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304 stainless steel demonstrates a low thermal conductivity and work hardening characteristics, resulting in its processing, and will adhere to the tip of the tool; as well as the phenomenon of chipping, shortening the life of the tool. AlTiN coatings are representative of coatings applied to carbide tools. In this paper, AlTiN coatings with different arc current processes were deposited on carbide milling inserts using arc ion plating. The microstructure, mechanical properties, and milling properties of the coatings were investigated by using the SEM, EDS, XRD, scratch meter, friction and wear meter, and vertical machining center. The findings revealed that all coatings displayed columnar crystal growth, free from cracks and voids. With an increasing arc current, there was a notable increase in surface droplets, pits, and coating thickness. The coating deposited at a 140 A arc current showed a pronounced (200) orientation preference. The adhesion force peaked at 56.0 N with a subsequent decline, and the friction coefficient hit its lowest point of 0.429 at 140 A, contrasting with its highest value of 0.55 at 160 A. After 39 min of dry milling, the tool with a 140 A AlTiN coating exhibited minimal wear of 0.196 mm, just below the 0.2 mm failure threshold, indicating superior performance at this arc current setting. [ABSTRACT FROM AUTHOR]

2195 aluminum–lithium (Al–Li) and 2XXX series aluminum alloys are joined using resistance spot welding for the first time. The macrostructure, microstructure, element distribution, microhardness, and tensile‐shear property of spot‐welded joints are investigated. The microstructure of the fusion zone of 2195/2195, 2195/2219, and 2195/2A14 joints is fine equiaxed spherical grains. It is found that solute segregation of Cu occurs in the grain boundaries in the fusion zone, forming Al2Cu. The microhardness shows that due to the dissolution of strengthening phase T1, the hardness of the fusion zone of the three types of joints is lower than that of the base material. The 2195/2195 joint has the best mechanical performance among the three combinations, with maximum tensile‐shear force and absorbed energy reaching 16893.7 N and 24.9 J, respectively. The fracture surfaces of all three types of joints exhibit mixed ductile‐brittle characteristics. [ABSTRACT FROM AUTHOR]

Due to the inhomogeneity and anisotropy of mine rock bodies, ionic rare earth ore bodies exhibit varying pore structures at different depths. This research focuses on an ionic rare earth mine in Fujian Province, where in situ ore samples rather than remodeled soil samples were studied. Samples from the fully weathered layer at depths of 1 m, 12 m, and 21 m, both before and after leaching, were collected for onsite analysis. Microscopic pore characteristics were evaluated using scanning electron microscopy, and digital image processing was utilized to study the evolution of the pore scale, distribution, and shape in rare earth ore samples at various depths pre- and post-leaching. The results indicate an increase in the ore body's porosity with the depth of the ore samples both before and after leaching. The variation in pore scale is predominantly dictated by the ratio of macropore and large pores. Pre-leaching, the middle ore sample showcased the highest uniformity, with the upper part being the most irregular. Post-leaching, the highest uniformity was observed in the lower ore samples, with the upper part remaining irregular. Pre-leaching, as depth increased, the pore distribution in ore samples became more dispersed, with decreasing orderliness. Post-leaching, the orderliness was most improved in upper ore samples, while middle ore samples became the least orderly. Additionally, before leaching, pore-shape roughness increased with depth; after leaching, the pore shape became more rounded as depth increased, simplifying the pore-shape structure of the ore samples both before and after leaching. [ABSTRACT FROM AUTHOR]

To improve the bonding strength of precision adhesive joints, mechanical and electrochemical surface treatments were combined to modify the original bonding surfaces. Microgrooves with different aspect ratios were manufactured on aluminum-alloy surfaces and phosphoric acid anodizing (PAA) was then applied to the surfaces. Wettability, shear strength, and fracture morphology were tested and analyzed. PAA treatment could change the original flat surface to be hydrophilic, and microgrooves could further enhance these characteristics. Compared with the original flat surface, the shear strength of the micro-structured surfaces without PAA treatment increased by 8.54% at an aspect ratio of 0.02, but decreased by 0.22% and 1.90% as the aspect ratio increased to 0.04 and 0.08, respectively. The shear strength of the flat surface only treated by PAA increased by 22.88%, while combining microgrooves could further improve the shear strength by 38.17%, 39.09%, and 42.24% at aspect ratios of 0.02, 0.04, and 0.08, respectively. Fracture morphology analysis and observation of interfacial wetting indicated that manufacturing microgrooves and applying PAA treatment on the aluminum-alloy surfaces could eliminate many tiny interface failures and greatly increase the effective bonding area, which significantly improved the shear strength. [ABSTRACT FROM AUTHOR]

Lead‐free polycrystalline manganese telluride holds great potential in the development of waste heat recovery due to its fascinating physical properties. However, the poor thermoelectric (TE) performance in the p‐type MnTe alloys always results from their inferior carrier concentration, leading to low power factor and high thermal conductivity which restrict the overall thermoelectric performance. In this work, the problem is solved by decoupling its electrical and thermal transports through the hole donor Ge‐deficiency in MnTe + x mol.% GeTe (0 ≤ x ≤ 4) compounds. Intrinsically, extra GeTe in MnTe + x mol.% GeTe compound offers free charge carriers due to a narrow bandgap comparatively, realizing not only a full assessment of stimulated electrical performance but also an enhanced power factor. Moreover, benefiting from the nano‐precipitates and tweed microstructures, the lattice thermal conductivity effectively reduces due to the intensive phonon scattering accordingly. Ultimately, a maximum ZT of ≈1.2 at 873 K in the 3 mol.% GeTe doped MnTe sample is realized. [ABSTRACT FROM AUTHOR]

In this work, the tungsten‐copper composites were fabricated by binder jet 3D printing technology. The effects of different printing layer thicknesses (50 μm to 100 μm) on the green density and green strength were investigated. Then, under the optimal layer thickness, the effects of different sintering temperatures (1300 °C to 1600 °C) on the microstructure and densification of tungsten‐40 wt.–% copper composites were studied. The experimental results showed that when the printing layer thickness was set as a lower value (50 μm), the tungsten‐40 wt.–% copper green part had the best strength and its density reached a maximum value of 60.73 %. After sintering for green parts printed with 50 μm layer thickness, the relative density, thermal conductivity and electrical conductivity of sintered parts first increased and then decreased with increasing sintering temperature. In our experiments, the tungsten‐40 wt.–% copper sample fabricated by binder jet 3D printing with a printing layer thickness of 50 μm under a sintering temperature of 1500 °C displayed the best properties, in which the relative density, thermal conductivity and electrical conductivity were 97.04 %, 228 W⋅m−1⋅K−1 and 46.5 % IACS, respectively. [ABSTRACT FROM AUTHOR]

Aluminum alloy adhesive bonding joint widely appears in many industrial products. Improving the mechanical performances of aluminum alloy bonding joints has been attracting much effort. To acquire more excellent bonding strength, this paper focused on the effects of different surface treatments, including laser ablation and milling superposed by phosphoric acid anodizing (PAA). The treated surfaces were characterized by roughness and contact angle, and the effects of the geometric parameters of microstructures on wettability, failure mode, and shear strength were examined. The results indicate that those surfaces where the spacing is smaller than the diameter present a hydrophilic property and the corresponding specimens are mainly subject to cohesive failure, and vice versa. Additionally, laser ablation with a properly designed dimple pattern can greatly improve the bonding strength, and the maximum average shear strength of specimens with a thickness of 50 μm reaches 32.82 MPa, which is an increase of 28.15% compared with the original milling specimen. Moreover, fabricating groove or grid patterns on the surfaces and applying PAA treatment can also significantly enhance the bonding strength, reaching up to 36.28 MPa.

In the present work, microalloying is put forward to improve the microstructure and tensile properties of A356.2-0.15Fe (wt.%) alloy by the co-addition of trace Mn and Mg. A suitable Mn/Fe mass ratio of 0.5 is obtained for alloys with 0.15Fe. The yield strength, ultimate tensile strength, and elongation of the A356.2-0.15Fe alloy with an Mn/Fe ratio of 0.5 and containing 0.42 wt.% Mg is 179 MPa, 286 MPa, and 9.1%, respectively, which is acceptable for automotive wheel hub applications. Optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and electron-probe microanalyzer (EPMA) methods are used to characterize the microstructure of the alloys. The results indicate that Mn addition promotes the transformation of the acicular β-Al5FeSi phase to the block-shaped α-Al(Fe, Mn)Si phase. The ratio of length/width of the Fe-rich phase in the alloy is reduced by 78.8% with an Mn/Fe ratio of 0.5 and containing 0.35 wt.% Mg, compared with that of the alloy without Mn addition and containing 0.35 wt.% Mg. The addition of Mg reduces the secondary dendrite arm spacing (SDAS) from 26.1 μm to 20.9 μm. The volume fraction of the precipitated Mg2Si phase in the alloy containing 0.42 wt.% Mg increases by 60% compared with that in the alloy containing 0.35 wt.% Mg. The morphology transformation of the Fe-rich phase, the reduction of SDAS, and the increase in volume fraction of precipitated Mg2Si phase comprehensively contribute to the improvement of A356.2-0.15Fe alloy. The microstructure evolution mechanism and the effect of microstructure on tensile properties are analyzed and discussed.

The hot compression of rolled 7075 alloys with different heat treatments was performed. The temperature ranged from 200 to 400 °C, and the strain rate was 0.01 s−1. The stress level decreases with the increasing temperature during compression, and the strength of the alloy in the original condition is higher than that of solution-treated (ST) alloy at the same deformation condition. The alloys with different heat treatments exhibit different anisotropic behaviors at 200 °C; the anisotropy for the alloys in both conditions becomes weaker with increasing temperature. Then, the corresponding microstructure was studied. The alloy’s microstructure in its original condition consists of fiber grains; however, many equiaxed grains are found after solution treatment due to the recrystallization. The grains with different shapes lead to different anisotropic mechanical properties. For the alloys in both conditions, the density of the dislocation decreases with increasing temperature during compression, and a certain number of subgrains were found when deformed at 400 °C due to the higher driving force and a higher rate of atomic migration. Meanwhile, it is observed that the precipitates of the alloy become coarser during higher-temperature deformation. Dynamic softening is dominant in high-temperature deformation, decreasing stress during hot deformation.

In this study, Ti-48Al-3Nb-1.5Ta powders were manufactured from cast bars by the supreme-speed plasma rotating electrode process (SS-PREP) and used to prepare hot isostatically pressed (HIPed) material at 1050–1260 °C with 150 MPa for 4 h. The phase, microstructure and mechanical performance were analyzed by XRD, SEM, electrical universal material testing machine and other methods. The results revealed that the phase constitution changed from γ phase to α2 phase and then to γ phase with the material changing from as-cast to powders and then to as-HIPed. Compared with the as-cast material, the grain size and element segregation were significantly reduced for both powders and as-HIPed. When the hot isostatic pressing (HIP) temperature was low, the genetic characteristics of the powder microstructure were evident. With the HIP temperature increasing, the homogeneity of the composition and microstructure increased, and the prior particle boundaries (PPBs) gradually disappeared. The elastic moduli of powder and as-HIPed were superior to those of as-cast, which increased with the HIP temperature increasing. The hardness of as-HIPed was lower than that of the powder. The compressive strength, compressive strain, bending strength, and tensile strength of as-HIPed were higher than those of as-cast. With an increase in the HIP temperature, the compressive strength decreased gradually, and the compressive strain first decreased and then increased.

The titanium/aluminum composite materials overcome the limitations of single metal materials and achieve lightweight, high-strength, and corrosion-resistant properties. However, there have been no reports on explosion-welded composites of titanium alloys and seven-series aluminum alloys. Therefore, TA1/Al1060/Al7075 explosion-welded plates with three different explosive thicknesses were successfully prepared using Al1060 as the transition layer. The SPH-FEM coupled algorithm was employed to analyze the detonation process in detail and predict the interface under different explosive thicknesses. The results showed that during the explosion welding process, the high temperature, pressure, and high-speed impact resulted in significant plastic deformation and jetting phenomena at the bonding interface, which were in good agreement with the experimental observations. With the increase in explosive thickness, the TA1/Al1060 bonding interface exhibited a flat shape, while the Al1060/Al7075 interface transitioned from a flat to a wavy morphology. Moreover, the crack, vortex, and TiAl3 were observed at the interface. Mechanical testing results revealed that the composite plate with a 35 mm explosive thickness exhibited the best tensile, shear, and bending performance, indicating the optimal process parameter. This study provides significant support and reference for the application of explosion welding technology in titanium alloys and seven-series aluminum alloy composite materials.

The effects of Fe, Cr and thermal exposure on the microstructure and mechanical properties of Al-Si alloy were investigated in this work. The results indicated that the main phases of the Al-Si-Cu-Ni-Mg-(0.6–0.9%) Fe (wt. %) alloy were α-Al, Si, Al5Cu2Mg8Si6, Al3CuNi, Al7Cu4Ni, Al2Cu, and AlFeSi at room temperature. The size of the AlSiFe phase increased with increasing the weight fraction of Fe. The shape of Fe-rich phase changed from rod-like to star-like, followed by long needle-like with Fe varying from 0.6% to 0.9%. The mechanical properties of the studied alloys at elevated temperatures increased with Fe. The ultimate tensile strength of the three alloys at 350 °C was 111.2 MPa, 124 MPa, and 128.7 MPa, respectively. In addition, the ductility and strength of the studied alloys at room temperature decreased with increasing the Fe, due to the large size of the hard and brittle Fe-rich phase strictly cleaved the aluminum matrix. After thermal exposure, the properties of the alloy at room temperature and elevated temperature decreased obviously at the beginning of 0.5~8 h, and then tend to be stabilized during thermal exposure at 350 °C for approximately 32~64 h. Fe-rich was a thermal stable phase at 350 °C.

Mg77+xNi20−xLa3 (x = 0, 5, 10, 15) alloys were successfully prepared by the vacuum induction melting method. The structural characterizations of the alloys were performed by using X-ray diffraction and scanning electron microscope. The effects of nickel content on the microstructure and hydrogen storage kinetic of the as-cast alloys were investigated. The results showed that the alloys are composed of a primary phase of Mg2Ni, lamella eutectic composites of Mg + Mg2Ni, and some amount of LaMg12 and La2Mg17. Nickel addition significantly improved the hydrogen-absorption kinetic performance of the alloy. At 683 K, Mg77Ni20La3 alloy and Mg82Ni15La3 alloy underwent hydrogen absorption and desorption reactions for 2 h, respectively, and their hydrogen absorption and desorption capacities were 4.16 wt.% and 4.1 wt.%, and 4.92 wt.% and 4.69 wt.%, respectively. Using the Kissinger equation, it was calculated that the activation energy values of Mg77Ni20La3, Mg82Ni15La3, Mg87Ni10La3 and Mg92Ni5La3 alloys were in the range of 68.5~75.2 kJ/mol, much lower than 150~160 kJ/mol of MgH2.

As the second most significant metal following steel, aluminum plays a vital role in the advancement of both strategic emerging industries and national economic development. The existing oil and gas drilling data indicate that the deep bauxite deposits is abundant around the Ordos Basin in China, at the depths ranging from several hundred meters to several kilometers. Based on the geological and hydrogeological characteristics analysis, it is found that deep bauxite deposits in the basin have distinct electrical characteristics, characterized by four highs and two lows. While there is scarcity of prior research on the exploration topic for the technique limitation. In this paper, a logging interpretation model has been developed, which allows the evaluation of bauxite deposits. An efficient technology was proposed for deep bauxite exploration, utilizing an in-situ leaching mining technique. This technology is well-suited to the geological conditions of the Ordos Basin, ensuring that the solution flows within the bauxite ore bed without any seepage loss. To prevent the leaching solution from seeping into and polluting the main aquifer around the basin, several measures have been proposed. These include filling with polymer resin, well pattern seepage control plugging, and establishing monitoring systems. The results of this study provide a theoretical basis for the adoption of environmentally sustainable mining techniques and the mitigation of water pollution in deep bauxite exploration.

The densification of a SiCp/Al–Fe–V–Si billet was achieved by reducing the pores and oxide film between the particles by rolling. The wedge pressing method was used to improve the formability of the composite after jet deposition. The key parameters, mechanisms, and laws of wedge compaction were studied. The results showed that the pass rate was reduced by 10 to 15 percent when using steel molds during the wedge pressing process if the distance between the two ends of the billet was about 10 mm, which was beneficial to improve the compactness and formability of the billet. The density and stress of the surface of the material were higher than those of the interior, where the distribution of density and stress tended to be uniform as the overall volume of the material shrank. During the wedge extrusion process, the material in the preforming area was thinned along the thickness direction, while the material in the main deformation area was lengthened along the length direction. Under plane strain conditions, the wedge formation of spray-deposited composites follows the plastic deformation mechanism of porous metals. The true relative density of the sheet was higher than the calculated value during the initial stamping phase, but was lower than the calculated value when the true strain exceeded 0.55. This was due to the accumulation and fragmentation of SiC particles, which made the pores difficult to remove.

Investigation about how to enhance the corrosion properties of Ti alloys is essential to their actual applications in corrosive environments. Herein, the specific influences of Zr content on the corrosion behavior of Ti-6Al-3Nb-xZr-1Mo alloys (x = 2, 6, 10, 20 and 40 wt%) are systematically investigated using microstructure characterization, electrochemical and weight loss measurements. The results signify that all investigated alloys are composed of α and β phases; however, the increase of Zr content endows alloys with the refined thickness of lamellar α phase and enhanced volume fraction of intergranular retained β phase. Meanwhile, the corrosion resistance monotonously improves along with increasing the Zr content, directly characterized by the decreased corrosion current density, improved polarization resistance as well as reduced corrosion rate. The improvement in corrosion performance is a result of the alleviated micro-galvanic corrosion formed between α and β phases, increased volume fraction of corrosion-resistant β phase and modified composition of oxide film. One should note that the corrosion mode changes from the uniform corrosion to the mixed pitting and uniform corrosion with the Zr addition up to 40 wt%. Besides, surface analysis of samples after immersion tests reveals that the lamellar α phase is more susceptible to corrosion compared to the adjacent intergranular β phase, attributed to its higher concentration of Ti and Al elements. The current findings provide data that can be referenced for designing high-corrosion resistance materials for marine, biomedical applications and hydrochloric acid industries through composition optimization.

The effects of hypereutectic Al-17Si-4Cu-0.5Mg alloy were prepared by semisolid extrusion. The effect of solution time on microstructure and properties of hypereutectic Al-17Si-4Cu-0.5Mg alloy was studied. Results show that spheroidization occurs in the Si phase with the increase of solution time. When the solution time reaches 10 h, the circularity of eutectic Si is 0.72. High concentration of Cu element is enriched around Si phase in as cast state. After solution for 1 h, Cu element is rapidly dissolved into the matrix. As solution time is increased from 1 h to 16 h, the diffraction peak intensity of θ(Al2Cu) and Q(Al5Si6Cu2Mg8) phases on the XRD curve is decreased, and the dislocation density in the alloy matrix is greatly reduced. After aging treatment at 180℃ is performed on the solution treated samples, the θ' and Q' phases precipitate. As the solution time increases, the alloy strength value shows a "double peak" phenomenon. After solution treatment for 1 h, the tensile strength of the alloy reaches 269 MPa and the yield strength is 233 MPa. Compared with the unheated alloy, they are increased by 43.3% and 42.7%, respectively. This is mainly because there is still larger dislocation density in the matrix at the initial stage of solution, and the precipitation has stronger pinning hindrance to the dislocation after aging treatment. When the solution time is 10 h, the tensile strength and yield strength of the alloy reach 311 MPa and 263 MPa, respectively. The roundness of Si phase and the strengthening effect of fine precipitates are the main reasons for the formation of the second strength peak.

In this study, W-Ag matrix composites were fabricated by a relatively low temperature (750 °C) via designing dual-metal-layer (Cu and Ag) coated W powders. The effects of Cu and Ag coated W powders on the densification, microstructure and properties of the composites were investigated. The results indicated that the Cu-Ag coating promotes the sintering process and favors the low-temperature densification of W-Ag matrix composites. Moreover, the Cu-Ag coating benefited the formation of Cu-Ag solution and improved the interfacial bonding. The hardness of W-Ag matrix composites was increased to 260.0 HV by adjusting the composition of the material, and compressive strength can reach 799 MPa. The electrical conductivity can reach 45.0% IACS.

There is limited measure available to quantify the effect of polycarboxylate-ether based superplasticizer (PCE) on the microstructure of cement-based systems during the first 24 h. To fill this gap, the backscattered electron image analysis (BSE-IA) alongside the ternary technique is used in this study to separate composed phases quantitively and then calculate the average spacing between cement particles. Besides, together with an examination of hydration heat, the skeleton development of reaction products is investigated. The results show that cement hydration is not a constant process, and the developing mode for hydration products region varies with the particle size of cement. In this regard, numerous hydration products may gather around small cement particles and then adsorb other unhydrated particles, forming the continuous region. By contrast, the particles possessing relatively large size are surrounded by noticeable pores, which interrupt the continuity of the hydration products region. When introducing PCE, the agglomeration of cement particles and the average spacing between cement particles reduced, manifesting as an enlarged hydration products region alongside a decreased porosity at the area surrounding large particles. However, this leads to a decreased hydration degree for cement and extends the setting time of cement paste.

Li2TiO3 and Li4SiO4 are considered as candidate tritium breeding materials due to its excellent physical, chemical and tritium release performance. Thermal conductivities of solid tritium breeding materials are determined by microstructure, sintering density and surface condition which will change during operation of fusion reactor. A comprehensive understanding of thermal performance of tritium breeding materials is essential due to the extreme operation condition in the fusion reactor. In this work, the microstructure and thermal conductivity was investigated for Li2TiO3 and Li4SiO4 annealed at the corresponding temperature of tritium breeding blanket. SEM (Scanning electron micrography) results presented the stable structure of Li2TiO3 and instability of Li4SiO4. XRD (X-ray diffraction) and Raman indicated the disorder of the crystal structure. It can be attributed to lithium loss during annealing process. EPR (Electron paramagnetic resonance) showed that there were almost no defects related unpaired electron. It is due to defect recovery at higher temperature, as well as tiny H2 amount in sweeping gas. There was no obvious change of thermal performance for Li2TiO3 during different annealing time. It is indicated that Li2TiO3 has a good thermal performance to resist heat load. But thermal performance of Li4SiO4 decreased largely after annealing. It is resulted from variation of the structure during annealing process. Based on the present work, it is illustrated that Li2TiO3 has stable thermal performance under annealing condition, however, the thermal performance of Li4SiO4 is not so stable for long service time at higher temperature.

Transient liquid phase sintering can successfully fabricate reliable high-temperature solder joints at a relatively low joining temperature by forming intermetallic compounds. In this work, microstructure, shear properties and corrosion resistance of Cu/Cu-In/Cu solder joints prepared by TLPS process were investigated. The shear strength of the Cu-In solder joints significantly increased during the initial aging period and then slightly decreased due to the increase of pores after continuous 24 h aging. The corresponding microstructure is that part of the Cu2In in the Cu-In solder joints transforms to Cu7In3 in the meanwhile. After continuous aging, the interfacial microstructure remained stable and contributed to good shear strength that exceeds 20 MPa after 96 h aging at 250 °C and 350 °C, which was 20.8 MPa and 23.4 MPa, respectively. Regarding corrosion resistance, the Cu-In interfacial layer (−0.24 V) has similar corrosion resistance to Cu substrate (−0.22 V) and shows superior to the commonly used Sn63Pb37 solder (-0.40 V) and Sn95.5Ag3.8Cu0.7 solder (−0.42 V).

Due to the large-scale infrastructure construction and environmental protection pressure in China, the demanded cement is in short supply and the price is rising, and the overcapacity of silica fume has caused its price to fall, thus replacing cement paste by silica fume could achieve better economic and environmental benefits. In this study, silica fume (SF) with SiO2 content of 86.3% and high purity silica fume (HSF) with SiO2 content of 96% were used to replace cement paste in different proportions. The effects of adding SF or HSF on the workability of fresh concrete, the mechanical properties and microstructure of hardened concrete were investigated. The microstructures (i.e., porosity, pore size distribution and micromorphological characteristics) were analyzed by using low field nuclear magnetic resonance (LF NMR) and field emission scanning electron microscopy (FE-SEM). The results showed that the slump and air content of the concrete gradually decreased as the amount of SF or HSF increased. When the replacement amount of SF was increased from 0% to 10%, the cubic compressive strength and splitting-tensile strength of concrete were increased by 26.7% and 40.7%, while the cost per cubic meter of concrete was only increased by 1.9%. When the replacement amount of HSF was increased from 0% to 10%, the cubic compressive strength and splitting-tensile strength of concrete were increased by 44.7% and 57.4% respectively, while the cost per cubic meter of concrete was only increased by 5.3%. The total porosity of concrete gradually decreased as the amount of SF or HSF increased, with the proportion of macropores (>1000 nm) decreasing, and the proportion of mesopores (100–1000 nm) and capillary pores (0–100 nm) increasing, significantly refining the pore structure and densifying the microstructure of concrete.

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]

A Mg-6Li-3Al-1Sn (LAT631) alloy with a bimodal-grained structure was prepared via hot extrusion, followed by room temperature rotary swaging (RTRS). The as-extruded LAT631 alloy undergoes dynamical recrystallization, and massive twins are introduced during RTRS. Especially, Al segregation is generated with massive Al solutes surrounding Sn-rich particles via RTRS. Introducing twins and Al-rich segregation are critical factors for enhancing strength, and the increased proportion of DRXed grains is beneficial to improving the elongation in RSed alloy. This research demonstrates that strategic control of recrystallization and segregation by rotary swaging provides an innovative approach to optimizing the mechanical properties of Mg-Li alloys. This paper proposes a potential solution of Al segregation combined with precipitates for optimizing mechanical properties in ultra-light bulk Mg-Li alloys. [ABSTRACT FROM AUTHOR]

Due to its excellent mechanical properties and high aspect ratio, graphene can significantly improve the water and chloride ion permeability resistance of cementitious materials. However, few studies have investigated the effect of graphene size on the water and chloride ion permeability resistance of cementitious materials. The main issues are as follows: How do different sizes of graphene affect the water and chloride ion permeability resistance of cement-based materials, and by what means do they affect these properties? To address these issues, in this paper, two different sizes of graphene were used to prepare graphene dispersion, which was then mixed with cement to make graphene-reinforced cement-based materials. The permeability and microstructure of samples were investigated. Results show that the addition of graphene effectively improved both the water and chloride ion permeability resistance of cement-based materials significantly. The SEM (scanning electron microscope) images and XRD (X-ray diffraction) analysis show that the introduction of either type of graphene could effectively regulate the crystal size and morphology of hydration products and reduce the crystal size and the number of needle-like and rod-like hydration products. The main types of hydrated products are calcium hydroxide, ettringite, etc. The template effect of large-size graphene was more obvious, and a large number of regular flower-like cluster hydration products were formed, which made the structure of cement paste more compact and thus significantly improved the resistance to the penetration of water and chloride ions into the matrix of the concrete.

Lightweight high-entropy alloys (HEAs) are a new class of low-density, high strength-to-weight ratio metallic structural material. Understanding their corrosion behavior is crucial for designing microstructures for their practical applications. This work investigates the electrochemical corrosion behavior of lightweight HEAs AlCrTiV0.5Cux (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) in a 0.6 M NaCl solution. These HEAs were produced by vacuum arc melting. In contrast to 304L stainless steel, all of the alloys exhibited lower current density levels caused by self-corrosion, with AlCrTiV0.5 demonstrating the highest corrosion resistance (0.131 μA/cm2). Corrosion resistance decreased along with the content of copper because copper segregation accelerated local corrosion throughout the alloy.

The purpose of this study is to explain the mechanism of porcine myofibrillar protein gel properties modulated by κ-carrageenan. The textural properties results showed that the stress at fracture of the composite gel with 0.4% κ-carrageenan had the highest value (91.33 g), which suggested that the 0.4% κ-carrageenan addition was the limitation. The strain at fracture was significantly reduced with κ-carrageenan addition. The composite gel with 0.4% κ-carrageenan had the lowest proportion of T22 (7.85%) and the shortest T21 relaxation time (252.81 ms). The paraffin section showed that the phase separation behavior of the composite gel transformed from single-phase behavior to dispersed phase behavior to bi-continuous phase behavior, and the ratio of CG/MP phase area significantly increased from 0.06 to 1.73. The SEM showed that the three-dimensional network of myofibrillar protein transformed from a loose structure to a compact structure to an unaggregated structure with κ-carrageenan addition. The myofibrillar protein network of the treatment with 0.4% κ-carrageenan had the highest DF value (1.7858) and lowest lacunary value (0.452). The principal component analysis was performed on the data of microstructure and textural properties, and the results showed that the dispersed phase behavior and moisture stabilization promoted the aggregation of myofibrillar protein and the composite gel had better water holding capacity and textural properties, while bi-continuous phase behavior hindered the aggregation of myofibrillar protein and the composite gel had worse water holding capacity and textural properties.

In this study, Ti-6Al-4V matrix composites reinforced with TiB ceramic whiskers were in situ synthesized and hydrogenated using the melt hydrogenation technique (MHT). The effects of MHT on the microstructure evolution and hot compression behavior of the composites were investigated by optical microscopy (OM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Hot compression tests were performed at strain rates of 0.1/s, 0.01/s, and 0.001/s and temperatures of 800 °C, 850 °C, and 900 °C; the hot workability of composites significantly improved after hydrogenation, for example, the 900 °C peak flow stress of hydrogenated composites (43 MPa) decreased by 53.76% compared with that of unhydrogenated ones (93 MPa) at a strain rate of 0.01/s. Microstructural observations show that MHT can effectively facilitate the dispersion of TiB whiskers and induce the α/β lath refinement of the matrix in our as-cast hydrogenated composite. During hot compression, MHT effectively promoted the as-cast composite microstructure refinement, accelerated the dynamic recrystallization (DRX) generation, and reduced the stress concentration at the interface between the reinforcement and matrix; in turn, the hydrogenated composites presented low peak stress during hot compression.

In this work, a series of multicomponent alloys (CoCrFeNi, CoCrNi, and CoNiV) were laser welded with 304 stainless steel (304ss), and detailed comparisons on microstructural characteristics and mechanical properties were conducted for dissimilar laser welded joints. It is revealed that all of the dissimilar laser welded samples possessed defect-free joints and the corresponding fusion zone consisting of fcc single-phase showed homogeneous element distribution accompanied by a narrow element gradient in the vicinity of the fusion zone boundary. After laser welding with identical welding parameters, equiaxed grain was observed on the side of multicomponent alloy, while coarse columnar grain was obtained on the side of 304ss. Especially, the columnar grains of the fusion zone on the side of 304ss disclosed preferential growth direction in the CoCrFeNi/304ss and CoCrNi/304ss welded joints. Furthermore, all of the dissimilar laser welded joints were fractured in the fusion zone, attributing to the drastic loss of strength in the fusion zone with coarsened grain. It is worth noting that a special lamellar structure that merged by dimples was found in the fracture surface of the CoNiV/304ss joint, closely related to the existence of the V-enriched region. Finally, a high strength–ductile synergy can be achieved by laser welding CoNiV alloy to 304ss, which showed a yield strength of 338 MPa, ultimate tensile strength of 686 MPa, and total elongation of 28.9%. These excellent mechanical properties prevailed in the potential of a CoNiV/304ss laser welded joint to be applied as a structural material.

Functional materials with high viscosity and solid materials have received more and more attentions in flexible pressure sensors, which are inadequate in the most used molding method. Herein, laser direct writing (LDW) method is proposed to fabricate flexible piezoresistive sensors with microstructures on PDMS/ MWCNTs composites with an 8% MWCNTs mass fraction. By controlling laser energy, microstructures with different geometries can be obtained, which significantly impacts the performances of the sensors. Subsequently, curved microcones with excellent performance are fabricated under parameters of f = 40 kHz and v = 150 mm·s-1. The sensor exhibits continuous multi-linear sensitivity, ultrahigh original sensitivity of 21.80 % kPa-1, wide detection range of over 20 kPa, response/recovery time of ~100 ms and good cycle stability for more than 1000 times. Besides, obvious resistance variation can be observed when tiny pressure (a peanut of 30 Pa) is applied. Finally, the flexible piezoresistive sensor can be applied for LED brightness controlling, pulse detection and voice recognition.

Abstract Background As a novel high magnification module (HMM) combining with OCT (OCT-HMM) is able to detect the microstructure of retina, we apply it to explore the ultrastructure of the macula after closure of the idiopathic macular hole (IMH) by surgery. Methods This is an observational case series study in which patients with full-thickness IMHs who had undergone successful macular closure by vitrectomy and internal limiting membrane peeling and healthy subjects were recruited. After comprehensive ophthalmic examinations, the images of macular area were obtained and collected by professional operators using OCT-HMM. Then images were independently analyzed by 4 masked vitreoretinal specialists. Results A total of 24 IMH eyes and 42 healthy eyes were examined. HMM images were obtained in 10 IMH eyes. Among them, 4 eyes whose macula closed completely with recovery of photoreceptor layer presented a dark arc nasal to the fovea, oriented to the optic, and the notch of arc faced temporally. Six eyes in which the macula closed incompletely with photoreceptor cells loss revealed a dark ring with uneven bright spots inside. The other 14 eyes failed to obtain clear images by OCT-HMM. The contra lateral eyes of the patients and the healthy subjects’ eyes succeeded to obtain the HMM images which displayed evenly grey background thickly covered with tiny bright dots that was in similar size and evenly and widely distributed and there no dark arc or ring. OCT B-scan and IR images could be acquired in all of the IMH and healthy eyes. Conclusion The preliminary application of HMM has supplied us a brand-new insight into the microstructure of closed IMH. A dark arc sign could be detected with OCT-HMM in the macula which was functionally closed after surgery that was probably the healing mark on a microstructure photoreceptors level. Its existence and shape indicated that the functional closure followed by a retinal displacement mainly horizontally from temporal side to nasal side but not symmetric centripetally.

Asymmetric rolling (ASR) is distinguished from conventional symmetric rolling (SR) process as the mismatched rolling speeds of two rolls introduce additional shear deformation to the rolled strips. Friction between the rolls and strip plays an important role in the formation of shear during ASR, which further impacts the microstructures of metallic strips. In this study, finite element (FE) simulations are used to probe the effects of friction in ASR of magnesium (Mg) alloy strips with varied roll speed ratios. The results on shear deformation distributions through the thickness of the strips reveal that the increase of friction coefficient or roll speed ratio induces greater shear deformation simultaneously. It is also found that the roll speed ratio can only promote the shear formation up to a threshold value which is dictated by the friction coefficient, further increasing the mismatch of the roll speeds provides negligible improvement on the plastic deformation of the strips. Experimentally, Mg–1Gd alloy strips are processed by SR and ASR, followed by electropulse treatment (EPT) to induce static recrystallization (SRX). The predictions of the numerical models are verified via EBSD and XRD observations on the grain refinement and texture weakening in Mg–1Gd alloy, which are the direct microstructure consequences of plastic deformations during rolling. At the roll speed ratio of 1.67, the alloy shows a weakened basal texture with an average grain size of 6.0 μ m after SRX. Further increasing the roll speed ratio to 5, however, does not enhance the grain refinement or texture weakening significantly. [ABSTRACT FROM AUTHOR]