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This paper describes the fabrication and characterization of porous SiC ceramics derived from highly-filled preceramic papers. The SiC ceramics were obtained by spark plasma sintering of stacked preceramic papers at temperatures of 2100 and 2200 °C under pressures of 5–60 MPa for 10 min. The microstructure and phase composition were analyzed by scanning electron microscopy and X-ray diffraction, respectively. Gas permeation tests were performed using hydrogen permeation cell at room temperature. It is revealed that the porosity of sintered SiC can be varied from 9 to 45 % depending on the sintering parameters. The shrinkage of the materials during spark plasma sintering occurs in four stages. The linear shrinkage value of the material increases from 7 to 47 % at 2100 °C and from 20 to 50 % for the samples sintered at 2100 and 2200 °C, respectively. Correlation dependencies between porosity and mechanical properties of the fabricated SiC were established. The obtained porous SiC ceramics exhibit high bending strength of 165 MPa and gas permeation flux of 78 molH 2 /m2/s at the porosity of 36 % that make it suitable for ceramic-based membranes. [ABSTRACT FROM AUTHOR]

The present paper investigates the effect of carbon nanofibers (CNFs) on the microstructure and mechanical properties of Carbon fiber reinforced carbon and silicon carbide binary matrix (C/C–SiC) composite prepared by using the reactive melt infiltration technique. The CNFs used in this paper were generated through in-situ reaction in the pores of C/C preforms using the chemical vapor deposition. Results indicate introducing additional carbon sources in the form of CNFs in the C/C preform can remarkably improve the permeability of molten Si, resulting in higher density and more uniform microstructure of the RMI-deriver C/C–SiC composites. Consequently, the in-situ formation of CNFs reduces the residual Si content by 64.71% and increases the mechanical strength and modulus at room temperature by [22.31% and 17.89%] and after heat treatment at 1500 °C by [35.6% and 47.48%] with respect to no-CNF containing composites due to a lower amount of residual Si content and additional reinforcement effect of the unreacted CNFs. [ABSTRACT FROM AUTHOR]

Solar thermal power generation is an important direction of energy utilization, and thermal storage materials are the key to ensure the continuous use of energy. In this paper, forsterite - zirconia composite ceramics were prepared by adding different contents of 3Y–ZrO 2 and their physical properties, phase composition, microstructure thermal shock resistance and thermal physical properties were studied. The results showed that the water absorption, bulk density and bending strength of sample A3 sintered at 1600 °C (59.10 wt% fused magnesia, 40.90 wt% quartz and 30 wt% 3Y–ZrO 2) were 0.35 %, 3.27 g/cm3 and 83.66 MPa, respectively. The crystal phase of sample A3 was forsterite and c-ZrO 2. Mg2+ and Y3+ replace Zr4+, formed oxygen vacancy in the anion position, distort the coordination layer and release some interlayer stress to promote the stability of c-ZrO 2. In the sintering process, the zirconia solid solution existed in the form of second phase, which reduced the growth rate of periclase, facilitated the pore discharge in the sample and promotes sintering. The thermal conductivity of forsterite - zirconia composite ceramics at room temperature was 5.52 W/(m·K). At 1000 °C, the specific heat capacity and heat storage density were 1.09 J/(g·K) and 1062.36 kJ/kg, respectively. The forsterite - zirconia composite ceramic prepared in this study was suitable for high temperature environment, its heat storage capacity was excellent, and it was suitable for high temperature heat storage system. [ABSTRACT FROM AUTHOR]

3D printing is an excellent choice for manufacture of ceramic cores; however, the inter-layer structures in 3D printed sample leads to anisotropy in microstructure and properties. In this paper, silica-based ceramic cores were prepared by digital light processing, and metallic Si powder was employed as mineralizer to relieve the anisotropy. The metallic Si powder converts into SiO 2 in oxidation reaction with significant volume expansion, which inhibits the shrinkage rate and partly fills the interlayer gaps of the ceramic core. Meanwhile, the metal Si powder leads to lower curing thickness in 3D printing, and thicken the interlayer gaps. Due to the cooperation of the oxidation reaction and decreased curing thickness by the metallic Si powder, the 0.4 wt% of metallic Si powder reduced the anisotropy in structure and mechanical property due to the alleviated inter-layer structure and the interlayer and intralayer strengths show optimal values of 11.4 MPa and 17.2 MPa at room temperature, respectively. This work inspires new guidance to 3D printing of ceramic cores with uniform microstructure and excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Insulators are vital components used in electrical transmission lines. It's crucial to keep their production cost low since they are widely used in electricity transmission. Instead of expensive alumina-based insulators, we can make cheaper ones using clay and bauxite found in nature. Adding more alumina makes them stronger, which is important for high voltage transmission. This paper aims to study the production process of bauxite-based insulators. We examined the insulators' structure using SEM images and EDAX spectrum analysis to see their formations, porosity ratio, and density. This research helps us learn more about these insulators and how they can be used effectively for high voltage transmission lines. [ABSTRACT FROM AUTHOR]

In this paper, the effects of frequency on the flash sintering behavior and microstructure of Li 6.4 Ga 0.2 La 3 Zr 2 O 12 (0.2Ga-LLZO) were investigated. The results showed that an increase in frequency had little effect on the onset temperature, but this increase reduced the duration of the weak current stage the incubation stage. Moreover, this phenomenon led to a decrease in the power loss during the constant current stage. Scanning Electron Microscope images showed that the microstructure was symmetrically distributed, and the uniformity increased with increasing frequency. Finite element simulations and an IR thermocamera were used to analyze the temperatures of the specimens. The symmetric distribution of temperature during the flash sintering process was the root cause. The results of AC impedance spectroscopy showed that when the frequency of flash sintering was ≥ 400 Hz, the ionic conductivity of Ga-LLZO was greater than that of conventional sintering. The results of this work demonstrated the important role of frequency in controlling the microstructures of ceramic materials in flash sintering. [ABSTRACT FROM AUTHOR]

In this paper, by adding Co, Mo, and Ni metal binder and using spark plasma coupling high-frequency induction (SP–HF) sintering technology, high-entropy (W,Nb,Mo,Ta,Ti)C cermet with good performance was successfully prepared at 1350 °C. The sintering temperature was much lower than that of the solid-state sintering temperature adopted for high-entropy carbide ceramics (about 2000 °C) while maintaining high hardness and fracture toughness. The effects of sintering temperature, holding time and sintering pressure on the mechanical properties of high-entropy (W,Nb,Mo,Ta,Ti)C cermet were investigated. The experimental results show that the SP-HF sintering can promote the liquid phase flow inside the high-entropy (W,Nb,Mo,Ta,Ti)C cermet and improve the density. The high-frequency induction sintering effect of the high-intensity magnetic metal binder phase (Co, Ni) promotes the rapid diffusion of the constituent phases using the vacancy mechanism and the metal liquid phase, which helps to form a high-entropy cermet solid solution at a lower temperature. The different high-entropy effects of the inner and outer layers of high-entropy (W,Nb,Mo,Ta,Ti)C cermet materials play a role in strengthening and toughening the materials, and effective solid solution strengthening is the main reason for improving mechanical properties. The mechanical properties of high-entropy (W,Nb,Mo,Ta,Ti)C cermet are the optimized at 1350 °C, holding time of 8 min, and sintering pressure of 35 MPa. The Vickers hardness, fracture toughness, and flexural strength are 18.38 ± 0.19 GPa, 9.65 ± 0.25 MPa · m1/2 and 970 ± 30 MPa, Vickers hardness was measured at 49 N load. [ABSTRACT FROM AUTHOR]

Zirconolite (CaZrTi 2 O 7) glass-ceramic is considered as a potential stable matrix for the immobilization of Pu or minor actinides (Np, Am, Cm). In this work, the phase combination and evolution of glass (SiO 2 –Al 2 O 3 –Na 2 O–CaO–ZrO 2 –TiO 2 –B 2 O 3) with La as an actinide surrogate were investigated during the process of heating and cooling. By employing controlled cooling process, the zirconolite glass-ceramic with a controllable crystal size was successfully fabricated in borosilicate glass. The results demonstrate that heating and cooling exhibit distinct phase combinations. Both crystallization temperature and duration exert a significant influence on the composition of crystalline phases and microstructure. During the cooling of the melt, an increased degree of supercooling leads to an enhanced crystallization of zirconolite and a significant reduction in crystal size. The experimental results demonstrate that the optimal condition for preparing zirconolite glass-ceramic is held at 950 °C, for 4 h by one-step method, at which time the crystal exhibits a slender acicular morphology with a size of about 30 μm. Most of the simulated nuclides are enriched in crystals, and the rest are dissolved in glass. Zirconolite exhibits thermodynamic instability at elevated temperatures (1000 °C–1100 °C). Following the phase transformation, a proportion of Zr sequestered by titanite, while any excess Zr is either remain dissolved in the glass or gets precipitated as baddeleyite. For La, Al and other elements previously fixed in zirconolite, they are re-released to the glass and partially fixed by titanite, which may be detrimental to the long-term release behavior of the waste forms. In the aqueous durability test, both zirconolite glass-ceramic and phase transformation samples exhibited a low leaching rate, with LR Si , LR Zr , and LR La values of approximately 5 × 10−3, 4 × 10−6, and 6 × 10−6 g·m−2·d−1, respectively, after 28 days of leaching. By controlling the cooling process (one-step method), this paper provides useful information on the preparation of zirconolite glass-ceramic. [ABSTRACT FROM AUTHOR]

This paper presents research on the impact of the material microstructure on the performance of Molten Carbonate Fuel Cells (MCFC). The study is motivated by the need to increase the operation time of MCFC stacks. As the MCFC stacks are mainly composed of porous materials, the paper shows the impact of the porosity on both fuel cell performance and degradation rate. The study is based on the mathematical model, validated through experiments with varying microstructure parameters, achieving an overall relative error of 8%. The study evaluated the performance of MCFC using anodes with different porosity and found that increasing anode porosity from 40% to 70% led to a nearly two-fold increase in maximum power density. However, from both the degradation test and polarization curves, the optimal level of porosity for the anode is around 55%. The porosity level at 55% ensures the highest catalytic surface of the electrodes and is a compromise between the mechanical properties of the electrode and its electrochemical properties. • New approach of 0D model of MCFC including materials microstructure influence is proposed. • The new model is prepared in MS Excel and Aspen HYSYS environments. • Experimental investigation for materials with predefined microstructire parameters was performed for model validation. • Variant analysis is presented for different porosity, tortuosity and constrictivity of MCFC anode. • An optimal scenario is suggested based on modleing results. [ABSTRACT FROM AUTHOR]

The paper uncovers microstructural evolution and bonding mechanism of yttrium iron garnet ferrite (YIG) and magnesium titanate ceramic (MTC) brazed by bismuth-based glass ceramic. The resulting mechanical and dielectric properties of the proposed YIG/MTC joint were investigated in detail. The reaction mechanism was thoroughly studied. Micro and nano CoFe 2 O 4 were generated in the glass seam. Besides, a CoFe 2 O 4 reaction layer was formed at the interface of MTC/glass ceramic. The atoms stacked along the plane (220), and a complete coherent boundary was emerged between the CoFe 2 O 4 reaction layer and MTC ceramic subsequently. YBO 3 clusters were formed at YIG/glass interface and Bi 9 Ti 3 Fe 5 O 27 stripe phases were generated in the glass matrix. The joint shear strength increased with the brazing temperature increasing, and reached a maximum value of 72 MPa at 800 °C. The dielectric constant of YIG/MTC joint varied from 16.5 to 17.9, and the dielectric loss tangent was nearly 0.001 at higher frequency. [ABSTRACT FROM AUTHOR]

Ti 3 SiC 2 , as one of the most typical MAX ceramics, has been extensively studied as a potential high-temperature structural material. However, the restrictive relations between strength and toughness of Ti 3 SiC 2 and Ti 3 SiC 2 -based materials have hampered their industrial applications. Herein, we reported the successful fabrication of Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) functionally graded materials (FGM) via hot-press sintering Ti 3 SiC 2 and short C f -derived preceramic papers. The microstructure evolution as well as the effect of sintering temperature on phase composition and interfacial reaction were investigated. Flexural strength and fracture toughness from ambient temperature to 1000 °C of the graded composites were determined to evaluate the mechanical performance. The results have shown that chemical reactions occurred between carbon fibers and Ti 3 SiC 2 matrix, which leads to the formation of SiC interfaces with strong covalent bonds. The newly developed Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) graded composite materials exhibited excellent comprehensive performance as compared to that of monolithic Ti 3 SiC 2. The flexural strength and fracture toughness of the graded composite at room temperature can be reached to 526 MPa and 7.46 MPa m1/2, respectively. However, there is no significant change in flexural strength and fracture toughness from RT to 1000 °C. The fracture micrographs also reveal that fiber breaking、pulling out and debonding are the primary mechanisms that contribute to the superior mechanical properties of composites. The exceptional performance demonstrated in Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) graded materials also makes them attractive choices for a variety of heatproof devices in aerospace sectors. [ABSTRACT FROM AUTHOR]

Due to the problems of low welding efficiency, large heat-affected zone, and poor welding quality in the process of welding thin-walled titanium tubes by argon arc welding, there are few studies on the use of high-frequency induction welding (HFIW) of thin-walled titanium alloy tubes. The evolution law of weld microstructure and mechanical properties of the thin-walled titanium tube needs to be further studied because of rapid welding speed and the small heat-affected zone of HFIW. Therefore, a novel manufacturing method via high-frequency induction welding is proposed in this paper to solve the existing problems. With an industrial-grade titanium TA2 tube (wall's thickness is 0.5 ​mm) as the research object, a comparative study is conducted in this research to examine the morphology, microstructure, microhardness, and tensile characteristics of welded joints at different welding power. The findings demonstrated a significant efficacy of HFIW in resolving these challenges. The mechanical properties and microstructue of heat-affected zone (HAZ) were characterized. The lowest hardness is measured at 202 HV, while the base material was recorded as 184 HV, when the welding speed of HFIW is set at 50 ​m/min. Meanwhile, the heat-affected zone has the highest hardness at 224 HV, a tensile strength of 446.8 ​MPa and a post-fracture elongation of 16%. The results showed that HFIW can not only greatly improve the welding efficiency, significantly improve the microstructure of weld joint and HAZ, and improve the mechanical properties of thin-walled titanium pipe, but also provide a highly feasible welding method for welding ultra-thin-walled pipes. • A novel method of high-frequency induction welding has been employed to achieve the welding of thin-walled pure titanium pipe. • An in-depth analysis of the microstructure of the welded joints was conducted, revealing the robust applicability of the technique. • Through the analysis of the mechanical properties of the welding, the results show that good expectations are obtained. [ABSTRACT FROM AUTHOR]

MgAl 2 O 4 -SiC composites were prepared under flowing nitrogen at 1500 °C by using MgAl 2 O 4 powder, SiC powder, Al powder and Si powder as raw materials. Through microstructural observation and analysis, the effects of in situ Mg-Sialon and β-Sialon with different amounts of Si powder addition were investigated in this paper. The results show that the samples without Si addition main contained MgAl 2 O 4 , SiC and well development plate structure Mg-Sialon phase. After addition of Si powder, not only the above three phases appeared, but also β-Sialon phase appeared. Meanwhile, with increasing Si contents, the content of β-Sialon phase increased and samples were more dense, limiting the development of the plate structure Mg-Sialon phase. With increasing Si content from 0 wt% to 20 wt%, the apparent porosity shows decreased trend, while the bulk density and cold module of rupture show increased. The samples with 20 wt% Si addition can get the minimum apparent porosity (33.5 %), maximum bulk density (2.13 g•cm−3) and cold module of rupture (87.0 MPa). Besides, the formation mechanism of Mg-Sialon and β-Sialon was discussed in detail and the role of Si was elucidated. [ABSTRACT FROM AUTHOR]

In this paper, a series of AlN–Al nanocomposite films are prepared by reactive magnetron sputtering. The effects of N 2 flow rate on the microstructure and mechanical properties of the films are studied. The formation and evolution mechanism of the nanocomposite structure are revealed. The results show that with the decrease of N 2 flow rate, the microstructure goes through three stages: pure AlN, amorphous Al surrounded nanocrystalline AlN and AlN nanoparticle reinforced Al matrix composite. Benefiting from the good wettability of Al on AlN ceramics, the film deposited at 6 sccm N 2 flow rate forms a nanocomposite structure of about 8 nm AlN grains wrapped by 1–2 nm amorphous Al. The hardness of the films increases first and then decreases with the decrease of N 2 flow rate, ranging from 4 GPa to 25 GPa. The toughness of the films is analyzed by the ratio of H/E, H3/E2, the normalized plastic depth (δ H) and the morphology of large load indentation. The results show that the toughness of the nanocomposite film obtained at 6 sccm N 2 flow rate is significantly improved while maintaining the hardness equivalent to that of pure AlN film. The improvement in toughness comes from the microcracks initiated in AlN hindered by the surrounding Al phase. [ABSTRACT FROM AUTHOR]

Calcium-magnesium-alumina-silicate (CMAS) resistance has become a key parameter to evaluate the properties of thermal barrier coating (TBC) materials. The CMAS corrosion behavior of BMT ceramic as a novel candidate material for TBC is poorly understood. In this paper, the solid-state sintering process was used to prepare the BMT bulks, and the evolution of microstructure, phase composition, thermophysical properties, and mechanical properties of the BMT bulks exposed to CMAS corrosion were studied. The results indicate that obvious elemental interdiffusion between the CMAS melt and BMT occurred at 1250 °C, which changed the original phase composition and formed multiple substances including Ba(Al, Ca)Si 2 O 8 , Ba 2 MgSi 2 O 7 , BaTa 2 O 6 , Ba 2 Si 4 O 10 , etc. The microstructure of BMT also underwent changes due to differences in the diffusion coefficients of different elements. As corrosion time prolongs, an obvious porous columnar reaction layer formed on the sample surface, causing the CMAS melt to sustainably corrode the deep BMT, resulting in intragranular corrosion. In terms of properties, the thermophysical and mechanical properties of the BMT bulks corroded by CMAS deteriorated. The thermal conductivity at 1100 °C increased from 1.43 W m−1 · k−1 to 1.67 W m−1 · k−1. The average coefficient of thermal expansion at 200–1400 °C decreased from 11.60 × 10−6 K−1 to 10.95 × 10−6 K−1. The hardness dropped by 21 % compared to the original BMT bulk. Therefore, it is necessary to improve the CMAS resistance of BMT ceramic in future studies. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 -A 3 S 2 (3Al 2 O 3 ·2SiO 2) composites are ideal Casting filter materials with excellent mechanical properties and thermal shock resistance. In this paper, 3Y–ZrO 2 (3 mol% Y 2 O 3 -stabilized ZrO 2) was added to kaolin and α-Al 2 O 3 to prepare ZrO 2 –Al 2 O 3 -A 3 S 2 composites by pressureless sintering. The results showed that when the addition amount of 3Y–ZrO 2 is 15 wt%, the bending strength and fracture toughness of the composites sintered at 1600 °C are 152.51 MPa and 3.52 MPa m1/2, respectively. The bending strength increased to 161.83 MPa after 30 thermal shocks (1100 °C to room temperature), with an increase rate of 6.11 %. The ZrO 2 crystals are evenly distributed between corundum and mullite crystals, effectively preventing abnormal growth of corundum and mullite crystals, and a small number of pores exist in the samples, which could act as a "buffer zone" to prevent the expansion of cracks in the thermal shock, resulting in high mechanical strength and excellent thermal shock resistance for composites. [ABSTRACT FROM AUTHOR]

Developing novel solid oxide fuel cells (SOFCs) with high stability running at low temperatures is an important objective in SOFC science. In the current paper, a comprehensive physics-based microstructure modeling using scanning electron microscope (SEM) image analysis was performed on several anode-support SOFCs operating at low temperatures with high stability. To bridge the gap in the literature regarding an accurate and realistic modeling, a new model was developed based on the variable fuel and air utilization factors and updated microstructure values (e.g., tortuosity, porosity, pore size, grain size). The model accuracy was verified by a thorough point-to-point validation for eight different cells with the configuration of Ni-YSZ (anode), YSZ (electrolyte), and GDC/PNO (cathode). Different temperatures, hydrogen, and air mass flow rates were used, for which an average error of less than 3% in the I-V curves was achieved. The microstructure of the cells, including cathode thickness (15–26 μm), anode-support thickness (350–460 μm), porosity (39 and 43%), grain size (1.1–1.4 μm), and pore radius (0.9–1.1 μm) were varied. Moreover, the effects of the critical operational and design parameters on the overpotential losses and cell performance were studied. The results show that a hydrogen flow rate of 43 sccm was ideal when the cell operated at 0.9 A/cm2 and 700 °C. Moreover, an average anode-support pore radius of 1.75 μm resulted in the best cell performance. It was also concluded that the electrolyte thickness has a higher effect on the cell performance compared to the cathode thickness. • Fabrication and testing of eight anode-supported tublar cells with different microstructures. • Introducing a physics-based microstructure model for SOFC based on variable fuel utilization factor. • Performing a comprehensive SEM image analysis for the fabricated cells. • Achieving an average error of less than 3% for the model compared to the experimental data. • Achieving an average optimum value of 1.75 μm for anode-support pore radius. [ABSTRACT FROM AUTHOR]

Calcium-magnesium-alumina-silicate (CMAS) resistance has become a key parameter to evaluate the properties of thermal barrier coating (TBC) materials. The CMAS corrosion behavior of BMT ceramic as a novel candidate material for TBC is poorly understood. In this paper, the solid-state sintering process was used to prepare the BMT bulks, and the evolution of microstructure, phase composition, thermophysical properties, and mechanical properties of the BMT bulks exposed to CMAS corrosion were studied. The results indicate that obvious elemental interdiffusion between the CMAS melt and BMT occurred at 1250 °C, which changed the original phase composition and formed multiple substances including Ba(Al, Ca)Si 2 O 8 , Ba 2 MgSi 2 O 7 , BaTa 2 O 6 , Ba 2 Si 4 O 10 , etc. The microstructure of BMT also underwent changes due to differences in the diffusion coefficients of different elements. As corrosion time prolongs, an obvious porous columnar reaction layer formed on the sample surface, causing the CMAS melt to sustainably corrode the deep BMT, resulting in intragranular corrosion. In terms of properties, the thermophysical and mechanical properties of the BMT bulks corroded by CMAS deteriorated. The thermal conductivity at 1100 °C increased from 1.43 W m−1 · k−1 to 1.67 W m−1 · k−1. The average coefficient of thermal expansion at 200–1400 °C decreased from 11.60 × 10−6 K−1 to 10.95 × 10−6 K−1. The hardness dropped by 21 % compared to the original BMT bulk. Therefore, it is necessary to improve the CMAS resistance of BMT ceramic in future studies. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 -A 3 S 2 (3Al 2 O 3 ·2SiO 2) composites are ideal Casting filter materials with excellent mechanical properties and thermal shock resistance. In this paper, 3Y–ZrO 2 (3 mol% Y 2 O 3 -stabilized ZrO 2) was added to kaolin and α-Al 2 O 3 to prepare ZrO 2 –Al 2 O 3 -A 3 S 2 composites by pressureless sintering. The results showed that when the addition amount of 3Y–ZrO 2 is 15 wt%, the bending strength and fracture toughness of the composites sintered at 1600 °C are 152.51 MPa and 3.52 MPa m1/2, respectively. The bending strength increased to 161.83 MPa after 30 thermal shocks (1100 °C to room temperature), with an increase rate of 6.11 %. The ZrO 2 crystals are evenly distributed between corundum and mullite crystals, effectively preventing abnormal growth of corundum and mullite crystals, and a small number of pores exist in the samples, which could act as a "buffer zone" to prevent the expansion of cracks in the thermal shock, resulting in high mechanical strength and excellent thermal shock resistance for composites. [ABSTRACT FROM AUTHOR]

Based on the improvement of the phase transition temperature of Ti by Al element and the excellent strengthening effect of TiC particles, this paper selects Ti 2 AlC as the precursor, striving to improve the high-temperature performance of the Ti matrix. The composites with 1–10 vol% Ti 2 AlC addition were fabricated by hot-pressing sintering. And a detailed study was conducted on the reaction process, microstructure, room and high temperature compression properties of the composites. The experimental results show that the separation of Al elements at the A-position occurs at around 700 °C in Ti 2 AlC, and the Al element is homogenized in the matrix during the subsequent sintering process. Micron sized TiC particles are mainly distributed at the Ti grain boundaries, while the content of sub-micron sized TiC particles entering the crystal increases with the increasing Ti 2 AlC addition. The interface mismatch between TiC and Ti is small, and the bonding is well. These microstructures enable composite materials to exhibit excellent mechanical properties, with 10 vol% Ti 2 AlC/Ti composite having a yield strength of 1858 MPa and an ultimate strength of 2200 MPa at room temperature, and maintaining a yield strength of 602 MPa and an ultimate strength of 1264 MPa at 500 °C. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 (ATZ) ceramics are attracting high interest in biomedical applications because of their desirable mechanical performance and biocompatibility. However, strength and toughness are mutually exclusive in structural ceramics. In this paper, based on digital light processing, novel textured ATZ ceramics with obvious crystallographic orientations were fabricated by incorporating Al 2 O 3 platelets with a high aspect ratio and equiaxed particles into the ZrO 2 matrix. The optimized fracture toughness of 16.9 ± 0.8 MPa m1/2 was achieved in the textured ATZ ceramic, which was about 67.3 % higher than non-textured ZrO 2 ceramics, without sacrificing strength. The coupling toughening effects of macrolayer structure, equiaxed and platelet-shaped Al 2 O 3 particles, and ZrO 2 particles were responsible for the enhanced mechanical performance. The macroscale toughening of 3D-printed lamellar architecture led to effective energy dissipation. Additionally, the crack deflection and crack branching induced by dual-morphology Al 2 O 3 particles, accompanied by the phase transformation of the ZrO 2 matrix, were significant microscopic toughening mechanisms. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 (ATZ) ceramics are attracting high interest in biomedical applications because of their desirable mechanical performance and biocompatibility. However, strength and toughness are mutually exclusive in structural ceramics. In this paper, based on digital light processing, novel textured ATZ ceramics with obvious crystallographic orientations were fabricated by incorporating Al 2 O 3 platelets with a high aspect ratio and equiaxed particles into the ZrO 2 matrix. The optimized fracture toughness of 16.9 ± 0.8 MPa m1/2 was achieved in the textured ATZ ceramic, which was about 67.3 % higher than non-textured ZrO 2 ceramics, without sacrificing strength. The coupling toughening effects of macrolayer structure, equiaxed and platelet-shaped Al 2 O 3 particles, and ZrO 2 particles were responsible for the enhanced mechanical performance. The macroscale toughening of 3D-printed lamellar architecture led to effective energy dissipation. Additionally, the crack deflection and crack branching induced by dual-morphology Al 2 O 3 particles, accompanied by the phase transformation of the ZrO 2 matrix, were significant microscopic toughening mechanisms. [ABSTRACT FROM AUTHOR]

The outbreak of the COVID-19 epidemic has led to a large number of waste disposable medical face masks (DMFMs) worldwide, which seriously pollute the environment and threaten human health. In this paper, waste DMFMs were recycled as mask fiber and mixed into self-compacting recycled aggregates concrete (SCRAC) to form a mask fiber reinforced self-compacting recycled aggregates concrete (FRSCRAC). The effects of recycled coarse aggregate (RCA) replacement ratio, DMFM fiber content, and length on the working and mechanical properties of FRSCRAC were investigated. The results show that the specimens meet the requirements of self-compacting concrete (SCC) in terms of working and mechanical performance, but the RCA and DMFM fiber could reduce the workability of the FRSCRAC, and the higher the amount of RCA and DMFM fiber, the more obvious the reduction. At the same time, the mechanical properties of FRSCRAC increased as the decreasing RCA replacement ratio and growing DMFM fiber content. Compared with specimens without DMFM fiber reinforcement, the compressive strength, split tensile strength, flexural strength, and elastic modulus were increased by 1.3%-9.6%, 1.46%-8.6%, 24.4%-54.69%, and 0.65%-4.73%, respectively. Moreover, the reduction of the DMFM fiber length is favorable to the mechanical properties of FRSCRAC as well. Furthermore, the X-ray CT and scanning electron microscope (SEM-EDS) techniques were applied to analyze the microstructure of typical specimens. The results showed that the DMFM fiber and surrounding mortar could form a multiphase composite, which reduces the porosity and improves interfacial stress transfer efficiency, thus enhancing the mechanical properties of FRSCRAC. In addition, based on the experimental results, the mechanical strength index of FRSCRAC and the calculation formula of its mutual conversion relationship were proposed. The research conclusions of this paper can provide a reference for the application of waste DMFM fibers in FRSCRAC. • Waste disposable medical face masks were recycled as fiber and mixed into self-compacting recycled aggregate concrete. • Parameters were investigated to make clear the influential mechanisms of waste fiber on recycled concrete performance. • The mechanical strength index of FRSCRAC and the calculation formula of its mutual conversion relationship were proposed. [ABSTRACT FROM AUTHOR]

Tuning the microstructure of composite energetic materials is an effective way to improve charging, safety, and combustion performance. In this paper, boron (B)/barium chromate (BaCrO 4) composite particles with controllable microstructure were prepared using droplet microfluidic technology (DMT). Based on the theory of droplet template self-assembly, composite particles with controllable morphology, size, and composition were prepared, revealing the regulation mechanism of the particle microstructure. The composite particles prepared using DMT exhibit a uniform distribution of characteristic elements, high circularity, smooth surface, enhanced bulk density, and excellent flow properties. The thermal decomposition characteristics, safety, and combustion properties of the samples were investigated by thermal weight loss, mechanical sensitivity, and combustion tests. Thermal weight loss and mechanical sensitivity tests showed that the samples had stable thermal decomposition properties and significantly increased mechanical stability compared to the control. The combustion test results showed that the DMT-prepared samples had a short ignition response time and significantly improved delay precision. This paper presents a straightforward method for preparing B/BaCrO 4 particles with high delay accuracy, which can serve as a reference for preparing other composites. [Display omitted] [ABSTRACT FROM AUTHOR]

The thermal stability of gun propellants is related to significant safety issues in their development, production, storage, or transportation. Therefore, the study of improving the thermal stability of propellants has urgent and important practical significance. In this work, glycidyl azide polymer (GAP) with a relative molecular weight of 330 was added to the gun propellant to prepare modified NG-NC-RDX gun propellants containing different contents of oligomeric GAP. The ability of the propellant to cause discoloration of methyl violet test paper due to thermal decomposition, as well as the thermal weight loss and adiabatic decomposition behavior of the propellant, were characterized. And the differential charge density of GAP and NG, as well as the free volume and microstructure of GAP/NC and NG/NC blends, were compared, and the mechanism by which GAP improves the thermal stability of the propellant was discussed. When the content of GAP in the propellant changes from 0% to 16%, the time for the methyl violet test paper to change from purple to orange is prolonged from 87 minutes to 98 minutes. The initial decomposition temperature of thermal weight loss increased from 164.7 °C to 176.4 °C. The maximum temperature rise rate during adiabatic decomposition decreased from 0.95 °C·min−1 to 0.12 °C·min−1. According to MS simulation calculations, GAP provides a larger free volume and improves the uniformity of the mesoscopic phase structure of the propellant. The covalent effect of bond C-N 3 in GAP molecules is stronger than that of bond O-NO 2 in NG molecules. The thermal stability of the NG-NC-RDX propellant increases with the addition of GAP, and it increases with the increase of GAP content in the propellant. This work provides a scheme for improving the thermal stability of the gun propellant and offers a way to reduce the risk of thermal stimulation. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the Zn additions combined with a novel severe plastic deformation (SPD) technology, screw twist extrusion (STE), is used to prepare Mg-xZn-1Mn alloys (x=0, 2, 4, 6) with fine grains and high ductility. By observing the microstructures, it is found that a gradient microstructure is obtained perpendicular to the extrusion direction (ED) in all four samples after STE. The STE process introduces twist extrusion strain into the samples, which causes the grain to twist and break, resulting in the weakening of the texture and the refinement of the grain. In addition, MgZn 2 phase is formed by the addition of high Zn, and the combination of MgZn 2 with twist shear strain further promoted dynamic recrystallization (DRX) to refine the grain and obtain the preferred texture, resulting in the increase of fracture elongation (FE). The FE of Mg-6Zn-1Mn sample improved from 18.4% to 27.8%, an 51.1% increase. This is mainly associated with the DRX mechanisms of continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX) and particle simulated nucleation (PSN). Meanwhile, the Schmid factor (SF) of basal slip increased with the addition of Zn, the basal slips in various samples are promoted obviously and FE is further enhanced. Thus, the novel STE technology combining with Zn additions provides an effective approach to improve the ductility of Mg-Zn-Mn alloys. • The ductility of Mg-Zn-Mn alloy is enhanced by Zn addition combined with STE process. • A variety of DRX behaviors have been studied in STEed Mg-χZn-Mn alloys. • The method proposed in this paper to enhance the ductility of Mg-Zn-Mn alloys is a good choice for the application of degradable biomedical devices. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the microstructure of high-viscosity modified asphalt binder (HVA) containing high-content polymers and its effect on fatigue performance, as well as the applicability of different analytical methods and failure criteria of linear amplitude sweep (LAS) test to HVA. In this paper, two types of HVAs with different polymer contents, a commercial HVA, a conventional polymer-modified asphalt binder, and a base asphalt binder were first prepared or selected. Fluorescence microscopy tests, time sweep tests, and LAS fatigue tests were then performed on these binders. Finally, the fatigue properties of the different binders were analyzed in depth using different analytical methods and failure criteria. The results show that the polymers in HVA crosslink with each other to form a strong cross-linking structure, and the phase inversion of the polymers renders them into a continuous phase, which significantly improves the fatigue damage resistance of the HVA; moreover, the evolutions of stress with shear strain for the fatigue process of HVAs is related to the polymer network. Besides, the two-dimensional damage characteristic curve (DCC) cannot accurately reflect the evolution of the fatigue performance of HVA, and this paper suggests the use of a three-dimensional DCC curve with strain information. Furthermore, the 35% reduction in C 0 in the dissipative energy method is not a suitable failure criterion, a more accurate fatigue performance ranking can be obtained by using the yield stress as the failure criterion. Although the fatigue resistance of HVA after yield stress is theoretically considered using the pseudo-strain energy approach, HVA does not show a peak of stored pseudo-strain energy even when the strain is increased to 60% in the LAS test. Therefore, the maximum strain value (30%) in the standard LAS test is not sufficient in characterizing high-polymer HVAs because there is not enough fatigue accumulation of HVAs in this range, consequently, the maximum shear strain parameter in the LAS experiment needs to be reconsidered. • Polymer morphology and its crosslinking networks in HVA with high-content polymers were analyzed. • The fatigue properties of HVAs based on LAS test and different analytical methods are compared. • The fatigue crack length and its evolution of HVA are characterized. • The deficiencies of the LAS test to evaluate the fatigue resistance of HVA and suggestions for modifications are presented. [ABSTRACT FROM AUTHOR]

Strip-casting is a key step among processes for manufacturing the Nd-Fe-B permanent magnets. Current research on the process parameters of the strip casting process mostly relies on the trial-and-error method. In this paper, the influence of the cooling roller speed on the strip-cast Nd-Fe-B flakes is investigated by a combination of simulation and experiment. The microstructures of the strip-cast flakes prepared at different roller speeds are observed and analyzed. The simulation is further performed by using the thermal-fluid coupling method. The temperature field and cooling water flow field of the cooling rollers at different roller speeds are obtained to explain the principle of the microstructural evolution. The temperature field distribution affects the uniformity of the columnar grains on both sides of the strip-cast flake. Higher or lower temperature can also lead to the formation of α-Fe, cluster rare earth (RE) rich phases, or ultra-fine equiaxed grains. An increase in cooling water flow rate is helpful to obtain the columnar grain with even thickness. The simulation results are consistent with the microstructural results. Furthermore, the simulated results and microstructural analyses are combined to indirectly evaluate the trend of magnetic properties of final sintered magnets from the tested strip-cast flakes. By verifying the performance of magnets prepared under the condition of only changing the roller speed during the entire process flow, the measurement results are consistent with the evaluation results, proving that the combined analysis proposed in this paper can reasonably predict the trend of magnetic properties of sintered Nd-Fe-B permanent magnet materials from the strip-cast flakes prepared at different roller speeds. This paper can provide a transferable idea and method for using numerical simulation to assist in the design and production of Nd-Fe-B flakes and sintered magnets. • Formation of the microstructure of Nd-Fe-B strip-cast magnetic flakes was explained. • Effect of roller speed on the microstructure of magnetic flakes was discussed. • Thermal-fluid coupling during strip-casting was adopted to understand heat transfer. • Simulation and microstructure were combined to predict the trend of properties. • A method based on test and simulation was proposed to help the development of magnet. [ABSTRACT FROM AUTHOR]

Mechanical vibration was utilized to enhance the mechanical properties of the WAAM 2319 aluminum alloy and address issues related to coarse grains and porosity in this paper. The research aims to investigate the impact of varying vibration accelerations on the microstructure and mechanical properties of the specimens. The mechanism of solutes transfer caused by vibration has been described in this paper, which significantly improved elongation. The dendrites during growth were broken by vibration, which led to microstructure refinement. The solutes located in the interstices of the dendrites were transferred to the liquid phase by vibration, reducing the concentration of solutes in the interstices of the dendrites. The continuous coarse precipitation phase becomes intermittent and fine; resulting in increased matrix plasticity. With the increase of vibration acceleration, the elongation was significantly enhanced. The longitudinal elongation was enhanced more significantly because of the alternating distribution of INZ and ITZ, with longitudinal elongation showing a 29.3% increase and transverse elongation a 52.5% increase, while the UTS and YS was not changed significantly in the presence of multiple factors. • Mechanical vibration increases the elongation without affecting the UTS and YS. • Mechanical vibration applies reciprocating force to the dendrite, causing the fracture of the dendrite and the refinement of the grain. • Mechanical vibration induces solutes located in the dendrite interstices toliquid phase, reducing the solute concentration in the INZ. • Intermittent precipitation phases and fewer intragranular precipitation phasesin the INZ lead to increased elongation. [ABSTRACT FROM AUTHOR]

To comprehensively utilize the abundant solid wastes of superfine river sand and fly ash, a mixed sand of superfine river sand with coarse manufactured sand and high-flowability concrete made of mixed sand and high-content fly ash were developed. To address the critical question about the long-term strength of this new concrete, this paper presents an experimental study on the long-term development of cubic compressive and tensile strengths of the concrete over a curing age from 7 days to 360 days. In the study, the mixed sand was a hybrid of 40 % superfine river sand and 60 % coarse manufactured sand, and the fly ash content varied from 30 % to 75 % of the total binders by weight. The law of strength development of concrete with fly ash content was analyzed, combined with explanations of the mechanism and observations of hydration exotherms and microstructures of the concrete. Equations were proposed for predicting the long-term development of cubic compressive and tensile strengths, incorporating coefficients to reflect the effects of fly ash on the binder's compressive strength and the development tendency of concrete strength. The validity of the proposed prediction equations was verified against the test results and compared with the extended application of the equation specified in CEB-FIP MC 2010. • Mixed sand of superfine river sand with coarse manufactured sand was developed. • High-flowability concrete made of mixed sand and high-content fly ash was produced. • Long-term strength of the concrete was measured within the curing age of 360 days. • Formulas for predicting strength development were proposed. • Coefficients reflecting the effect of fly ash on strength development were suggested. [ABSTRACT FROM AUTHOR]

To further enhance our understanding of the microstructure of SRM and its intrinsic relationship with macroscopic properties, this paper conducted indoor freeze-thaw cycles, EIS and uniaxial compression tests. The results indicated that the number of freeze-thaw cycles has a significant exponential relationship with R CPP , R CPP 1 and C DSRP. As the number of cycles increased, R CPP and R CPP 1 exhibited a decreasing trend, whereas C DSRP showed an increasing pattern. The freeze-thaw cycles led to the expansion and connection of different pores, resulting in the widening or multiplication of channels in CPP , leading to a decrease in both R CPP and R CPP 1. However, in DSRPP , the liquid-filled pores underwent radial expansion during freeze-thaw cycles, connecting with gas-filled pores around them. This transition led the conductive path to transform into CPP , reducing the accumulated thickness of non-continuous points. Consequently, C DSRP exhibited an increasing trend. Furthermore, the increase in porosity weakened the deformation resistance, increasing the compaction stage of pores and the peak strain, while reducing its peak strength and secant modulus. The peak strength, strain and secant modulus also exhibited significant exponential relationships with different cycles. There was a good exponential correlation between ∆ R CPP of CPP and the uniaxial strength, and the freeze-thaw deterioration model constructed with it as an influence factor could better assess its peak mechanical strength after freezing and thawing. • An electrochemical circuit model for different conductive paths was proposed. • The microstructure was characterized by EIS parameters of the equivalent model. • The influence and mechanism of freeze-thaw cycles on EIS parameters were analyzed. • A degradation model for the uniaxial strength was established with EIS parameters. [ABSTRACT FROM AUTHOR]

The development of fiber-reinforced polymer (FRP) composites, striking a balance between high strength and toughness, is a pressing requirement for the contemporary aerospace industry. Regarding the design of microstructures for enhancing strength and toughness, bionic crossed-lamellar and bouligand structures serve as noteworthy examples. However, individual biomimetic microstructures have approached the upper limit of their strengthening and toughening effects. This paper firstly proposed a "Meta-Biomimetic" design concept : hybridizing biological microstructures with defensive functionalities and those with offensive functionalities in mechanical design, aiming to achieve a metamaterial with both offensive and defensive capabilities. Namely this work retains the three-layer cross-lamellar microstructure of conch shells to stimulate subcritical damage for enhanced energy dissipation, while introducing a bouligand microstructure of lobster homarus americanus to increase the high load-bearing capacity at both tension and compression ends. The optimal design for enhancing the strength and toughness is the three-layer crossed-lamellar microstructure modified with a full bouligand structure, which increases strength and toughness simultaneously by more than 500% compared to natural structures. These studies are poised to not only steer the design of FRP microstructures towards enhanced strength and toughness but also furnish a foundation for interdisciplinary research in biomimetics within composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The effects of overlap rate and defects on the corrosion resistance of laser fusion clad austenitic stainless steel coatings were studied. In this paper, the Ni transition layer and Fe-based coating were sequentially prepared on grey cast iron, and the corrosion morphology and corrosion mechanism of the coating were comprehensively analyzed through physical phase, microstructure and electrochemical tests. The coating phase was mainly γ-Fe, which formed strong selective orientation and texture strength at the (100) crystal plane; overlap ratio and defects affected the recrystallization changes, and the stresses near the defects were high. Increased overlap rate (Fe-based alloy 50 % → 66.7 %) could result in microstructure refinement, reduced corrosion rate v (A8 6.22×10−4 g/m2·h→A9 3.12×10−5 g/m2·h), and improved corrosion resistance. Corrosion cracking extended the crack and embrittled the alloy at the tips of the cracks, so that its (|Z| max 0.67 ∼ 1.31×104 Ω cm2) influence on the corrosion resistance was much higher than that of the pore (|Z| max 5.85 ∼ 10.2×104 Ω cm2). The best corrosion resistance of the process was achieved with an overlap ratio of 66.7 % for both the Ni transition layer and the Fe-based coating. • Different laser overlap cladding manufactured transition layer – Fe-based coating. • Defect characteristics and change mechanisms were analyzed. • Overlap rate and defects on corrosion resistance of coating mechanism were analyzed. [ABSTRACT FROM AUTHOR]

With the development of science and technology, the traditional single nickel-based coatings cannot meet the service needs of industrial parts. In this paper, the directional structure of Ni-based alloy coatings with La 2 O 3 were prepared in order to further improve the corrosion resistance of nickel-based coatings, and the effect of La 2 O 3 on microstructures and corrosion behavior of the directional structure Ni-based coatings were investigated. The results showed that with increase of La 2 O 3 content, the corrosion resistance of the composite coating shows the tendency of first increasing and then decreasing, and the optimum amount of La 2 O 3 is about 1 %. The corrosion potential of Ni60/1%La 2 O 3 composite coating is −0.697 V, which increase 0.057 V compared to −0.754 V of Ni60 coating, and the self-corrosion current density is reduced to 2.776 × 10−6 A/cm2 that is 0.053 times of 5.235 × 10−5 A/cm2 of Ni60 coating, which shows that the addition of 1 %La 2 O 3 effectively improves the corrosion resistance of the coating. • The directional structure coatings of Ni60 and Ni60/La2O3 were prepared, respectively. • La 2 O 3 resulted in the microstructural evolution of directional structure Ni60 coating. • Moderate amount of La 2 O 3 can promote the growth of uniform and dense passivation film. • The corrosion resistance of coatings can be improved by controlling the addition of La 2 O 3. [ABSTRACT FROM AUTHOR]

• Direct ink writing combined with acoustofluidics enhances material control. • Organizing microparticles in flowing multiphase bioink. • Creating patterned and interconnected porous microstructures in 3D scaffolds. • Fibroblasts exhibit patterned distribution following the scaffold's microstructure. Vascular scaffolds with well-organized pore characteristics are crucial for promoting infiltration, adhesion, growth, tissue-specific arrangement, and substance-exchanges of biological cells. However, their controllable fabrication is extremely challenging, especially for those with specially designed three-dimensional (3D) tubular and porous microstructures. In this paper, a new methodology based on acoustofluidics-assisted direct ink writing (DIW) technique is developed to fabricate vascular scaffolds with controlled porosity distributions and well-defined porous microstructures. Calcium carbonate (CaCO 3) particles and alginate are uniformly mixed as the printing ink, which is printed along a rotating rod to form a vessel-like structure. Distributions of these CaCO 3 particles in the printed structure are precisely controlled using bulk acoustic waves. The particles within the vessel-like structure are dissolved in situ using hydrochloric acid, resulting in the formation of 3D vascular scaffolds with intrinsically patterned porous microstructures. The scaffolds printed by the acoustofluidics-assisted DIW method exhibit a 69% improvement in pore connectivity compared to conventional 3D-printed scaffolds. Fibroblast cells are successfully seeded onto these scaffolds, achieving distinctive distributions along the patterned porous microstructures. This innovative methodology, with its excellent microfabrication capabilities, holds great promise for applications in tissue engineering, drug release, composite formation, microfluidic chips, and biosensors. [ABSTRACT FROM AUTHOR]

Utilizing element substitution to enhance the hydrogen storage capabilities of Mg-based alloys represents a promising approach in the quest for efficient energy storage solutions. Thereby, in this paper, Ni is chosen to substitute a portion of Mg in a Ce–Mg-based alloy aimed at improving its hydriding and dehydriding performance. Mg 77+ x Ni 20- x Ce 3 (x = 0, 5, 10, 15) alloys are successfully prepared by the vacuum induction melting method. The structural characterizations of the alloys are performed using X-ray diffraction and scanning electron microscope. The alloys are composed of a primary phase of Mg 2 Ni, lamella eutectic composites of Mg + Mg 2 Ni, and some amount of CeMg 12 and Ce 2 Mg 17. In the as-cast Mg 87 Ni 10 Ce 3 alloy, the Mg 2 Ni phase disappears, transforming into a typical eutectic structure of hundreds of nanometers thick Mg–Mg 2 Ni lamellas. This structure significantly enhances the hydrogen storage kinetics, with a hydrogen absorption capacity of 5.66 wt% at 653 K and a desorption capacity of 5.45 wt% over 2 h at 683 K, outperforming other alloys. Moreover, its peak hydrogen release temperature is significantly lower than that of the Mg 92 Ni 5 Ce 3 alloy. The formation of the CeH 2.29 phase within the alloy acts as a catalyst, effectively improving the exothermic and endothermic kinetics of hydrogen absorption and desorption, resulting in a much lower hydrogen desorption activation energy compared to MgH 2. However, the variation in the activation energy of the alloy remains limited, ranging between 66.6 ∼71.1 kJ/mol. [Display omitted] • Mg 77+ x Ni 20- x Ce 3 (x = 0, 5, 10, 15) alloys were prepared in an induction furnace. • Ni substituting for Mg significantly lowers the peak temperature of hydrogen release. • Ni substituting for Mg reduces the desorption activation energy values. • The Mg 87 Ni 10 Ce 3 alloy can absorb more than 5.66 wt % H 2 within 120 min at 653K. [ABSTRACT FROM AUTHOR]

The Bi 2 Sr 2 CaCu 2 O 8+ x (Bi-2212) material, a high-temperature superconductor, holds significant promise for future high-field applications because of its multifilamentary, twistable production capabilities, coupled with a high upper critical field. Bi-2212 round wire (RW) is made by the powder-in-tube (PIT) technique, and Bi-2212 coils are usually being developed using the wind-and-react method and a high temperature and over-pressure (OP) heat treatment (50 atm, 890℃) is then required to achieve the high current performance. However, over-pressure (OP) heat treatment can lead to a reduction in wire diameter, compromising the stability of the coil structure. Addressing this issue, the pre-overpressure (pre-OP) heat treatment is used and proves effective in mitigating the reduction in Bi-2212 wire diameter. In this paper, to comprehensively investigate the impact of pre-OP heat treatment on the microstructure of Bi-2212 wire, a metallographic analysis of two kinds of Bi-2212 wires was carried out by the scanning electron microscope (SEM) and the ImageJ software. It was found that larger-area filaments experienced a greater reduction in area after pre-OP heat treatment, that pre-OP heat treatment increases the aspect ratio of filaments, and polygonal bundle structure helps maintain filament structure stability during pre-OP heat treatment. Additionally, the impact of pre-OP heat treatment on the performance of Bi-2212 wires was analyzed through critical current testing under high fields. [ABSTRACT FROM AUTHOR]

• Innovative low-temperature impact testing with a gradient setting of pendulum angle was proposed. • Complex relationship between microstructure and impact toughness was elucidated. • Blocky M−A constituents lead to stress concentration and crack initiation. • Coarsening of prior austenite grains diminishes hindering effect on crack propagation. As the most brittle areas of welded S690QL high-strength steel structures, coarse-grained heat-affected zone (CGHAZ) was crucial for the structural integrity of components. This paper designed an innovative low-temperature impact testing method with a gradient setting of pendulum angle to investigate the micro-mechanism of crack initiation and propagation in the CGHAZ of S690QL welded joints. The results reveal that continuous blocky M−A constituents were distributed along prior austenite grain boundaries (PAGBs), leading to stress concentration and crack initiation. During low-temperature impact processes, cracks propagate in a transgranular mode along {1 0 0} or {1 1 0} crystal planes. Due to the interaction between compressive stress and the crack tip, regions with high kernel average misorientation (KAM) such as PAGBs can divert the crack. The coarsening of prior austenite grains in the CGHAZ leads to a diminished hindering effect of PAGBs on crack propagation. The findings elucidate the complex relationship between microstructure and impact toughness of CGHAZ, providing insights into crack behavior and mechanisms in CGHAZ. [ABSTRACT FROM AUTHOR]

• Multi-layer multi-track laser cladding can eliminate the martensite structure. • Multi-layer multi-track laser cladding without additional thermal treatment equipment. • Tempering sorbite does not cause cracks in the heat affected zone. • The hardness of tempered sorbite meets the requirements of rail use. This paper studied the macroscopic morphology and properties of the heat affected zone (HAZ) in multi-layer multi-track cladding layers on rail. The results showed that in the two-layer laser cladding, there are martensitic structures and cracks in the HAZ. With the increase of the number of laser cladding layers, the tempering structure in the HAZ expands gradually from the bottom to the top, from the middle to the edge, and no cracks appear in the HAZ. At ten-layer laser cladding, the martensitic structure has been completely eliminated and transformed into tempered sorbite. Finally, the hardness test shows that the hardness of cladding layer, HAZ and substrate are basically the same, which meets the performance requirements of rail repair. [ABSTRACT FROM AUTHOR]

In this paper, a new type of diamond/Cu composite with diamond bars inserted in the normal direction is designed and prepared by vacuum brazing. In order to reduce the negative effect of the low thermal conductivity of Cu-Sn-Ti solder, diamond particles were added into the solder area. The microstructure, thermal conductivity, and heat dissipation performance of the diamond/Cu composite under water-free and water-cooling conditions were studied and compared. Besides, the heat dissipation mechanism of the composite was explored through finite element analysis. The results show that the diamond bars and diamond particles can be connected well by the CuSnTi solder, and the diamond particles scatter in the solder area. The TC tests show that the sample with 2000 mesh diamond particles has the highest TC (515.25 W/(m·K)). Besides, both the heating experiments on the electronic heating platform and the actual heat dissipation performance under water-cooling conditions affirm the excellent heat dissipation effect of the composite with 2000 mesh diamond particles. In conclusion, the diamond/Cu composite with diamond bars inserted vertically possess an excellent structural design, which is promising in heat dissipation material for electronic devices. • Diamond/Cu composite with diamond bars inserted vertically were obtained. • Diamond particles were added to enhance the thermal conductivity of Cu-Sn-Ti solder. • Diamond bars acts as highly efficient heat conduction channels. • Thermal conductivity of 22.58 vol% diamond/Cu composite reaches 515.25 W/(m⋅K). [ABSTRACT FROM AUTHOR]

[Display omitted] • Deposited HEFs showed a higher capacity for HAp formation and bioactivity. • Low working pressure yielded a dense and compact structure with no cracks. • Ti content disparity occurred due to its lower atomic weight during sputtering. • In the dense microstructure, oxygen diffusion through the depth has been minimized. • HEA-1500-Ar25-P0.5 caused robust protection lowering Ni ion release in AS and SBF. This paper presents the experimental findings on the effect of deposition conditions on the microstructure of the corrosion-resistant TiTaNbZrMo high entropy alloy (HEA) thin films deposited on NiTi substrates with the purpose of enhancing biocompatibility of the NiTi shape memory alloy (SMA). For this purpose, RF magnetron sputtering was employed to fabricate TiTaNbZrMo HEA films with 750 nm and 1500 nm thicknesses. Static immersion experiments were conducted in simulated body fluid (SBF) and artificial saliva (AS) solutions for 1, 14, and 28 days to establish the relationship between Ni ion release and deposition parameters. The results revealed that thin films grown under low working pressure exhibited crystalline body-centered cubic (BCC) microstructure with a highly dense, compact, and crack-free structure, while those deposited under high-pressure conditions exhibited an amorphous structure with inherent cracks. The biocorrosion test results indicated that the dense and compact thin film fulfilled the expected corrosion resistance requirements for prolonged utility in human body. Moreover, the HEA films revealed an outstanding amount of hydroxyapatite (HAp) formation, indicating remarkable bioactivity and favorable bone-bonding capabilities. The findings suggest that the HEA films deposited under low working pressures could constitute promising alternatives to conventional coatings on NiTi SMAs. [ABSTRACT FROM AUTHOR]

The use of supplementary cementitious materials (SCMs) is an effective way to reduce CO 2 emissions within the cement industry. In this paper, the Cement-Metakaolin (MK)-Sugarcane Bagasse ash (SCBA) ternary composite was designed based on the simplex centroid design method. The influence of MK and SCBA on mechanical properties of ternary composite was investigated. In addition, the hydration products and microstructure of ternary composite were analyzed by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), low-field nuclear magnetic resonance (LF-NMR). At the same time, the life cycle assessment (LCA) method was used to quantitatively analyze the environmental impact and economic cost of the ternary composite system. A multi-performance indicator was used to optimize the mix ratio of the ternary composite based on the simplex centroid design method, and it was concluded that the Cement: MK: SCBA ratio was 75%: 20%: 5% (by weight) to achieve the optimal synergistic effect. The findings of this study can offer a design methodology that considers both performance and environmental factors, while also providing a theoretical foundation for the utilization of SCBA in cement-based materials. • The proportion design of Cement-MK-SCBA cementitious material was carried out by using the simplex-centroid design method. • The macroscopic mechanical properties and hydration reaction of Cement-MK-SCBA ternary composites were analyzed. • The life cycle assessment (LCA) method was used to consider the CO 2 emissions and economic benefits of MK and SCBA. • The synergistic effect of both SCBA and MK can achieve the performance of cement gel and reduce the economic cost. [ABSTRACT FROM AUTHOR]

[Display omitted] • A physics-based approach is utilized to develop a new hybrid heat source model. • The model analyzes the thermal condition of a melt pool solidification. • Modeled Thermal variables are used to predict melt pool geometry and microstructure. Among metal Additive Manufacturing (AM) methods, Laser Powder-bed Fusion (LPBF), is a proven fabrication method to produce complex-shaped parts with tailored properties. To achieve the desired properties, proper LPBF modelling facilitates the understanding of the correlation between input process parameters and output microstructure. In this paper, a numerical heat transfer modelling with a novel hybrid volumetric heat source has been proposed to simulate the LPBF of metastable beta titanium alloy (Ti-5553). The developed hybrid model provides a reliable estimation of temperature distribution and thermal variables (e.g., temperature gradient G and solidification rate R), for any location of the melt pools, during solidification. For the process parameters which provide conduction melting mode, the simulated results agree well with experimentally measured melt pool dimensions where the verified model can also predict grain morphology, grain growth direction, and dendrite size. An in-depth analysis of predicted G/R values at the solidification front reveals that the center of the melt pool has a higher preference for equiaxed grain structure formation, while columnar grains are always dominant at melt pool boundaries. In addition, the scanning speed parameter was found to have a stronger influence on thermal conditions compared to laser power. [ABSTRACT FROM AUTHOR]

• Review numerical simulation applications in selective laser melting of aluminum alloy. • The physical process of laser-material interaction is reviewed. • Review and discuss simulations of different problem scales and physical phenomena, including thermodynamic processes, microstructure evolution, and mechanical properties analysis. • A guideline for process-structure-performance modeling and simulation technique for particular problems. • Suggestions for future studies, especially the application of data-driven approaches in numerical simulation. Selective laser melting (SLM) has found extensive applications in the realm of metal printing as an additive manufacturing technique. The performance of metals fundamentally dictates their industrial utility. Aluminum alloys, the second most utilized alloy following steels, have extensive applications in aerospace, automotive components, biomedicine, etc. Among these alloys, AlSi10Mg stands out as one of the most extensively researched aluminum alloys in SLM. Nevertheless, conducting experimental trials with varying materials and process parameters proves not only to be expensive but also time-consuming. Numerical simulations have emerged as viable solutions to address this challenge. Consequently, in order to more successfully conquer this challenge, based on the solidification theory, this paper provides an exposition on the formation process of SLM and metallurgical defects. It comprehensively reviews the current state of numerical simulations for SLM formed AlSi10Mg, addressing three crucial aspects: heat and mass transfer processes, microstructure evolution, and mechanical properties. These discussions are structured around different problem scales and physical phenomena, encompassing thermodynamic process numerical simulations (based on high-fidelity heat analysis models at the powder scale and heat conduction models relying on the continuum assumption), microstructure evolution prediction simulations (utilizing phase field methods and cellular automaton approaches), and mechanical performance analysis simulations (encompassing models that do not consider any defects, those that consider defects, and those that factor in underlying grain structures). The applicability and distinct characteristics of each model are analyzed, followed by an exploration of the process-structure-performance relationship modeling. On this basis, the challenges and trends facing numerical simulation of SLM formed AlSi10Mg are summarized, especially the application of data-driven in numerical simulation. [ABSTRACT FROM AUTHOR]

Spheroidal graphite cast irons (SGCIs) have been commonly used in automotive and energy sectors where superior mechanical strength and wear resistance are required. This paper investigated the performance of the SGCIs under severe wear conditions as a function of Ti content and cooling rate. SGCIs alloyed with various Ti content (0, 0.1, 0.2, 0.3, and 0.5 wt%) were produced by green sand-casting process in different section sizes (10, 30, and 50 mm). Ball-on-disk type wear equipment with an Al 2 O 3 ball was used to determine the wear rates of the SGCI samples. With increasing Ti content, up to 45% of nodular graphite turned into vermicular graphite, depending on the Ti addition and section sizes. Carbide precipitation was observed in the matrix due to the carbide-forming effect of Ti. The hardness and wear resistance of the SGCIs were improved by adding Ti owing to the combined effects of increasing pearlite and TiC particles precipitated in the matrix. Thinner-wall castings provided a faster cooling rate, which improved hardness and wear resistance. Alloying with 0.5 wt% Ti decreased the wear rates up to 35%. • Increasing Ti changed graphite morphology from nodular to vermicular. • Ti addition increased hardness by solid-solution hardening and TiC formation. • Increasing Ti content and cooling rate provided a decrease in wear rates. • Ti-alloyed SGCIs predominantly suffered from abrasion and adhesion. • The highest wear resistance was achieved in 0.5 wt% Ti at 10 mm wall thickness. [ABSTRACT FROM AUTHOR]

• Cyclic deformation behaviors of distinct heat-treated 42CrMo steels were studied. • Isothermal annealed and annealed 42CrMo steels roughly present cyclic stabilizing features. • Tempered and normalized steels exhibit cyclic softening behaviors. • The dramatic increases in dislocation density, substructures and grain refinement induce cyclic stabilizing. • Dislocation cells and slips through cutting precipitates promote cyclic softening and ratchetting. The aim of this paper is to investigate the cyclic deformation behaviors and microstructure evolution mechanisms of 42CrMo steels (which were machined mechanically from the M42 bolt) with various microstructures obtained under four different heat-treatments, i.e., isothermal annealing, annealing, high-temperature tempering and normalizing treatments. Cyclic stress–strain response curves were measured at the uniaxial constant stress- and strain-controlled cyclic loading with positive mean stress/strain. The tested results show that ratchetting can be induced under cyclic loading with positive non-zero mean stress, causing severer fatigue damage. Moreover, it is found that isothermal annealed and annealed 42CrMo steels roughly show cyclic stabilizing features, but tempered and normalized cases present remarkable cyclic softening characteristics. Compared to the formers, the latter two exhibit serious ratchetting and cyclic deformation evolution, which quickens fatigue fracture. Additionally, the microstructure analyses reveal that cyclic stabilizing behavior is mainly related to the dramatic increases in cross-slip dislocation density, substructures, grain refinement and plastic strain. And, cyclic softening behavior is highly correlated with the dislocation development from low-density patterns (i.e., dislocation lines and tangles) to high-density modes (i.e., dislocation cells), as well as dislocation slip through cutting the precipitates. Therefore, we can conclude that cyclic stabilizing/softening features play significant roles in cyclic deformation behavior i.e., ratchetting of 42CrMo steels based on the different microstructure evolution mechanisms, which should be carefully taken into account for optimizing fatigue properties by considering these factors. [ABSTRACT FROM AUTHOR]

• The failure analysis of 6 welded joints with cracks excavated on site in a gas transmission company was carried out. • The relationship between root welding, weld microstructure and crack generation was clarified. • The influence mechanism of grain boundary distribution and inclusions on crack propagation path in weld microstructure was revealed. The girth weld is the weak link of high-pressure pipeline, which is easy to crack under the combined action of internal and external loads, defect and stress concentration. At present, the safety hazards of high-strength pipeline girth welds are prominent, and it is of great significance to study the failure law of girth welds to ensure the safe operation of pipelines. In this paper, the failure analysis of 6 welded joints with crack defects excavated on site in a gas transmission company was carried out. Through metallographic analysis, scanning electron microscope (SEM) observation and electron backscatter diffraction (EBSD) analysis, the relationship between root welding, weld microstructure and crack generation was analyzed in detail. The influence of grain boundary distribution behavior of weld microstructure on crack propagation path was studied, and the mechanism of welding inclusions on crack propagation and aggregation nucleation was revealed. The results show that the cracks in root welding, hot welding, filling welding and heat affected zone are all transgranular propagation types, and the deflection of crack propagation path may be related to the complex stress state at the welded joint. Local strain concentration often exists in the near crack surface, secondary crack and crack deflection position on the crack propagation path, which indicates that the formation and propagation of root cracks are likely to be related to the deterioration of weld metal properties caused by local strain concentration at the root. The research conclusions have certain reference value for the intrinsic safety design, construction, and integrity operation and maintenance of pipeline girth welds. [ABSTRACT FROM AUTHOR]

In this paper, gallium was used as alloying element to improve hydrogen storage properties of magnesium. Therefore, Mg– x wt% Ga (x = 5, 10, 25, 50) binary alloys were prepared by induction melting method. The microstructure and phase composition of Mg–Ga alloy were analyzed using X-ray diffractometer and scanning electron microscope. The results show that Mg–Ga binary alloys consist of Mg and Mg 5 Ga 2 phases. The Mg and Mg 5 Ga 2 react with H 2 to form Mg 2 Ga and MgH 2 during hydrogenation process. The hydrogen storage kinetics and thermodynamic properties of the alloys were tested using a Sieverts-type apparatus. It is found that the dehydrogenation rates of the samples increase with increasing gallium content, and they are all better than pure magnesium. Thermal analysis results indicate that increasing gallium content decreases dehydrogenation temperature of Mg–Ga alloy. The beneficial effects of adding gallium in magnesium is that interfaces and secondary phase resulted from alloying can promote the hydrogen desorption process of the alloy. The Mg–50 wt% Ga alloy has the lowest dehydrogenation activation energy. However, increasing gallium content inevitably reduces the hydrogen storage capacity of the Mg–Ga alloys. Furthermore, alloying with gallium does not change the thermomechanical properties of magnesium. [Display omitted] • Hydrogenation leads to the formation of Mg 2 Ga and MgH 2 in Mg–Ga alloy ingot powder. • Alloying Mg and Ga significantly reduces the hydrogen desorption temperature of MgH 2. • The hydrogen release kinetics of MgH 2 is greatly improved by increasing Ga content. • The dehydrogenation activation energy of the alloy decreases by increasing Ga content. • The E a of Mg–50 wt% Ga alloy is 116 kJ mol−1, which is 47 kJ mol−1 lower than MgH 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new out-of-plane ordered double-transition-metal MAX phase, Mo 2 VAlC 2 , was experimentally synthesized. • The significant chemically ordering behavior of Mo and V occupying the outer and inner M layers, respectively, was confirmed. • The derivative Mo 2 VC 2 MXene was realized by etching the Al layer of Mo 2 VAlC 2. Herein we demonstrate the synthesis of a new out-of-plane ordered double-transition-metal MAX phase known as Mo 2 VAlC 2. Annealing the elemental powder mixture at 1540 °C with 2.0Mo: 1.0 V: 1.3Al: 1.8C results in a high yield of 91.2 wt% for Mo 2 VAlC 2. The crystal structure of Mo 2 VAlC 2 is determined using Rietveld refinement of powder XRD, and which crystalizes into a hexagonal lattice structure with space group P6 3 /mmc. Employing the double spherical aberration corrected transmission electron microscopy, we confirm its chemically ordering behavior of one V layer sandwiched between two Mo layers. Additionally, its two-dimensional derivative Mo 2 VC 2 T x MXene has been successfully realized by etching the Al layer of Mo 2 VAlC 2 with hydrofluoric acid. The chemical composition and microstructure of Mo 2 VC 2 T x are inspected with SEM and EDX. The resulting multilayer and intercalated Mo 2 VC 2 T x exhibit the characteristic accordion-like and paper-like appearances, respectively. This work further expands the diversity of chemically ordered double-transition-metal MAX and MXene families. [ABSTRACT FROM AUTHOR]