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Existing additively manufactured aluminum alloys exhibit a sharp decrease in yield strength at moderate temperatures (200°C-400 °C), failing to meet the high-temperature resistance required in the complex service environments of aerospace applications. In this paper, an Al-2.5Fe–2Cu-0.6Sc-0.3Zr alloy material was designed and formed by laser powder bed fusion (L-PBF) technology. The optimal composition ratio was obtained by comparing the formed structures and properties, and then the phase composition, microstructure, precipitation distribution and mechanical properties were characterized and analyzed at high temperature. The result shows that the alloy's primary precipitate phases are Al6Fe (Al23CuFe4) and L12-Al3(Sc, Zr) at nano scale. Adding Zr and Sc, the thermal stability of Al6Fe is enhanced, delaying its transformation to the θ-Al13Fe4 phase and refining the particle size. The Al23CuFe4 phase, stabilized thermodynamically by substituting of Cu for Al atoms in the orthorhombic structure (oC28), also contributes to the stabilization of the Al6Fe phase. Moreover, This aluminum alloy obtained a yield strength of 449 MPa at room temperature and a yield strength of 142 MPa at 300 °C. In addition, it also shows excellent brittleness resistance under high temperature, which is better than most L-PBF aluminum alloys reported so far. These findings offer valuable insights for the future development of aluminum-based alloys with heat-resistant performance, and promising strategies for addressing particle coarsening under high temperature and intermediate-temperature brittleness.

In modern aerospace engineering, the demand for innovative and adaptable solutions is paramount. This study focuses on enhancing aircraft engine components, specifically variable-geometry inlets, to meet evolving aviation technology requirements. We utilise custom Ni51Ti alloy powder to create 4D printed variable-geometry inlets. A comprehensive examination of thermal history and residual stress reveals differences in the behaviour of NiTi alloys at various points of the 4D printed inlet. After post-treatment, the printed inlet demonstrates stable two-way shape memory effects, undergoing adaptive deformation with temperature changes, mimicking the operational conditions of a commercial aircraft. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) tests confirm that the 4D printed NiTi alloys maintain very stable phase transformation temperatures and two-way shape memory performance. Fluid dynamics simulations further reveal that the variable-geometry inlet design is potentially more efficient in certain operational scenarios with a total pressure recovery factor of 0.9919.

N and Ti co-doped Fe45Mn35Co10Cr10 alloys were prepared by Laser-Directed Energy Deposition (L-DED). We find that precipitate reinforcement of TiN particles introduced by harnessing N solid solution can result in a microstructure featuring attached MnO and TiN composite nanoparticles. Co-doped samples exhibit a notable 69% increase in yield strength compared with that of the free-doped, rising from 310 MPa to 533 MPa, maintaining 44.5% elongation. Even at 77 K, the co-doped alloy displays ultra-high strength, approximately 1400 MPa. These findings on metastable high entropy alloys through additive manufacturing open new avenues for their application in various fields.

CoCrMoW alloys with different nitrogen (N) additions (0, 0.05, 0.1, and 0.2 ​wt%) were prepared via laser powder bed fusion (LPBF). The effects of N content on the microstructure and mechanical properties were investigated. The results indicate that the LPBFed CoCrMoW alloy with 0.1 ​wt% N addition (0.1 ​N alloy) shows the best combination of mechanical properties with a yield strength of ∼983 ​MPa and an elongation of ∼19 ​%. Both the LPBF process and the N addition impose great effects on suppressing the γ to ε martensitic transformation, resulting in a decrease in the width and amount of ε laths/stacking faults. Besides, the N addition promotes the segregation of elements Mo, W, and Si along the cellular sub-grain boundaries (CBs), forming fine and discontinuous precipitates rich in Mo, W and Si along the CBs in the 0.1 ​N alloy, but dense and continuous (Mo,W)5Si3 precipitates along the CBs in the 0.2 ​N alloy. The (Mo,W)5Si3 precipitates with a tetragonal structure were observed and characterized for the first time in the Co–Cr based alloys. The negative mixing enthalpy between the non-metallic elements N, Si and the metallic elements Mo, W, Cr, and the rapid solidification induced segregation of high melting point elements such as Mo and W along CBs during LPBF process, synergistically contribute to the chemical heterogeneity in the alloys. The pure FCC matrix, the slightly increased segregation of Mo, W, Si elements and fine precipitates along the CBs contribute to the good combination of strength and elongation of the 0.1 ​N alloy. However, though pure FCC phase was present in the 0.2 ​N alloy, the dense and continuous (Mo,W)5Si3 precipitates along CBs acted as nucleation sites for cracks, deteriorating the elongation of the alloy. Overall, it is possible to tune the mechanical properties of the LPBFed CoCrMoW alloy by adjusting the local chemical heterogeneity.

The effect of scanning strategy on the microstructure and properties of GH3536 Ni-based superalloy prepared by Laser Powder Bed Fusion was investigated, for the purpose of building high quality hydrocyclone part. The results show that the strength of Z67° (a zone with 67° hatch angle strategy) specimen is the highest among the four scanning strategies (0°, 67°, 90°and Z67°), with yield strength and tensile strength of 681 ​MPa and 837 ​MPa, respectively. Selective orientation of crystals occurs during the forming process because the longitudinal section of the specimen exhibits a high texture strength in (001). As the stretching proceeds, the plastic deformation mechanism of the specimen gradually changes from slip to twin-dominated, a substantial amount of twinning is observed in the region where the deformation of the specimen reaches 80%. The additive manufacturing simulation suite: Ansys Additive is used to simulate the stress and deformation of the part during the process, and the displacement results are consistent with the experimental phenomena. According to the simulation results, the structure design is optimized and the surface quality of the part is improved. The results show that the support of the part is more reasonable when the overhang angle is 45°.

In this study, we report an unconventional precipitation and martensitic transformation behaviour of directly aged Ni-rich NiTi alloys fabricated via laser-directed energy deposition (LDED). Ni4Ti3 particles precipitate uniformly under all ageing conditions and no traditional multiple-step martensitic transformations are observed. We conclude this unique behaviour to the intrinsic characteristics of the LDED technique, which are metastable microstructures and high residual stresses. On the one hand, these features make grain boundaries no longer a fevered location for precipitation and, on the other hand, significantly suppress the martensitic transformation when ageing at low temperatures (300°C/400°C). As the aging temperature increase (500°C), residual stresses release significantly, accompanied by the growth of Ni4Ti3 precipitates from several nanometres to 452 ± 181 nm with increased interparticle spacing. At the same time, reverse martensitic transformations change from two-step (B19′ → R → B2) to single-step (B19′ → B2).

This study presented a comprehensive investigation into the microstructures, strengthening mechanisms and deformation behaviours of a novel N-doped Co-28Cr-6Mo (CCMN) alloy fabricated by laser powder bed fusion (LPBF). In addition to the well-known cellular structures, lattice defects including dislocations and stacking faults (SFs), the near-spherical shaped Cr2N precipitates with two typical size distributions were detected. Tensile test results revealed that the LPBF fabricated CCMN alloy demonstrated superior yield strength of 845 ± 49 MPa and elongation to fracture of 12.7 ± 1.9%. The grain boundaries (∼277 MPa), high density of dislocations (∼176–193 MPa), Cr2N precipitates (∼243 MPa) and SFs (∼131 MPa) are regarded as the dominate strengthening contributors. On the other hand, HCP phase triggered by strain induced martensite transformation (SIMT) and the Lomer-Cottrell locks (L-C locks) associated with the numerous SFs significantly enhanced the alloy strain hardening rate. More importantly, the formed Cr2N nanoprecipitates effectively suppressed the strain localisation and the premature failure along the HCP/FCC interfaces by deflecting the continuous growth of SFs, further contributing to the high ductility of the LPBF processed CCMN alloy. The present study is expected to shed light on the future development of N-doped high-performance cobalt-based alloy for the LPBF process.

A novel high-efficiency industrialized clean production technology based on multi-stage gradient batching and smelting was proposed for the production of high-quality ferrovanadium. The thermodynamic mechanism of aluminothermic reduction equilibrium, alloy settlement and raw material impurity distribution were confirmed, and a multi-stage double-gradient aluminum addition pattern (DG-ADP), the highly efficient separation of molten slag and alloy, and typical impurity control standards of raw materials were achieved on the basis of a self-propagating high-temperature synthesis with an electric auxiliary heating (SHS-EAH) process. The reduction efficiency, separation efficiency and the comprehensive utilization rate of the secondary resources were significantly improved, as the whole total vanadium (T.V) content in the industrially produced residue slag reduced from 2.34 wt.% to 0.60 wt.%, while the corresponding smelting yield increased from 93.7 wt.% to 98.7 wt.% and the aluminum consumption decreased from 510 kg·t−1 to 400 kg·t−1. The multi-stage DG-ADP process enabled the internal circulation of vanadium-bearing materials in the ferrovanadium smelting system, as well as the external circulation of iron and residue slag in the same system, and finally achieved the zero discharge of solid and liquid waste from the ferrovanadium production line, which provides a brand-new perspective for the cleaner production of ferrovanadium alloy.

Lightweight aluminum (Al) alloys have been widely used in frontier fields like aerospace and automotive industries, which attracts great interest in additive manufacturing (AM) to process high-value Al parts. As a mainstream AM technique, laser-directed energy deposition (LDED) shows good scalability to meet the requirements for large-format component manufacturing and repair. However, LDED Al alloys are highly challenging due to their inherent poor printability (e.g. low laser absorption, high oxidation sensitivity and cracking tendency). To further promote the development of LDED high-performance Al alloys, this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys. The porosity, cracking, distortion, inclusions, element evaporation and resultant inferior mechanical properties (worse than laser powder bed fusion) are the key challenges in LDED Al alloys. Processing parameter optimizations, in-situ alloy design, reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys. The underlying correlations between processes, alloy innovation, characteristic microstructures, and achievable performances in LDED Al alloys are discussed. The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized. This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys. Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.

The activation of mast cells (MCs) and mediator release are closely related to the pathophysiology of irritable bowel syndrome (IBS). However, the exact underlying mechanisms are still not completely understood. The nuclear receptor subfamily 4a (Nr4a) is a family of orphan nuclear receptors implicated in regulating MC activation, degranulation, cytokine/chemokine synthesis and release. Acute and chronic stress trigger hypothalamic–pituitaryadrenal axis (HPA) activation to induce the release of corticotropin-releasing hormone (CRH), resulting in MC activation and induction of the Nr4a family. Our newest data showed that Nr4a members were specially over-expressed in colonic MCs of the chronic water-avoidance stress (WAS)-induced visceral hyperalgesia mice, suggesting that Nr4a members might be involved in the pathophysiology of visceral hypersensitivity. In this review, we highlight the present knowledge on roles of Nr4a members in the activation of MCs and the pathophysiology of IBS, and discuss signaling pathways that modulate the activation of Nr4a family members. We propose that a better understanding of Nr4a members and their modulators may facilitate the development of more selective and effective therapies to treat IBS patients.

Oxide dispersion strengthened (ODS) superalloys are widely used in aerospace and nuclear reactors due to their exceptional creep strength and fatigue crack resistance at elevated temperature. In this work, an ODS NiCrFeY alloy for high temperature applications was fabricated by laser powder bed fusion (L-PBF). The microstructure and mechanical properties at room and elevated temperature of the L-PBF processed ODS NiCrFeY alloy were investigated. It was demonstrated that equiaxed grains with large fraction of low angle grain boundaries and cellular structures with high density of dislocations were obtained in the as-built alloy. Dispersed Y2O3 nanoparticles were in-situ formed in the ODS NiCrFeY alloy. Most of the Y2O3 nanoparticles were located at the cellular walls and pinned with a large number of dislocations. Due to the strengthening effects by dispersed Y2O3 nanoparticles and fine cellular structures, the ODS NiCrFeY alloy showed high ultimate tensile strength of 810, 560 and 250 ​MPa at room temperature, 600 ​°C and 800 ​°C, respectively.

Abstract Background Calcitonin gene-related peptide (CGRP) as a mediator of microglial activation at the transcriptional level may facilitate nociceptive signaling. Trimethylation of H3 lysine 27 (H3K27me3) by enhancer of zeste homolog 2 (EZH2) is an epigenetic mark that regulates inflammatory-related gene expression after peripheral nerve injury. In this study, we explored the relationship between CGRP and H3K27me3 in microglial activation after nerve injury, and elucidated the underlying mechanisms in the pathogenesis of chronic neuropathic pain. Methods Microglial cells (BV2) were treated with CGRP and differentially enrichments of H3K27me3 on gene promoters were examined using ChIP-seq. A chronic constriction injury (CCI) rat model was used to evaluate the role of CGRP on microglial activation and EZH2/H3K27me3 signaling in CCI-induced neuropathic pain. Results Overexpressions of EZH2 and H3K27me3 were confirmed in spinal microglia of CCI rats by immunofluorescence. CGRP treatment induced the increased of H3K27me3 expression in the spinal dorsal horn and cultured microglial cells (BV2) through EZH2. ChIP-seq data indicated that CGRP significantly altered H3K27me3 enrichments on gene promoters in microglia following CGRP treatment, including 173 gaining H3K27me3 and 75 losing this mark, which mostly enriched in regulation of cell growth, phagosome, and inflammation. qRT-PCR verified expressions of representative candidate genes (TRAF3IP2, BCL2L11, ITGAM, DAB2, NLRP12, WNT3, ADAM10) and real-time cell analysis (RTCA) verified microglial proliferation. Additionally, CGRP treatment and CCI increased expressions of ITGAM, ADAM10, MCP-1, and CX3CR1, key mediators of microglial activation in spinal dorsal horn and cultured microglial cells. Such increased effects induced by CCI were suppressed by CGRP antagonist and EZH2 inhibitor, which were concurrently associated with the attenuated mechanical and thermal hyperalgesia in CCI rats. Conclusion Our findings highly indicate that CGRP is implicated in the genesis of neuropathic pain through regulating microglial activation via EZH2-mediated H3K27me3 in the spinal dorsal horn.

Aluminum alloy is an important material used in railway train structures. It is of great significance to repair aluminum alloy through directional energy deposition to reduce cost and improve the performance of the aluminum alloy. In this study, 7N01 aluminum alloy was repaired by means of laser-directed energy deposition (DED) with the powder of Sc-modified Al-Zn-Mg aluminum alloy as raw material. The microstructure and mechanical properties of the repaired specimens were studied through the metallographic microscope, scanning electron microscope, electron backscatter diffraction, universal tensile test, and Vickers hardness test in combination. The results show that the bonding interface of the repaired aluminum alloy is satisfactory, and the porosity is 2.8%. The grains in the repaired area are the columnar crystals growing vertically along the boundary of the melt pool with an obvious temperature gradient. Fine equiaxed crystals are distributed along the boundary of the melt pool, and Al3(Sc,Zr) particles play a role in grain refinement. The average grain size of the fine grain area in the repair zone next to the fusion zone is 9.1 μm, and the average grain size of the coarse grain area is 20 μm. The average tensile strength in the area of repair approaches 349 MPa, which is 91% that of the base material, and the elongation rate is 10.9%, which is 53.2% that of the base material. The hardness ranges between 122 HV and 131 HV, which is comparable to the base material. However, there is a significant decrease in the tensile strength and hardness of the base material (heat-affected zone).

Ni _51 Ti _49 at.% bulk was additively manufactured by laser-directed energy deposition (DED) to reveal the microstructure evolution, phase distribution, and mechanical properties. It is found that the localized remelting, reheating, and heat accumulation during DED leads to the spatial heterogeneous distribution of columnar crystal and equiaxed crystal, a gradient distribution of Ni _4 Ti _3 precipitates along the building direction, and preferential formation of Ni _4 Ti _3 precipitates in the columnar zone. The austenite transformation finish temperature ( A _f ) varies from −12.65 °C ( Z = 33 mm) to 60.35 °C ( Z = 10 mm), corresponding to tensile yield strength ( σ _0.2 ) changed from 120 ± 30 MPa to 570 ± 20 MPa, and functional properties changed from shape memory effect to superelasticity at room temperature. The sample in the Z = 20.4 mm height has the best plasticity of 9.6% and the best recoverable strain of 4.2%. This work provided insights and guidelines for the spatial characterization of DEDed NiTi.

The surface of copper-chromium alloy was processed by Al-Si-Ni multi-permeation and friction stir processing, and the microstructure and mechanical properties of the surface layer were tested by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness tester and friction testing machine. The results show that Al, Si and Ni elements are fully permeated into the surface of copper-chromium alloy after multielement co-infiltration and friction stir processing. In the observation of the microstructures, we found that the reticular structure is fragmented and distributed in the stir zone region. Microstructure becomes finer and grains refinement. The micro hardness of the copper-chromium alloy increased to 129 HV, 44.9% higher than that of the original matrix. The main reasons of microhardness enhancement are solid solution strengthening, fine grains strengthening and dispersion strengthening. The friction test results show that the friction coefficient is basically stable at 0.69 and the wear mass is only 0.0017 g after 10 min of friction test. The improvement of wear resistance was attributed to the increase of microhardness of the alloy surface. Keywords: Copper-chromium alloy, Al-Si-Ni multi-permeation, Friction stir processing, Microstructure, Mechanical properties

The synthesis of Fe40Mn40Cr10Co10/WC composites by a combination of ball milling and spark plasma sintering is reported and corresponding mechanical and tribological properties of these composites are investigated. Compared with the Fe40Mn40Cr10Co10 MEA (medium entropy alloy), the addition of 10 vol.% WC nanoparticles led to an increase in the compressive strength and hardness from 1.571 GPa and 320 HV to 2.324 GPa and 788 HV, respectively. Meanwhile, tribological tests demonstrated that the friction coefficient, wear depth and width of the composite decreased in comparison with Fe40Mn40Cr10Co10 MEA. Load transfer effect, thermal mismatch mechanism, Orowan strengthening and grain refinement resulting from synergistic effects between ex-situ WC nanoparticles and in-situ M23C6 nanoprecipitates are responsible for the improvement in mechanical properties, especially thermal mismatch mechanism and grain refinement. In addition, the enhancement in tribological properties is also ascribed to these synergistic effects. Keywords: Composites, Medium entropy alloys (MEAs), Microstructure, Mechanical property, Tribological property

The corrosion behaviors of equiatomic CoCrFeMnNi high-entropy alloys (HEAs) were comparatively investigated between selective laser melting (SLM) and casting. The cast sample shows better corrosion resistance in 3.5 wt.% NaCl solution than the SLM printed sample due to the higher density of dislocations, pores, and cracks in SLM samples, which significantly reduces their corrosion resistance. Furthermore, it is found that the corrosion resistance is different between the planes parallel and perpendicular to the building direction of SLM sample because of the differences in grain orientation, grain size, and surface morphology. Electrochemical anode dissolution rates of the SLM printed CoCrFeMnNi HEAs on their planes parallel and perpendicular to the building direction are calculated and the results show that the pores and cracks dominate the corrosion resistance rather than the grain boundary and the grain orientation.

Additive manufacturing Al-Mg-Sc-Zr alloys offer significant advantages for lightweight application with complex shapes. The paper systematically investigated the effects of aging treatment on microstructural evolution and mechanical properties of SLM printed Al-3.02Mg-0.2Sc-0.1Zr alloy. The SLM printed sample with a relative density of 99.2% was achieved at an optimal laser parameters. After aging, the hardness was improved from initial 85 HV of as-printed sample to 120 HV. The strength and ductility trade-off of the printed sample can be tailored by regulating aging parameters; the maximal tensile strength of 400 MPa and yield strength of 327 MPa can be obtained at an optimal aging parameters. The XRD patterns show the secondary peak of Al3(Sc,Zr) after aging treatment due to Al3(Sc,Zr) particles separation from the α-Al matrix and the diffraction angles shifts to a higher value owing to the release of residual stress. Moreover, Nano-sized Al3(Sc,Zr) precipitates on the grains boundaries hamper grain growth, which was responsible for the grain sizes maintaining after aging treatment. Keywords: Selective laser melting, Aging treatment, Al-Mg-Sc-Zr alloy, Mechanical properties

Selective laser melting (SLM) and direct energy deposition (DED) are two widely used technologies in additive manufacturing (AM). However, there are few studies on the combination of the two technologies, which can synthetically combine the advantages of the two technologies for more flexible material design. This paper systematically studies the Al-Mg-Sc-Zr alloy by combination of SLM and DED with emphasis on its bonding properties, microstructure, and metallurgical defects. It is found that the aluminum alloy prepared by the two methods achieves a good metallurgical combination. The microstructure of aluminum alloy prepared by DED is composed of equiaxed crystals, and there are a large number of Al3(Sc, Zr) precipitated phase particles rich in Sc and Zr. The microstructure of SLM aluminum alloy is composed of equiaxed crystals and columnar crystals, and there is a fine-grained area at the boundary of the molten pool. With the decrease of laser volumetric energy density (VED), the width and depth of the molten pool at the interface junction gradually decrease. The porosity gradually increases with the decrease of VED, and the microhardness shows a downward trend. Tensile strength and elongation at fracture of the SLM printed sample at 133.3 J/mm3 are about 400 MPa and 9.4%, while the direct energy depositioned sample are about 280 MPa and 5.9%. Due to the excellent bonding performance, this research has certain guiding significance for SLM–DED composite aluminum alloy.

The interdiffusion behaviors of elements at the W/Co interface under the application of current during SPS were investigated. It is found that Co _7 W _6 and Co _3 W are formed at the W/Co bonding interface. The growth of the Co _3 W layer is apparently improved by the high current during SPS. The growth rate constant of the Co _3 W layer undercurrent is 1.73–3.03 times faster than that without current. The research shows that the growth rate is increased with the current density. The growth activation energy of the Co _3 W layer is calculated to be 229.51 ± 27 kJ mol ^−1 undercurrent, which is smaller than that without current (279.38 ± 11 kJ mol ^−1 ). Moreover, the growth activation energy of the Co _3 W layer is decreased with the increase of the current density. The mechanism of current-improved growth of the Co _3 W layer is suggested to be the fact that the current lowers the nucleation barrier of intermetallic layer, which accordingly promotes chemical reactions.