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Ultra-high-performance concrete (UHPC) is a cementitious composite combining high-strength concrete matrix and fiber reinforcement. Standing out for its excellent mechanical properties and durability, this material has been widely recognized as a viable choice for highly complex engineering projects. This paper proposes (i) the review of the influence exerted by the constituent materials on the mechanical properties of compressive strength, flexural tensile strength, and elastic modulus of UHPC and (ii) the determination of optimal quantities of the constituent materials based on simplified statistical analyses of the developed database. The data search was restricted to papers that produced UHPC with straight steel fibers at a content of 2% by volume. UHPC mixture models were proposed based on graphical analyses of the relationship of constituent materials versus mechanical properties, aiming to optimize the material's performance for each mechanical property. The results proved to be in accordance with the specifications present in the literature, characterized by high cement consumption, significant presence of fine materials, and low water-to-binder ratio. The divergences identified between the mixtures reflect how the constituent materials uniquely impact each mechanical property of the concrete. In general, fine materials were shown to play a significant role in increasing the compressive strength and flexural tensile strength of UHPC, while water and superplasticizers stood out for their influence on the material's workability. [ABSTRACT FROM AUTHOR]

Laser powder bed-fused Ti6Al4V alloy has numerous applications in biomedical and aerospace industries due to its high strength-to-weight ratio. The brittle α′-martensite laths confer both the highest yield and ultimate tensile strengths; however, they result in low elongation. Several post-process heat treatments must be considered to improve both the ductility behavior and the work-hardening of as-built Ti6Al4V alloy, especially for aerospace applications. The present paper aims to evaluate the work-hardening behavior and the ductility of laser powder bed-fused Ti6Al4V alloy heat-treated below (704 and 740 °C) and above (1050 °C) the β-transus temperature. Microstructural analysis was carried out using an optical microscope, while the work-hardening investigations were based on the fundamentals of mechanical metallurgy. The work-hardening rate of annealed Ti6Al4V samples is higher than that observed in the solution-heat-treated alloy. The recrystallized microstructure indeed shows higher work-hardening capacity and lower dynamic recovery. The Considère criterion demonstrates that all analyzed samples reached necking instability conditions, and uniform elongations (>7.8%) increased with heat-treatment temperatures. [ABSTRACT FROM AUTHOR]

Waterborne polyurethane asphalt emulsion (WPUA) is an environmentally friendly bituminous material, whose performance is highly dependent on the phase structure of the continuous phase. In this paper, WPUAs in the vicinity of phase inversion were prepared using waterborne polyurethane (WPU) and asphalt emulsion. The chemical structures, thermal stability, dynamic mechanical properties, phase-separated morphology and mechanical performance of WPUAs were studied. Fourier-transform infrared (FTIR) spectra revealed that there are no –NCO bonds in either the pure WPU or WPUAs. Moreover, the preparation of WPUA is a physical process. The addition of WPU weakens the thermal stability of asphalt emulsion. WPU improves the storage modulus of asphalt emulsion at lower and higher temperatures. The glass transition temperatures of the WPUA films are higher than that of the pure WPU film. When the WPU concentration increases from 30 wt% to 40 wt%, phase inversion occurs; that is, the continuous phase shifts from asphalt to WPU. The WPUA films have lower tensile strength and toughness than the pure WPU film. However, the elongations at break of the WPUA films are higher than that of the pure WPU film. Both the tensile strength and toughness of the WPUA films increase with the WPU concentration. Due to the occurrence of phase inversion, the elongation at break, tensile strength and toughness of the WPUA film containing 30 wt% WPU are increased by 29%, 250% and 369%, respectively, compared to the film with 40 wt% WPU. [ABSTRACT FROM AUTHOR]

The primary focus of the current paper centers on the microstructures and mechanical properties exhibited by a Ti-30Nb-12Zr-5Ta-2Sn-1.25Fe (wt. %) (TNZTSF) alloy that has been produced through an intricate synthesis process comprising cold-crucible induction in levitation, carried out in an atmosphere controlled by argon, and cold-rolling deformation (CR), applying systematic adjustments in the total deformation degree (total applied thickness reduction), spanning from 10% to 60%. The microstructural characteristics of the processed specimens were investigated by SEM and XRD techniques, and the mechanical properties by tensile and microhardness testing. The collected data indicate that the TNZTSF alloy's microstructure, in the as-received condition, consists of a β-Ti phase, which shows polyhedral equiaxed grains with an average grain size close to 82.5 µm. During the cold-deformation processing, the microstructure accommodates the increased applied deformation degree by increasing crystal defects such as sub-grain boundaries, dislocation cells, dislocation lines, and other crystal defects, powerfully affecting the morphological characteristics. The as-received TNZTSF alloy showed both high strength (i.e., ultimate tensile strength close to σUTS = 705.6 MPa) and high ductility (i.e., elongation to fracture close to εf = 11.1%) properties, and the computed β-Ti phase had the lattice parameter a = 3.304(7) Å and the average lattice microstrain ε = 0.101(3)%, which are drastically influenced by the applied cold deformation, increasing the strength properties and decreasing the ductility properties due to the increased crystal defects density. Applying a deformation degree close to 60% leads to an ultimate tensile strength close to σUTS = 1192.1 MPa, an elongation to fracture close to εf = 7.9%, and an elastic modulus close to 54.9 GPa, while the computed β-Ti phase lattice parameter becomes a = 3.302(1) Å. [ABSTRACT FROM AUTHOR]

The study and utilization of fully recycled aggregate concrete (FRAC), in which coarse and fine aggregates are completely replaced by recycled aggregates, are of great significance in improving the recycling rate of construction waste, reducing the carbon emission of construction materials, and alleviating the ecological degradation problems currently faced. In this paper, investigations were carried out to study the effects of steel fiber (0.5%, 1.0%, and 1.5%) and polypropylene fiber (0.9 kg/m3, 1.2 kg/m3 and 1.5 kg/m3) on the properties of FRAC, including compressive strength, splitting tensile strength, the splitting tensile load–displacement curve, the tensile toughness index, flexural strength, the load–deflection curve, and the flexural toughness index. The results show that the compressive strength, splitting tensile strength, and flexural strength of fiber-reinforced FRAC were remarkably enhanced compared with those of ordinary FRAC, and the maximum increase was 56.9%, 113.3%, and 217.0%, respectively. Overall, the enhancement effect of hybrid steel–polypropylene fiber is more significant than single-mixed fiber. Moreover, the enhancement of the crack resistance, tensile toughness, and flexural toughness obtained by adding steel fiber to the FRAC is more significant than that obtained by adding polypropylene fiber. Furthermore, adding polypropylene fiber alone and mixing it with steel fiber showed different FRAC splitting tensile and flexural properties. [ABSTRACT FROM AUTHOR]

This paper presents the results of physical modelling of the process of multi-pass rolling of a wire rod with controlled, multi-stage cooling. The main goal of this study was to verify the possibility of using a torsion plastometer, which allows conducting tests on multi-sequence torsion, tensile, compression and in the so-called complex strain state to physically replicate the actual technological process. The advantage of the research methodology proposed in this paper in relation to work published so far, is its ability to replicate the entire deformation cycle while precisely preserving the temperature of the deformed material during individual stages of the reproduced technological process and its ability to quickly and accurately determine selected mechanical properties during a static tensile test. Changes in the most important parameters of the process (strain, strain rate, temperature, and yield stress) were analyzed for each variant. After physical modelling, the material was subjected to metallographic and hardness tests. Then, on the basis of mathematical models and using measurements of the average grain size, chemical composition, and hardness, the yield strength, ultimate tensile strength, and plasticity reserve were determined. The scope of the tests also included determining selected mechanical properties during a static tensile test. The obtained results were verified by comparing to results obtained under industrial conditions. The best variant was a variant consisting of physically replicating the rolling process in a bar rolling mill as multi-sequence non-free torsion; the rolling process in an NTM block (no twist mill) as non-free continuous torsion, with the total strain equal to the actual strain occurring at this stage of the technological process; and the rolling process in an RSM block (reducing and sizing mill) as tension, while maintaining the total strain value in this block. The differences between the most important mechanical parameters determined during a static tensile test of a wire rod under industrial conditions and the material after physical modelling were 1.5% for yield strength, approximately 6.1% for ultimate tensile strength, and approximately 4.1% for the relative reduction of the area in the fracture and plasticity reserve. [ABSTRACT FROM AUTHOR]

The effects of Mn addition on the room temperature tensile strength and deformation mechanisms of as-cast Mg-8Al-1Nd-1.5Gd-xMn alloys (x = 0, 0.3, 0.5, 1.0 wt.%) are investigated in this paper. The results indicate that the addition of Mn contributes to the precipitation of Al-Mn-RE intermetallics and the refinement of α-Mg matrices, thereby improving the tensile strength of the 1.0 Mn alloy at 190 MPa. The fracture mechanism of Mn-containing alloys transforms from a cleavage fracture to a ductile fracture as the Mn content increases from 0.3 to 1.0 wt.%. The presence of intermetallic particles in the dimples confirms the hindrance effect of Al10Mn2 (Nd,Gd) on dislocation slips. The novel technology of in-grain misorientation axes (IGMAs) is used to identify activated slip modes and deformation twins. It can be concluded that the activated pyramidal slip during tensile deformation significantly promotes the ductility of the 1.0 Mn alloy with an elongation rate of 9.8%. It is worth noting that reducing the coarse 10 1 ¯ 2 tensile twins and enhancing the proportion of 10 1 ¯ 1 compressive twins and 10 1 ¯ 1 - 10 1 ¯ 2 double twins contributes to maintaining the continuous plastic deformation of Mg alloy. [ABSTRACT FROM AUTHOR]

Zinc (Zn)-based biodegradable materials show moderate degradation rates in comparison with other biodegradable materials (Fe and Mg). Biocompatibility and non-toxicity also make them a viable option for implant applications. Furthermore, Pure Zn has poor mechanical behavior, with a tensile strength of around 100–150 MPa and an elongation of 0.3–2%, which is far from reaching the strength required as an orthopedic implant material (tensile strength is more than 300 MPa, elongation more than 15%). Alloy and composite fabrication have proven to be excellent ways to improve the mechanical performance of Zn. Therefore, their alloys and composites have emerged as an innovative category of biodegradable materials. This paper summarizes the most important recent research results on the mechanical and biological characteristics of biodegradable Zn-based implants for orthopedic applications and the most commonly added components in Zn alloys and composites. [ABSTRACT FROM AUTHOR]

Strengthening the CoCrFeNi high entropy alloy with a face-center cubic structure has become a research prospect in the last decade. Alloying with double elements, Nb and Mo, is an effective method. In this paper, to further enhance the strength of the Nb and Mo contained high entropy alloy, CoCrFeNiNb0.2Mo0.2 was annealing treated at different temperatures for 24 h. As a result, a new kind of Cr2Nb type nano-scale precipitate with a hexagonal close-packed structure was formed, which is semi-coherent with the matrix. Moreover, by adjusting the annealing temperature, the precipitate was tailored with a considerable quantity and fine size. The best overall mechanical properties were achieved in the alloy annealed at 700 °C. The yield strength, ultimate tensile strength, and elongation are 727 MPa, 1.05 GPa, and 8.38%, respectively. The fracture mode of the annealed alloy is a mixture of cleavage and necking-featured ductile fracture. The approach employed in this study offers a theoretical foundation for enhancing the mechanical properties of face-centered cubic high entropy alloys via annealing treatment. [ABSTRACT FROM AUTHOR]

The effects of Al addition on the microstructure and mechanical properties of Mg-Zn-Sn-Mn-Ca alloys are studied in this paper. It was found that the Mg-6Sn-4Zn-1Mn-0.2Ca-xAl (ZTM641-0.2Ca-xAl, x = 0, 0.5, 1, 2 wt.%; hereafter, all compositions are in weight percent unless stated otherwise) alloys have α-Mg, Mg2Sn, Mg7Zn3, MgZn, α-Mn, CaMgSn, AlMn, Mg32(Al,Zn)49 phases. The grain is also refined when the Al element is added, and the angular-block AlMn phases are formed in the alloys. For the ZTM641-0.2Ca-xAl alloy, the higher Al content is beneficial to elongation, and the double-aged ZTM641-0.2Ca-2Al alloy has the highest elongation, which is 13.2%. The higher Al content enhances the high-temperature strength for the as-extruded ZTM641-0.2Ca alloy; overall, the as-extruded ZTM641-0.2Ca-2Al alloy has the best performance; that is, the tensile strength and yield strength of the ZTM641-0.2Ca-2Al alloy are 159 MPa and 132 MPa at 150 °C, and 103 MPa and 90 MPa at 200 °C, respectively. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of semi-continuous casting Mg-Gd-Y-Zr magnesium alloys with different Zn contents were studied in this paper. The results showed that an increase in Zn content resulted in gradual refinement of the grains and a gradual increase in the volume fraction of the second phase. At a Zn content of 0.7 wt%, the microstructure was mainly composed of the α-Mg matrix and the Mg5(GdY) and long-period stacking order (LPSO) phases. An increase in the Zn content lowered the volume fraction of the Mg5(GdY) phase and increased the volume fraction of the LPSO phase. At a Zn content of 3.3 wt%, the microstructure was mainly composed of the α-Mg matrix and the LPSO phase. Among these alloys, the alloy without Zn addition showed an optimal ultimate tensile strength and yield strength of 229 MPa and 185 MPa, respectively, while the alloy with 3.3 wt% Zn showed an excellent elongation after fracture of 4.5%. The tensile fracture analysis indicated that the cracks of the alloy without Zn mainly originated at the trigeminal junction of the grain boundary, the cracks of the 0.7 wt% Zn and 1.5 wt% Zn alloy mainly originated at the interface of the Mg/lamellar LPSO phase, and the cracks of the 3.3 wt% Zn alloy mainly originated at the bulk LPSO phase of the grain boundary and then propagated along the bulk LPSO phase. [ABSTRACT FROM AUTHOR]

This paper focuses on the study of the structure and mechanical properties of CoCrCuxFeNi high-entropy alloys and their adhesion to single diamond crystals. CoCrCuxFeNi alloys were manufactured by the powder metallurgy route, specifically via mechanical alloying of elemental powders, followed by hot pressing. The addition of copper led to the formation of a dual-phase FCC + FCC2 structure. The CoCrCu0.5FeNi alloy exhibited the highest ultimate tensile strength (1080 MPa). Reductions in the ductility of the CoCrCuxFeNi HEAs and the tendency for brittle fracture behavior were observed at high copper concentrations. The equiatomic alloys CoCrFeNi and CoCrCuFeNi demonstrated high adhesion strength to single diamond crystals. The diamond surface at the fracture of the composites having the CoCrFeNi matrix had chromium-rich metal matrix regions, thus indicating that chromium carbide, responsible for adhesion, was formed at the composite–diamond interface. Copper-rich areas were detected on the diamond surface within the composites having the CoCrCuFeNi matrix due to the predominant precipitation of the FCC2 phase at the interfaces or the crack propagation along the FCC/FCC2 interface, resulting in the exposure of the Cu-rich FCC2 phase on the surface. [ABSTRACT FROM AUTHOR]

AlSi10Mg has a good forming ability and has been widely accepted as an optimal material for selective laser melting (SLM). However, the strength and elongation of unmodified AlSi10Mg are insufficient, which limits its application in the space industry. In this paper, yttrium oxide (Y2O3) nanoparticles modified AlSi10Mg composites that were manufactured using SLM. The effects of Y2O3 nanoparticles (0~2 wt.% addition) on the microstructure and mechanical properties of AlSi10Mg alloys were investigated. An ultimate tensile strength of 500.3 MPa, a yield strength of 322.3 MPa, an elongation of 9.7%, a good friction coefficient of 0.43, and a wear rate of (3.40 ± 0.09) ×10−4 mm3·N−1·m−1 were obtained with the addition of 0.5 wt.% Y2O3 nanoparticles, and all these parameters were higher than those of the SLMed AlSi10Mg alloy. The microhardness of the composite with 1.0 wt.% Y2O3 reached 145.6 HV0.1, which is an increase of approximately 22% compared to the unreinforced AlSi10Mg. The improvement of tensile properties can mainly be attributed to Orowan strengthening, fine grain strengthening, and load-bearing strengthening. The results show that adding an appropriate amount of Y2O3 nanoparticles can significantly improve the properties of the SLMed AlSi10Mg alloy. [ABSTRACT FROM AUTHOR]

The Markforged Metal X (MfMX) printing machine (Markforged Inc., Massachusetts, USA) is one of the latest introduced additive manufacturing (AM) devices. It is getting popular because of its safety, simplicity, and ability to utilize various types of powders/filaments for printing. Despite this, only a few papers have so far reported the various properties and performances of the components fabricated by the MfMX printer. In this study, the microstructure and mechanical properties of MfMX-fabricated 17-4 stainless steel (ss) in the as-printed and heat-treated conditions were investigated. XRD and microscopy analyses revealed a dominant martensitic microstructure with some retained austenite phase. The microstructure is generally characterized by patterned voids that were unfilled due to a lack of fusion between the adjacent filaments. Disregarding these defects (voids), the porosity of the dense region was less than 4%. Depending on the heat treatment conditions, the hardness and tensile strength were enhanced by 17–28% and 21–27%, respectively. However, the tensile strength analyzed in this work was low compared with some previous reports for L-PBF-fabricated 17-4 ss. In contrast, the hardness of the as-printed (331 ± 28 HV) and heat-treated samples under the H900 condition (417 ± 29 HV) were comparable with (and even better than) some reports in the literature, despite the low material density. The results generally indicated that the Markforged printer is a promising technology when the printing processes are fully developed and optimized. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) show great promise for various applications in many fields. However, it still remains a challenge to obtain the ideal match of the tensile strength and the ductility. In this paper, Al0.5FeCoCrNi walls were fabricated through laser melting deposition (LMD) technology with laser power ranging from 1000 W to 1800 W. Along with the increase in laser power, the average size of the Al0.5FeCoCrNi walls increased from 14.31 μm to 34.88 μm, and the B2 phase decreased from 16.5% to 2.1%. Notably, the ultimate tensile strength and the ductility of the 1000 W bottom wall were 737 MPa and 24.6%, respectively, while those of 1800 W top wall were 641 MPa and 27.6%, respectively, demonstrating that the tensile strength of the walls decreased and the ductility increased with the increase in laser power. Furthermore, quantitative calculation revealed that grain boundary strengthening and dislocation strengthening were the two major forms of strengthening compared to the others. This study concluded that the mechanical properties of HEAs could be regulated by laser power, enabling broader applications in industry with favorable tensile strength or ductility. [ABSTRACT FROM AUTHOR]

AISI 316L stainless steel (SS) is one of the extensively used biomaterials to produce implants and medical devices. It provides a low-cost solution with ample mechanical properties, corrosion resistance, and biocompatibility compared to its counterpart materials. However, the implants made of this material are subjected to a short life span in human physiological conditions leading to the leaching of metal ions, thus limiting its use as a biomaterial. In this research, the addition of boron, titanium, and niobium with varying concentrations in the SS matrix has been explored. This paper explores the impact of material composition on modified SS alloy's physical and mechanical properties. The study's outcomes specify that the microhardness increases for all the alloy compositions, with a maximum increase of 64.68% for the 2 wt.% niobium added SS alloy. On the other hand, the tensile strength decreased to 297.40 MPa for the alloy containing 0.25 wt.% boron and 2 wt.% titanium additions compared to a tensile strength of 572.50 MPa for pure SS. The compression strength increased from 776 MPa for pure SS to 1408 MPa for the alloy containing niobium and titanium additions in equal concentrations. [ABSTRACT FROM AUTHOR]

In order to obtain high-performance aluminum alloy parts fabricated by selective laser melting, this paper investigates the relationship between the process parameters and microstructure properties of AlSi10Mg. The appropriate process parameters are obtained: the layer thickness is 0.03 mm, the laser power is 370 W, the scanning speed is 1454 mm/s, and the hatch spacing is 0.16 mm. With these process parameters, the ultimate tensile strength of the as-printed status is 500.7 ± 0.8 MPa, the yield strength is 311.5 ± 5.9 MPa, the elongation is 7.7 ± 0.5%, and the relative density is 99.94%. After annealing treatment at 275 °C for 2 h, the ultimate tensile strength is 310.8 ± 1.3 MPa, the yield strength is 198.0 ± 2.0 MPa, and the elongation is 13.7 ± 0.6%. The mechanical properties are mainly due to the high relative density, supersaturate solid solution, and fine dispersed Si. The supersaturate solid solution and nano-sized Si formed by the high cooling rate of SLM. After annealing treatment, the Si have been granulated and grown significantly. The ultimate tensile strength and yield strength are reduced, and the elongation is significantly improved. [ABSTRACT FROM AUTHOR]

The impact of water-induced degradation on the mechanical properties of the chosen two PTFE-coated, glass threads woven fabrics is investigated in this paper. The paper begins with a survey of literature concerning the investigation and determination of coated woven fabric properties. The authors carried out the uniaxial tensile tests with an application of flat and curved grips to establish the proper values of the ultimate tensile strength and the longitudinal stiffness of groups of specimens treated with different moisture conditions. Despite the water resistance of the main materials used for fabrics manufacturing, the change of the mechanical properties caused by the influence of water immersion has been noticed. The reduction in the tensile strength resulting under waterlogged is observed in the range from 5% to 16% depending on the type of investigated coated woven fabric and direction of weft or warp. [ABSTRACT FROM AUTHOR]

In the present research, the impacts of Ce additions at various concentrations (0, 1.0, 3.4, and 4.0 wt.%) on the evolution of the microstructure, mechanical properties, and thermal conductivity of as-cast and as-extruded Mg-3Sn alloys were investigated. The findings demonstrate that adding Ce caused the creation of a new ternary MgSnCe phase in the magnesium matrix. Some new Mg17Ce2 phases are generated in the microstructure when Ce levels reach 4%. The thermal conductivity of the Mg-3Sn alloy is significantly improved due to Ce addition, and the Mg-3Sn-3.4Ce alloy exhibits the highest thermal conductivity, up to 133.8 W/(m·K) at 298 K. After extrusion, both the thermal conductivity and mechanical properties are further improved. The thermal conductivity perpendicular to the extrusion direction of Mg-3Sn-3.4Ce alloy could achieve 136.28 W/(m·K), and the tensile and yield strengths reach 264.3 MPa and 227.2 MPa, with an elongation of 7.9%. Adding Ce decreases the dissolved Sn atoms and breaks the eutectic α-Mg and Mg2Sn network organization, leading to a considerable increase in the thermal conductivity of as-cast Mg-3Sn alloys. Weakening the deformed grain texture contributed to the further enhancement of the thermal conductivity after extrusion. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of as-cast Al-10Ce-3Mg-xZn (x = 0, 1, 3, 5 wt.%) alloys were systematically investigated, with a focus on the effect of Zn on the Al11Ce3 reinforcing phase in the alloy. The results showed that the Al-10Ce-3Mg alloy consists of α-Al, a Chinese-script Al11Ce3 eutectic phase, and a massive Al11Ce3 primary phase. With the addition of Zn content, most of the Zn atoms are enriched in the Al11Ce3 phase to form the acicular-like Al2CeZn2 phase within the Al11Ce3 phase. Increasing the Zn content can increase the volume fraction of the Al11Ce3 phase. Compared to the alloy without Zn addition, the microhardness and elastic modulus of the Al2CeZn2-reinforced Al11Ce3 phase in the alloy with 5 wt.% Zn increased by 18.9% and 9.0%, respectively. Moreover, the room-temperature mechanical properties of Al-10Ce-3Mg alloys were significantly improved due to the addition of Zn element. The alloy containing 5 wt.% Zn had the best tensile properties with an ultimate tensile strength of 210 MPa and a yield strength of 171MPa, which were 21% and 77% higher than those of the alloy without Zn, respectively. The alloy containing 5 wt.% Zn demonstrated a superior retention ratio of tensile strength at 200–300 °C, indicating that the alloy has excellent heat resistance. The improvement in the mechanical properties is primarily attributed to second-phase strengthening and solid solution strengthening. [ABSTRACT FROM AUTHOR]

This paper deals with various selective laser melting (SLM) processing strategies for aluminum 2618 powder in order to get material densities and properties close to conventionally-produced, high-strength 2618 alloy. To evaluate the influence of laser scanning strategies on the resulting porosity and mechanical properties a row of experiments was done. Three types of samples were used: single-track welds, bulk samples and samples for tensile testing. Single-track welds were used to find the appropriate processing parameters for achieving continuous and well-shaped welds. The bulk samples were built with different scanning strategies with the aim of reaching a low relative porosity of the material. The combination of the chessboard strategy with a 2 x 2 mm field size fabricated with an out-in spiral order was found to eliminate a major lack of fusion defects. However, small cracks in the material structure were found over the complete range of tested parameters. The decisive criteria was the elimination of small cracks that drastically reduced mechanical properties. Reduction of the thermal gradient using support structures or fabrication under elevated temperatures shows a promising approach to eliminating the cracks. Mechanical properties of samples produced by SLM were compared with the properties of extruded material. The results showed that the SLM-processed 2618 alloy could only reach one half of the yield strength and tensile strength of extruded material. This is mainly due to the occurrence of small cracks in the structure of the built material. [ABSTRACT FROM AUTHOR]

The 2319-Al alloy is widely used in aviation industry. The crack-free 2319 alloy thin-walled sample was fabricated utilizing the laser-CMT composite additive manufacturing technique, achieving a material utilization rate of 96.43%. The impact of deposition parameters and deposition height on the microstructure and mechanical properties was studied. The microhardness of the additive manufacturing samples exhibited a gradual decrease from construction direction, with values reaching 90 HV, 78 HV, and 72 HV, respectively. The tensile property also exhibited a gradual decrease from the bottom to the top; the highest tensile strength was 296 MPa. The grain size along the construction direction of the deposited sample gradually increased, exhibiting respective sizes of 34.7 um, 36.6 um, and 45.7 um. With the increase in the height of the second phase, the segregation at the grain boundary is intensified, and as the size inside the grain increases, the corresponding density decreases. The good laser-CMT composite additively manufactured 2319 aluminum alloy samples could be obtained under the optimized deposition parameters. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of a hot-pressing process on the mechanical properties of ultra-high molecular weight polyethylene (UHMWPE) fiber non-woven fabrics with stretch and in-plane shear, UHMWPE non-woven fabric samples were prepared by adjusting the temperature, time, and pressure of the hot-pressing process, and mechanical property tests were carried out so as to clarify the influence of the hot-pressing process on the mechanical properties of the samples. The results show that the hot-pressing process mainly affects the silk–glue bonding strength of the samples; in the test range, with the increase in hot-pressing temperature and time, the tensile strength and in-plane shear strength of the samples increase and then decrease, and the best mechanical properties are obtained at 130 °C and 7 min of hot pressing, respectively; at 130 °C, the in-plane shear strength is 39.94 MPa and the tensile strength is 595.43 MPa; at 7 min, the in-plane shear strength is 63.0 MPa and the tensile strength is 643.30 MPa; with the increase in the hot-pressing pressure, the in-plane shear strength of the samples increases and then decreases, and the highest is 52.60 MPa, achieved at 8 MPa; in the range of 5–8 MPa, the tensile strength of the specimens did not change significantly, and increased significantly at 9 MPa, reaching a maximum strength of 674.55 MPa. [ABSTRACT FROM AUTHOR]

Magnesium (Mg)-matrix composites have excellent damping and electromagnetic shielding properties. However, the mismatch between their strength and toughness limits their wide application. The aim of this work is to overcome the strength-toughness mismatch by constructing micro- and nanostructures while maintaining the good functional properties of Mg-matrix composites. Electrophoretic deposition (EPD) was used to spread carbon nanotubes (CNTs) out evenly on a Mg foil matrix. After spark plasma sintering (SPS), the grain organisation was refined, and the interlayer bonding was strengthened by hot rolling deformation. Finally, the microstructure, mechanical properties, damping properties, and electromagnetic shielding properties of the composites were analysed. Compared with the pure Mg laminates, the tensile strength and elongation of the CNT/Mg laminates were increased by 6.4% and 108.4%, respectively, with the significant improvement in toughness resulting from the increase in energy required for crack propagation due to the laminate structure. When the total rolling deflection reaches 80%, the interlayer bond strength of the material is significantly increased, the grain is further refined, and the strength and elongation of the composite material reaches the optimum, with the tensile strength reaching 241.70 MPa and the elongation reaching 6.90%. The interlayer interface and grain refinement also affected the damping Mg and electromagnetic shielding effect of the composites. This work provides an experimental idea for the preparation of high-performance structure-function integrated Mg-based materials. [ABSTRACT FROM AUTHOR]

A sub-eutectic high-entropy alloy composed of CoCrFeNiNb0.25 was prepared using a combination of mechanical powder mixing and selective laser melting (SLM). The mechanical properties of the alloy were enhanced by employing an interlayer laser remelting process. This study demonstrates the feasibility of using mechanical mixing and SLM to form an CoCrFeNiNb0.25 alloy. The interlayer laser remelting process can effectively promote the melting of Nb particles introduced by mechanical mixing, release the stresses near the unfused Nb particles, and reduce their degradation of the specimen properties. The results indicate that the CoCrFeNiNb0.25 alloy, prepared using the interlayer laser remelting process, had an average microhardness of 376 HV, a tensile strength of 974 MPa, and an elongation at break of 10.51%. This process offers a viable approach for rapidly adjusting the composition of high-entropy alloys for SLM forming. [ABSTRACT FROM AUTHOR]

A promising method for additive manufacturing that makes it possible to produce intricate and personalized parts is selective laser melting (SLM). However, the mechanical properties of as-corroded SLM parts are still areas of concern. This research investigates the mechanical behavior of SLM parts that are exposed to a saline environment containing a 3.5% NaCl solution for varying lengths of time. The exposure times chosen for this study were 10 days, 20 days, and 30 days. The results reveal that the tensile strength of the parts is significantly affected by the duration of exposure. Additionally, the study also examined the influence of porosity on the corrosion behavior of the parts. The analysis included studying the mass loss of the parts over time, and a regression analysis was conducted to analyze the relationship between exposure time and mass loss. In addition, the utilization of scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS) techniques yielded valuable insights into the fundamental mechanisms accountable for the observed corrosion and mechanical behavior. It was found that the presence of corrosion products (i.e., oxide layer) and pitting contributed to the degradation of the SLM parts in the saline environment. This research emphasizes the importance of considering part thickness in the design of SLM components for corrosive environments and provides insights for enhancing their performance and durability. [ABSTRACT FROM AUTHOR]

In the present work, the effect of Zn on the aging precipitates and mechanical properties of Al-Cu-Li alloys was investigated by Vickers hardness, tensile tests, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results indicated that the addition of Zn reduced the activation energy of the T1 phase and makes it easier to precipitate. The activation energy of the T1 phase, which was 107.02 ± 1.8 KJ/mol, 94.33 ± 1.7 KJ/mol, 90.33 ± 1.7 KJ/mol and 90.28 ± 1.6 KJ/mol for 0Zn, 0.4Zn, 0.8Zn and 1.2Zn alloy, respectively. The area number density of the T1 precipitate ranged from 97.0 ± 4.4 pcs/μm2 to 118.2 ± 2.8 pcs/μm2 as the Zn content increased from 0 to 1.2 wt.%. Consequently, the addition of Zn promoted the precipitation of the T1 phase. Therefore, the peak hardness and tensile strength of the alloy also increased with the increase in the Zn content, and the hardness of the alloy with Zn content of 1.2 wt.% increased by 16.5 ± 1.4 HV; meanwhile, the ultimate tensile strength increased by 46.5 ± 2.5 MPa. Therefore, the area number density of precipitates increased and improved the strength of the Zn-containing alloy. [ABSTRACT FROM AUTHOR]

This paper provides a state-of-the-art report on the up-to-date research on the emerging 3D concrete printing technology from the concrete materials perspective. It reviews the recent research focused on understanding and characterizing the rheological necessities of the concrete printing process and discusses how the researchers are tailoring compatible mix proportions for the 3D concrete printing process by using eco-friendly binders, waste aggregates, chemical admixtures, and nano-additives. This paper systematically evaluates anisotropic behavior in the mechanical properties of printed concrete and establishes an order for anisotropic behavior in the compressive, flexural, and tensile strengths along three different axes (X, Y, and Z axes) of printed concrete. It evaluates the ratio of flexural strength to the compressive strength of printed concrete along the above three axes. This article explains the influence of variation of printing process parameters on the mechanical properties and discusses reinforcement approaches used for increasing structural performance. The microstructure at the interface of adjacent layers and also at the interface of the reinforcement-cement matrix is discussed. The recent research on the durability performance of printed concrete is critically discussed and future research needs for 3D concrete printing are identified in this paper. [ABSTRACT FROM AUTHOR]

Polyvinyl chloride (PVC) foam, valued for its mechanical and thermal properties along with cost-effectiveness, is extensively utilized across diverse industries. However, its high volatile organic compound (VOC) emissions hinder its adoption in eco-friendly synthetic leather. This study proposes a solution by optimizing the formulation design and foaming processes and achieving mechanical property enhancement via carbon-fiber-reinforced PVC composite foam (CF/PVC). The aim is to reduce PVC usage via enhancing its intrinsic properties. Systematic investigations were carried out on the impact of foaming raw materials, foaming processes, fiber content, and fiber length on the foaming performance, mechanical properties, and VOC emissions. The material formulation and process parameters were successfully optimized. Further assessment of various indicators such as the density, mechanical properties, and tear resistance of synthetic leather samples confirmed that the innovative CF/PVC foam developed in this study meets the requirements for automotive interior applications. Notably, the tensile strength and tear resistance of CF/PVC composite synthetic leather increased by 50% and 29%, respectively, compared to pure PVC, while VOC emissions decreased by 28%. It is anticipated that a more pronounced reduction in VOC emissions will be achieved in practical automotive interior leather applications when further considering the reinforcing effect of fibers, which leads to a reduction in PVC usage. The findings present a technical reference for innovative applications, aiming to enhance PVC foam performance and minimize emissions. [ABSTRACT FROM AUTHOR]

In the present work, the effects of aging treatment on the microstructures of a TC18 alloy are studied. The influence of aging treatment on the tensile properties and failure mechanisms is systematically analyzed. It is found that the size and morphology of the primary α (αp) phases are insensitive to aging temperature and time. Furthermore, the aging temperature and time dramatically influence the precipitation of the secondary α (αs) phases. Massive αs phases precipitate and gradually coarsen, and finally weave together by increasing the aging temperature or extending the aging time. The variations in αp and αs phases induced by aging parameters also affect the mechanical properties. Both yield strength (YS) and ultimate tensile strength (UTS) first increase and then decrease by increasing the aging temperature and time, while ductility first decreases and then increases. There is an excellent balance between the strengths and ductility. When the aging temperature is changed from 450 to 550 °C, YS varies from 1238.6 to 1381.6 MPa, UTS varies from 1363.2 to 1516.8 MPa, and the moderate elongation ranges from 9.0% to 10.3%. These results reveal that the thickness of αs phases is responsible for material strengths, while the content of α phases can enhance material ductility. The ductile characteristics of the alloy with coarser αs phases are more obvious than those with thinner αs phases. Therefore, the aging treatment is helpful for the precipitation and homogeneous distribution of αs phases, which are essential for balancing the strengths and ductility of the studied Ti alloy. [ABSTRACT FROM AUTHOR]

In this work, squeeze casting experiments of flywheel housing components with a large wall thickness difference and a complex shape were carried out with AlSi9Mg aluminum alloy. The defects, microstructures, and mechanical properties under different process parameters were investigated. Furthermore, the local pressurization process was applied to the thick-walled positions to force-feed the cast defects. The mechanical properties and microstructures at these positions were analyzed. The results showed that the surface quality of formed components was good and that local pressurization could effectively reduce the shrinkage cavity and shrinkage porosity in thick walls, but the scope and effect of forced feeding were limited. The optimum process parameters were a pouring temperature of 650 °C, a specific pressure of 48 MPa, a mold temperature of 220 °C, a local pressurization of 800 MPa, and pressure delay times of 15 s (side A) and 17 s (side B). The ultimate tensile strength, yield strength, and elongation of the formed component under validation experiments of the optimum process parameters were 201 MPa, 103 MPa, and 5.1%. Meanwhile, the fine grains of primary α-Al were mainly rosette and equiaxed grains, and the average grain size was about 40 μm. The microstructure of the eutectic silicon was acicular and was prone to segregation under pressure. According to profile morphology, the positions after pressurization were divided into a deformation zone, a direct action zone, and an indirect action zone. The coexistence of as-cast and plastic deformation microstructures was observed. The effect of local pressurization mainly involved a change in the solidification process, plastic deformation, and forced feeding. [ABSTRACT FROM AUTHOR]

Generally, to produce film-type thermoplastic composites with good mechanical properties, high-performance reinforcement films are used. In this case, films used as a matrix are difficult to impregnate into tow due to their high melt viscosity and high molecular weight. To solve the problem, in this paper, three polypropylene (PP) films with different melt viscosities were used separately to produce film-type thermoplastic composites. A film with a low melt viscosity was stacked so that tow was impregnated first and a film with a higher melt viscosity was then stacked to produce the composite. Four different composites were produced by regulating the pressure rising time. The thickness, density, fiber volume fraction (Vf), and void content (Vc) were analyzed to identify the physical properties and compare them in terms of film stacking types. The thermal properties were identified by using differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). The tensile property, flexural property, interlaminar shear strength (ILSS), and scanning electron microscopy (SEM) were performed to identify the mechanical properties. For the films with low molecular weight, impregnation could be completed fast but showed low strength. Additionally, the films with high molecular weight completed impregnation slowly but showed high strength. Therefore, appropriate films should be used considering the forming process time and their mechanical properties to produce film-type composites. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental research on the strength properties of porous structures with different degrees of density manufactured of Ti6Al4V titanium alloy by Laser Power Bed Fusion. In the experiment, samples with diamond structure of porosity: 34%, 50%, 73% and 81% were used, as well as samples with near-zero porosity. Monotonic tensile tests were carried out to determine the effective values of axial modulus of elasticity, ultimate tensile strength, offset yield strength, ultimate elongation and Poisson ratio for titanium alloys with different porosities. The paper also proposes relationships that can be easily used to estimate the strength and rigidity of a porous material manufactured by 3D printing. They were obtained by the approximation of two quotients. The first one refers to the relationship between the tensile strength of a material with a defined porosity to the strength of full-filled material. The second similarly determines the change in the value of the axial modulus of elasticity. The analysis of microscopic observations of fracture surfaces and also microtomography visualization of the material structure are also presented. [ABSTRACT FROM AUTHOR]

The reuse system proposed by the authors is an overall business system for realizing a cyclic reuse flow through the processes of design, fabrication, construction, maintenance, demolition and storage. The reuse system is one of the methods to reduce the environmental burden in the field of building steel structures. These buildings are assumed to be demolished within approximately 30 years or more for physical, architectural, economic and social reasons in Japan. In this paper, focusing on building steel structures used for plants, warehouses and offices without fire protection, the performance of steel structural members for reuse is evaluated by a non-destructive test. First, performance evaluation procedures for a non-destructive test, such as mechanical properties, chemical compositions, dimension and degradation, are shown. Tensile strengths are estimated using Vickers hardness measured by a portable ultrasonic hardness tester, and chemical compositions are measured by a portable optical emission spectrometer. The weldability of steel structural members is estimated by carbon equivalent and weld crack sensitivity composition using chemical compositions. Finally, the material grade of structural members of the building steel structure for reuse is estimated based on the proposed procedures. [ABSTRACT FROM AUTHOR]

In this study, the effects of the combined addition of CeLa and GdY on the microstructure and mechanical properties of as-cast Al-4Cu-1Mn alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile testing. The results show that the minor addition of CeLa and GdY leads to a refinement of grain size. The addition of CeLa results in the formation of supersaturated vacancies in the Al matrix, whereas the addition of GdY leads to a decrease in the precipitation temperature of the Al2Cu phase. The combined CeLa and GdY additions can significantly increase ultimate tensile strength (UTS) while losing only a small amount of elongation (EL). Compared with the unmodified alloy, the grain size and SDAS of the alloy (0.2 wt.% CeLa + 0.1 wt.% GdY) were diminished by 67.2% and 58.7%, respectively, while maximum hardness and UTS rose by 31.2% and 36.9%, respectively. [ABSTRACT FROM AUTHOR]

Statistical analysis of mechanical properties of thin-walled samples (~500 microns) obtained by selective laser melting from AlSi10Mg material and subjected to heat treatment for 1 h at temperatures from 260 °C to 440 °C (step of aging temperature change 30 °C) has shown that the maximum strain hardening in the stretching diagram section from yield strength to tensile strength is achieved at the heat treatment temperature equal to 290 °C. At carrying out of correlation analysis, a statistically significant positive correlation between deformation corresponding to yield strength and the sum of heights of the largest protrusions and depths of the largest depressions of the surface roughness profile within the basic length of the sample (Rz) and the full height of the surface roughness profile (Rmax) was established. It was found that the reason for the correlation is the presence of cohesive states between the extreme values of the surface roughness profile that persist along the entire length of the specimen. [ABSTRACT FROM AUTHOR]

A series of five-element CoCrFeNi-Nbx (x = 0, 1, 3, 5, 7, and 9 wt%) high-entropy alloys were prepared using high-energy ball milling and discharge plasma sintering methods. Then, the effects of doping with Nb elements on the organization and properties of the CoCrFeNi HEAs were systematically investigated by tensile testing, hardness testing, and examining their micro-morphologies. The results show that with the addition of the Nb element, the lattice distortion of the alloy due to the large size of the Nb atoms causes the microstructure of CoCrFeNi HEAs to change from a single-phase FCC structure to a dual-phase structure of FCC and Laves. With the increase in the Nb content, the increase in the volume fraction of the hard and brittle Laves phase leads to the enhancement of the HEA's tensile strength, yield strength, and hardness, and a decrease in plasticity. The Nb5 alloy showed the most excellent comprehensive performance, with a tensile strength, yield strength, and plasticity of 879.1 MPa, 491.8 MPa, and 39.8%, respectively, and all the properties were improved compared with those of the HEAs obtained by the arc melting method. The increase in the hardness of the HEAs was nearly proportional to the increase in the volume fraction of the Laves phase, which was the direct cause of the increase in the hardness of the HEA. Therefore, since the Laves phase is the direct cause of the increase in HEA hardness, the doping of CoCrFeNi HEAs with Nb can significantly improve the properties of HEAs. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies on the effects of heat treatment and cold-work parameters on the mechanical properties and microstructure of the tungsten heavy alloy (WHA) with the composition W91-6Ni-3Co. Tungsten heavy alloy (WHA) is used in conditions where strength, high density, and weight are required. The material for testing as rod-shaped samples was produced by the method of powder metallurgy and sintering with the participation of the liquid phase and then subjected to heat treatment and cold swaging. The study compares the effect of degree deformation on the strength, hardness, microhardness, and microstructure of WHA rods. The conducted tests showed that heat treatment and cold-work allowed to gradually increase the strength parameters, i.e., tensile strength σ u t s , yield strength σ y s , elongation ε, hardness, and microhardness. These processes made it possible to increase the tensile strength by over 800 MPa (from the initial 600 MPa after sintering to the final value of over 1470 MPa after heat treatment with cold swaging deformation with reduction of 30%) and the hardness from 32 to 46 HRC. [ABSTRACT FROM AUTHOR]

In the present paper, the Mg-11Gd-2Y-1Zn alloys with different Al addition were fabricated by the gravity permanent mold method. The effect of Al content on microstructure evolution and mechanical properties of as-cast Mg-11Gd-2Y-1Zn alloy was studied by metallographic microscope, scanning electron microscope, XRD and tensile testing. The experimental results showed that the microstructure of as-cast Mg-11Gd-2Y-1Zn alloy consisted of α-Mg phase and island-shaped Mg3 (RE, Zn) phase. When Al element was added, Al2RE phase and lamellar Mg12REZn (LPSO) phase were formed in the Mg-11Gd-2Y-1Zn alloy. With increasing Al content, LPSO phase and Mg3 (RE, Zn) phase gradually decreased, while Al2RE phase gradually increased. There were only α-Mg and Al2RE phases in the Mg-11Gd-2Y-1Zn-5Al alloy. With the increase of Al content, the grain size decreased firstly and then increased. When the Al content was 1 wt.%, the grain size of the alloy was the minimum value (28.9 μm). The ultimate tensile strength and elongation increased firstly and then decreased with increasing Al addition. And the fracture mode changed from intergranular fracture to transgranular fracture with increasing addition. When Al addition was 1 wt.%, the maximum ultimate tensile strength reached 225.6 MPa, and the elongation was 7.8%. When the content of Al element was 3 wt.%, the maximum elongation reached 10.2% and the ultimate tensile strength was 207.7 MPa. [ABSTRACT FROM AUTHOR]

Electrospinning is an innovative new fibre technology that aims to design and fabricate membranes suitable for a wide range of tissue engineering (TE) applications including vascular grafts, which is the main objective of this research work. This study dealt with fabricating and characterising bilayer structures comprised of an electrospun sheet made of polycaprolactone (PCL, inner layer) and an outer layer made of poly lactic-co-glycolic acid (PLGA) and a coaxial porous scaffold with a micrometre fibre structure was successfully produced. The membranes' propriety for intended biomedical applications was assessed by evaluating their morphological structure/physical properties and structural integrity when they underwent the degradation process. A scanning electron microscope (SEM) was used to assess changes in the electrospun scaffolds' structural morphology such as in their fibre diameter, pore size (μm) and the porosity of the scaffold surface which was measured with Image J software. During the 12-week degradation process at room temperature, most of the scaffolds showed a similar trend in their degradation rate except the 60 min scaffolds. The coaxial scaffold had significantly less mass loss than the bilayer PCL/PLGA scaffold with 1.348% and 18.3%, respectively. The mechanical properties of the fibrous membranes were measured and the coaxial scaffolds showed greater tensile strength and elongation at break (%) compared to the bilayer scaffolds. According to the results obtained in this study, it can be concluded that a scaffold made with a coaxial needle is more suitable for tissue engineering applications due to the improved quality and functionality of the resulting polymeric membrane compared to the basic electrospinning process. However, whilst fabricating a vascular graft is the main aim of this research work, the biological data will not present in this paper. [ABSTRACT FROM AUTHOR]

The large differential-thermal extrusion (LDTE) process, a novel approach for efficiently fabricating a high-strength Mg-10.3Gd-4.4Y-0.9Zn-0.7Mn (wt.%) alloy, is introduced in this work. Unlike typical isothermal extrusion processes, where the ingot and die temperatures are kept the same, LDTE involves significantly higher ingot temperatures (~120 °C) compared to the die temperature. For high-strength Mg-RE alloys, the maximum isothermal extrusion ram speed is normally limited to 1 mm/s. This research uses the LDTE process to significantly increase the ram speed to 2.0 mm/s. The LPTE-processed alloy possesses a phase composition that is similar to that of isothermal extruded alloys, including α-Mg, 14H-type long-period stacking ordered (LPSO) and β-Mg5(Gd, Y) phases. The weakly preferentially oriented α-Mg grains in the LDTE-processed alloy have < 10 1 ¯ 0 > Mg//ED fibrous and <0001>Mg//ED anomalous textures as their two main constituents. After isothermal aging, high quantitative densities of prismatic β′ and basal γ′ precipitates are produced, which have the beneficial effect of precipitation hardening. With a yield tensile strength of 344 MPa, an ultimate tensile strength of 488 MPa, and an elongation of 9.7%, the alloy produced by the LDTE process exhibits an exceptional strength–ductility balance, further demonstrating the potential of this method for efficiently producing high-strength Mg alloys. [ABSTRACT FROM AUTHOR]

Polyethylene (PE), one of the most popular thermoplastic polymers, is widely used in various areas, such as materials engineering and biomedical engineering, due to its superior performance, while 3D printing via fused deposition modeling (FDM) provides a facile method of preparing PE products. To optimize the performance and assess the degradation of FDM-printed PE materials, we systematically investigate the influences of printing parameters, such as fiber diameter (stretching) and printer head temperature, and degradation, such as UV exposure and thermal degradation, on the mechanical performance of FDM-printed PE fibers. When FDM-printed PE fibers with a smaller diameter are prepared under a higher collecting speed, they undergo stronger stretching, and thus, show higher tensile strength and Young's modulus values. Meanwhile, the tensile strength and Young's modulus decrease as the printer head temperature increases, due to the lower viscosity, and thus, weaker shearing at high temperatures. However, degradation, such as UV exposure and thermal degradation, cause a decrease in all four mechanical properties, including tensile strength, Young's modulus, tensile strain and toughness. These results will guide the optimization of FDM-printed PE materials and help to assess the durability of PE products against degradation for their practical application. [ABSTRACT FROM AUTHOR]

U-Mo alloys were considered to be the most promising candidates for high-density nuclear fuel. The uniaxial tensile behavior of nanocrystalline U-10Mo alloys with average grain sizes of 8–23 nm was systematically studied by molecular dynamics (MD) simulation, mainly focusing on the influence of average grain size on the mechanical properties and deformation mechanisms. The results show that Young's modulus, yield strength and ultimate tensile strength follow as average grain size increases. During the deformation process, localized phase transitions were observed in samples. Grain boundary sliding and grain rotation, as well as twinning, dominated the deformation in the smaller and larger grain sizes samples, respectively. Increased grain size led to greater localized shear deformation, resulting in greater stress drop. Additionally, we elucidated the effects of temperature and strain rate on tensile behavior and found that lower temperatures and higher strain rates not only facilitated the twinning tendency but also favored the occurrence of phase transitions in samples. Results from this research could provide guidance for the design and optimization of U-10Mo alloys materials. [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]

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]

Nanocrystalline (NC) structure can lead to the considerable strengthening of metals and alloys. Obtaining appropriate comprehensive mechanical properties is always the goal of metallic materials. Here, a nanostructured Al-Zn-Mg-Cu-Zr-Sc alloy was successfully processed by high-pressure torsion (HPT) followed by natural aging. The microstructures and mechanical properties of the naturally aged HPT alloy were analyzed. The results show that the naturally aged HPT alloy primarily consists of nanoscale grains (~98.8 nm), nano-sized precipitates (20–28 nm in size), and dislocations (1.16 × 1015 m−2), and exhibits a high tensile strength of 851 ± 6 MPa and appropriate elongation of 6.8 ± 0.2%. In addition, the multiple strengthening modes that were activated and contributed to the yield strength of the alloy were evaluated according to grain refinement strengthening, precipitation strengthening, and dislocation strengthening, and it is shown that grain refinement strengthening and precipitation strengthening are the main strengthening mechanisms. The results of this study provide an effective pathway for achieving the optimal strength–ductility match of materials and guiding the subsequent annealing treatment. [ABSTRACT FROM AUTHOR]

The high aesthetic demands of patients have increased their requests to align their teeth using clear aligners, including Invisalign. Patients also want to have their teeth whitened for the same purpose; the use of Invisalign as a bleaching tray at night has been reported in few studies. However, whether 10% carbamide peroxide affects the physical properties of Invisalign is unknown. Therefore, the objective of this study was to evaluate the effect of 10% carbamide peroxide on the physical properties of Invisalign when used as a bleaching tray at night. Twenty-two unused Invisalign aligners (Santa Clara, CA, USA) were used to prepare 144 specimens to test their tensile strength, hardness, surface roughness, and translucency. The specimens were divided into four groups: a testing group at baseline (TG1), a testing group after application of bleaching material at 37 °C for 2 weeks (TG2), a control group at baseline (CG1), and a control group after immersion in distilled water at 37 °C for 2 weeks (CG2). Statistical analysis was conducted using a paired t-test, Wilcoxon signed rank test, independent samples t-test, and Mann–Whitney test to compare samples in CG2 to CG1, TG2 to TG1, and TG2 to CG2. Statistical analysis showed no statistically significant difference between the groups for all physical properties, except for hardness (p-value < 0.001) and surface roughness (p-value = 0.007 and p-value < 0.001 for the internal and external surface roughness, respectively), which revealed a reduction in hardness values (from 4.43 ± 0.86 N/mm2 to 2.2 ± 0.29 N/mm2) and an increase in surface roughness (from 1.6 ± 0.32 Ra to 1.93 ± 0.28 Ra and from 0.58 ± 0.12 Ra to 0.68 ± 0.13 Ra for the internal and external surface roughness, respectively) after 2 weeks of dental bleaching. Results showed that Invisalign can be used for dental bleaching without excessive distortion or degradation of the aligner material. However, future clinical trials are required to further assess the feasibility of using Invisalign for dental bleaching. [ABSTRACT FROM AUTHOR]

The mechanical properties and impact resistance of conventional self-compacting concrete (SCC) need to be further improved. In order to explore the dynamic and static mechanical properties of copper-plated steel-fiber-reinforced self-compacting concrete (CPSFRSCC), the static mechanical properties and dynamic mechanical properties of CPSFRSCC with a different volume fraction of copper-plated steel fiber (CPSF) are tested, and a numerical experiment is carried out to analyze the experimental results. The results show that the mechanical properties of self-compacting concrete (SCC) can be effectively improved by adding CPSF, especially for the tensile mechanical properties. The static tensile strength of CPSFRSCC shows a trend that increases with the increase in the volume fraction of CPSF and then reaches the maximum when the volume fraction of CPSF is 3%. The dynamic tensile strength of CPSFRSCC shows a trend that increases first and then decrease with the increase in the volume fraction of CPSF, and then reaches the maximum when the volume fraction of CPSF is 2%. The results of the numerical simulation show that the failure morphology of CPSFRSCC is closely related to the content of CPSF; with the increase in the volume fraction of CPSF, the fracture morphology of the specimen gradually evolves from complete fracture to incomplete fracture. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the effect of different second phases on the composite spinning-extrusion forming and mechanical properties of Al–Cu–Li alloy. With that purpose, four kinds of second phases blanks were controlled using preheating treatment, composite spinning-extrusion forming and mechanical properties test. Then, the correlation between the second phases and mechanical properties was further analyzed using electron backscattered diffraction and transmission electron microscopy. The results indicated that different second phases of Al–Cu–Li alloy can be regulated via reasonable preheating treatment. In addition, different second phases in the blank have various influences on composite spinning-extrusion forming, microstructure and mechanical properties of cylindrical parts. Dissolving the coarse second phases particles and precipitating the Al3Zr dispersoid in the blank can effectively improve the composite spinning-extrusion forming, inhibit the abnormal growth of recrystallized grains, and significantly enhance the mechanical properties of cylindrical parts with ribs. After regulation, the average grain size of the cylindrical parts is refined from about 90 μm to about 45 μm, and the average diameter of T1 phase is refined from 107 nm to 77 nm. In addition, the ultimate tensile strength, yield strength and elongation of cylindrical parts are increased from 555 MPa to 588 MPa, 530 MPa to 564 MPa, and 9.1% to 11%, respectively. [ABSTRACT FROM AUTHOR]

Professionals in industries are making progress in creating predictive techniques for evaluating critical characteristics and reactions of engineered materials. The objective of this investigation is to determine the optimal settings for a 3D printer made of acrylonitrile butadiene styrene (ABS) in terms of its conflicting responses (flexural strength (FS), tensile strength (TS), average surface roughness (Ra), print time (T), and energy consumption (E)). Layer thickness (LT), printing speed (PS), and infill density (ID) are all quantifiable characteristics that were chosen. For the experimental methods of the prediction models, twenty samples were created using a full central composite design (CCD). The models were verified by proving that the experimental results were consistent with the predictions using validation trial tests, and the significance of the performance parameters was confirmed using analysis of variance (ANOVA). The most crucial element in obtaining the desired Ra and T was LT, whereas ID was the most crucial in attaining the desired mechanical characteristics. Numerical multi-objective optimization was used to achieve the following parameters: LT = 0.27 mm, ID = 84 percent, and PS = 51.1 mm/s; FS = 58.01 MPa; TS = 35.8 MPa; lowest Ra = 8.01 m; lowest T = 58 min; and E = 0.21 kwh. Manufacturers and practitioners may profit from using the produced numerically optimized model to forecast the necessary surface quality for different aspects before undertaking trials. [ABSTRACT FROM AUTHOR]