Wen Chen

Bioinspired hierarchical microstructures offer a route toward engineered fatigue resistance in additively manufactured alloys. However, it remains unclear how discrete structural constituents independently govern damage accumulation, particularly during the critical fatigue initiation regime where short cracks strongly interact with local microstructure. Here, we investigate multiscale fatigue initiation in a dual-phase, nanolamellar AlCoCrFeNi 2.1 high-entropy alloy. By comparing microscale specimens that isolate the nanolamellar structure against macroscale specimens containing the full melt-pool architecture, we identify size-dependent fatigue initiation mechanisms. We find that failure is dictated by nanolamellar interfaces at the microscale, whereas mesoscale melt pool boundaries serve to initiate fatigue at the macroscale. This mechanistic shift is accompanied by a transition from macroscale quasi-brittle failure to microscale plasticity-driven crack extension. Our results provide a physical framework for understanding how structural hierarchy governs the transition from discrete microstructural deformation to continuum fatigue fracture behavior, informing the design of damage-tolerant, additively manufactured alloys.

We report a pressure-induced structural phase transformation in an additively manufactured (AM) AlCrFe2Ni2 high-entropy alloy. High laser scan-speed processing during AM has been shown to strongly suppress FCC formation, yielding BCC/B2-dominant microstructures. Synchrotron x-ray diffraction reveals a reversible BCC/B2 → HCP transition near ∼13 GPa that mirrors the α-Fe → ɛ-Fe transformation in elemental iron. Notably, this iron-like phase change occurs despite substantial chemical disorder and multi-element site occupancy, demonstrating that the BCC lattice instability leading to close-packed polymorphs can persist in a highly disordered matrix. At ambient pressure, AlCrFe2Ni2 exhibits robust ferromagnetic behavior associated with the BCC/B2 phase. The observation of an α-Fe–like polymorphic pathway in a chemically complex alloy shows that classic cubic-to-close-packed transformation physics is not extinguished by compositional complexity. As a result, AlCrFe2Ni2 emerges as a model system for exploring pressure-driven polymorphism and potential magneto-structural coupling in high-entropy alloys.

High entropy alloys (HEAs) are a new class of metals that exhibit unique mechanical performance. Among HEAs, additively manufactured eutectic high entropy alloys (AM EHEAs) have recently emerged as candidate materials for use in extreme conditions due to their simultaneous high strength and ductility. However, the deformation and structural evolution of AM EHEAs under conditions of high pressure have not been well characterized, limiting their use in extreme applications. Dynamic compression experiments and molecular dynamics simulations are presented to study the structural evolution of AM EHEA AlCoCrFeNi 2.1 when compressed to pressures up to 400 GPa. In situ X‐ray diffraction measurements capture the appearance of face‐centered cubic and body‐centered cubic phases at different pressure conditions, with pure‐ and mixed‐phase regions. Understanding the phase stability and structural evolution of the AM EHEA offers new insights to guide the development of high‐performance complex materials for extreme conditions.

Developing structural materials with ultrahigh-temperature capabilities is crucial for aerospace and energy applications, yet achieving a balance of strength, heat-softening resistance, and plasticity remains challenging. Here, we report a tungsten-based W-Re-Os alloy with exceptional mechanical properties up to 1400 °C. Utilizing multi-principal element alloy design principles, three refractory metals with melting points above 3000 °C—W, Re, and Os elements are alloyed using combinatorial additive manufacturing. This approach enabled rapid fabrication of ~500 compositions in a single run. High-throughput micro-indentation testing identified W42Re30Os28 as a standout candidate, exhibiting an ultrahigh yield strength of ~1.8 GPa and ~9% compressive plasticity at room temperature, while retaining ~1.4 GPa yield strength with remarkable strain-hardening at 1400 °C, far surpassing other high-temperature alloys reported to date. These properties arise from its dual-phase hypoeutectic microstructure and multiple deformation mechanisms, including basal and non-basal dislocation slip, deformation twinning, and hetero-deformation-induced geometrically necessary dislocations. A W-Re-Os refractory multi-principal element alloy is developed by high-throughput combinatorial additive manufacturing. This alloy exhibits outstanding mechanical properties and thermal stability over a wide range of temperatures up to 1400 °C.

Eutectic high-entropy alloys (EHEAs), such as nano-lamellar AlCoCrFeNi₂.₁, have gained widespread attention due to their excellent mechanical properties, high hardness, wear resistance, and corrosion resistance—even at elevated temperatures (e.g., >1000 °C). In this study, we investigated the corrosion behavior of AlCoCrFeNi₂.₁ EHEAs fabricated via laser powder bed fusion (L-PBF) 3D printing, as a function of annealing temperature. These EHEAs are composed of two phases: a ductile FCC L1₂ phase and a high-strength BCC B2 phase. Due to the rapid solidification inherent to L-PBF, the as-printed microstructure is far from equilibrium, resulting in a nearly homogeneous elemental distribution across phases. Upon annealing, the system evolves toward equilibrium, leading to enrichment of Cr, Co, and Fe in the FCC phase and Al and Ni in the BCC phase. Additionally, because Cr has limited solubility in the B2 phase, Cr-rich precipitates (on the order of tens of nanometers) form and become more prominent with higher annealing temperatures. Three processing conditions were considered in this study: (1) as printed, (2) annealed at 600 °C for 5 hours, and (3) annealed at 1000 °C for 1 hour. With increasing annealing temperature, the lamellar B2 phase coarsened, Cr-rich precipitates grew, and elemental segregation became more pronounced. Samples were characterized using electron backscatter diffraction to determine crystallographic orientation and energy-dispersive spectroscopy to assess local composition. Further, in situ electrochemical Atomic Force Microscopy was deployed to investigate the relationship between microstructure and corrosion behavior. These studies revealed preferential corrosion of the B2 phase and was most pronounced in regions adjacent to Cr-rich precipitates, where the matrix is depleted in Cr. Corrosion was found to be greater in samples subject to increased annealing temperature. For instance, after 5 hours exposure in 0.05 M H 2 SO 4 , corrosion pit depths increased from ~ 10 nm in the as-printed structure to ~360 nm on the sample annealed at 1000°C, while the pitted area increased from ~2% to 12%. Additionally, electrochemical impedance spectroscopy was used to quantify the charge transfer resistance-an indicator inversely proportional to the corrosion rate- and to monitor oxide evolution. Laser confocal microscopy was used to assess corrosion over larger areas and extended time scales. We expect that such a multimodal approach will inform processing methodologies to design materials systems for high mechanical performance and robust corrosion resistance. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Ni40Co20Fe10Cr10Al18W2 additively manufactured using laser powder bed fusion (LPBF) is among the toughest as-built alloys reported and is a promising candidate for use in extreme environments. However, its behavior under multi-megabar pressure regimes remains unexplored. We used femtosecond in situ X-ray diffraction to investigate the shock response of LPBF Ni40Co20Fe10Cr10Al18W2 under laser-driven shock compression and release. Our results reveal that the initial dual-phase face-centered + body-centered structure transforms to a single face-centered phase over a wide pressure range of 84 +/- 10 to 277 +/- 55 GPa, followed by a transition to a single body-centered phase at 431 +/- 48 GPa. We establish the Hugoniot equation-of-state of LPBF Ni40Co20Fe10Cr10Al18W2 and compare it to the benchmark alloy AlCoCrFeNi2.1, demonstrating the effects of W-doping and increased Al content. High stacking fault probabilities, close to those measured in Au and Ag, are observed upon compression. A portion of the stacking faults are annihilated upon release to ambient pressure.

PID control has been always preferred for basic control technology in the field of industrial process control. With the increase of complexity, time delay and time varying of control object, PID control cannot meet the control requirements. Replacing the existing PID control represents a correct direction of development, and when existing PID control can be replaced depends on people's understanding of the essential problems of PID control. In this paper, the mechanism of conventional integrator (CI) in PID control tracking constant disturbances was revealed, which leads to its low efficiency. A novel feedback controller(NFC) which has better performance than PID controller based on fastest tracking filter(FTF) was proposed, but it can’t meet the requirement of complex system control. For this reason, engineering researchers proposed the problem of engineering reconstruction of FTF and obtained an engineering fastest tracking filter (EFTF), An engineering fastest controller (EFC) based on EFTF was constructed, significantly improved feedback control performance. According to mathematical calculation analysis, simulation experiments, and actual engineering applications, it was concluded that EFC breaks through the performance upper limitation of PID control.

Abstract Laser additively manufactured microscale metallic lattices show great potential for high-performance applications, yet trade-offs among geometric precision, structural integrity, and computational efficiency still persist. Here, we introduce a stereolithography file format-free (STL-free) hybrid toolpath generation method for laser-based powder bed fusion (PBF-LB) that synergizes implicit geometric modeling with optimized laser scanning strategy, overcoming these limitations. By circumventing traditional mesh-based workflows, our method directly translates implicit lattice geometries into laser toolpaths while precisely regulating energy deposition trajectories. This mesh-free process enables the fabrication of complex shell lattices with ultra-thin walls and enhanced surface quality. In addition to reducing memory usage and processing time by up to 90%, the method yields a synergistic enhancement in mechanical performance, notably improving both strength and toughness. By bridging computational design and fabrication, this framework enables the scalable production of high-performance microscale lattices and unlocks their potential for industrial applications.

Abstract High‐entropy alloys (HEAs) are promising candidates for advanced structural applications due to their excellent mechanical properties. Additive manufacturing (AM), with its rapid solidification conditions, enables the creation of unique nonequilibrium microstructures. To fully leverage the synergy between AM and HEAs, understanding how processing affects structure and properties is essential. Here, how solidification rate influences microstructure evolution and phase transformation pathway in laser additively manufactured AlCrFe 2 Ni 2 eutectic HEAs is investigated. By increasing the laser scan speed and hence the solidification rate, distinct solidification modes evolving from coupled eutectic to anomalous eutectic and eventually to single‐phase solidification are revealed. These transitions result in distinct microstructures and a wide range of mechanical properties. Thermodynamic modeling and molecular dynamics simulations reveal that low cooling rates allow for sufficient atomic diffusion and phase separation, facilitating coupled eutectic growth. In contrast, rapid cooling suppresses diffusion and destabilizes the solid–liquid interface, promoting anomalous or single‐phase solidification. This integrated experimental and computational approach provides a multiscale understanding of solidification mechanisms in HEAs and underscores how kinetic effects can over‐ride thermodynamic predictions under nonequilibrium conditions. These results demonstrate that AM can serve as a powerful tool to design HEAs with tailored microstructures and properties.

We report on a pressure induced irreversible phase transformation in an ordered eutectic high-entropy alloy (EHEA) AlCoCrFeNi 2.1 . The suction cast sample was synthesized by arc melting of raw elements resulting in an ordered B2 and FCC phase mixture for eutectic AlCoCrFeNi 2.1 alloy. This phase mixture was confirmed by transmission electron microscopy (TEM) where superlattice reflections corresponding to ordered B2 phase were observed while the FCC phase remains disordered. The B2 phase was observed to be enriched in Nickel and Aluminum while the surrounding FCC phase is enriched in Fe, Cr and Co. The suction-cast EHEA sample was studied by X-ray diffraction under high pressure in a diamond anvil cell with platinum pressure marker to 73 GPa at ambient temperature. The B2 to FCC phase transformation is completed by 3 GPa in sharp contrast to BCC to FCC phase transition of 21 GPa in additively manufactured EHEA samples. The X-ray diffraction and TEM studies of pressure recovered samples show presence of only FCC grains without any specific orientation with respect to starting sample. These results are consistent with molecular dynamics simulations that the presence of B2 phase aids in the formation of the B2 to FCC phase transition under high pressures.

Diabetic retinopathy (DR) is characterized by pathological angiogenesis, inflammation, and retinal neurodegeneration, leading to vision loss. Current therapies, such as anti-VEGF agents, face challenges of low bioavailability and frequent invasive injections. Connexin43 (Cx43), a gap junction protein, plays a key role in DR progression through its modulation of inflammation and vascular dysfunction. A thermosensitive hydrogel composite was developed to encapsulate siRNA targeting Cx43 (si-Cx43) nanoparticles (NPs) and anti-VEGF (Avastin). The hydrogel was characterized for gelation, injectability, and degradation. In vitro studies evaluated the cytotoxicity, anti-angiogenic effects, and permeability regulation in hyperglycemic retinal cells under hyperglycemic conditions. In vivo therapeutic efficacy was assessed in a diabetic retinopathy rat model. si-Cx43-NPs demonstrated high siRNA encapsulation efficiency and stability, effectively silencing Cx43 expression in retinal endothelial cells. The hydrogel exhibited excellent injectability, temperature-sensitive gelation, and controlled degradation. In vitro, si-Cx43-NPs@Avastin-hydrogel significantly suppressed VEGF expression, reduced angiogenesis, and restored cell permeability under hyperglycemic conditions. In vivo , the hydrogel composite reduced neovascularization, inflammation, and apoptosis, restoring retinal structure and function more effectively than either single-agent treatment alone. Biocompatibility studies confirmed minimal toxicity and favorable degradation. The si-Cx43-NPs@Avastin-hydrogel provides a synergistic and minimally invasive therapeutic strategy for DR by targeting angiogenesis, inflammation, and neuroprotection with sustained drug delivery.

• Both the anomalous tensile strength (ATS) behavior and the higher strain-strengthening rate under high temperature of Mg-RE alloy was observed in their homogenization treated (solid solution, SS) alloy, while it vanished after the peak-aging treatment. • The atomic ATS process was successfully built for the Mg-RE SS alloys by molecular dynamics simulation, and this behavior was closely related to RE atoms distribution on the non-basal pyramid planes and the atoms near neighbor correlation. • Formation of more stacking faults (SFs), and the locked dislocation at the intersection of non-basal plane and basal plane were the main reason for the ATS of Mg-RE alloys. This study systematically investigates the unusual tensile mechanical behavior of Mg-RE solid solution (SS) alloys, exhibiting anomalous tensile strengths (ATS) and an enhanced strain-hardening rate at high temperature. Both the peak ultimate tensile strength (UTS) and tensile yield strength (TYS) values occur at 150–200 °C, which are 12–50% higher compared to those at room temperature (RT). Meanwhile, the strain-hardening rate increases with the temperature rising from RT to 200 °C during the plastic deformation process. The results reveal that the formation of stacking faults (SFs) and the locking of dislocations, particularly immobile 〈c〉 partial dislocations, enhance resistance to plastic deformation, leading to higher strengths at high temperature. Furthermore, the interactivity between SFs and 〈 c + a 〉 dislocations intensify with rising of temperature. The presence of RE atoms in the SS plays a critical role in this unique mechanical behavior, as they preferentially occupy non-basal planes rather than basal planes, thereby reducing the stacking fault (SF) formation energy. This study provides new insights into the high-temperature strengthening mechanisms of Mg-RE based alloys, offering potential guidance for the design of advanced lightweight materials with superior mechanical properties.

Nanoparticles or precipitates are long used to block dislocations to strengthen metals. However, this strengthening mechanism unavoidably adds stress concentrations at the obstacles, instigating crack initiation that hampers ductility. Here, we demonstrate a strategy that replaces the traditional crystalline dispersions with dense amorphous nanoparticles, which is made possible via laser powder bed fusion. Porosity-free copper-based nanocomposites are demonstrated as a prototype, consisting of densely and uniformly distributed amorphous boron–carbide nanoparticles (~47 nm in average diameter, up to 12% volume fraction) via an in situ nanofragmentation and melt-quench process. The amorphous nanoparticles act as dislocation sinks, thereby alleviating local stress concentration. They also self-harden along with tensile deformation, promoting strain hardening and therefore homogeneous plastic flow. The as-built composite achieves a tensile strength of more than one gigapascal and a total elongation of approximately 10%, more than twice that of its crystalline dispersion counterpart. Defect accumulation is also suppressed upon cyclic deformation of the as-built bulk nanocomposites, delivering a fatigue strength limit (at > 107 cycles) of more than 70% of the tensile strength. Our results demonstrate an effective strategy for additive manufacturing of metallic materials with superior properties. Crystalline dispersoids are commonly used to strengthen metals by obstructing dislocation movement, but this often comes at the cost of ductility. Here, the authors demonstrate that amorphous nanoparticles, introduced via additive manufacturing, enhance both the tensile strength and fatigue resistance of metallic materials.

Laser additive manufacturing of pure copper (Cu) with complex geometries opens vast opportunities for the development of functional devices in microelectronics and telecommunication. However, laser additive manufacturing of high-resolution pure Cu remains a challenge. Here we report a facile oxide-dispersion-strengthening (ODS) strategy that enables additive manufacturing of Cu with sub-100 μm (~70 μm) resolution by laser powder-bed fusion. This ODS strategy starts with oxygen-assisted gas atomisation to introduce ultrafine Cu2O nanoparticles into the pure Cu powder feedstock. These nanoscale dispersoids not only improve the laser absorptivity and the viscosity of the melt but also promote dynamic wetting behaviour. The ODS Cu exhibits a remarkable yield strength of ~450 MPa and a large uniform elongation of ~12%, while preserving a high electrical conductivity. As an example, we printed an ODS Cu micro-architected terahertz antenna, which demonstrates a 2.5-fold improvement in signal intensity compared with traditional 3D-printed pure Cu antennas. This paper introduces an oxide-dispersion-strengthening strategy that enables sub-100 μm. high-precision additive manufacturing of copper, thereby addressing the limitations of current processes for microscale technologies.

Additively manufactured (AM) High Entropy Alloys (HEAs) are notable for their exceptional high-yield strength and large tensile ductility. The nanolamellar Eutectic HEA (EHEA) AlCoCrFeNi 2.1 was fabricated by laser powder bed fusion (L-PBF) in the as-printed form (EHEA1) and subsequently annealed at 1000 °C (EHEA2) and 600 °C (EHEA3) to achieve a broad range of mechanical properties. EHEA2 and EHEA3 samples were studied using Scanning transmission electron microscopy (STEM), energy dispersive X-ray diffraction (EDXRD) at high-pressures and high temperatures, nanoindentation hardness and modulus measurements. According to EDXRD EHEA2 and EHEA3 are composed of B2 and L1 2 phases. High-pressure high-temperature EDXRD studies show melting for EHEA2 at 1698 ± 25 K at a pressure of 6.5 GPa and melting for EHEA3 at 1598 ± 25 K at a pressure of 5.8 GPa. Post-melt and recrystallized samples were recovered at ambient conditions, and XRD analysis showed retention of B2 and L1 2 phases, although a new σ phase appeared for both EHEA2 and EHEA3 samples due to high-pressure and high-temperature melting and recrystallization experiment. SEM analysis also demonstrated the preservation of the nanolamellar morphology. Nanoindentation studies revealed that recrystallized EHEAs retain their original mechanical property hierarchy, with EHEA3 being 47 % harder than EHEA2, largely related to higher content of B2-phase and retention of nanolamellar morphology. We also present Pressure-Volume-Temperature (P-V-T) data for 3-D printed and annealed eutectic high entropy alloys and extract mechanical and thermal properties data. • AlCoCrFeNi 2.1 samples synthesized via 3-D printing and subsequent annealing • X-ray Diffraction confirmed B2 (BCC) and L1 2 (FCC) phases in annealed samples. • Melting and recrystallization of samples under high-pressures and high-temperatures. • Recrystallized samples retain the nano lamellar structure like annealed samples.

With the continuous growth of global demand for renewable energy, the utilization of rainwater resources has gradually become a focal point of research. Piezoelectric energy harvesting has received significant attention because the harvester has simple structure, high energy conversion efficiency, and self-powering capability. However, traditional piezoelectric energy harvesters are limited by the narrow resonance frequency bandwidth and the insufficient waterproofing ability, which restricts the adaptability of energy conversion to variable environmental excitations. To solve this problem, a broadband piezoelectric cantilever energy harvester for rainwater energy harvesting is designed in this work. The influence mechanisms of droplet impact parameters, waterproof encapsulation technology, and MFC cantilever structure on the electrical output performance are studied through theoretical analysis, numerical simulation, and experimental validation. It reveals that the droplet’s Weber number exhibits a direct proportionality with the impact force, which is distributed within the 0–80 Hz frequency range. Simulations and experimental results demonstrate that the U-shaped piezoelectric energy harvester significantly outperforms other designs in terms of broadening the resonant frequency range and extending oscillation duration, achieving an oscillation time of 23.7 s, a charge transfer of 2.82 μC, and an output power density of 37.76 W/m<sup>2</sup> under a single impact. It demonstrates its efficient energy harvesting capability in a wide resonance frequency range. Additionally, the U-shaped design also improves its waterproof performance, thus further enhancing its applicability in rainwater environments. This study provides a novel, universally applicable approach for collecting rainwater energy, expands the application scenarios of piezoelectric energy harvesting technology, and provides theoretical references and practical guidance for designing and applying broadband energy harvesters.

Abstract Nanostructured multi-principal element alloys (MPEAs) have been explored as next-generation engineering materials due to unique mechanical and functional properties which have significant advantages over traditional dilute alloys. However, the practical applications of nanostructured MPEAs are still limited due to the lack of scalable processing approaches to prepare a large quantity of nanostructured MPEAs, as well as lack of an efficient pathway for high-throughput discovery of better functional nanostructured MPEAs within their vast compositional space. Here we tackle these challenges by presenting an integrated approach by combining direct-ink-writing-based additive manufacturing, solid-state sintering, and chemical dealloying to manufacture hierarchically porous MPEAs. The hierarchical structure is comprised of macro- and micro-scale pores introduced via extrusion printing and polymer decomposition during sintering, as well as nanoscale pores formed via chemical dealloying. The macro- and micro-scale pores allow efficient dealloying of a large mass of material as the diffusion length that the corroding medium must penetrate remains at the scale of the ligaments formed after sintering (∼10 μ m), despite the large volume of the 3D-printed samples. In addition, this integrated approach enables versatile control of the alloy composition via precisely tuning the ratio of elemental powders in the starting ink, thus offering a pathway for high-throughput discovery of novel functional MPEAs. As a case study, multiscale macro/micro/nanoporous NiFeMn MPEAs with three different compositions were investigated as catalysts to reduce the overpotential of oxygen evolution reaction (OER), where NiFeMn-based electrocatalysts display composition-dependent performance such that the overpotential measured at a current of 0.5 A g −1 for OER increases in the order of Ni 58 Fe 29 Mn 13 ⩽ Ni 64 Fe 26 Mn 10 < Ni 76 Fe 18 Mn 6 . This introduced manufacturing process offers new opportunities for scalable fabrication and rapid screening of nanostructured multi-component complex alloys.

The growing demands for high-temperature materials, especially in aerospace and energy production, compel thorough explorations of innovative materials. Here, we demonstrate signi fi cantly enhanced high-temperature mechanical properties of Inconel 625 (In625) based metal matrix composites (MMCs) fabricated by laser powder bed fusion (LPBF) additive manufacturing. The MMC feedstocks for LPBF were fabricated with fi ne ceramic particles (i.e., titanium diboride (TiB 2 ), titanium carbide (TiC), zirconium diboride (ZrB 2 ) and zirconium carbide (ZrC)) separately mixed with In625 powders. Among the printed specimens, the In625 + TiB 2 showed an exceptional strength-ductility combination at 800 (cid:1) C as well as an outstanding creep resistance at 800 (cid:1) C under 150 MPa tensile stress. The detailed microstructural characterization, along with thermodynamic calculation and atomic simulations, reveal that the addition of TiB 2 results in the formation of serrated grain boundaries, (Cr, Mo)-boride phases near the grain boundaries, and nano-dispersed (Ti, Al, Nb)-oxide phases within the matrix. These features effectively suppress the formation of detrimental high-temperature phases and enhance the material ’ s high-temperature properties. Beyond amplifying the inherent thermal attributes of

Abstract Recent research in multi-principal element alloys (MPEAs) has increasingly focused on the role of short-range order (SRO) on material performance. However, the mechanisms of SRO formation and its precise control remain elusive, limiting the progress of SRO engineering. Here, leveraging advanced additive manufacturing techniques that produce samples with a wide range of cooling rates (up to 10 7 K s −1 ) and an enhanced semi-quantitative electron microscopy method, we characterize SRO in three CoCrNi-based face-centered-cubic (FCC) MPEAs. Surprisingly, irrespective of the processing and thermal treatment history, all samples exhibit similar levels of SRO. Atomistic simulations reveal that during solidification, prevalent local chemical order arises in the liquid-solid interface (solidification front) even under the extreme cooling rate of 10 11 K s −1 . This phenomenon stems from the swift atomic diffusion in the supercooled liquid, which matches or even surpasses the rate of solidification. Therefore, SRO is an inherent characteristic of most FCC MPEAs, insensitive to variations in cooling rates and even annealing treatments typically available in experiments.

consisting of nanolamellar BCC and FCC phases. The direct lattice imaging of 3D-printed samples shows the Kurdjumov-Sachs (K-S) orientation relation {111} FCC parallel to {110} BCC planes in the dual-phase lamellae. Unlike traditional iron and steels, this alloy shows an irreversible BCC-to-FCC phase transformation under high pressures. The nanolamellar morphology is maintained after pressure cycling to 30 GPa, and nano-diffraction studies show both layers to be in the FCC phase. The chemical compositions of the dual-phase lamellae after pressure recovery remain unchanged, suggesting a diffusion-less BCC-FCC transformation in this EHEA. The lattice imaging of the pressure-recovered sample does not show any specific orientation relation between the two resulting FCC phases, indicating that many grain orientations are produced during the BCC-FCC phase transformation. Molecular dynamics simulations on phase transformation in a nanolamellar BCC/FCC in K-S orientation show that phase transformation from BCC to FCC is completed under high pressures, and the FCC phase is retained on decompression aided by the stable interfaces. Our work elucidates the irreversible phase transformation under static compression, providing an understanding of the orientation relationships in 3-D printed EHEA under high pressures.

Abstract The far-from-equilibrium solidification during additive manufacturing often creates large residual stresses that induce solid-state cracking. Here we present a strategy to suppress solid-state cracking in an additively manufactured AlCrFe 2 Ni 2 high-entropy alloy via engineering phase transformation pathway. We investigate the solidification microstructures formed during laser powder-bed fusion and directed energy deposition, encompassing a broad range of cooling rates. At high cooling rates (10 4 −10 6 K/s), we observe a single-phase BCC/B2 microstructure that is susceptible to solid-state cracking. At low cooling rates (10 2 −10 4 K/s), FCC phase precipitates out from the BCC/B2 matrix, resulting in enhanced ductility (~10 %) and resistance to solid-state cracking. Site-specific residual stress/strain analysis reveals that the ductile FCC phase can largely accommodate residual stresses, a feature which helps relieve residual strains within the BCC/B2 phase to prevent cracking. Our work underscores the value of exploiting the toolbox of phase transformation pathway engineering for material design during additive manufacturing.

The fault cavern type reservoir in Block 1 of Shunbei area is located in the ultra-deep layer and is classified as a volatile oil reservoir. The reservoir is characterized by very deep burial with an oil/gas ratio between 250 and 500 m 3 /tone and a saturation pressure range of 28–36 MPa. As of March 2021, the formation pressure has dropped to 30.5 MPa and the pressure retention rate is 35.8%. In order to effectively develop this reservoir, it was decided to use a water injection development method with a planned transition to natural gas injection in March 2022 to further enhance recovery and maintain formation pressure. Through evaluation and research, the pressure distribution, production capacity change and reservoir dynamic response during the water injection development stage were analyzed with respect to the characteristics of fracture-controlled fracture-cave type reservoir in Shunbei-1 block. On this basis, the necessity, feasibility, and expected effects of conversion to natural gas injection are explored, including improvement of displacement efficiency, reduction of fluid output, and enhancement of formation energy replenishment. In addition, this study also carries out in-depth research and prediction on the optimization of natural gas injection parameters, the selection of injection methods and possible problems, aiming to provide scientific basis and technical support for the efficient and sustainable development of this block. In order to smoothly promote the implementation of natural gas injection development, a special reservoir description technique applicable to fault cavern type reservoirs was adopted. Based on this foundation, an in-depth study was conducted on the mechanism of natural gas displacement, so as to optimize the layout of the well network and the setting of injection and extraction parameters. In addition, a set of evaluation system for natural gas injection effect in fault cavern type reservoirs was constructed. By adopting the natural gas injection development method and combining the corresponding supporting technology development and optimization measures, the reservoir development efficiency and oil (gas) production rate have been effectively improved, and the risk of gas flaring has been reduced at the same time. These research results are of great significance for ensuring the comprehensive development and effective utilization of oil and gas resources, and provide strong technical support for future development work.