degree of degradation of FRP bars exposed to the offshore environment was found to be more sensitive to the magnitude of alkalinity and stress levels; GFRP bars were more resistant to seawater corrosion than BFRP bars. Moreover, the long-term mechanical properties of FRP bars were predicted, and the predicted result is more conservative than the field data. Based on the summarized and analyzed results of this review, recommendations for future work are presented, also for a comprehensive and better understanding of the degradation behavior of FRP bars. [ABSTRACT FROM AUTHOR]

Selective electron beam melting (SEBM) has been recently employed for additive manufacturing (AM) Al alloys but showing comparatively low hardness and strength. In this work, SEBM technique was employed to additive manufacture an in-situ TiB2 particle reinforced AlSi10Mg composite. With optimized processing parameters, the SEBM TiB2/AlSi10Mg composite showed good surface quality and a high relative density. The as-printed composite exhibited a refined equiaxed grain structure with an average size of 27.7 µm. The eutectic Si phase was mostly spherical and uniformly distributed in the Al matrix, while the nano-sized TiB2 particles were partly agglomerated. The resultant microstructure was associated with the combined effect of the rapid solidification and annealing-like process during SEBM. Additionally, TiB2 particles facilitated grain refinement by enhancing the heterogeneous nucleation and retarding grain growth. The SEBM TiB2/AlSi10Mg composite presented a yield strength (YS) and ultimate tensile strength (UTS) of 103.6 MPa and 165.4 MPa, respectively, with an appreciable elongation of 15% at as-printed state. After a T6-like treatment, the YS and UTS of the composite were further improved to 225 MPa and 316 MPa, respectively, and an elongation of 12% was maintained. This paper shows the potency of SEBM in AM metal matrix composites (MMCs) with both agreeable strength and ductility. [ABSTRACT FROM AUTHOR]

Many important properties of bacterial cellulose (BC), such as moisture absorption capacity, elasticity and tensile strength, largely depend on its structure. This paper presents a study on the effect of the drying method on BC films produced by Medusomyces gisevii using two different procedures: room temperature drying (RT, (24 ± 2 °C, humidity 65 ± 1%, dried until a constant weight was reached) and freeze-drying (FD, treated at − 75 °C for 48 h). BC was synthesized using one of two different carbon sources—either glucose or sucrose. Structural differences in the obtained BC films were evaluated using atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction. Macroscopically, the RT samples appeared semi-transparent and smooth, whereas the FD group exhibited an opaque white color and sponge-like structure. SEM examination showed denser packing of fibrils in FD samples while RT-samples displayed smaller average fiber diameter, lower surface roughness and less porosity. AFM confirmed the SEM observations and showed that the FD material exhibited a more branched structure and a higher surface roughness. The samples cultivated in a glucose-containing nutrient medium, generally displayed a straight and ordered shape of fibrils compared to the sucrose-derived BC, characterized by a rougher and wavier structure. The BC films dried under different conditions showed distinctly different crystallinity degrees, whereas the carbon source in the culture medium was found to have a relatively small effect on the BC crystallinity. [ABSTRACT FROM AUTHOR]

In this paper, the effect of deep cryogenic treatment (DCT) on the microstructure and properties of automotive 6063 aluminum alloy at different times was investigated with automotive 6063 aluminum alloy as the research object. The results show that under the conditions of deep cryogenic treatment, the lattice distortion occurs in the alloy matrix microstructure, and the resulting internal stress promotes the large proliferation of dislocations within the alloy and the increase of dislocation density; meanwhile, after the deep cryogenic treatment, the deformed grains are transformed into recrystallized and sub-crystals structural grains, the grains are refined, and the size of the grains is refined from the original 25.2 μm to 20.3 μm, with fine equiaxed crystals. Among them, the mechanical properties of the DCT36h specimen were the best, and its hardness, tensile strength, yield strength and elongation reached 142.44 HV, 328.32 MPa, 177.42 MPa, and 29.29%, which were 34.17%, 5.62%, 11.10%, and 32.77% higher than the original sample, respectively. We believe that the main mechanism for the increase in toughness is multiple reinforcement such as dislocation strengthening, grain refinement strengthening, precipitated phase strengthening and texture strengthening. [ABSTRACT FROM AUTHOR]

Small specimen test techniques (SSTTs), developed for scarce materials, industrial products, in-service equipment, etc., could be challenging to obtain sufficient materials for routine testing. This review focuses on the research on millimeter- and micron-scale SSTTs of metallic materials in the past decade. Mainstream small specimens are divided into similarity, penetration, and semi-penetration. Representative tests of the above three categories are analyzed in detail, including the small tensile test, small punch test, and indentation test. The macro- or micro-correlation methods of deformation and failure parameters between the SSTTs and conventional tests are discussed, including Young's modulus, yield strength, ultimate tensile strength, damage evolution, fracture strain, and the stress–strain full-history relationships. Meanwhile, the extensive requirements for material testing are also considered, such as anisotropy and strain rate, temperature, and stress triaxiality sensitivities. The characteristics and modification strategies of the SSTTs are described from the aspects of size effects, inhomogeneous structures, and manufacturing defects. Finally, this paper discusses the application of SSTTs in forging, stamping, welding, and additive manufacturing and highlights the potential development directions of SSTTs. [ABSTRACT FROM AUTHOR]

In the present paper, the evolutions of material flow and intermetallic compounds (IMCs) during friction stir welding (FSW) of dissimilar Al/Cu with two different plate positions are analyzed to elucidate the correlations with mechanical properties of the joints. Under the tool rotation speed of 700 rpm and the welding speed of 110 mm/min, the Al or Cu plate is located at the advancing side (AS) and the retreating side (RS), which are marked as Al-AS/Cu-RS and Al-RS/Cu-AS, respectively. The results demonstrate that material flow plays a significant role on both the formation and the distribution features of IMCs during FSW with different plate positions. For Al-AS/Cu-RS, the dissimilar material was deposited immediately behind the tool without being drawn into the pin rotating, so that a regular two-layer IMCs within a thickness of 1.5 μm are formed throughout the Al/Cu bonding interface. For Al-RS/Cu-AS, the dissimilar material is sticking with the tool and rotating for multiple circles before it is finally deposited, both two-layer and three-layer IMCs are observed with the thickness ranging from 0.5 to 4.0 μm at the Al/Cu bonding interface, and a multitude of IMCs are also formed in the intermixing zone, which are both confirmed to be detrimental to the joint mechanical performance. Therefore, the ultimate tensile strength of the Al/Cu joint improves by over 20% with changing the position of Cu plate from the AS to the RS in FSW. [ABSTRACT FROM AUTHOR]

The present paper studies the effect of reprocessing, on both dry and wet reprocessing conditions, on the rheological and mechanical properties of a biocomposite made of a bio-based, biodegradable polymer with 40 wt% wood flour. The results show that the viscosity of the matrix decreases as the number of extrusions increases, with the greatest reduction for samples processed under wet conditions. The same behavior was observed for the biocomposite, but since the viscosity of the biocomposite is much higher than that of the matrix, this causes a greater reduction of molecular weight. Mechanical results show that properties such as tensile strength and elongation decrease as the number of extrusions increases for the matrix. In terms of maximum variations, the tensile strength experiences a decrease of approximately 18%, while the elongation at break shows a more significant reduction of about 40%. Conversely, the biocomposite shows an increase in tensile strength (about 30%) and elongation at break (about 90%) after the first extrusion and then a slight decrease, but with values of tensile strength and elongation higher than those of the virgin biocomposite. [ABSTRACT FROM AUTHOR]

This paper studied the effects of basalt fibers (BF), polypropylene fibers (PF), end-hooked steel fibers (HSF), and wavy steel fibers (WSF) on the durability (impermeability and frost resistance) and mechanical properties (compressive, flexural, uniaxial tensile, and splitting tensile strength) of concrete based on the original mix proportion (water-binder ratio of 0.41). The results demonstrate that 0.5% of HSF has the best impact on enhancing concrete's compressive, flexural, and splitting tensile strength, with improvements of 10.88%, 21.02%, and 16.76%, compared to the control group. Meanwhile, 0.2% of BF has the best impact on improving the uniaxial tensile strength of concrete, with an improvement value of 18.91%. For concrete impermeability and frost resistance, 0.1% and 0.2% BF were the optimal fiber and content. However, PF was not very effective in improving the durability and mechanical property of concrete. Considering the scope of the investigated fiber content, the mechanical properties of concrete declined as fiber content rose. Still, the uniaxial and splitting tensile strengths improved as BF content rose. As the content of fiber in concrete increased, its impermeability weakened, and its ability to frost resistance improved. The above conclusions are highly significant for selecting fiber concrete types in future studies. [ABSTRACT FROM AUTHOR]

The purpose of this paper was to design an Al–Cu–Ag–C material system to address the deterioration of mechanical properties caused by intermetallic compounds generated during Al–Cu sintering. The in situ pyrolytic C layer was encapsulated on the surface of the raw material particles, which prevented Al–Cu diffusion and reduced the generation of intermetallic compounds. The microstructure of the Al–Cu–Ag–C composites illustrates that several alloy phases of Al2Cu, Al4Cu9, and Ag2Al are formed. The addition of Ag significantly improved the mechanical properties of the composite due to the formation of the Ag2Al phase and Cu–Ag solution. The tensile strength and compressive strength of Al–52Cu–3Ag–C are increased by 123.9% and 64.9% over Al–52Cu–C, and the strain is also considerably improved. The strength enhancement derived from the Orowan strengthening contributed by Ag2Al, and the solid solution strengthening contributed by Ag–Cu solid solution, respectively. The presence of Ag2Al also enhances the hardness of the composite. [ABSTRACT FROM AUTHOR]

The effects of rare-earth (RE) inoculants are excellent, but RE is rare and expensive. Consequently, it is necessary to choose other elements to reduce the use of RE. In this paper, research was done to investigate the effects of different content La–O–S complex inoculant on the microstructure and mechanical characteristics of ductile iron (DI) through SEM, EDS, XRD, etc. Studies have shown that the as-cast structures of the samples are graphite nodules, ferrites, and a few pearlites. The graphite core consists of oxides (Al2O3, SiO2, Fe2O3), sulfides (La2S3, LaS), and XO·SiO2·Al2O3 silicate (X: Ca, Ba, Sr). The amount of graphite nodules increases firstly and then slightly decreases, ferrite increases gradually, and pearlite decreases by degrees with the increase in S or O content, which makes the Brinell hardness and tensile strength of the sample decrease, and the elongation of the sample slightly decreases after increasing. When both O and S are 0.3%, mechanical characteristics of the samples are best, Brinell hardness is 163.3 BHW, tensile strength is 513 MPa, and elongation is 16.1%. [ABSTRACT FROM AUTHOR]

Hybrid aluminum matrix composites have attracted researchers in the world because of their more excellent mechanical properties than metal matrix composites with single reinforcement. In this paper, TiC@TiN–Ti2N–Al4C3/Al composite was prepared by high-energy ball milling and spark plasma sintering (SPS) with Al–10Ti powders and g-C3N4 powders. TiC, TiN, Ti2N and Al4C3 reinforcements were synthesized by in situ reaction during the high-energy ball milling and SPS processing. Then, TiC@TiN–Ti2N–Al4C3/Al composite ribbons were prepared by melt spun. Next, the ribbons were added to the Al–Zn–Mg–Cu melt to prepare TiC@TiN–Ti2N–Al4C3/Al–Zn–Mg–Cu composite. It was found that TiC@TiN, Ti2N and Al4C3 reinforcements had good refining and reinforcing effects on the Al–Zn–Mg–Cu alloy. The average grain size of the composite is from ~ 95 to ~ 35 μm. Besides, there is a 14.0% increase on the ultimate tensile strength and a 21.9% increase on the elongation of the composite. The microstructure, orientation relationship and mechanical properties of the TiC@TiN–Ti2N–Al4C3/Al–Zn–Mg–Cu composite were investigated. Besides, the strengthening mechanism of the TiC@TiN core–shell structure on the composite was mainly discussed by first principles. [ABSTRACT FROM AUTHOR]

A low-alloyed Mg-1.2Zn-0.1Ca (wt%) alloy was extruded at different temperatures (150 °C, 200 °C, 250 °C, 300 °C), and the effect of extrusion temperature on the microstructure and tensile properties was investigated systematically. While the as-cast alloy presented many cracks on the surface when extruded at 150 °C, it demonstrated good extrudability at temperatures above 200 °C. With increasing extrusion temperature from 200 to 300 °C, the average dynamic recrystallization (DRX) grain size increased from ~ 2.6 to ~ 6.4 μm, and < 10–10 > texture gradually transformed to < 11–21 > rare-earth texture component. Solute segregation was observed along grain boundaries and dislocations. The sample extruded at 200 °C exhibited a superior combination of both strength and ductility, with a yield strength of 179 MPa, an ultimate tensile strength of 228 MPa and an elongation of 35%. The improved tensile properties were mainly attributed to the fine grain size together with a high density of dislocations. The basal slip Schmid factor increased with increasing extrusion temperature due to the attainment of full DRX microstructure and the presence of non-basal texture component, which resulted in a lower yield strength at higher extrusion temperatures. The findings pave the way for the development of low-cost and low-alloyed high-performance magnesium alloys via the strategy of tailoring extrusion temperatures. [ABSTRACT FROM AUTHOR]

Enhancing the high temperature mechanical properties and the thermal stability of aluminum alloys are in urgent demand for the lightweight application scenarios (such as pistons, fan blades, crankshafts) working at elevated temperatures. The fabrication of aluminum matrix composites is a promising solution. In this work, TiB2 nanoparticles were in-situ introduced to a typical heat resistant Al–Cu–Mg–Fe–Ni (Al2618) alloy matrix and subjected to hot extrusion. Microscopically, the extruded TiB2/Al composite exhibited refined and bimodal sized grain structure, which was stable after long-time thermal exposure associated with TiB2 particle banding along the extrusion direction. The TiB2/Al composite showed an evident improvement in high temperature strength as well as the strength retention after long-time thermal exposure up to 300 °C, compared to the unreinforced alloy. The strengthening effect was remarkable especially at 200 °C with an increase of ~ 20% (60–70 MPa) in tensile strength and strength retention after thermal exposure but without the trade-off of ductility. The effects of TiB2 particles on the temperature-dependent strengthening mechanisms and microstructure evolutions were investigated. This work inspires the design, processing and evaluation of novel high strength and heat resistant particle-reinforced aluminum matrix composites for the potential applications under elevated temperature service conditions. [ABSTRACT FROM AUTHOR]

The lack of ductility is known to be a major drawback in the mechanical properties of amorphous alloys. A temperature impact is often used, as a factor to improve the mechanical parameters of these thermally unstable materials. A thick Ni82.1Cr7.8Si4.6Fe3.1Mn0.2Al0.1Cu0.1B2 metallic glass ribbon was subjected to a series of one-hour anneals between 50 and 700 °C. Annealing at 250 °C revealed an increase in the density of the ribbon accompanied by structure rearrangement responsible for the β-relaxation process. In addition, the metallic glass demonstrated high ductility along with high tensile strength and hardness under load. Based on the analysis of transformation of excess free volume in the vicinity of the β-relaxation temperature, a mechanism explaining the attainment of ductility maximum realized in metallic glass under loading has been proposed. [ABSTRACT FROM AUTHOR]

Introducing of thermodynamically stable strengthening phases is an important means enhancing the properties of magnesium alloys. To introduce a stable Al2Nd strengthening phase, the Mg-Al-Nd alloys were prepared with a fixed atomic ratio of 2:1 for Al and Nd. The total content of Al and Nd was varied at 1%, 3%, 5%, and 7%, respectively. The effects of Al2Nd phase on the microstructure and mechanical properties of the Mg-Al-Nd alloys were systematically studied in this work. The experimental results indicated that the as-cast alloy primarily consisted of the acicular Al11Nd3 phase as a secondary phase. After undergoing a homogenization treatment at 500 °C for 12 h, the secondary phase underwent a transformation, resulting in the formation of short rod shape Al2Nd structures. Simultaneously, layered Al2Nd precipitated within the α-Mg matrix. The formation of twinning was inhibited, while the Al2Nd phase promoted recrystallization and refined the microstructure through the mechanism of particles stimulated nucleation (PSN), as the Al and Nd contents increased during thermal deformation. At the same time, the increases of Al2Nd phase can enhance the strength and the plasticity of the alloy. The mechanical properties of extruded Mg-1.36Al-3.64Nd (AE5) alloy were excellent with yield strength of 175 MPa, ultimate tensile strength of 249 MPa, and the elongation of 15.4%. The enhanced performance can be primarily attributed to the refined microstructure and the presence of Al2Nd precipitates with small size, which contributed to effective fine grain strengthening and secondary phase strengthening. [ABSTRACT FROM AUTHOR]

The need for 2219 aluminum alloy and 2195 Al–Li alloy dissimilar friction stir welding (FSW) arises as the conventional 2219Al alloy was gradually replaced by the novel 2195Al alloy in fabrication of fuel tanks. However, the systematic investigation about the effect of welding parameters and material positioning on the microstructure evolution and mechanical properties of dissimilar FSW 2219Al/2195Al joints is lacking. In the present study, 2219Al-T8/2195Al-T8 plates were subjected to FSW under rotation rates of 800–1200 rpm and welding speeds of 200–800 mm min−1 with placing 2219Al-T8 alloys on the advancing side (AS) and retreating side (RS), respectively. The results showed that sound FSW joints were obtained under all the welding conditions. Welding parameters and material positioning affected the joint strength and fracture failure behavior. The FSW thermal cycle resulted in low hardness zones (LHZs) on both the 2219Al-T8 and 2195Al-T8 sides. The LHZ on the 2219Al-T8 side, characterized by partial coarsening of θ′ (Al2Cu) precipitates and dissolution of the residual precipitates, showed the minimum hardness in the entire FSW joints. When 2219Al-T8 alloy was placed on the AS, the LHZ on the 2219Al-T8 side experienced higher peak temperature, and therefore more dissolution of θ′ than that on the RS, thereby obtaining higher tensile strength. The tensile strength of the FSW joints at room temperature and − 196 °C largely increased as the welding speed increased from 200 to 400 mm min−1. The FSW joints presented much higher tensile strength at − 196 °C than that at room temperature under the identical welding parameters and material position. The FSW joints fractured along the LHZ on the 2219Al-T8 side during tension. For the bending testing, the up and down bending failure angles were about 91–117° and 88–109°, respectively, with the weak zone appearing in "S" line or HAZ on the 2195Al-T8 side. [ABSTRACT FROM AUTHOR]

In recent decades, graphene has become a very promising thermal management material due to its excellent thermal performance and flexibility. The interaction between adjacent graphene nanosheets, on the other hand, is Van der Waals, limiting the improvement of thermal performance and flexibility of graphene-based heat-conducting films. In this work, a poly(ethylenimine) (PEI)/graphene oxide (GO) /carbon nanotubes (CNTs) heat-conducting film was fabricated, in which PEI acts as a cross-linking agent to form cross-links between GO nanosheets, followed by carbonization and graphitization. Further investigations illustrate that the graphitized PEI/GO/CNTs film has excellent mechanical properties with a tensile strength of 198.3 ± 15.6 MPa and excellent thermal performance with an in-plane thermal conductivity of 1038.4 ± 25.07 W m−1 K−1 and a through-plane thermal conductivity of 7.14 ± 0.25 W m−1 K−1. The graphene-based thermal conducting films have great potential in various fields, such as electronics, aerospace, 5G, etc. [ABSTRACT FROM AUTHOR]

The current major challenge is to impart homogeneous nanocrystalline Ni–Co alloys simultaneously with high strength and sufficient ductility as well as low internal stress to achieve a desirable strength–ductility and internal stress combination. We successfully produced homogeneous nanocrystalline Ni–Co alloys exhibiting ultrahigh strength, appreciable ductility and low internal stress, using abrasive-assisted electroforming (AAEF) with free ceramic beads. Distinctively, the AAEF process exerts uniform shear by the friction of ceramic beads rather than the conventional direct current electroforming, which makes it feasible to synthesize homogeneous nanocrystalline Ni–Co alloys with outstanding mechanical properties. Our results demonstrated that the structure of the Ni–Co alloys (AAEF) consists of equiaxed nanocrystals with an average grain size in the range of 43.0–54.7 nm. Surprisingly, the homogeneous nanocrystalline Ni–Co alloys (AAEF) exhibited excellent microhardness, yield strength, tensile strength, fracture elongation and low internal stress. Consequently, AAEF is a promising method for synthesizing homogeneous nanocrystalline Ni–Co alloys simultaneously with ultrahigh strength and respectable ductility as well as low internal stress. This work provides a novel practical strategy for designing and fabricating homogeneous nanocrystalline materials with desirable mechanical properties for applications in metallic molds and X-ray telescopes. [ABSTRACT FROM AUTHOR]

TiB whisker-reinforced Ti2AlNb (TiBw/Ti2AlNb) composites with a network architecture were fabricated by the spark plasma sintering (SPS) technique at the temperature ranging from 950 to 1250 °C with the pressure range of 15–50 MPa for 5–30 min and followed by furnace cooling. The effects of SPS parameters and the volume fraction of TiB2 on the microstructure, densification, phase composition and mechanical properties of the sintered composites were studied in detail. The results revealed that the microstructure of TiBw/Ti2AlNb composites was related to the degree of in situ reaction, which was linked to sintering temperature, time, pressure and the volume fraction of TiB2. The TiBw/Ti2AlNb composite exhibited the highest strength and plasticity at room temperature with the sintering process of 1200 °C/15 min/50 MPa/2.5 vol. % TiB2, and its ultimate tensile strength was nearly 240 MPa higher than that of SPS sintered Ti2AlNb-based alloy. However, its high-temperature mechanical properties were lower than those of SPS sintered Ti2AlNb-based alloy, which is due to the fact that the bonding strength between high-strength TiB whiskers and Ti2AlNb matrix was worse during hot deformation, the interface deboned before fracture, and the strengthening effect of TiBw decreased. Compared with the traditional TiBw-titanium alloys system, this work systematically discussed the influence of various parameters on the microstructure and mechanical properties of the composites under TiBw-Ti2AlNb-based alloys system, which can eventually enrich the application of network architecture in the field of powder metallurgy to improve the mechanical properties of materials and provide guidance for the optimization of process parameters. [ABSTRACT FROM AUTHOR]

In this project, thermo-responsive shape memory polymer blends containing copolyester thermoplastic elastomer (COPE) and semi-crystalline polycaprolactone (PCL) were prepared by solution blending method. Shape memory behavior, tensile and dynamic mechanical properties as well as creep performances of the blends were discussed by paying attention to effect of blend composition and morphology. The blends containing 10, 20, and 30 wt% PCL exhibited droplet matrix morphologies, while those having 40% (COPE60) and 50 wt% PCL (COPE50) showed co-continuous morphologies. In the blend composition, the elastic modulus values tended to increase with the increase of the PCL switch phase, and the highest value was obtained in the COPE50 blend. On the other hand, blends containing high amount of rigid PCL phase showed lower ductility and accordingly the elongation at break and toughness values decreased. Creep deformation and creep recovery values increased with the increase in the amount of elastomer component COPE in the blend. In terms of shape memory, optimum shape fixing and shape recovery ratios were obtained in the COPE60 blend which has co-continuous morphology. The same polymer blend has also been found to have repeatability in shape memory property at least in three cycles. On the other hand, the COPE60 blend exhibited definite shape recovery ratios at different temperatures and it was determined that its shape recovery was adjustable with temperature changes. Moreover, self-healing properties of COPE60 blend were examined and it was determined that the blend exhibited higher tensile strength and toughness values after repair compared to its damaged condition. [ABSTRACT FROM AUTHOR]

Accurate and consistent constitutive model is required to characterize the material behavior in a variety of thermo-mechanical problems. Herein, widely used Johnson–Cook (J–C) model parameters are evaluated for Fe–30Mn–9Al–0.8C low-density steel to predict the flow stress in various forming applications. For this low-density steel prepared in our laboratory, the material compositions are optimally chosen to yield the best ductility (> 70%) with good tensile strength. Tensile tests have been performed at strain rates varying from 10–4 to 10–1 s−1 and at various temperatures such as 150 °C, 300 °C and 450 °C to determine the J–C parameters. Thereafter, genetic algorithm (GA) technique has been used to obtain optimum values of J–C parameters that best fit the experimental stress–strain data. The improved values of the J–C parameter are implemented in ABAQUS explicit software to replicate the experimentally observed tensile test data. It has been observed that the developed constitutive model can produce a fairly accurate and precise estimation of flow stress with a good correlation to experimental data under various strain rates and temperature conditions. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of a novel Cr and Si co-alloying Fe–0.6C–15Mn steels, labeled as 2Cr(3Si), 4Cr(3Si), 6Cr(3Si), and 4Cr(0Si), were investigated. All samples for mechanical property test and microstructure analysis were subjected to solution treatment at 1100 °C for 1 h after forging. The results indicate that the microstructure for the 2Cr(3Si), 4Cr(3Si) and 4Cr(0Si) steels mainly consists of the full austenite, and grain size is about 100 μm, whereas the microstructure of the 6Cr(3Si) steel exhibits austenite and some undissolved Cr7C3 carbides. The refined austenite grain size of 48 μm is obtained in 6Cr(3Si) steel. The strength and elongation of the experiment steels with Si and Cr increase significantly with the Cr contents. Among the steels, the 6Cr(3Si) steel has the maximum yield strength, tensile strength and elongation of 490 MPa, 987 MPa and 41.5%, respectively. And the impact toughness is 151 J cm−2. The Si-free steel (4Cr(0Si)) exhibits a low yield strength (372 MPa) and a high tensile strength (992 MPa). The high elongation of 74.8% and impact toughness of 320 J cm−2 are obtained. The results also demonstrate that the Cr and Si co-alloying in high-Mn steels is beneficial to improve work hardening capability, and the work hardening capability increases with the increase of Cr content. According to the results analyzed by the electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), the strain-induced ε-martensite is dominant at the low strain level and the content of ε-martensite increases with the increase of the tensile strain. The maximum amount of the ε-martensite is found in the 6Cr(3Si) steel. With the strain increasing, α'-martensite appears in microstructure, which is formed on the ε-martensite. In addition, the stacking faults (SF) and mechanical twins (MT) are also observed. [ABSTRACT FROM AUTHOR]

Epoxy resins are widely used in a variety of application fields, thanks to their good mechanical strength, chemical resistance and adhesion to several substrates. Nowadays, the quite majority of epoxy resins are based on derivatives of bisphenol A (BPA), which poses serious health concerns. This issue is pushing the research towards suitable bio-based alternatives to this product, being furan-based epoxies very promising in this respect. In a previous work, 2,5-bis[(oxiran-2-ylmethoxy)methyl]furan (BOMF) was cured with methyl nadic anhydride (MNA), and successfully used as tinplate coating. Herein, in a view of increasing the sustainability of these epoxy resins, we have replaced MNA with maleic anhydride (MA), which can be derived from vegetable feedstocks, thus obtaining a fully bio-based epoxy resin. This latter has then been used as adhesive for carbon fiber-reinforced thermosetting plastics (CFRP). The curing process of the resin was monitored by differential scanning calorimetry (DSC) and chemo-rheological analysis. The results highlighted the significantly higher reactivity of BOMF towards MA compared to the diglycidyl ether of BPA (DGEBA). The crosslinked samples were characterized in their thermal, mechanical and adhesive properties. In comparison to DGEBA/MA and BOMF/MNA, BOMF/MA showed higher ultimate strain and slightly lower glass transition temperature, tensile modulus and ultimate strength. Interestingly, BOMF/MA displayed outstanding adhesive strength on CFRP joints, outperforming the DGEBA-based counterpart by three times. Indeed, by properly selecting the anhydride curing agent, a highly ductile fully bio-based material was developed for high performance adhesive applications. The overall results demonstrate that the properties of BOMF-based epoxy resins can be tailored to meet technical and safety requirements of downstream applications, representing a sustainable alternative to traditional systems containing DGEBA. [ABSTRACT FROM AUTHOR]

Precipitation strengthening/hardening technique is known to significantly improve the strength of multicomponent/high-entropy (MCA/HEA) alloys at the expense of their serious embrittlement. Therefore, a proper adjustment of precipitated particles' type, size, and volume fraction is critical to achieve a good strength-plasticity balance. This study proposes a new MCA design approach involving doping trace amounts of boron to strengthen the ductile face-centered cubic (FCC) matrix phase instead of conventional thermomechanical processes to achieve excellent performance. A 90 ppm boron doping in the Fe2NiCr0.5Cu0.2Al0.3Ti0.1 MCAs significantly improved their mechanical properties, increasing their yield strength by 33.2% and ultimate tensile strength by 25.1% at relatively high ductility (21.3–25.2%). The addition of trace amounts of boron inhibited the formation and segregation of coarse BCC-based Heusler particles at the grain boundaries while promoting the formation of fine L12-type nanoscale precipitates, possessing a coherent relationship with the matrix. These findings are considered instrumental in designing the optimal strategy for enhancing balanced strength/ductility properties of FCC-based MCAs/HEAs with high economic feasibility and a wide range of industrial applications. [ABSTRACT FROM AUTHOR]

The effect of aging temperature on martensite reversion and mechanical behavior of a 2304-lean duplex stainless steel (LDSS) was analyzed after cold rolling to 74% reduction and aging at 400–600 °C for 1800 s. Strain-induced martensite (SIM) formation results from cold rolling. After cold rolling, the results revealed a Nishiyama–Wasser (N–W) relationship between the ∝ '-martensite laths and the metastable austenite. Increasing the aging temperature led to a rise in the steel strength, resulting in very low ductility, but with high yield and tensile strength of the specimens. The SIM reversion started between 500 and 550 °C for 1800 s soaking time. At temperatures between 400 and 500 °C, substantial embrittlement occurred. Precipitation of the ∝ + ∝ ′ (spinodal decomposition) in solid solution in ferrite was not observed. Hence, it is not the cause of the steel embrittlement. The mechanisms involved in the increase of strength and embrittlement were the aging of the austenite phase due to the formation of a substructure with ultrafine or nano-deformation twins, stacking faults, and shear bands in a lamellar array, and possibly Suzuki effect mechanism occurrence. [ABSTRACT FROM AUTHOR]

Historically, titanium alloys have been developed disregarding the addition of eutectoid β-stabilisers as they generally lead to the formation of brittle intermetallic phases upon solidification of the alloy. However, such phenomenon can be prevented using powder metallurgy. Thus, this study considered the concurrent addition of cheap strong eutectoid β-stabilisers, namely Mn and Fe, for the development of new ternary Ti–Mn–Fe alloys, reducing the intrinsic cost of Ti alloys. It is found that the progressive addition of Mn and Fe in equal concentration enhances the densification of Ti during sintering, leading to lower amount of residual porosity, the transformation of the microstructure from purely lamellar to metastable, and the associated refinement of the microstructural features (grains and lamellae), as well as the stabilisation of a greater amount of β phase, and the formation of the metastable α″ phase. Such microstructural changes result in the strengthening (higher yield and ultimate tensile strength and hardness) and embrittlement of the alloy by changing the fundamental strain hardening mechanism of the ternary Ti–Mn–Fe alloys. [ABSTRACT FROM AUTHOR]

In the present study, friction stir processing (FSP) was carried out on as-cast Mg-Zn-Dy alloy to tailor grain size and texture which alter the mechanical properties and corrosion behaviour. The grain size of the as-cast alloy was reduced from 60 ± 2 µm to 3 ± 0.1 µm after FSP due to dynamic recrystallization. The effect of grain size, crystallographic orientation and fine precipitates on mechanical properties were investigated using field emission scanning electron microscope (FESEM) and electron back scattered diffraction (EBSD). The ultimate tensile strength, yield strength, % elongation and hardness of FSPed alloy improved by 55%, 60%, 53% and 46% when compared to as-cast alloy. The FSPed Mg-Zn-Dy alloy exhibited a 79% decrease in corrosion rate when compared to as-cast alloy which can be attributed to grain refinement, uniform distribution of secondary precipitates and strong basal texture. The surface of FSPed sample after immersion corrosion exhibited calcium phosphate rich minerals which help in apatite formation on the sample surface. Cytotoxicity studies using MTT assay revealed more than 80% cell viability for both as-cast and FSPed alloy illustrating non-toxic nature of both the samples. The results of this study indicate that FSPed Mg-Zn-Dy alloy is a potential material for biodegradable implants due to its high strength, corrosion resistance and biocompatibility. [ABSTRACT FROM AUTHOR]

The coarse columnar grains in wire arc additive manufacturing (WAAM) usually lead to performance anisotropy and greatly degrade the mechanical properties. Herein, a novel approach was developed by synchronously introducing a high-intensity ultrasound into the WAAM process. The effect of ultrasound on microstructure and mechanical properties of AM part along the build direction was explored for the first time. Experimental results show that the columnar grains of each layer are replaced by equiaxed grains under the effect of high-intensity ultrasound, and the grain morphology varies along the build height. Due to the acoustic cavitation induced by ultrasound in the molten pool, the grain size is significantly reduced, and the grain refinement strengthening enhances the mechanical properties. The yield strength and ultimate tensile strength (UTS) increase in the vertical direction by 16.4% and 15.8%, respectively. The in-plane anisotropy of UTS declines from 9.39% to 5.12%. The propagation law of ultrasound in large-size AM part is revealed. When the build height is less than 74 mm, the ultrasonic intensity gradually decreases with the height, leading to a reduction in the degree of grain refinement, which is consistent with the experimental observation. The research provides a theoretical basis and technical solution for controlling the grain structure during the WAAM process assisted with high-intensity ultrasound. [ABSTRACT FROM AUTHOR]

For modern advanced high-strength steels, metastable retained austenite (RA) is introduced into a multiphase microstructure to achieve better strength–ductility balance through interphase deformation accommodation and the transformation-induced plasticity effect. Examples include the quenching and partitioning (QP) process and the bainite isothermal process, where carbon enrichment in austenite is achieved by implementing isothermal around the martensite start temperature, thus improving the mechanical stability of the RA. In this study, the dissimilation of the initial microstructure of high-Si alloy before isothermal treatment was realized by adjusting the quenching process over an extensive range. The effects of the partitioning process and initial isothermal microstructure on the mechanical behavior of Fe–0.28C–2.52Si–2.62Mn–0.05Nb steel were investigated. The two-step QP steel exhibited a better strength–ductility balance than the one-step steel. The tensile strength of the two-step sample reached 1700 MPa and had a product of tensile strength and total elongation of 26.2 GPa %. The results showed that the initial formation of athermal martensite accelerated the subsequent bainite transformation kinetics during partitioning. During isothermal holding, the formation of martensite or (and) bainite contributed to the stability of RA via carbon redistribution. Specimens with stable RA exhibited a lower initial work-hardening rate during deformation. A relatively higher volume fraction of RA leads to a continuous work-hardening behavior, thereby significantly improving the total elongation. [ABSTRACT FROM AUTHOR]

The negative Poisson's ratio fiber reinforced concrete (NPR-FRC) was prepared using a new type of negative Poisson's ratio fiber (NPRF), with PVA fiber as the core and carbon fibers as the wrapping fibers by spiral treatment. The NPR-FRC's compressive strength, splitting tensile strength, and flexural toughness were tested and its energy absorption capacity was calculated. More importantly, the deformation behavior and global Poisson's ratio are analyzed by the digital speckle correlation method (DSCM), and the static loading deformation mechanism with NPR-FRC is revealed. The results show that when V f (the volume fraction of fiber) = 0.3 vol% the compressive strength of NPR-FRC increases by 18.5%, the splitting tensile strength increases by 43.20%, the flexural strength increases by 24.95%, and the energy absorption capacity increases by 69.691 times. With the addition of 3% NPRF, the Poisson's ratio of concrete will be reduced by 22.8%, and the NPRF expands more energy in the deformation process. The negative Poisson's ratio effect of the layered NPRF reduces the plastic deformation and the Poisson's ratio, improving strain bearing capacity and energy absorption capacity. It is expected to provide a reference for NPR-FRC application in tunnels, airport runways, underground pipe corridors, bridges, and other building structures. [ABSTRACT FROM AUTHOR]

Titanium (Ti) alloys suffer from poor mechanical strength and inferior wear resistance. Herein, we introduced the calcium hexa boride (CaB6) into Ti matrix to manufacture high-strength and high-wear in situ Ti matrix composites (TMCs) by powder metallurgy method. The effects of CaB6 addition on the microstructure, mechanical and tribological properties of TMCs were studied. Results show that the formation of hard in situ TiB and nano-size CaTiO3 particles contributes to a remarkable refinement of average grain size from 163 μm in pure Ti to 74 μm in Ti–1.0 wt.% CaB6 composite. The hardness is significantly increased from 191 ± 15 HV in pure Ti to 321 ± 13 HV in Ti–0.8 wt.% CaB6 composite. The Ti–0.8 wt.% CaB6 composite obtains the best comprehensive mechanical properties with an ultimate tensile strength of 740.3 ± 28.3 MPa, yield strength of 598.4 ± 23.1 MPa and elongation of 10.6 ± 1.5% and displays the optimal wear resistance with friction coefficients of 0.45, 50% less than pure Ti, under constant conditions (3 N, 0.03 m/s). [ABSTRACT FROM AUTHOR]

PLA-based blends were prepared with different ratios of PBS, PBAT and TPS additives to adjust their mechanical and processing properties in various temperatures (− 20 °C, 0 °C, 20 °C, 40 °C). Biodegradable polymeric specimens were obtained by preliminary extrusion and subsequent injection molding. Tensile properties, e.g., tensile strength, elongation at break, Young's modulus and yield strength were evaluated. Next, melt flow and melt volume ratios were established. Softening, glass transition, cold crystallization and crystallization temperatures were determined with the use of the DSC method. Heat Deflection Temperatures for 1.8 MPa (HDT A) and 8 MPa (HDT C), as well as Vicat Softening Temperatures at 10 N (VST A) and 50 N (VST B), were examined. The manufacturing method was intentionally simplified to eliminate the need for additional mixture's modification with compatibilizers. Each of the ductile compounds enhanced the deformability of PLA—most significantly in the case of PBAT and TPS, while at the same time reducing its tensile strength. The effect of the test conditions (strain rate and temperature) on the specimens was evaluated in order to determine the stability of the manufactured blends in dependence on these parameters. [ABSTRACT FROM AUTHOR]

For the sake of reducing the interface reaction between graphene (GR) reinforcement and Ti6Al4V (TC4) alloys matrix, the nano-TiB2 particles were incorporated into GR/Ti interface after 3D dynamic mixing process, and TiB whiskers (TiBw) were formed by the subsequent reaction between TiB2 and Ti after spark plasma sintering (SPS) process. The network structured GR-TiBw/TC4 composites were fabricated by 3D dynamic mixing and SPS with a subsequent hot rolling deformation. Effects of GR-TiBw hybrid reinforcement and hot rolling on the microstructure and mechanical properties of the composites were investigated. The results showed that the in situ formed TiBw reduced GR/Ti interface reaction and the content of GR-TiBw hybrid reinforcements had a great influence on the interface structure and mechanical properties of the composites. The suitable GR content combined with low content of nano-TiBw can form a quasi-continuous network interface structure and achieve a good trade-off between strength and ductility with a higher tensile strength and acceptable ductility. After obtaining a high rolling reduction, the quasi-continuous network interface structure was reconstructed and brought a noticeable increase of tensile strength with a slight loss of ductility. [ABSTRACT FROM AUTHOR]

In the current study, the biocorrosion resistance and mechanical properties of the Ti–XAl–2Fe–3Cu (wt%) (X = 6, 4, 2 wt%) alloy produced by powder compact extrusion of blended elemental powders were optimized by using the response surface methodology in order to gain the best combination of processing parameters. To run the optimization process, central composite design with three equal levels of oxygen, hydrogen and aluminum was used and, by employing ANOVA, the analysis of variance was implemented. The results showed that the content of aluminum has a significant effect on the microstructure, mechanical properties, biocorrosion resistance and fracture behavior of the extruded rods. The highest aluminum content corresponds to the highest alloy strength and biocorrosion resistance. This was due to the reduction of the lamella thickness and of the material colonies as the aluminum content increases. Also, by running the experimental and optimization tests, the mechanical properties resulted 1245 MPa in yield strength and 1340 MPa in ultimate tensile strength with 0.1 µAcm−2 in corrosion current. [ABSTRACT FROM AUTHOR]

Precipitation evolution and strengthening effect of Al-15wt%Mg2Si-5wt%Cu alloy were studied by characterizing the change of morphology and tensile properties after ageing at 200 °C for various times. At the under-ageing condition (ageing for 0.5 h), metastable θ″, θ′, fine dots and σ phases are formed. After ageing for 1 h (peak-ageing condition), θ″ and θ′ are dominant phases, and the high number density of precipitates produces a significant improvement of the hardness (173 Hv) and ultimate tensile strength (356 MPa). As ageing time is prolonged (ageing for 24 h), plenty of σ phases are formed at the expense of θ"/θ′ phases and act as the main strengthening precipitates. The over-aged microstructure consequently causes a decrease in the hardness (134 Hv) and ultimate tensile strength (311 MPa) of the alloy. [ABSTRACT FROM AUTHOR]

Novel TiO2 nanoparticles-coated CNTs (TiO2@CNTs) fabricated by the alcohol-thermal method were used as the reinforcement to prepare aluminum matrix composites through high-intensity ultrasonic-assisted casting, followed by heat treatment. The results of optical microscope showed that the optimum heat treatment process was solution treatment (495 °C, 2 h) + aging treatment (180 °C, 12 h). Under this condition, the Al2Cu and Al2CuMg phases were uniformly precipitated in the composites, and most of them were in a discrete state. TEM results revealed that TiO2 nanoparticles dispersed on the surface of CNTs played the role of an interlayer structure between CNTs and matrix, locking the CNTs and improving the CNTs–Al interfacial bonding. The ultimate tensile strength (UTS) and yield strength (YS) of 1.0 wt%TiO2@CNTs/2024 composite after T6 heat treatment reach 324 MPa and 219 MPa, respectively, which exhibited enhanced UTS and YS than the monolithic 2024 alloy. This was attributed to the synergistic strengthening of multi-mechanisms, such as grain refinement strengthening, load transfer strengthening, dislocation strengthening and, especially, Orowan strengthening. [ABSTRACT FROM AUTHOR]

In recent years, the utilization of Al as a grain refiner in Mg–RE alloys has gained widespread attention because of its advantages such as low cost. In this study, Mg–5Y–4Sm–xAl (x = 0, 0.6, 1.2 and 1.8 wt.%) alloys were fabricated, and high grain refinement efficiency of Al addition was obtained. Subsequently, the effect of different Al addition on the grain refinement was investigated and the refinement mechanism was discussed deeply in two major aspects. Firstly, Al2RE particles were formed in the solidification process and acted as the nucleation sites of α-Mg. The numerical density and diameter of those particles were obviously increased by increasing Al addition. Secondly, the addition of Al reduced the solute elements content in the α-Mg melt, resulting in a decrease in the grain growth restriction factor (Q value). Furthermore, the synergistic effect of solute elements and nucleation particles on grain refinement was described by the interdependent theory. Finally, the Al addition is beneficial to improve the mechanical properties of alloy. When the Al addition was 1.8%, the room temperature tensile strength of the alloy reached a maximum of 221 MPa and the maximum elongation was 9.2%. When the Al addition was 1.2%, the yield strength of the alloy reached a maximum of 142 MPa. [ABSTRACT FROM AUTHOR]

The manufacturability of metallic alloys using laser-based additive manufacturing methods such as laser powder bed fusion has substantially improved within the last decade. However, local melting and solidification cause hierarchically structured and crystallographically textured microstructures possessing large residual stress. Such microstructures are not only the origin of mechanical anisotropy but also pose metrological challenges for the diffraction-based residual stress determination. Here we demonstrate the influence of the build orientation and the texture on the microstructure and consequently the mechanical anisotropy of as-built Inconel 718. For this purpose, we manufactured specimens with [001]/[011]-, [001]- and [011]/[ 1 ¯ 11 ]-type textures along their loading direction. In addition to changes in the Young's moduli, the differences in the crystallographic textures result in variations of the yield and ultimate tensile strengths. With this in mind, we studied the anisotropy on the micromechanical scale by subjecting the specimens to tensile loads along the different texture directions during in situ neutron diffraction experiments. In this context, the response of multiple lattice planes up to a tensile strain of 10% displayed differences in the load partitioning and the residual strain accumulation for the specimen with [011]/[ 1 ¯ 11 ]-type texture. However, the relative behavior of the specimens possessing an [001]/[011]- and [001]-type texture remained qualitatively similar. The consequences on the metrology of residual stress determination methods are discussed. [ABSTRACT FROM AUTHOR]

Silicone elastomer and fluoroelastomer blend is an immiscible blend as they have huge solubility parameter variance. The entire study establishes the effect of glutaraldehyde (GA) in the compatibilization of fluoroelastomer and silicone rubber blend with silica as filler. The study endorses a novel strategy of immobilizing GA at the interface that enables binding the pre-dispersed filler particles in the individual rubber phases together. The reaction between the silanol groups of silica dispersed separately in the FKM and MVQ phases and the carbonyl groups of GA results in the improvement of interfacial force of adhesion among the two component rubber phases. This results in the extraordinary increase in tear strength (107%) and tensile strength (34%) along with elevated crosslink density with an optimum loading of GA of 2.5% with the filler loading. Moreover, the shifting in Tg of the corresponding rubbers phases towards each other with almost 3 °C determined through DSC and DMA study confirms the enhancement of the compatibility between the FKM and MVQ rubber phases. The heat and oil ageing behaviours are also significantly enhanced with the addition of GA in the system. The morphological studies indicate the decrease in FKM domain sizes in the MVQ matrix with GA incorporation which is one of the prime validations of the compatibilization of FKM/MVQ rubber blend system. [ABSTRACT FROM AUTHOR]

Without any chemical agent, gold nanosheets (AuNSs) were controllable synthesized through a facile photo-induced reduction within bacterial cellulose (BC) biopolymers. Compared with traditional polymers, AuNSs modified BC biopolymers (AuNSs@BC) biopolymers exhibited similar levels of softness, ductility, and better tensile strength. The in situ constructing of AuNSs@BC biopolymers was demonstrated to provide great reusability and antibacterial activities and towards both of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The optimized AuNSs@BC biopolymers remain at least 95% antibacterial activities after three cycles. The facile and shape-controlled synthesis of AuNSs@BC biopolymers is believed to be useful for the design and application of biomass-based medical dressing. [ABSTRACT FROM AUTHOR]

The effects of rare-earth lanthanum (La) on the microstructure and tensile properties of Al7Si4CuMg alloys prepared by squeeze casting were studied by microscopy technologies, thermal analysis and tensile tests. The results demonstrate that La can refine α-Al grains, modify eutectic Si and improve tensile properties of the Al7Si4CuMg alloys. The refinement mechanism of α-Al grains with the addition of La has been discussed based on the classical nucleation theory, interdependence model and thermodynamics. These results indicate that the added La increased constitutional supercooling and heterogeneous nucleation cores ahead of the melt/α-Al interface and thus La promoted the nucleation of α-Al. This refinement effect of La on α-Al was further promoted by the squeeze pressure during solidification. Moreover, the formation of twinned Si particles was attributed to the adsorption of La-rich clusters along the ⟨ 112 ⟩ Si growth direction and at the intersection of two 111 Si facets. This is consistent with the poisoning of the twin plane re-entrant edge and the impurity-induced twinning modification mechanisms. With the La addition of 0.15 wt.% (squeeze pressure was 75 MPa), the Al7Si4CuMg alloys obtained the finest α-Al grains, and optimal mechanical properties with the ultimate tensile strength of 297 MPa and elongation of 2.5%. When La addition was further increased to 0.20 wt.%, the refinement of α-Al and modification of eutectic Si were both limited by the occurrence of eutectic reaction L → α-Al + Si + Al x (La , Cu , Ti) , because this eutectic reaction reduced the undercooling and produced the needle-like La-rich particles. [ABSTRACT FROM AUTHOR]