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The transportation and disposal of tunnel muck have detrimental environmental impacts. For this reason, the practice of reusing such a resource in engineering materials has substantial environmental and economic benefits. Seasonal frozen regions are extensively distributed worldwide, and freeze–thaw (F-T) cycles can largely degrade the performance of engineering materials, underscoring the importance of knowledge on the F-T resistance of tunnel muck. This study investigates the impact of F-T cycles on the mechanical and microscopic behavior of slurry shield tunnel muck stabilized with basalt fiber (BF) and inorganic curing agent (ICA). The qualities of muck discharged from slurry shield tunneling were improved in the composite formation of fine sand and muddy silty clay. Then tests were conducted to obtain the stress-strain characteristics, uniaxial compressive strength (UCS), and microstructure of the improved tunnel muck with different numbers of F-T cycles (N) and BF contents. Based on the Weibull probability distribution function, the damage evolution model of ICA-BF stabilized tunnel muck was proposed. The results show that the UCS decreases parabolically when the F-T cycle increases, and the F-T damage degree is 24.5%–40.6% after 12 cycles. Increasing BF content can effectively improve tunnel muck's F-T resistance (an optimal ratio of 0.5%). The failure strain of the reinforced tunnel muck is linearly correlated to the BF content and has a weak correlation with the number of F-T cycles. The F-T damage to material strength can be divided into rapid (N=0–3), slow (N=3–9), and stable (N>9) stages. The established F-T damage model can accurately predict the evolution of the F-T damage degree. [ABSTRACT FROM AUTHOR]

Particle agglomeration poses the principal challenge in the solidification of particulate-reinforced metal matrix composites (MMNCs). Here, we present an approach aimed at achieving a uniform dispersing of nanoparticles (NPs) in an aluminum matrix via ultrasonic-assisted fast cooling schemes. Microstructure analysis reveals that the distribution of NPs in the matrix transforms from intergranular distribution to intragranular distribution at the microscale and the interface between NP and the matrix changes from incoherent to coherent at the nanoscale under the action of ultrasonic melt treatment. Theoretical analysis underscores the significance of NP size and cooling rate as the two prominent factors influencing NP distribution during the solidification of nanocomposites. Through the ultrasonic dispersion of NPs and particle engulfment during the fast cooling process, the ductility of highly dispersed nanocomposites exhibits significant enhancement, with an increase of 82.7 and 18.4 pct compared to that of pure aluminum and non-ultrasonic-treated samples, respectively. [ABSTRACT FROM AUTHOR]

This study utilized an innovative unalloyed CoCrFeNiTiMo hybrid powder as a joining filler to fabricate high‐strength SiC/HEA/SiC joints via in‐situ reaction. The investigation systematically examines the effects of joining parameters on microstructural evolution and mechanical properties. The filler exhibits high reactivity with SiC, addressing carbon enrichment and low‐strength issues. The resulting joining layer comprises HEA‐rich Si, Mo1.5Cr1.5Si, MoTiC2, and TiC phases. Increasing the temperature facilitates carbon diffusion, transforming TiC into MoTiC2 and forming a MoTiC2‐wrapped TiC structure. At 1400°C for 60 min, the joints attain peak flexural and shear strengths of 312 ± 16 and 137 ± 10 MPa, respectively. Additionally, the joints demonstrate excellent oxidation resistance, with a residual strength of 270 ± 7 MPa after 20 h at 900°C, and favorable high‐temperature mechanical strength, retaining 155 ± 14 MPa at 1000°C. A detailed analysis of the joint formation mechanism is conducted based on experimental results and first‐principles calculations. [ABSTRACT FROM AUTHOR]

In this work, the static water and oxygen corrosion behavior of SiCf/SiC–SiYBC composites was systematically studied at 1 300°C to 1 500°C. With the increase in corrosion temperature from 1 300°C to 1 500°C, both the residual strength and strength retention rate of SiCf/SiC–SiYBC composites initially increased and then decreased. The highest strength retention rate achieved was 132%, which was 35% higher than that of SiCf/SiC composites. During water and oxygen corrosion of composites, self‐healing boron silicate glass and the Y2Si2O7 phase with excellent resistance to water and oxygen were generated in situ. The oxidation products are fluid at high temperatures and can fill internal pores and microcracks, thus improving the residual strength of the SiCf/SiC–SiYBC composite. The water corrosion resistance of SiCf/SiC–SiYBC materials has been confirmed to be superior to that of SiCf/SiC composites. [ABSTRACT FROM AUTHOR]

The as-cast (Fe50Mn30Co10Cr10)97C2Mo1 HEA (high entropy alloy) was prepared and cold-rolled at 70%. Subsequently, annealing heat treatment at different temperatures (900 °C, 950 °C, 1000 °C) was carried out. The microstructure evolution and mechanical properties of the HEA were systematically investigated. The results showed that the HEA annealed at 900 °C and 950 °C exhibited uneven grain size and rich σ precipitation phase at grain boundaries. The grains began to grow and complete recrystallization, and no σ phases were observed in HEA annealed at 1000 °C, which resulted in a higher tensile strength of ~885 MPa and elongation of ~68% compared with other annealed HEAs. The higher volume fraction of annealing twins with 60°<111> orientation was produced in HEA annealed at 1000 °C, which enhanced the tensile strength and plasticity via the Twinning-induced plasticity (TWIP) mechanism. [ABSTRACT FROM AUTHOR]

The as-cast [Co40Cr25(FeNi)35−yMoy]100−xCx (x = 0, 0.5, y = 3, 4, 5 at.%) HEAs (high-entropy alloys) were prepared by a vacuum arc melting furnace and were then hot rolled. The effect of C and Mo elements on the microstructure evolution and mechanical properties of HEAs was systematically analyzed. The results showed that when no C atoms were added, the HEAs consisted of FCC + HCP dual-phase structure. In addition, as the Mo content increased, the grain size of the alloy increased from 17 μm to 47 μm. However, only the FCC phase appeared after adding 0.5 at.% carbon in Mo microalloyed HEAs, and the grain size of the Mo4C0.5 HEA decreased significantly. Due to the Mo atom content exceeding the solid solution limit, the carbides of Mo combined with the C element appeared in the Mo5C0.5 HEA. The strength of C and Mo microalloyed HEAs significantly increased compared to HEAs with no C added. However, the Mo4C0.5 HEA exhibited excellent comprehensive mechanical properties, which was superior to a majority of reported HEAs and conventional metal alloys. Its yield strength, tensile strength, and elongation were 757 MPa, 1186 MPa, and 69%, respectively. The strengthening mechanism was a combination of fine grain strengthening, TWIP effect, and solid solution strengthening. [ABSTRACT FROM AUTHOR]

The layered oxyselenide BiCuSeO has attracted significant attention due to its ability to demonstrate low thermal conductivity and a high Seebeck coefficient. This research project involved the synthesis of Bi1−xNaxCuSeO1−xFx (x = 0, 0.05, 0.10, 0.15, and 0.20) ceramics using high-energy ball milling and cold isostatic pressing techniques. A comprehensive investigation was conducted to examine the influence of co−doping NaF on the thermoelectric properties of BiCuSeO ceramics. The substitution of Bi3+ with Na+ introduces a substantial number of holes, resulting in a remarkable improvement in the electrical conductivity and power factor. The conductivity was significantly increased from 9.10 S cm−1 (BiCuSeO) to 94.5 S cm−1 (Bi0.85Na0.15CuSeO0.85F0.15) at 323 K. Additionally, at 823 K, the power factor of the Bi0.85Na0.15CuSeO0.85F0.15 sample reached 44.8 × 10−5 W/m K2. Furthermore, the Bi1−xNaxCuSeO1−xFx ceramics demonstrated a minimum thermal conductivity of 0.43 W m−1 K−1. Consequently, the Bi0.85Na0.15CuSeO0.85F0.15 sample achieved a maximum ZT value of 0.78, which is 7.09 times higher than that of the pure BiCuSeO sample (0.11). [ABSTRACT FROM AUTHOR]

This research integrates the stable pressuring of the flat surface of roll-to-plate (R2P) imprinting, the fast production features of roll-to-roll (R2R) imprinting, and compound layer ring-type microstructure mold cavity manufacturing technology. Using the compound multilayer method with air molecule assistance, the stability of the roller imprinting process is enhanced. In addition, with precision modulation of the triangle roll-to-plate (TR2P) system, a stable microstructure roller imprinting manufacturing process is achieved. The experimental results indicate that the developed triangle roll-to-plate system can stabilize the imprinting process of the continuous microstructure array components. Also, by modulating the angles of the roller axis and the ring, the exterior features of the microstructure can also be adjusted. Gas-molecule-assisted continuous pressuring effectively elevated the roll imprinting angle and continuous pressuring time and reached a high replication rate of 99.14%. The optical waveguide microstructure component produced by this process and the average waveguide propagation losses of approximately 1.2~1.4 dB/cm show that it has optical stability and transparency after optical testing. The research proves that the manufacturing process can effectively provide an innovative process for the equipment and application of the microstructure component. [ABSTRACT FROM AUTHOR]

In this study, the bonding of a CuW/Al composite with a Ni interlayer was designed and established by vacuum hot-pressing diffusion bonding. The interfacial microstructure was systematically discussed based on experimental characterization and first-principles calculations. The result indicated that the interface consisted of intermetallic compounds (IMCs) of Al3Ni2 and a few of Al3Ni. The interfacial microstructure significantly differed from the interface without the Ni interlayer. The growth kinetics of the Al3Ni2 layer followed a parabolic behavior, which was mainly affected by the volume diffusion mechanism. The interfacial thickness decreased significantly, and the average thickness was ~35 μm. The microstructural evolution revealed that Al3Ni2 was the phase that was formed first. By introducing a Ni interlayer, the interfacial strength was significantly enhanced due to the IMCs that were changed from Al–Cu and Al–W IMCs to Al–Ni IMCs. The maximum shear strength reached 90.9 MPa, which was increased by 76% compared to that of the sample without the Ni interlayer. An analysis of the fracture morphology analysis showed that the crack was prone to exist at the Al3Ni2/Ni interface and presented a cleavage fracture characteristic. [ABSTRACT FROM AUTHOR]

Aluminized AISI 321 steels applied as heat exchange tube are generally subjected to creep–fatigue (C‐F) exposure during service. Remaining tensile and creep performance of this steel at 620°C were therefore studied under prior C‐F deformation. Results revealed that residual properties exhibit an initial increase and followed degradation with rising lifetime fraction of prior C‐F. The tensile strength and creep lifespan reach highest at 30% lifetime fraction, since dislocation cell networks are well developed and secondary nanotwins are activated at substrate. Additionally, dynamic recovery and wavy slips occurred in coatings partially accommodate local plastic deformations and inhibit defect initiations, avoiding premature material fracture. On the other hand, these networks could restrain the increase in coating thicknesses. When the lifetime fraction of prior C‐F increases to 80%, declined remnant properties are observed, which is attributed to the recovery of dislocation cells and carbide coarsening. Meanwhile, coating microcracks also accelerate steel failure. [ABSTRACT FROM AUTHOR]

Micro-arc oxidation (MAO) ceramic coatings were prepared on TC4 titanium alloys by adding CuSO4 to a (NaPO3)6 base solution. The microstructures of the MAO coatings were characterized by scanning electron microscopy (SEM), energy dispersive (EDS), and X-ray photoelectron spectroscopy (XPS). The corrosion resistance and wear resistance of these coatings were evaluated via hydrochloric acid immersion of weight deficit and friction tests. Those results indicated the presence of Cu in the MAO coating in the form of CuO and Cu2O. Incorporation of CuSO4 results in a thickness and roughness increase in the coating. The coating has a lower coefficient of friction (0.2) upon the addition of 4 g/L of CuSO4. The antibacterial properties of the MAO coatings were maximized at 6 g/L of CuSO4. However, the corrosion resistance of the copper-doped MAO coating did not exceed the undoped coating. This study shows that the addition of CuSO4 to the electrolyte successfully prepared copper-containing micro-arc oxidation coatings, which improved the wear resistance and antibacterial properties of the coating. [ABSTRACT FROM AUTHOR]

Laser cladding is a promising surface modification technology to fabricate high-performance parts. However, defects such as porosity, cracks and residual tensile stress are easily produced in laser cladding, leading to significant property reduction and poor reliability. In this study, laser cladding with multidimensional high-frequency vibration was investigated. The effects of multidimensional high-frequency vibration on the improvement of microstructure and mechanical properties were analyzed and discussed based on the vibration-assisted laser cladding experiments. In addition, a numerical model was conducted to help understand the significance of the vibration on flow field and temperature field. Results show that 3D vibration led to the primary dendrite spacing reduction from 11.1 to 6.8 μm, microhardness increase from 199 to 221 HV0.2, and a nearly 110% improvement in the elongations. The findings of this study confirmed the significant benefits of multidimensional high-frequency vibration applied in laser cladding and provided a basis to uncover the underlying mechanisms of multidimensional vibration on the rapid melting and solidification. [ABSTRACT FROM AUTHOR]

Accurate and non-destructive technology for detection of subsurface defect has become a key requirement with the emergence of various ultra-precision machining technologies and the application of ultra-precision components. The combination of acoustic technique for sub-surface detection and atomic force microscopy (AFM) for measurement with high resolution is a potential method for studying the subsurface structure of workpiece. For this purpose, contact-resonance AFM (CR-AFM) is a typical technique. In this paper, a CR-AFM system with a different principle from commercially available instruments is set up and used for the detection of sub-surface Si samples with grating structures and covered by different thickness of highly oriented pyrolytic graphite (HOPG). The influence of subsurface burial depth on the detection capability is studied by simulations and experiments. The thickest HOPG film allowing for sub-surface measurement by the proposed method is verified to be about 30 μm, which is much larger than the feature size of the subsurface microstructure. The manuscript introduces the difference between this subsurface topography measurement principle and the commercially available AFM measurement principle, and analyzes its advantages and disadvantages. The experimental results demonstrates that the technique has the capability to reveal sub-surface microstructures with relatively large buried depth and is potential for engineering application in ultra-precision technologies. [ABSTRACT FROM AUTHOR]

The separator is the weakest mechanical part of a lithium‐ion battery. The displacement load formed by the expansion of an electrode induces the microstructure evolution of the separator, such as decreasing porosity and increasing tortuosity, which affects its ability to transport Li+ and degrades battery performance. Herein, an in situ mechanical loading device combined with focused ion beam–scanning electron microscopy (FIB–SEM) is designed to reveal the real microstructure evolution of a separator under displacement loading. An image‐based finite‐element model is tailored to investigate the microstructure evolution and its nonuniformities of the separator at different deformation levels. The quantitative relationship between the separator porosity and external displacement load is presented based on the experimental and simulation results. Herein, new insight into the degradation mechanisms of commercial lithium‐ion batteries is provided. [ABSTRACT FROM AUTHOR]

To investigate the microstructure evolution and dynamic deformation behavior of a CoCrNi medium entropy alloy under an ultrahigh explosive loading rate, CoCrNi-shaped charged liners were fabricated and fired into steel targets. Targets with residual jet fragments were recovered for detailed microstructural analysis using scanning electrical microscopy, X-ray diffraction, electron backscattered diffraction, and transmission electron microscopy. The results indicate that the grain size was reduced by more than 3 times and grains were found to be equiaxed in the residual jet, which indicates that dynamic recrystallization (DRX) occurred during this extremely high strain rate and large plastic deformation. Furthermore, the content of Cr element in CoCrNi at the grain boundaries increased significantly after detonation deformation. The reduced grain sizes are believed to reduce the bulk diffusion path of Cr from grain interior into grain boundaries with the support of sufficient energy provided by the ultrahigh temperature. The enrichment of Cr at grain boundaries promotes the formation of nanosized Cr-rich precipitates with body-centered cubic (BCC) structures, which were found to be widely distributed along grain boundaries in the residual jet. These precipitates were considered obstacles for grain boundary movement and promotion of crack initiation along the grain boundaries, which might cause ductility loss of the CoCrNi-shaped charge jet and loss of penetration capability. [ABSTRACT FROM AUTHOR]

In this study, the dissimilar metal cladding from a pressure vessel pipe–nozzle mockup for PWR was studied using an optical microscope, scanning electron microscopy, energy-dispersive X-ray spectrometry, electron back-scattering diffraction, and micro-hardness measurement. The microstructure of the SA508 side is non-uniform along the fusion boundary, especially at the concave and convex areas. Martensitic layer (type I and type II) boundaries are found at the fusion boundary area. The chemical composition, residual strain, and microstructure across the SA508–309L fusion boundary are very complex and hence result in a complicated micro-hardness distribution. [ABSTRACT FROM AUTHOR]