The modulation of structural and mechanical properties through construction of interpenetrating (IPN) hydrogels offers significant potential for expanding their applications as drug carriers. In this study, a silk fibroin (SF)/ Polyvinyl alcohol (PVA)/polydopamine particles (PDA) hydrogel with IPN structure for near-infrared (NIR)responsive controlled release of drugs were prepared by combining enzyme crosslinking with freeze-thaw cycles treatment. Compared with SF/PVA hydrogels prepared solely by enzyme crosslinking, the IPN hydrogels exhibited enhanced stability, a more ordered pore structure, and improved mechanical property. The hydrogels withstood 90 % of compressive deformation without breaking, and the maximum tensile strain at break reached 140.07 %. Moreover, the mechanical properties of the hydrogels were tunable by adjusting the ratio and concentration of SF and PVA. The incorporation of PDA particles into the IPN SF/PVA hydrogel endowed the material with excellent NIR responsiveness. Upon 808 nm NIR irradiation for 10 min, the temperature increased by 19.8 degrees C, with stable photothermal conversion performance maintained over three irradiation cycles. In addition, SF/PVA/PDA hydrogels exhibited good biocompatibility and NIR-responsive drug release capability. These findings highlight the potential of this SF/PVA/PDA hydrogel as a promising material for drug-controlled release applications.

Friction self-piercing riveting (FSPR) is a unique hybrid joining technique that combines the advantages of mechanical interlocking, frictional heat, and solid-state joining (if metallurgically compatible) to produce crack free joints in high strength and/or low-ductility alloys at room temperature. In the current study, Al-7055 sheets were joined using FSPR for lightweight automotive applications and significant microhardness variations were observed across the joint cross-section. A detailed microstructural characterization at multiple length scales was carried out using advanced electron microscopy and X-ray scattering techniques to provide a fundamental understanding of the process-structure-property relationships. The relative contributions of microstructural characteristics at various length scales (i.e., grain size, dislocation density, solute concentration, precipitate nature) to strengthening were estimated using existent formulations (i.e., Hall-Petch, Taylor, precipitate bypass/shear equations) and correlated to the observed microhardness values across different regions. Small-angle X-ray scattering and scanning transmission electron microscopy revealed significant changes in the size and volume fraction of precipitate species, i.e., GP-I Zones, eta ', and Mg/Zn solute co-clusters, depending on the process region. It was observed that the dissolution of the small eta '/GP-I zones (T similar to 150-200 degrees C) in the heat-affected zone were the key reason for the hardness drop. Further, it was shown that solid-solution, dislocation, grain size and solute co-cluster strengthening played a key role in the thermo-mechanically affected zone and grain-refined zone (GRZ). Finally, these observations were leveraged along with the Zener-Holloman relationship and grain size in the GRZ to estimate the peak joining temperature of the GRZ (similar to 350 degrees C) near the steel rivet.

In this study, we demonstrate that spatially resolved cooling curves derived from real-time infrared (IR) thermography during additive manufacturing (AM) can capture spatial variations in phase transformation temperatures through cooling curve analysis (CCA). Using this approach, we show that during laser hot-wire deposition of 410 stainless steel (410SS), the martensite start temperature (Ms) evolves dynamically throughout the build. The Ms temperature is spatially nonuniform, ranging from 185 ∘C to 348 ∘C, with the lowest values toward the build center and higher values toward the upper region of the deposit. In the lower portion of the build, no Ms inflection is detected via CCA, consistent with transformation occurring earlier during thermal cycling followed by tempering during subsequent thermal cycles. These trends in Ms are corroborated by characterizing the microstructure by electron backscatter diffraction (EBSD). Traditionally, Ms is assumed to be constant, and a single interpass temperature is applied during both deposition and residual stress modeling. Our results demonstrate that IR-derived cooling curves provide a route to spatially and temporally resolved transformation temperature tracking for dynamic interpass control and improved residual-stress modeling.

Chronic infectious wounds often delayed in healing due to their complex pathogenic factors. Currently, multifunctional hydrogel dressings offer a cost-effective and efficient therapeutic strategy to accelerate chronic wound healing by overcoming healing barriers. In this study, a multifunctional hydrogel named HOCP2 was developed by incorporating ultrasmall platinum (Pt) nanoparticles-loaded hollow HCuS (HCuS-Pt) nanozymes into a hydrogel matrix composed of adipic acid dihydrazide modified hyaluronic acid (HA-ADH) and oxidized sodium alginate (OSA), which were crosslinked via Schiff base bonds. The loading of ultrasmall Pt NPs reduced the bandgap of HCuS, achieving a dual-plasmonic synergistic enhancement effect that further improved photothermal performance, and synergistically enhanced the ability to scavenge ROS. Moreover, HOCP2 hydrogel exhibited favorable injectability, self-healing and adhesive properties. In vitro experiments demonstrated that HOCP2 hydrogel had reliable biocompatibility, could promote cell migration and enhance angiogenesis. Additionally, it exhibited antioxidant and anti-inflammatory properties while promoting M2 macrophage polarization, thereby modulating the wound immune microenvironment. The HOCP2 hydrogel also demonstrated photothermal antibacterial effects against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In vivo studies further certificated its ability to accelerate infectious wound healing. In conclusion, HOCP2 hydrogel dressing shows significant potential for application in the treatment of chronic infectious wounds.

In this study, we use dilatometry to construct an extended Continuous Cooling Transformation (CCT) diagram for 410 stainless steel, capturing both delta ->gamma and gamma ->alpha(y) transformations specifically for directed energy deposition (DED) additive manufacturing (AM) applications. To ensure that the findings are representative of AM specific microstructures and compositions, dilatometry coupons were extracted from a wire arc DED wall, thereby preserving the inherent microstructural and compositional variability within the material. The on-heating phase transformations, including Ac1, Ac3, and gamma ->delta, were found to be essentially location independent, despite the typical heterogeneity associated with AM. Conversely, increasing cooling rates were observed to shift the start and finish temperatures of both delta ->gamma and gamma ->alpha(y) transformations to lower values. The resulting extended CCT diagram offers a more complete depiction of phase transformation behavior in the system, enabling accurate microstructure evolution modeling and residual stress predictions specifically for directed energy deposition additive manufacturing applications.

Angiogenesis plays a vital role in the treatment of full-thickness wounds. Deferoxamine (DFO) has been employed to promote neovascularization, however, smart drug delivery systems are needed to optimize its utilization. In this study, an injectable extracellular matrix (ECM)-mimicking hydrogel (HOG@P&D) was developed by leveraging the dynamic Schiff base and hydrogen bonds among a chitosan derivative (HACC), oxidized alginate (OSA), gelatin, and DFO-loaded polydopamine nanoparticles (P&D) for efficient wound healing. The incorporation of P&D enables HOG@P&D to respond to near-infrared (NIR) irradiation, converting laser energy into heat to trigger an on-demand, rapid release of DFO, thereby effectively enhancing angiogenesis. In vitro tube formation assays revealed that the number of meshes in the HOG@P&D group was fourfold higher than that of the control group. Additionally, HOG@P&D exhibited superior mechanical properties, tissue adhesion, and injectability, allowing it to cover wounds seamlessly. This hydrogel also demonstrated antibacterial and antioxidant properties, creating a conducive microenvironment for wound healing. In vivo studies further confirmed that HOG@P&D promoted angiogenesis and mitigated inflammation by upregulating angiogenic growth factor expression, thereby accelerating full-thickness wound healing. This nanocomposite hydrogel shows significant potential as a high-performance wound dressing.

Solar-driven desalination is a promising solution to freshwater shortages, yet common photothermal materials like metals, semiconductors, and polymers may release harmful substances during production and use. Moreover, current research on solar-driven desalination primarily focuses on enhancing evaporation efficiency, while studies on the biosafety of evaporator materials and the purified water remain insufficient. To address this issue, this study constructs a CS/PVP/Gr aerogel via Schiff base reaction. Under 1 sun illumination, the aerogel achieved a high evaporation rate of 2.57 kgm(-2)h(-1) when treating 3.5 % NaCl solution, outperforming most previously reported bio-based evaporators. Notably, even under high salinity conditions (20 % NaCl), the evaporation rate decreased by only 12.8 %, demonstrating excellent salt tolerance. Moreover, this study is the first to conduct a comprehensive cytotoxicity evaluation of both the material and the purified water. Additionally, the purified water produced from CS/PVP/Gr aerogel successfully facilitates radish seed germination, effectively avoiding the adverse effects of salt stress. The cell viabilities of the CS/PVP/Gr aerogel-treated group and the pure water group reached 104 % and 108 %, respectively, indicating that both the evaporator and its condensed water exhibit good biocompatibility. These results further validate the potential of this system for applications in agricultural irrigation and domestic water supply. Furthermore, the evaporator exhibits outstanding wastewater purification abilities. This research contributes valuable understanding regarding the integration of highly biosafety materials in the field of desalination, contributing to the sustainable development of solar-driven desalination.

The study investigated how post-weld heat treatment (PWHT) temperature affects the microstructure and localized deformation/fracture during bend testing of rotary inertia friction welds (RIFW) between AISI 422 stainless steel and AISI 4140 steel. RIFW produced a fully martensitic interface with approximately 550 HV hardness in both the thermo-mechanically affected (TMAZ) and heat-affected zones (HAZ). Due to differences in temper resistance, the 4140 TMAZ/HAZ softened progressively under PWHT temperatures from 525 degrees C to 700 degrees C, while the 422 TMAZ unexpectedly maintained about 550 HV up to 600 degrees C before significantly softening at temperatures >= 625 degrees C. This asymmetric softening generated steep hardness gradients across the interface at temperatures <= 600 degrees C. Furthermore, carbon migration across the interface was minimal up to 600 degrees C, moderate at 625 degrees C, and by 700 degrees C produced a carbide-rich eutectoid layer in the 422 TMAZ alongside a carbon-depleted soft ferrite layer in the 4140 TMAZ. Strain during bending was PWHT-dependent, concentrating on the 4140 side; in as-welded joints, the high hardness led to deformation and crack initiation in the base metals, whereas in PWHT samples, cracking initiated in the softened 4140 TMAZ near the interface. The intermediate PWHT temperature of 625 degrees C offered the best balance of limited carbon diffusion across the interface, relatively low peak weld hardness and minimized hardness gradients across the interface, more homogenous deformation, and good bend test performance.

A single-class joiningJoining process known asFriction self-piercing riveting “friction self-piercing riveting (F-SPR)” has been developed for joiningJoining various low-ductility lightweight materials on a laboratory scale. The frictional heat generated during the F-SPR process improved local ductility, resulting in crack-free joints and robust mechanical performance. This innovative joiningJoining technology was further advanced through the scale-up of the process using a new system with several key features (e.g., automatic rivet feeding and clamping system, vacuum system) toward industry readiness. The new integrated F-SPR systems were effectively demonstrated for joiningJoining different material combinations (e.g., carbon fiber composite to 7075 Al alloy, 7075 Al alloy to 7075 Al alloy, and 7075 Al alloy to casting AlCasting Al Aural 5) with a unified technique. Crack-free jointCrack free joint with adequate mechanical interlocking resulted in good mechanical joint strength for each material combination. Then, the process was successfully scaled up by producing multiple joints without any cracks on larger CFC-Al and Al-Al components by the new integrated system, bringing it closer to industrial application.

Extending the concept of complex concentrated alloys (CCAs) to the refractory alloys (solidus temperature over 2000 °C) space potentially facilitates the design of lightweight structural alloys with service temperatures that exceed those of Ni and Co‐based alloys. However, the room and elevated temperature tensile properties of the current refractory‐CCAs (R‐CCAs) are inferior to those of the Ni/Co‐based alloys. Furthermore, the manufacturing scalability of R‐CCAs remains challenging, in that cracks are prevalent in all R‐CCAs when processed using near‐net shape manufacturing processes, such as fusion‐based additive manufacturing (F‐BAM). Still, mechanisms governing the poor F‐BAM processability of R‐CCAs remain unexplored. To this end, this work unveils the atomistic mechanisms underlying F‐BAM process‐induced cracking in a NbTiTaMoHfZrC R‐CCA. The implications of light elements’ presence for intrinsic ductility and grain boundary cohesion, and subsequently for F‐BAM processability and mechanical behavior, are revealed. Leveraging the insights, we accomplish what is, to the best of the knowledge, the first instance of crack‐free F‐BAM processing of any R‐CCA. Additionally, the R‐CCA exhibits over 20% tensile ductility and ≈160 MPa tensile yield strength at 1200 °C. In addition to facilitating the design of lightweight R‐CCAs, findings enable scalable manufacturing of these ultra‐high temperature alloys for structural applications.

Recently, injectable hydrogels with synergistic antioxidant and antimicrobial properties have emerged as promising candidates for diabetic wound treatment. However, the outstanding flowability of injectable hydrogels often compromises their mechanical properties, and few systems provide the multiple synergistic cues needed for rapid healing. Here, we designed an injectable dual-cross-linked hydrogel (SCO@M) that integrated MXene nanosheets (NNs) to furnish simultaneous photothermal antibacterial activity and intrinsic immunomodulation. At first, a dynamic network was formed in situ through reversible Schiff-base and hydrogen bonds among oxidized hyaluronic acid, carboxymethyl chitosan, and methacrylated silk fibroin (SF-MA), endowing the precursor with shear-thinning behavior and easy injectability. Brief UV exposure then photo-cross-linked residual SF-MA to form a covalent secondary network, markedly reinforcing mechanical strength without sacrificing injectability. Importantly, the incorporation of MXene NNs not only enhanced the mechanical properties but also imparted robust photothermal antibacterial activity under near-infrared irradiation alongside excellent reactive oxygen species (ROS) scavenging capacity. Both in vitro and in vivo results demonstrated that SCO@M normalized the inflammatory response by modulating the M1/M2 macrophage balance via IL-17/MAPK/TNF-α pathways, enhanced angiogenesis and cell migration, and accelerated wound closure in diabetic rats, representing a promising strategy for chronic wound healing.

A coupled Calculation of Phase Diagrams (CALPHAD), machine learning, and data mining approach was used to design a new, highly wear-resistant nanostructured bainitic steel. Arc melting of the designed compositions, dilatometry, and advanced microscopy indicate that the designed steel had a nanoscale dual-phase structure of ferrite and austenite (approximately 50 nm) with kinetics 7x faster for the onset of bainite and 2x faster for complete transformation. Under dry sliding conditions using the current state-of-the-art AISI 52100 bearing steel as the counter sample, the designed steel little to no wear, indicating its potential for applications in high-wear service conditions.

A recent study shows that powder metallurgy and pressureless sintering are a viable pathway to realize full-density bulk components of nanostructure bainitic steels. A scalable, pressureless supersolidus liquid phase sintering (SLPS) approach to process nanostructured bainitic steel is evaluated. To address the oxidation issues associated with the mechanical alloying of elemental powders, powder atomization is used to produce pre-alloyed nanostructured bainitic steel powders.

Increasing operation conditions (temperature and pressure) of the methane reforming process is crucial for improving hydrogen production efficiency, which unavoidably induces more severe high temperature hydrogen attack (HTHA) damages in pressure vessel components fabricated with carbon steels and low-alloy steels. In this work, multiple designed experiments were conducted to further investigate HTHA mechanisms. SA516 Grade 70 carbon steel and its weldment were exposed to low-pressure 100% pure hydrogen at elevated temperature for different periods (up to 1000 hours). HTHA-induced microstructure and mechanical property degradation were comparably characterized and evaluated. Creep performance of the as-welded steel weldment under a low-pressure 4% hydrogen-96% Ar gas exposure was also tested with in-situ digital image correlation (DIC). The characterization results show the HTHA exhibits a progressive breaking and dissolution of cementite in pearlite bands of this carbon steel, but no visible voids or cavities were formed in the steel under low-pressure hydrogen and without applying external stresses. There was also no obvious matrix grain growth associated with the carbide dissolution. The creep test shows the

AISI 422 martensitic stainless steel with superior hightemperature performance (oxidation resistance and strength) is under evaluation for replacing current heavy-duty piston crown materials, AISI 4140 martensitic steel and microalloyed steel (MAS) 38MnSiVS5, to fabricate a multimaterial piston (Refs. 1, 2). This multimaterial piston concept further improved power density and fuel economy by allowing heavyduty diesel engines to operate at higher temperatures and pressures (Ref. 3). Joining AISI 422 steel piston crowns with AISI 4140 steel piston skirts is a key manufacturing step for this multimaterial piston. However, the significant differences in strength, elevated temperature flow stress, alloy chemistry, and temper resistance between these two martensitic steels cause some weldability issues (cracking) and metallurgical challenges (alloying element migration/segregation) when using conventional fusion-based welding processes (Refs. 4–6). Rotary inertia friction welding (RIFW), a solid-state welding process, has been the preferred method to join 4140 crowns to 4140 skirts (and MAS crowns to MAS skirts) in high-volume production of current heavy-duty diesel engine pistons. It has been used to join these two materials with relatively comparable alloy chemistry to fabricate pistons with MAS skirts and 4140 crowns. Meanwhile, RIFW has also been a preferred method of dissimilar metal welding (Refs. 7, 8). However, RIFW of dissimilar high-strength martensitic steels has yet to be widely pursued. The interfacial microstructure complexities created by the thermomechanical process and highly nonequilibrium phase transformations during RIFW are a significant challenge for understanding and predicting their joining behavior and have not been reported in detail. In this work, defect-free AISI 422 steel-AISI 4140 multimaterial pistons were successfully fabricated using the RIFW process. The interfacial microstructure and mechanical properties of dissimilar 422/4140 steel RIFW in the as-welded condition were experimentally studied in detail. The results provide critical baseline information for understanding RIFW mechanisms and guiding subsequent postweld heat treatment (PWHT) practice.

Abstract In this work, two unique heats of 9Cr creep strength enhanced ferritic (CSEF) steels extracted from a retired superheat outlet header after 141,000 hours of service were evaluated. These two CSEF steels were a forging manufactured to SA-182 F91 (F91) reducer and a seamless pipe produced to SA-335 P91 (P91) pipe. Their creep deformation and fracture behavior were assessed using a lever arm creep frame integrated with in-situ high-temperature digital image correlation (DIC) system. Critical metallurgical and microstructure factors, including composition, service damage, grain matrix degradation, precipitates, and inclusions were quantitatively characterized to link the performance of the two service aged F91 and P91 CSEF steels. The creep test results show the F91 and P91 steels exhibit a large variation in creep strength and creep ductility. The F91 steel fractured at 572 hours while P91 steel fractured at 1,901 hours when subjected to a test condition of 650 °C and 100 MPa. The nominal creep strains at fracture were 12.5% (F91) and 14.5% (P91), respectively. The high-resolution DIC strain measurements reveal the local creep strain in F91 was about 50% while the local creep strain in P91 was >80%. The characterization results show that the F91 steel possessed pre-existing creep damage from its time in service, a higher fraction of inclusions, and a faster matrix grain coarsening rate. These features contribute to the observed reduction in performance for the F91 steel. The context for these findings, and the importance of metallurgical risk in an integrated life management approach will be emphasized.

The microstructure and crystallographic textures of API X65 grade linepipe steel were studied in the base metal, the weld interface after high-frequency electric resistance welding (HF-ERW), and the weld interface following post-weld heat treatment (PWHT). Optical microscopy, scanning electron microscopy (SEM), and electron-backscattered diffraction (EBSD) were used to study the microstructure and texture evolution and correlated with Charpy V-notch impact toughness. The Charpy values were 172.9 +/- 5.2 J for the base metal, 7.5 +/- 1.6 J for the as-welded weld interface, and 69 +/- 24 J after PWHT, with the latter still significantly lower than the base metal. Base metal showed a low fraction of low-indexed cleavage planes at about 9% and major texture components were (113)[110], (112)[110], and (332)[113]. In the as-welded condition, major intensities of rotated Cube (001)[110] and Goss (110)[001] texture components were observed near the weld interface. Although PWHT reduced the texture intensities, rotated Cube and Goss components were still observed. The fraction of cleavage planes was about 44% for the as-welded and about 30% for the PWHT-ed weld interface. Clearly, PWHT has reduced but not eliminated the detrimental rotated Cube and Goss textures at the weld interface. These detrimental textures likely have contributed to the low Charpy toughness after welding and continuing after PWHT.

In this work, creep performance of an as-built Grade 91 steel using wire-arc additive manufacturing (WAAM) was tested using a unique creep testing system integrated with in-situ hightemperature digital image correlation (DIC) strain mapping capability. The test results show creep lifetime of this as-built Grade 91 steel is much higher than that of Grade 91 steel weldments, even slightly above the mean lifetime of the conventional Grade 91 steels. In addition, highly nonuniform creep deformation in the as-built specimen was clearly captured by the DIC measurements, and correlated to the characterized inhomogeneous microstructures in multi-scales. Microstructure heterogeneities, including different martensite lath sizes, tempering degree of martensite matrix, and variations in precipitates, exist in two distinctive regions. A soft region, considered as the reheated "heat affected zone" (HAZ), has fine equiaxed grains, smaller martensite blocks, more precipitates, and a lower hardness. These microstructure features made these reheated HAZ regions more vulnerable to creep strength degradation, showing a larger creep deformation in the DIC measurements. A hard region with coarse columnar grains, less-tempered martensite matrix, and finer precipitates, exhibits a higher hardness and a better creep resistance. This study has clearly demonstrated that microstructure and creep strength variations at the meso-scale exist in the WAAM builds and should be carefully considered in WAAM process and material qualifications.