Advanced Engineering Materials

During the cold spray deposition of nickel‐based superalloy powders, particles with insufficient deformation and weak bonding inevitably form, which significantly degrades the coating performance. To enhance the coating's performance, a laser‐assisted cold spraying process is employed to prepare the GH3536 coating. The laser assistance softens the substrate and particles by heating, and during deposition, the powder particles undergo recrystallization and “weld” the pores, improving the coating's density. Compared to the cold‐sprayed (CS‐GH3536) coating, the laser‐assisted cold‐sprayed (LACS‐GH3536) coating exhibits a remarkable 96.2% reduction in porosity and a 63.4% decrease in wear rate. The wear mechanisms of all coatings include oxidative wear, abrasive wear, and adhesive wear. In a 3.5 wt% NaCl solution, the LACS‐GH3536 coating shows outstanding corrosion resistance, with a low Icorr of only 10.321 μA cm⁻². Laser heating facilitates recrystallization within the coating, improving grain uniformity and significantly enhancing both passivation and corrosion resistance.

A modified near‐α titanium alloy of Ti‐5.2Al‐3.7Sn‐3.6Zr‐0.5Mo‐0.5Si‐0.02C is subjected to hot compression experiment using Gleeble‐3800 at deformation temperatures (T) from 940 °C to 1060 °C and strain rates (ε) from 0.01 to 1 s⁻¹. The β‐phase transus temperature of this alloy is decreased about 20 °C, which leads to lower deformation temperature. By fine‐tuning the contents of Al, Sn, Mo, Ta, and C elements, the machinability of alloy is optimized while maintaining its mechanical properties. According to stress–strain curves, an Arrhenius constitutive model for Ti‐5.2Al‐3.7Sn‐3.6Zr‐0.5Mo‐0.5Si‐0.02C alloy is established with a linear correlation coefficient (R) of 0.9868. The thermal mechanical processing map of the Ti‐5.2Al‐3.7Sn‐3.6Zr‐0.5Mo‐0.5Si‐0.02C alloy reveals its optimal processing parameters, ranging from 980 to 1010 °C, with a strain rate of 0.01 s⁻¹. The instability region of the Ti‐5.2Al‐3.7Sn‐3.6Zr‐0.5Mo‐0.5Si‐0.02C alloy is reduced about 75% compared to that of the Ti60 alloy, and the energy dissipation rates within the processing regions remain at relatively high levels. Combined with the microstructure of the Ti‐5.2Al‐3.7Sn‐3.6Zr‐0.5Mo‐0.5Si‐0.02C alloy, the mechanism of microstructure evolution is discontinuous dynamic recrystallization with a large accumulation of dislocations near the high‐angle grain boundaries, which leads to the nucleation of grains occurred discontinuous dynamic recrystallization.

Resistance element welding is performed using AZ31B magnesium alloy (MA) as the upper plate and A6061 aluminum alloy (AA) as the lower plate. Rivets with leg diameters of 4, 6, 8, and 10 mm are utilized as the element. The impact of welding current (WC) and welding time (WT) on the tensile shear load (TSL) of the joint is investigated, in addition to conducting an analysis of the microstructure of joint. The TSL of the joint reached the maximum value of ≈6.99 kN when a rivet with a leg diameter of 10 mm is used under the conditions of a WC of 35 kA, a WT of 120 ms, and an electrode pressure of 4.8 kN. The results reveal that a reaction layer developed at the interface between the AA rivet leg and the MA upper plate and it comprises a single row of Al12Mg17 grains that are elongated parallel to the interface plane.

The creep behaviors and deformation mechanism of nitrogen‐containing nickel‐based welding materials deposited metal in a wide temperature range (600–900 °C) and stress range (50–500 MPa) have been studied. At 600 °C, the microstructure of the creep sample includes γ matrix, M(C, N), γ′ phase, Laves phase, and M23C6. Continuous stacking faults can be observed, resulting in mixed type fracture; At 700 and 800 °C/200 MPa, M23C6 phase dissolves back into the matrix. The dislocation loops can be seen. Resulting in mixed mode fracture dominated by transgranular fracture; At 900 and 800 °C/80 MPa, the M(C, N) and γ′ phases exhibit excellent high‐temperature stability. The large number of dislocation networks appearing, resulting in mixed mode fracture dominated by intergranular fracture.

Nanopolycrystalline hydroxyapatite (HAP) ceramics are proposed to possess superior mechanical and optical properties, making them suitable for use as windows for implantable biodevices. However, sintering transparent ceramics typically requires high temperatures to eliminate scattering centers, which often leads to significant grain growth, resulting in coarse micron‐sized grains that increase light scattering and reduce transparency. In this work, the densification process of nanopowder HAP compacts using high pressure without the aid of temperature is explored. High pressure alone can initiate and drive densification in nanopowder HAP compacts. At pressures exceeding 5 GPa, the samples exhibited high transparency and transmission in both infrared and visible wavelengths. By applying high pressure, densification can be achieved without the need for externally applied thermal energy. High‐pressure sintering shows the advantageous in preventing grain growth and promoting the formation of bulk nanostructure ceramics, maintaining the grain size of the initial particles. High‐pressure compaction at room temperature provides a way to prepare highly dense ceramics with nanosized grains while avoiding excessive grain growth.

With the increasingdemand for sustainable energy harvesting and advanced engineering materials, coupled nanogenerators present promising applications as an emerging energy conversion device. The limitations of conventional materials regarding strength and durability have stimulated the development of novel coupled nanogenerator sutilizing a porous core‐shell structured nanofiber architecture: porous polyurethane@polyvinylidene difluoride‐ zinc oxide* polyamide 66 (porous PU@PVDF‐ZnO*PA66). In this study, thefriction‐negative and piezoelectric layers were composed of porous PU@PVDF‐ZnO,which were fabricated using a cost‐effective and straightforward electrospinning technique. This research investigates the impacts of ZnO concentration, surface morphology, contact area, and separation distance on the performance of the nanogenerator. It was determined that the nanogenerator incorporating 10 wt% ZnO yielded the maximum output voltage, short‐circuitcurrent, and output power density of 129.3 V, 0.644 μA, and 0.0021 μW/m², respectively. Additionally, it exhibited a mechanical strength of 8.8 MPa andan elongation at break of 196.7%. The nanofiber membrane demonstrated a water contact angle of 104.75° and maintained excellent morphology at 160 °C, with stable output observed after 5000 cycles of contact separation. We posit that coupled nanogenerators, characterized by their flexibility and washability, hold significant promise for applications in wearable electronics, addressing the challenges associated with fabric durability.

Flexible micro‐supercapacitors (FSCs), with their outstanding flexibility and low weight, offer great potential for a wide range of applications in the field of flexible electronics. Herein, the few‐layer Ti3C2Tx MXene hybridized with commercial PEDOT:PSS dispersion are used as ink for aerosol jet printing (AJP) to fabricate interdigitated and double‐helix electrodes on 2D polyethylene terephthalate (PET) films and 1D thermoplastic polyurethane fibers, respectively. By controlling the evaporation behavior of aerosol microdroplets during the printing process, a transformation from 2D Ti3C2Tx MXene nanosheets to 3D wrinkled spherical structures on the surface of the flexible substrate is achieved, which increases the accessibility of ions to the electrochemical active sites. In addition, the introduction of PEDOT:PSS as a “bridge” connecting the Ti3C2Tx MXene‐wrinkled spheres not only enhances the electronic conductivity within the electrode but also improves the bending stability of the electrode. Consequently, the optimized MXene/PEDOT:PSS‐based planar and fiber‐architectured FSCs exhibit excellent areal capacitance and flexible stability. This work highlights the significant potential of AJP technology in developing electronic devices with fascinating functionalities on various flexible substrates.

Cu‐based self‐lubricating composites have excellent mechanical properties and enhanced friction characteristics, rendering them ideal for aerospace wear parts. However, the significant mismatch in coefficients of thermal expansion (CTE) between them and counterparts, typically steel, would limit their widespread application. To address this issue, Ni50Fe powders with a low CTE are incorporated into Cu15Ni8Sn‐MoS2 composites via mixing and hot‐pressed sintering, resulting in Cu15Ni8Sn‐Ni50Fe‐MoS2 composites. The addition of Ni50Fe significantly reduces the CTE of the composites. When added in moderation, Ni50Fe can enhance the mechanical properties and wear resistance, despite a slight degradation in lubricity. The variations in mechanical and friction properties of the composites are attributed to the reaction of Cu and Fe with MoS2 and the change of matrix composition. The composite containing 40 vol% Ni50Fe (N40) has the best comprehensive performance. Compared to the Cu15Ni8Sn‐MoS2 composite, the CTE of N40 is reduced by 13.7%, along with increases in hardness (5.2%), transverse rupture strength (19.1%), radial crushing strength (11.3%), and a reduction in wear rate (8.8%), although its friction coefficient increases by 15.4%.

Preparing appropriate micro–nano structures can change surface properties, enabling them to play a significant role in industrial production. Surface wettability is one of the fundamental characteristics of solid surfaces, and different micro–nano structures and application environments can greatly affect wettability performance. Wettability can also have a certain impact on corrosion resistance and biocompatibility. Frictional performance is another key characteristic of solid surfaces, and drag reduction and wear resistance are crucial for mechanical stability and durability. Therefore, research on micro–nano structured surfaces based on wettability and drag reduction and wear resistance has become a new trend. Femtosecond laser processing, with its high precision and low thermal effect, has a unique advantage in the preparation of material micro–nano structured surfaces. This article outlines the technology of femtosecond laser preparation of micro–nano structured surfaces, summarizes the current status and processing effects of femtosecond laser preparation of different morphologies of micro–nano structures, focuses on their functional characteristics, including surface wettability, biocompatibility, corrosion resistance, and frictional performance, and prospects the development trend of femtosecond laser preparation of superior micro–nanostructured surfaces.

Combining supercritical CO2 (s‐CO2) cycles with particle‐based heat transfer media for concentrated solar power (CSP) plants offers great potential if the material challenges can be overcome. The core challenge in integrating these systems is the particle/s‐CO2 heat exchanger, which must handle extreme conditions, such as high temperatures, high pressures, and erosion from both CO2 and hot particles. The mechanical requirements for such a heat exchanger are exceedingly high, demanding materials that can resist CO2‐corrosion and high stresses due to the operating conditions in the supercritical fluid. In addition, the heat exchanger material must also withstand severely erosive conditions due to the hot heat‐carrying particles sliding on the outside of the tube walls. The best selection of an appropriate heat exchanger alloy is discussed, considering cross‐references from supercritical and ultrasupercritical steam boilers and supercritical CO2 cycles in nuclear power applications. A method is shown to estimate the mechanical requirements, as well as the challenge of determining the corrosion and erosion allowance. Ultimately, the material requirements and challenges are summarized for creating a practical and durable heat exchanger to support the integration of supercritical CO2‐based cycles with CSP plants. Future research and material testing are defined to overcome the final hurdles.

Polyimide foam, a lightweight porous material with thermal insulation and acoustic absorption properties, has demonstrated significant potential for aerospace applications. However, advancing technologies urgently require enhanced mechanical performance in these materials. This study introduces a novel method for preparing rigid polyimide foam (RPIF) by adjusting the content of the surfactant polysiloxane‐polyether copolymer (trade name AK8805). The impact of microscopic pore structures on the mechanical properties of RPIF is analyzed. Results show that while AK8805 does not significantly alter the molecular structure or thermal properties, it enhances porosity, closed‐cell ratio, and pore distribution, optimizing mechanical performance. At 6 wt% AK8805, RPIF achieves a compressive strength of 5.45 MPa and modulus of 60.74 MPa. Low porosity, high closed‐cell ratio, and uniform pore distribution significantly improve load transfer and mechanical properties. This study provides an effective approach for optimizing structural foams for advanced applications.

The excellent recovery performance of TiNiFe shape memory alloy is closely related to the predeformation in the martensitic state. Based on the classical phenomenological constitutive model, the constitutive relationship suitable for the mechanical properties of TiNiFe alloy is constructed by introducing plastic strain. Aiming at the problems of uneven size and difficulty in characterizing stress and strain state in the deformation of ring parts after expansion deformation, the finite element simulation model of cryogenic temperature expansion deformation of shape memory alloy is established by using the UMAT interface of Abaqus. The effects of die angle and ring wall thickness on the stress state and geometric size of the TiNiFe alloy ring expansion process are investigated. The results show that for the same wall thickness, as the die angle α increases, the Mises stress increases significantly. As the wall thickness increases, the peak value of the expansion force increases significantly. The finite element simulation model established in this study can accurately predict the size of the TiNiFe alloy ring after expansion, evaluate the stress and strain state during the expansion process, and provide data support and theoretical guidance for subsequent applications.

To meet the demand for industrial production of calendering or rolling, it is necessary to detect the onset of chatter before chatter marks appear on the workpiece. Therefore, mode decomposition techniques (empirical, bivariate empirical, and variational) combined with machine learning (ML) are used to detect impending failures. Signals from acceleration sensors are decomposed into a discrete number of modes, isolating the high‐frequency oscillations by identifying local minima and maxima. Feature sets (peak to peak, standard deviation, etc.) of true intrinsic mode functions are extracted for training an ML model to detect the vibration states followed by the prediction of chatter marks. This innovative prediction model based on mode decompositions and ML shows its feasibility for early chatter identification.

Based on the sol‐gel principle of tetraethyl orthosilicate (TEOS) and vacuum pressure impregnation (VPI) principle, this study constructs and characterizes two types of 2D/3D heterostructures: reduced graphene oxide‐modified silica‐95S corrosion inhibitor (rGO‐SiO2‐95S) hybrid materials in situ. This was achieved by modifying the experimental steps of the ‘two‐step method’ (methods I and II) and varying the duration (24, 48, and 72 h). The study investigated the impact of various process conditions on the efficiency of the hybrid‐loaded 95S by altering the impregnation pressure (−0.1 to 0.1 MPa) and impregnation time (1 to 5.5' h). The addition of hybrids significantly improves bonding strength and barrier qualities of epoxy coatings, and markedly enhances the corrosion protection efficiency with 90.51% while the impedance modulus at the lowest frequency (|Z|0.01 Hz) showing enhancements of 1 ≈ 2 order of magnitude compared to EP. It was observed that hybrids prepared using method I after 48 h displayed the optimal mechanical and anti‐corrosion properties.

Polylactic acid (PLA) foam, known for its biodegradability and biocompatibility, faces limitations due to poor melt viscosity and low crystallinity. To address these issues, this research utilizes ethylene‐glycidyl methacrylate copolymer as a chain extender (CE) to enhance PLA and incorporates the nucleating agent diphenylhydrazide sebacic acid (ST‐NAB3) to adjust its crystallization characteristics. The CEPLA/ST‐NAB3 material is developed and foamed using supercritical CO2 and an intermittent method. Observations by polarizing microscope and differential scanning calorimeter show increases in both the crystallization rate and crystallinity of the CEPLA/ST‐NAB3 sample. When the ST‐NAB3 content is 0.4 wt%, a transformation from spherulite to string crystal morphology occurs. Rheological tests show higher melt strength compared with pure PLA, thereby improving its foaming behavior. When the foaming temperature is 108 °C, the PLA foam with 0.4 wt% ST‐NAB3 has the smallest cell size and the highest cell density, which are 55.38 μm and 3.95 × 10⁶ cells cm⁻³, respectively. Following annealing treatment, the compressive strength of the CEPLA/ST‐NAB3 foam containing 0.4 wt% ST‐NAB3 increases to 5.35 MPa, while its Vicat softening temperature rises to 87.4 °C. This study offers an effective approach to enhance the performance of PLA foams, expanding their potential applications in various industries.

The high corrosion rate of magnesium alloys in body fluids represents a serious drawback for biomedical applications. Grain refinement through of equal channel angular pressing (ECAP) processing seems to be quite promising to overcome this issue. This work investigates the conditions for depositing layered double hydroxides (LDHs) coatings through coprecipitation and hydrothermal treatment on AZ31 alloy subjected to 1, 2, and 4 ECAP passes. Owing to their tunable structure and ion‐exchange capacity, LDHs have the capability to load and release drugs. Synthesis is made by using two distinct synthesis times (30 min and 12 h) and then the samples are examined by light microscopy, scanning electron microscopy, and X‐ray diffraction. The results show that LDH deposition is strongly affected by the substrate microstructure. LDH nucleation occurs on screw dislocations emerging at the surface of substrate: fine and homogeneous distribution of LDH crystals is achieved if, in addition to homogeneous nuclei distribution, surface diffusion occurs. This condition is favored by the 0002‐texture component. The deposition on AZ31 alloy subjected to 1 ECAP pass with a synthesis time of 30 min gives rise to a complete surface coating and a crystal morphology that seems suitable for medical and biomedical applications.

Magnesium (Mg) alloys are promising lightweight structural materials whose limited strength and room‐temperature ductility limit applications. Precise control of deformation‐induced twinning through microstructural alloy design is being investigated to overcome these deficiencies. Motivated by the need to understand and control twin formation during deformation in Mg alloys, a series of magnesium‐yttrium (Mg–Y) alloys are investigated using electron backscatter diffraction (EBSD). Analysis of EBSD maps produces a large dataset of microstructural information for >40000 grains. To quantitatively determine how processing parameters and microstructural features are correlated with twin formation, interpretable machine learning (ML) is employed to statistically analyze the individual effects of microstructural features on twinning. An ML classifier is trained to predict the likelihood of twin formation, given inputs including grain microstructural information and synthesis and deformation conditions. Then, feature selection is used to score the relative importance of these inputs for twinning in Mg–Y alloys. It is determined that using information only about grain size, grain orientation, and total applied strain, the ML model can predict the presence of twinning and that other parameters do not significantly contribute to increasing the model's predictive accuracy. Herein, the utility of ML for gaining new fundamental insights into materials processing is illustrated.

In this article, a chessboard metasurface is proposed to reduce the radar cross section (RCS) of the dihedral corner reflector (DCR). By loading a checkerboard metasurface on one side of the DCR, a broadband RCS reduction is achieved. The simulation results show that the proposed DCR has a significant RCS reduction of more than −10 dB in the frequency ranges of 6.5–13.53 GHz with fractional bandwidths of 70.2% under transverse electric (TE) polarization and in the frequency ranges of 6.2–13.6 GHz with fractional bandwidths of 74.75% under transverse magnetic (TM) polarization. Additionally, the RCS reduction properties of the proposed DCR at various azimuth angles are investigated, and the wide‐angle RCS reduction from 0° to 65° is realized. To obtain more wide‐angle RCS reduction, double‐sided checkerboard loading is performed on the DCR. The RCS reduction angle range increases from 65° to 90° for TE polarization and TM polarization. Namely, the RCS is reduced from 0° to 90° for TE polarization and TM polarization, as calculated by numerical simulations. The measured results are in great agreement with the simulation results. This method verifies the novelty and effectiveness of wide‐angle and wideband RCS reduction of DCR.

This study attempts to utilize the oxide dopants as dispersoids for Nb3Sn superconducting bulk prepared through the mechanical alloying route. The functional behavior is characterized by the generation of artificial flux pinning centers (APCs) through cost‐effective nano oxide dispersoids. Further attempt is made to dope Y2O3 and TiO2 simultaneously in Nb3Sn. An influence of extended pinning is observed in this synergic‐doped sample due to combined pinning provided by magnetic Δ$\text{Delta;}$κ TiO2 pins and nonmagnetic Y2O3 APCs. Furthermore, an increase in the critical temperature, Tc by 2 K has been achieved for the co‐doped Nb3Sn samples and 1 K each by individually doped samples with reference to pristine Nb3Sn. At 2 T, the Jc for a co‐doped sample is 58% higher than the reference pristine Nb3Sn, while Y2O3 doped shows 13% higher and TiO2 doped shows 28% lower Jc than the reference. A comparable irreversibility field, Birr values are evaluated using both the Jc extrapolation method and Kramer's plot.

Bound metal deposition (BMD) is a valid 3D printing solution from an economic perspective. Still, the resulting mechanical properties are intrinsically lower than selective laser melting and electron beam melting ones and, in some cases, are also lower than metal injection molding (MIM). The optimization of the printing parameters is fundamental to level off this issue and to ensure mechanical performance competitive with MIM ones. In light of this, the present work focuses, for the first time, on the optimization of the printing parameters for a Ti6Al4V alloy. The effect of three fundamental parameters, that is, layer thickness, nozzle temperature, and printing speed, is investigated, and the 3D printing process is optimized by exploiting the design of experiment and the surface response analysis techniques. The results are extremely auspicious, considering that the optimum configurations display a tensile strength of 915 MPa, which is perfectly comparable with MIM components. The statistical analysis demonstrates that nozzle temperature, printing speed, and their interaction are the most relevant parameters and the 3D printing optimum is achieved with a nozzle temperature of 160 °C and a printing speed of 15 mm s⁻¹.

Hexagonal close‐packed (HCP) metals are widely used in various applications due to their unique mechanical and functional properties. The ductility and toughness, however, remain intrinsically limited because of the restricted slip systems. The slip of <c + a> dislocations, a critical ‐axis deformation mode, can provide sufficient ‐axis strain but needs high critical resolved shear stress to operate. This perspective highlights the nature of <c + a> dislocation—a typical limp dislocation—that leads to the difficulty in self‐multiplication and relies on the existing dislocation source to proliferation. Owing to the marked difference in mobility between edge and screw components, the limp <c + a> dislocations have poor self‐multiplication ability, which can be resolved by directly incorporating a high density of interfacial dislocation sources. For example, twin boundaries or phase interfaces are unique interface structures that can readily nucleate <c + a> dislocations to mediate ‐axis plasticity. This strategy can substantially enhance the uniform deformation and strain‐hardening ability of HCP metals, offering an effective approach to overcome their intrinsic limitations in plasticity and toughness.

Composite metal foams (CMFs) are promising materials for applications requiring high strength and impact resistance, yet their high‐temperature mechanical behavior remains underexplored. This study examines the mechanical performance and coefficient of thermal expansion (CTE) of steel–steel (S‐S) CMFs at temperatures up to 1000 °C. CTE measurements indicate reduced expansion relative to bulk 316L stainless steel, with stable values between 100 and 400 °C, followed by a linear increase up to 1000 °C, indicating S‐S CMF's enhanced thermal stability compared to bulk 316L stainless steel. Quasi‐static compression tests show that S‐S CMFs maintain excellent mechanical performance up to 600 °C, beyond which strength degradation accelerates due to thermal softening, oxidation, and plastic buckling. At 800 °C, the structural integrity of S‐S CMF is significantly compromised, with lateral expansion and energy absorption capacity reduced by over 80%. Scanning electron microscopy (SEM) links the mechanical changes to microstructural evolution, including grain boundary void formation and oxidation at high temperatures. These findings provide the first comprehensive assessment of the thermomechanical behavior of S‐S CMFs, bridging a critical knowledge gap and establishing their operational limits for high‐temperature structural applications.

Carbon nanotubes (CNTs) have been considered as promising reinforcements for various composites due to their excellent mechanical properties. However, CNT/resin composites prepared so far still suffer from bad dispersion, low mass fraction, and poor alignment of CNTs and their weak bonding with the resin matrix. Herein, an effective strategy toward preparing CNT/epoxy (EP) composite films with excellent mechanical properties is reported. Benefiting from a high CNT content (60.56 wt%), excellent CNT alignment from repeated prestretching, and uniform resin distribution between CNTs from pressurized impregnation and low temperature pressing, the composite film can achieve excellent mechanical properties, including a tensile strength of 4.1 GPa, elongation at break of 3.8%, and toughness of 77.9 J cm⁻³. Such a strength and toughness are superior to those for the previous CNT and carbon fiber composites published in the literature.

The bond strength between carbon fiber (CF) and sizing agent and the surface roughness of CF play a vital role in improving the interfacial properties of composite materials. In order to solve this problem, a new multiscale enhancement strategy is developed. Through the hydrolysis reaction of anhydrous silica sol in self‐emulsifying highly hydrophilic waterborne polyurethane (WPU) emulsion, the generated crosslinked network of SiOSi bonds generates hydrogen bond interaction between CF surface and WPU, which enhances the bonding strength of sizing agent to CF. At the same time, the nano‐SiO2 generated by hydrolysis further improves the interfacial stress transfer of the composites through the interlocking mechanism. The surface roughness, O/C ratio, and compatibility with the resin matrix of the CF after sizing are significantly improved, and the interlaminar shear strength and flexural strength of the corresponding composites are increased by 53.06 and 50.89%, respectively. In addition, the sizing agent prepared by this method overcomes the shortcomings of poor storage stability of traditional inorganic nanomaterial‐modified sizing agent. In short, this work provides assistance for the development and application of high‐performance sizing agents.