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Purpose: To measure and compare the mean temperature values due to heat generated during the grinding of different prosthetic materials with diamond burs using a high-speed instrument with and without water cooling. Materials and Methods: In total, 120 disk-shaped specimens (10 × 2 mm), each with a smaller disk in the center (3 × 2 mm), were fabricated from yttrium-stabilized zirconia, monolithic zirconia, glass-ceramic, indirect composite, polyetheretherketone (PEEK), and cast metal (Ni-Cr alloy). The specimens were divided into six groups (n = 20) according to material type. The specimens in each group were ground continuously with a high-speed handpiece and diamond burs with (n = 10) and without (n = 10) water cooling until the smaller disks were removed. Two different methods (thermocouple and thermal camera) were used to measure the temperature during the grinding process. Results were analyzed using two-way ANOVA and paired-samples t test (P < .05). Results: PEEK had the lowest mean temperature and metal had the highest values, both with and without water cooling, according to data measured with a thermocouple. Zirconia and monolithic zirconia samples without water cooling had the highest mean temperature when measured with a thermal camera. Both with and without water cooling, composite samples had the lowest mean temperatures for thermal camera measurements. Conclusions: Water cooling is strongly recommended when grinding all prosthetic materials. The heat transferred to the supporting teeth may depend on the thermal conductivity of the material used. [ABSTRACT FROM AUTHOR]

To alleviate residual stress of ZrO 2 /GH536 brazed joints, the micro-scale structures were fabricated on ZrO 2 via selective laser melting technology before its vacuum brazing with GH536 superalloy. The effects of micro-scale structures on the interfacial microstructure and residual stress of brazed joints were studied. The characterization results indicated that due to its reaction with excessive Ti elements from filler, the micro-scale structures prevented the detrimental effect of over-thick brittle reaction layer on the mechanical properties of joints. Furthermore, the Invar effect of the micro-scale structures facilitated the transfer of residual stress from the ceramic side to the micro-scale structures. According to the numerical simulation results, the maximum residual stress in the brazed joint with micro-scale structures decreased from 622 MPa to 310 MPa. As a result, the fracture path was changed from the flat shape to zigzag. This work reveals the stress-relaxed mechanism of micro-scale structures and provides a new method for fabricating the ceramic/metal joints with low residual stress. [ABSTRACT FROM AUTHOR]

Surface integrity—comprising abrasive embedding, work hardening, and residual stress—is crucial for the performance of nickel-based superalloy components milled by abrasive waterjet (AWJ). Effective evaluation of this integrity is therefore essential. First, the effects of pure waterjet and small-size AWJ on the milled surface were analyzed, with abrasive embedding as a key indicator. It was found that small-size AWJ significantly reduced both the number and depth of abrasive particles embedded. Next, single-factor experiments determined the influence of AWJ process parameters on abrasive embedding, leading to the identification of optimal modification schemes (modification scheme 1 and modification scheme 2) for minimizing the number and depth of abrasives. Recommended processing parameters are waterjet pressure = 100 MPa, and step-over distance = 0.38 mm. Finally, it was observed that both modification schemes decreased surface hardness while significantly increasing residual compressive stress compared to the unmodified surface. These findings offer a theoretical and practical foundation for achieving high surface integrity in the milling of nickel-based superalloys using AWJ. [ABSTRACT FROM AUTHOR]

ATI 718plus is a novel nickel-based high-temperature alloy that delivers superior mechanical properties and higher working temperatures compared to the In718 superalloy. In order to study the machinability of ATI 718plus, a combination of experiments and finite element simulation is used to explore the mechanism of serrated chip formation and the evolution of microstructure under high-speed cutting conditions. Firstly, the Johnson-Cook constitutive model parameters of the ATI 718plus alloy were obtained through a split Hopkinson pressure bar experiment. Secondly, we established a 2D orthogonal cutting model on the AdvantEdge FEM platform by implementing the Johnson-Cook constitutive model and damage model via a custom subroutine. Through the comparison of orthogonal cutting experimental data and finite element simulation results, we verified the accuracy of the finite element model and analyzed the mechanism of serrated chip formation. Finally, combining the multi-physics field distribution of different parameters from the finite element simulation and EBSD test results, it is revealed that the microstructural evolution mechanism during the high-speed cutting of ATI 718plus involves grain lamellar refinement induced by CDRX and grain growth induced by DDRX. The interaction of these two processes results in different forms of microstructures. Under specific cutting parameters, a superfine grain layer with a thickness of 10 µm was formed on the machined surface, which holds great referential significance for our control and improvement of the surface properties in cutting machining. [ABSTRACT FROM AUTHOR]

This study examined the adsorption capacities of biochars derived from kenaf (KF‐BCs) for the removal of heavy metals such as Cu(II) and Pb(II). The thermal decomposition temperature (300–750°C) significantly influenced the morphology and composition of KF‐BCs, enhancing their surface area, pore structure, and alkalinity. Among them, kenaf pyrolyzed at 750°C (KF‐750) was the most effective in removing Cu(II) and Pb(II), as validated by kinetic, equilibrium, and isotherm model analyses. Adsorption kinetics revealed that equilibrium was attained after 24 h, with chemisorption governing the process rate. Equilibrium adsorption conformed to the Langmuir and Freundlich models for Cu(II) and Pb(II), respectively. KF‐750 exhibited midrange adsorption capacities for Cu(II) and Pb(II) (23.47 ± 0.3 mg/g and 50.07 ± 0.9 mg/g, respectively), compared with the literature. The thermodynamic assessment revealed an endothermic process with positive ∆H0, indicating that higher temperatures favor metal adsorption. At low pH, adsorption decreased due to electrostatic repulsion, particularly affecting Cu(II). More than 99.8% of Cu(II) and Pb(II) were removed with a 5.00 g/L KF‐750 dose. The cation effect order on KF‐750 was Ca2+ > Mg2+ > Na+ > K+. Overall, KF‐750 demonstrates promising potential as an adsorbent for the efficient heavy metal removal from aqueous solutions, presenting a viable option for environmental remediation. [ABSTRACT FROM AUTHOR]

This paper focuses on the difficulties in high-quality and high-efficiency micro-milling nickel-based superalloy micro thin-walled parts. The second-generation Non-dominated Sorting Genetic Algorithm (NSGA-II) is improved. A central composite experiment is designed, and a surface roughness prediction model is developed for micro-milling thin-walled parts. A prediction model for surface residual stress on thin-walled parts is developed using an L9(34) orthogonal simulation experiment. Using the NSGA-II algorithm, the four cutting parameters (spindle speed, feed per tooth, axial cutting depth, and radial cutting depth) are optimized to achieve low surface roughness and high material removal rate, while stable cutting and surface compressive residual stress are considered constraints. Finally, the high-quality and high-efficiency micro-milling of the Inconel 718 cross-shaped thin-walled parts is realized. [ABSTRACT FROM AUTHOR]

GH4169 superalloy is an outstanding material used in aerospace, and precision grinding is widely applied to machine GH4169 superalloy, where the grinding force plays essential role on the ground surface quality and the achieved surface topography. In this paper, the material removal mechanism under different machining parameters is analyzed in cylindrical grinding of GH4169 superalloy. The interaction process between abrasive grain and workpiece material is investigated to establish the simulation model of material removed based on the kinematics. The random wheel topography is constructed statistically using the probability density function that characterizes the distribution of the grains. The simulated grinding force and surface topography are in good agreement with the experimental results. Specifically, the errors of the tangential and normal grinding force are 5.33% and 6.33% and the errors of the roughness Sa and Sz are 5.51% and 7.40%, respectively. Based on the simulation model and calculation results, the machining parameters are optimized for cylindrical grinding of GH4169 (vs = 45 m/s, f = 150 mm/min, ap = 3 μm, vw = 0.262 m/s) to improve the achieved surface quality. [ABSTRACT FROM AUTHOR]

This article outlines techniques for optimizing input parameters for the welding process, such as welding current, speed, and gas flow rate in relation to weld bead geometry and Dilution, using Response Surface Methodology (RSM). In the wire arc additive manufacturing (WAAM) process, single-weld bead stability and quality play a prominent role in the final manufactured part's quality and shape. A single-bead geometry model was initially established using RSM, and experiments were carried out using a central composite design of experiments for depositing Inconel 718 in WAAM. The design factors and responses were analyzed using multiple regression equations, and the validity of the resulting regression equations was evaluated using ANOVA. The researchers fabricated a multi-layer structure with optimal parameters, including a welding current of 210 A, 6.91 mm/s speed, and a gas flow rate of 25 l/min. Optical microscopy characterized the microstructures, revealing small dendritic grains in the top layer, equiaxed in the middle and side regions, and columnar in the lower region. The current study benefits industrial applications for developing the Inconel 718 superalloy WAAM structure. [ABSTRACT FROM AUTHOR]

The substantial development that the additive manufacturing technique of powder bed fusion using a laser beam (PBF-LB) underwent in the past decades, though expressive, has been restricted to particular materials and applications. When coming to Ni-based superalloys, the technology has been mostly developed regarding a few polycrystalline Ni–Cr–Fe and Ni–Cr alloys, particularly Inconel 718 and 625. However, when produced using PBF-LB, these materials should undergo tailored heat treatment sequences to adjust its microstructure to industrial standards, which must be developed according to the behavior of each particular alloy. In view of such restrictiveness, this study assessed 77 experimental heat treatments for PBF-LB Inconel X-750, an alloy with comparatively limited research volume when considering additive manufacturing, aiming at providing guidelines for its post-processing after PBF-LB manufacturing. These heat treatments were based on the standard ASM 5668 sequence for maximization of creep resistance, and, contradicting the known precipitation behavior of the conventional material, often resulted in coarse precipitation of detrimental bulk η-Ni3Ti intermetallic phases. This indicates insufficient chemical homogenization after heat treatment, evidencing a different microstructural response of the material when processed using PBF-LB and the importance of optimizing the post-processing of such materials. [ABSTRACT FROM AUTHOR]

In binder-jetting of superalloys, challenges remain as the highly porous green bodies struggle to sinter to full density. Particle rearrangement during supersolidus sintering helped remove printing defects and promote densification, but the segregated elements are often detrimental. Here, a new two-step sintering process was applied to alloy 625. Results indicated that during the first step the material efficiently densified at supersolidus temperatures. Then, segregated elements diffused back into the bulk, resulting in a homogeneous microstructure. [ABSTRACT FROM AUTHOR]

Microtwinning is observed as an important mechanism in γ′ precipitate-strengthened Ni-based superalloys during service at intermediate temperatures. Here, the effect of crystal orientation and stress direction on microtwinning was investigated. The result indicates that the formation of microtwins exhibits orientation dependence and tension-compression asymmetry. Based on the analysis of slip and twinning competition behavior under different conditions, it is deemed that the a/2〈110〉 matrix dislocations would dissociate into a/6〈112〉 Shockley partials in the γ matrix and then a Shockley partial sheared γ' phase and formed microtwins. IMPACT STATEMENT: For the first time, this work explains why microtwinning exhibits orientation dependence and tension-compression asymmetry while stacking faults do not, although they both originate from the activity of {111} 〈112〉 slip systems. [ABSTRACT FROM AUTHOR]

The sensitivity of grain boundary (GB) cracks often limits the high-temperature plasticity of superalloys. The 750 ℃ tensile deformation of fine-grained Ni-Co based wrought superalloys was observed in situ using a scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) probe to clarify the texture formation and GB response. The GB stress concentration depends on the grain orientation and slip system alignment on both sides. This reflects the ability of GBs to cope with deformation incompatibility. This study provides valuable insights for predicting the failure of polycrystalline superalloys and offers new ideas for microstructure evaluation and GB design. IMPACT STATEMENT: The lattice rotation and GB response of Ni-Co based fine-grained wrought superalloys under 750 ℃ deformation were explained through in-situ observation, which helps predict the superalloys' service behavior. [ABSTRACT FROM AUTHOR]

The flow behavior and deformation mechanisms of the [001]-oriented single-crystal nickel-based superalloy PWA1483 are investigated under quasi-static compressive and tensile loading conditions at 750°C. We found that the tensile yield strength is larger as compared to the compressive strength, and the serrated flow only appears on the compressive stress–strain curves. Microstructural observations uncover that stacking fault shearing and microtwinning are prone to initiate in PWA1483 during tensile deformation, and the appearance of the Protevin–Le Châtelier effect in compression derives from the abrupt frequent bursts of the two mechanisms on a mesoscale, rather than the simple occurrence of these procedures. [ABSTRACT FROM AUTHOR]

CoCrNi-based multi-principal element alloys (MPEAs) often lack strength at elevated temperatures. Here, to overcome this deficiency, a novel oxide-dispersion strengthening (ODS) CoCrNi-based MPEA was designed by incorporating nano-scale yttria via LPBF. The ODS MPEA possesses superior strength-ductility synergy at both ambient and elevated temperatures to most reported CoCrNi-based MPEAs and state-of-the-art superalloys. TEM investigations revealed dislocation forest and slip traces in the interior of solidification dislocation cell structure, along with extended stacking faults and nano-twins. These features contributed to the excellent strength-ductility of the MPEA. Lastly, quantitative analyses uncovered the contributions of operating strengthening mechanisms to its high strength. [ABSTRACT FROM AUTHOR]

Nickel-based single-crystal superalloys are widely used in aerospace and industrial gas turbine blades due to their excellent material properties. However, these alloys are also known for their difficulty in machining due to their superior physical properties. To improve the surface quality of machined parts, this study investigates the effects of different grinding conditions (dry grinding, flood, minimum quantity lubrication (MQL)) on the surface morphology, grinding-induced damage layer, and subsurface microstructure of nickel-based single-crystal superalloys. The experiments show that under MQL conditions, as the wheel speed increases, the grinding marks become more uniform, surface micro-defects decrease, and surface quality improves. A comparison of the thickness of the grinding-induced damage layer (D) obtained from dry grinding, flood, and MQL reveals that MQL cooling is more effective in reducing the damage layer thickness of nickel-based single-crystal superalloys compared to flood cooling. With an increase in wheel speed from 15 to 35 m/s, the thickness of the subsurface damage layer reduced from 14.2 to 11.4 µm using emulsion cooling and from 12.8 to 9.1 µm using MQL cooling. Unlike dry grinding, the use of grinding fluid significantly impacts the subsurface microstructure of the alloy, effectively suppressing work hardening and reducing the thickness of the grinding-induced damage layer, thereby improving the surface quality. It has important theoretical and practical significance to improve the quality of grinding surface. [ABSTRACT FROM AUTHOR]

Nickel-based powder metallurgy superalloys with high W and high γ’ content exhibit excellent high-temperature properties, but their high deformation resistance poses significant challenges for hot processing. In this study, the hot compression behaviour of an extruded nickel-based powder superalloy FGH4109 with high W (6.1%) and high γ’ phase contents (60%) was systematically investigated at temperatures ranging from 1060 ℃ ~ 1140 ℃, strain rates from 0.001 s−1 ~1 s−1, and maximum true strains of 0.7. Combined with the hot working map and the microstructure evolution in different hot working zones, the optimal hot working window for the alloy was determined to be in the temperature range of 1060 ℃ ~ 1140 ℃ and strain rates of 0.001 s−1 ~0.012 s−1, where the power dissipation efficiency η was greater than 0.5, and the dominant deformation mechanism was discontinuous dynamic recrystallisation. [ABSTRACT FROM AUTHOR]

The unstable anode/electrolyte interphase induces severe lithium dendrite growth hindering the practical application of lithium metal batteries. The lithium alloy interphase presents a promising strategy for regulating Li+ plating/stripping behavior. However, binary or ternary alloys are insufficient to address various challenges in lithium metal batteries and the high temperature required for alloy preparation hampers their direct applications on lithium metal surfaces. In this study, a high‐entropy alloy (HEA) interphase is developed on lithium metal surfaces via room‐temperature magnetron sputtering, showcasing multifunctional advantages in regulating Li+ plating/stripping behavior. The cocktail effect of the (HEA) facilitated the formation of a homogeneous amorphous interphase with abundant lithiophilic sites and magnetic properties, promoting uniform Li+ nucleation and deposition. Furthermore, the high mechanical strength and corrosion resistance of HEA provided physicochemical stability for the lithium anode interphase, consistently suppressing dendrite growth. Consequently, lithium metal anodes with HEA interphases exhibited robust cycling performance lasting over 4000 h at 2 mA cm−2. The LFP full battery demonstrated high‐capacity retention of 90% with an average Coulombic efficiency of 99.7%. Thus, the HEA interphases on lithium metal surfaces offer controllable regulation of Li+ deposition behavior through high‐entropy manipulation, opening novel strategies for stable lithium metal batteries. [ABSTRACT FROM AUTHOR]

ABSTRACT In this research, the microstructure and precipitate characteristics of the dissimilar inertia friction welded (IFW) joints of deformed and powder metallurgy (PM) nickel‐based superalloys were studied using optical, scanning electron, and transmission electron microscopy. In addition, several creep tests were conducted. The high‐temperature mechanical properties of the IFW joints were systematically analyzed. Under the creep testing condition of 680°C, the specimens exhibited creep fracture at the thermomechanically affected zone (TMAZ) of the PM superalloys. Further, the failure lifetime is enhanced with a reduction in the applied creep loading. Owing to the IFW process, various γ′ precipitates and carbide distributions were observed in the various zones of a dissimilar IFW joint. Undissolved powder particle boundary (PPB) defects in the TMAZ of the PM superalloy initiated creep cracks under creep loading. Based on the experimental results and theoretical analysis, the creep fracture mechanisms of the dissimilar IFW joints were revealed. Thus, the findings of this study provide guidance for controlling the microstructures and properties of dissimilar deformed/PM nickel‐based superalloy IFW joints. [ABSTRACT FROM AUTHOR]

The reverse water‐gas shift (RWGS) reaction is significant for the resource utilization of CO2. However, this reaction requires high temperatures and metal catalysts are prone to agglomeration, leading to loss of activity. In this work, a Pt catalyst supported on Mo₂N formed via phase transition and metal reverse sintering under a high‐temperature NH₃ atmosphere is developed. This catalyst exhibits excellent RWGS activity, achieving a CO production rate of 294.8 mmolgcat−1 h−1 at 623 K, with CO selectivity maintained at 93%. Moreover, under continuous testing conditions for 100 h, the catalyst's activity shows no significant decline. Notably, further investigation reveals that the surface reaction mechanism at 623 K differs from the previously reported associative mechanism, instead following a redox mechanism in the presence of H₂. This research not only provides a deeper theoretical understanding of the mechanism of CO2 hydrogenation but also offers valuable insights for developing novel and efficient metal catalyst regeneration technologies. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) reduce the surface temperature of superalloy components but may affect the mechanical properties of the substrate. This study investigates the creep-fatigue behavior of TBC-coated single-crystal superalloys under 1 s, 60 s, and 180 s dwell times. The results indicate that TBCs are beneficial at a 1 s dwell time. The comparison of fracture morphology between coated and uncoated samples showed no change in the failure mechanism due to TBCs under creep-fatigue loading. A creep-fatigue lifetime prediction method based on continuous damage mechanics was also proposed. The predicted results were all within a double dispersion coefficient, showing good agreement with the experimental results. This study provides insights into the durability of TBC-coated single-crystal superalloys under creep-fatigue loading. [ABSTRACT FROM AUTHOR]

This study aims to advance the application of magnesia-zirconia (MgO–ZrO 2) refractories in non-ferrous metal smelting furnaces by enhancing their thermal shock resistance. To fabricate MgO–ZrO 2 –MgAl 2 O 4 refractories, tabular corundum particles and activated α-Al 2 O 3 powder are integrated into MgO–ZrO 2 refractories. The analysis of thermal shock resistance, phase composition, and microstructure of the samples was conducted to gain insights into the toughening mechanisms. The results reveal a substantial enhancement in thermal shock resistance with the addition of 15 wt% tabular corundum (1–0.5 mm) and activated α-Al 2 O 3. Compared to samples without these additives, a notable increase of over 50.0 % in the ratio of residual cold modulus of rupture is shown. The enhancement in thermal shock resistance is primarily attributed to the in-situ generated MgAl 2 O 4 spinel. This process involves volume expansion and increased thermal expansion mismatch, which induce microcrack toughening. Additionally, larger tabular corundum particles form in-situ MgAl 2 O 4 spinel, causing crack deflection and branching, thus extending the crack propagation pathway. Furthermore, the presence of micropores in the spinel zone absorbs the energy required for crack propagation, thereby improving toughness and thermal shock resistance. Consequently, the MgO–ZrO 2 –MgAl 2 O 4 refractories containing in-situ MgAl 2 O 4 spinel with micropores are promising candidate for chrome-free refractories used in non-ferrous metal smelting furnaces. [ABSTRACT FROM AUTHOR]

The high‐temperature deformation behavior of an equiatomic TiNbTaVW refractory high entropy alloy (RHEA) was studied at temperatures of 950, 1000, and 1050 °C and a strain rate of 10−3 s−1. The flow stress, high‐temperature strength, and softening mechanisms were analyzed and compared with the IN718 nickel‐based superalloy. The results indicate that the flow stress of both TiNbTaVW and IN718 is sensitive to deformation temperature, with high temperatures resulting in reduced flow stress. Globular grains and elongated grains were observed at 950 and 1000 °C for TiNbTaVW, signifying both dynamic recovery and dynamic globularization as the softening mechanisms. Globular grains were only observed at 1050 °C for TiNbTaVW, signifying dynamic globularization as the softening mechanism. The TiNbTaVW RHEA has a higher temperature strength of 910, 870, and 658 MPa compared to the IN718 alloy with 72, 87, and 61 MPa at 950–1000 °C/10−3 s−1. By demonstrating comparable or superior performance in specific aspects, RHEAs can be considered in the near future for potential applications traditionally dominated by nickel‐based superalloys. [ABSTRACT FROM AUTHOR]

A 220 GHz GaN‐based monolithic integrated frequency doubler with high continuous‐wave output power has been developed. The doubler achieves improved heat dissipation by establishing the terahertz (THz) monolithic integrated circuit topology with GaN Schottky barrier diodes integrated on a high thermal conductivity SiC substrate. It features six anodes to enhance the power‐handling capabilities. A refractory Schottky metal stack is adopted for better thermal stability. The doubler realizes satisfactory performance by introducing the suspended microstrip and an all‐in‐one output structure. For verification, a prototype of the proposed frequency doubler was fabricated and tested. Measured results show that the proposed doubler produces a continuous‐wave output power of 255 mW at 220 GHz with an efficiency of 14.6%, exhibiting excellent potential for powerful THz sources. [ABSTRACT FROM AUTHOR]

Creep crack growth experiments were performed at 750°C, 850°C, and 950°C on nominally 3 and 12.7 mm thick compact type specimens of alloy 247LC‐DS, a Ni‐base superalloy used for hot‐section gas turbine blades. The primary crack plane was transverse to the solidification direction. The crack path–microstructure interaction was characterized. Crack growth occurred in a creep‐ductile manner and data analyses utilized time‐dependent fracture mechanics. No measurable crack growth occurred at 750°C. Cracks grew by formation, growth, and coalescence of cavities on interdendritic carbides in both the primary crack plane and normal to said plane at 850°C and 950°C. The variability in the crack growth rate was higher in thicker specimens, but the mean creep crack growth rate versus Ct relationship in 247LC‐DS was neither sensitive to test temperature ≥850°C nor specimen thickness. Quantitative relationships between da/dt and Ct were derived for mean, upper, and lower bound creep crack growth rate trends. Highlights: Creep crack growth occurred in a creep‐ductile manner at 850°C and 950°C.Creep crack growth rates correlated with Ct/C*.Crack tip damage accumulation increased the variability in crack growth rates.Measuring creep crack growth via unloading compliance is preferred for DS materials. [ABSTRACT FROM AUTHOR]

This work systematically investigates the orientation deviation effect on the elastoplastic deformation of a dual‐phase, nickel‐based single‐crystal superalloy through a combined experimental study and crystal plasticity finite element modelling method (CPFEM). Physically based, dual‐phase microstructural model was developed based on scanning electron microscopy (SEM), which was implemented by finite element (FE) modelling using a representative volume element (RVE) with periodic boundary conditions. An extended equivalent yield criterion coupled with CPFEM was adopted to describe the non‐uniform yield behavior induced by octahedral and cubic slip systems. The predicted results have shown that both the bulk behavior and localized stress–strain nature are orientation deviation dependent and that the first Euler angle plays a more important role in elastoplastic behavior than the second Euler angle. This study has thus advanced the basic understanding of the relationship between orientation deviation and the bulk deformation behavior of the dual‐phase nickel‐based single crystal. Highlights: Physically based dual‐phase microstructural model was constructed.The orientation deviation of [001] for nickel‐based single crystal was characterized.An extended equivalent yield criterion coupled with CPFEM was validated.The elastoplastic behavior with orientation deviation was numerically analyzed. [ABSTRACT FROM AUTHOR]

Nickel-base superalloys contain high amounts of solutes like Cr, Mo, W, Nb, Ti, etc. These solutes promote the formation of different types of carbide and boride phases that may contain multiple elements. Researchers have mostly discussed the roles of primary elements responsible for the formation of a given carbide/boride phase, often ignoring the role of other solutes on its stability. In the present work, thermodynamic stability of carbide and boride phases in seven commercial superalloys, namely, Alloy 625, Alloy 690, Alloy 718, MAR M246, Rene 100, Udimet 710 and Nimonic 80A, has been studied using the CALPHAD based Thermo-Calc software. The aim of the study was to understand the role of different alloying elements on temperature stability and chemical compositions of equilibrium phases in superalloys. As the accuracy of CALPHAD based predictions depends upon the database used, a detailed examination of its inadequacies has also been carried out to ascertain the limitations of the predicted data. From the calculated equilibrium chemical compositions, major and minor constituents promoting the formation of carbides and borides have been identified. The individual effect of a given solute as well as the synergistic effect of two solutes on the relative thermodynamic stability of carbide/boride phases has been identified using property diagrams and isothermal sections of the temperature-composition diagrams. Most of the simulated results have been found to be consistent with the experimental data available in the literature. From a comparison of the experimental literature and the simulated data of the stable carbide and boride phases in the studied alloys, the interplay of different solutes has been deduced to define conditions under which these phases form, within the limitations of the database used. This study has helped in better understanding of general tendencies of solutes to form different carbide and boride phases in nickel-based superalloys. [ABSTRACT FROM AUTHOR]

This document is a summary of a special issue of the journal "Materials" titled "Development of Advanced Aluminum and Magnesium Alloys: Microstructure, Mechanical Properties and Processing." The special issue focuses on the latest progress in the development of advanced aluminum alloys, magnesium alloys, and their composites. Thirteen articles are included in the special issue, with six papers on aluminum alloys, two papers on magnesium alloys, and five papers on light metal composite materials. The articles cover a range of topics including optimization of aluminum alloys for casting processes, the effect of torch angle on the properties of aluminum alloys fabricated using additive manufacturing, and the development of high-strength aluminum metal-matrix composites. The special issue provides valuable insights into the relationships between microstructure, mechanical properties, and processing conditions, and aims to contribute to the future development and industrial applications of lightweight alloys. [Extracted from the article]

In industrial production, the identification and characterization of micron-sized second phases, such as carbonitrides in alloys, hold significant importance for optimizing alloy compositions and processes. However, conventional methods based on threshold segmentation suffer from drawbacks, including low accuracy, inefficiency, and subjectivity. Addressing these limitations, this study introduced a carbonitride instance segmentation model tailored for various nickel-based superalloys. The model enhanced the YOLOv8n network structure by integrating the SPDConv module and the P2 small target detection layer, thereby augmenting feature fusion capability and small target detection performance. Experimental findings demonstrated notable improvements: the mAP50 (Box) value increased from 0.676 to 0.828, and the mAP50 (Mask) value from 0.471 to 0.644 for the enhanced YOLOv8n model. The proposed model for carbonitride detection surpassed traditional threshold segmentation methods, meeting requirements for precise, rapid, and batch-automated detection in industrial settings. Furthermore, to assess the carbonitride distribution homogeneity, a method for quantifying dispersion uniformity was proposed and integrated into a data processing framework for seamless automation from prediction to analysis. [ABSTRACT FROM AUTHOR]

This study investigates the impact of the cooling rates, from 18 to 1.5 °C/s, on the as-cast microstructure of the CMSX-4 Ni-based superalloy, especially on morphological changes in primary γ′ precipitates in the dendrite core and border. Microstructural characterization along the height of directionally solidified samples included the measurement of grain density, secondary dendrite arm spacing, γ–γ′ eutectic morphology and volume fraction, solute segregation, and primary γ′ precipitate morphology & size in both dendrite core and border. A simple thermodynamic model was employed to investigate the morphological transitions observed during coarsening of primary γ′ precipitates, from sphere to cube, concave cube, octocube and solid-state dendrite. The γ–γ′ lattice misfit, the γ/γ′ elastic strain energy values within the γ matrix, and the critical precipitation sizes for morphological changes were extrapolated for the dendrite core and border. The thermodynamic model, which considers the balance between elastic and interfacial energies, does not completely explain the differences in size and shape of the primary γ′ particles between the dendrite border and core. The more varied γ′ particle morphologies in the dendrite border are due to faster precipitate coarsening, driven by lower Re and W contents, higher atomic diffusivity, increased solvus temperature, and reduced supercooling for the precipitation reaction. [ABSTRACT FROM AUTHOR]

The dehydrogenative coupling of alcohols and amines to form amide bonds is typically catalysed by homogeneous transition metal catalysts at high temperatures ranging from 130–140 °C. In our pursuit of an efficient and recyclable photocatalyst capable of conducting this transformation at room temperature, we report herein a COF‐mediated dehydrogenative synthesis. The TTT‐DHTD COF was strategically designed to incorporate a high density of functional units, specifically dithiophenedione, to trap photogenerated electrons and effectively facilitate hydrogen atom abstraction reactions. The photoactive TTT‐DHTD COF, synthesized using solvothermal methods showed high crystallinity and moderate surface area, providing an ideal platform for heterogeneous amide synthesis. Light absorption by the COF across the entire visible range, narrow band gap, and valence band position make it well‐suited for the efficient generation of excitons necessary for targeted dehydrogenation. Utilizing red light irradiation and employing extremely low loading of the COF, we have successfully prepared a wide range of amides, including challenging secondary amides, in good to excellent yields. The substrates' functional group tolerance, very mild reaction conditions, and the catalyst's significant recyclability represent substantial advancements over prior methodologies. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy serves as the principal component in fabricating turbines and engine combustion chambers, with numerous applications in aerospace and automotive manufacturing. Nonetheless, this metal presents significant cutting challenges, and traditional machining methods face various obstacles. Electrochemical micromachining is an unconventional technology in the machining field. Electrochemical micromachining has many advantages including outstanding surface quality, neglected cathode depletion, and high elimination rate. The ultrashort pulse power supply is used widely in electrochemical micro-machining to resolve the issue of excessive machining of the non-processing area. However, ultrashort pulse power is costly and restricts the development of other signals. In this study, electrochemical micromachining with sinusoidal voltage signals was employed to optimize input parameters for producing the most accurate hole, and the effects of MRR, conicity, and overcut on the workpiece were investigated. In addition, microstructures on hard-to-cut superalloy plates were successfully machined, further illustrating the proposed method's potential. [ABSTRACT FROM AUTHOR]

The thermal compression experiments of the GH99 alloy were carried out at different strains from 1020 °C to 1170 °C and 0.001 s−1–1 s−1 conditions using a Gleeble-3800 thermal compression simulation tester. Construction of thermal processing maps with four instability criteria were superimposed on Murty, Prasad, Gegel, and Malas at different strains based on stress-strain data. Based on the theoretical basis, prediction results, and EBSD microstructure characterization method of four instability criteria, the suitable forming processing region and rheological instability region of the alloy were predicted. It was found that the Prasad instability criterion had the most accurate prediction results. The instability range predicted by Murty was accurate under minor strains, but as the strain increased, the expected instability range slightly increased compared to the actual range. However, the Gegel and Malas criteria have biases in predicting alloys under low-rate conditions at different strains. A scientific and rational optimization was carried out to select hot working process parameters for GH99 alloy in response to the influence of strain on its hot deformation behavior. [ABSTRACT FROM AUTHOR]

To investigate the effect of the primary γ′ phase on the high-temperature endurance performance of GH4720Li superalloy, samples with different volume fractions of the primary γ′ phase were prepared by adjusting the heat treatment process. The high-temperature endurance performance was tested, and the microstructure was examined. Results indicate that samples with a higher volume fraction of the γ′ phase exhibit a greater stress rupture life. Additionally, alloy samples with varying γ′ phase volume fractions show improved plasticity and toughness at 760 °C/530 MPa. Fracture morphology results reveal that high-volume-fraction primary γ′ phase samples primarily undergo transgranular fracture, whereas low-volume-fraction samples exhibit intergranular fracture due to grain boundary sliding. During high-temperature endurance, the secondary γ′ phase in the crystal is affected. Long-term aging refines the secondary γ′ phase, resulting in a more uniform distribution. Finally, the influence of the primary γ′ phase and the creep behavior of each material group on high-temperature endurance performance are discussed. [ABSTRACT FROM AUTHOR]

Hot isostatic pressing (HIP) is a near-net shape powder metallurgy (PM) technique, which has emerged as an efficient technique, offering precise control over the microstructure and properties of materials, particularly in high-performance alloys. This technology finds applications across a wide range of industries, such as aerospace, automotive, marine, oil and gas, medical, and tooling. This paper provides an overview of powder metallurgy and hot isostatic pressing, covering their principles, process parameters, and applications. Additionally, it conducts an analysis of PM-HIPed alloys, focusing on their microstructure and fatigue behavior to illustrate their potential in diverse engineering applications. Specifically, this paper focuses on nickel-based superalloys and martensitic tool steels. The diverse microstructural characteristics of these alloys provide valuable insights into the PM-HIP-induced fatigue defects and properties. [ABSTRACT FROM AUTHOR]

Friction and high temperatures greatly affect the hardness and processing efficiency of superalloys. Therefore, it is important to provide a coating on their surfaces with a hard layer. In this study, pack boronizing was applied on Inconel 601 to improve its microstructure and tribological properties. In this regard, tribological tests were performed under MQL, nano-MQL1 (MQL + CuO), and nano-MQL2 (MQL + TiO2) environments. The research results showed that the lowest wear depth, friction force, coefficient of friction (CoF), and volume loss values were obtained in pack-boronized Inconel 601 in a nano-MQL2 environment. In the nano-MQL2 environment, the wear depth decreased by 17.81% (from 57.922 µm to 47.605 µm) with package-boronized Inconel 601 compared to as-received Inconel 601 at a 45 N load. Pack-boronized Inconel 601 experienced an average reduction of 30.23%, 41.60%, and 52.32% in friction force when switching from dry to MQL, nano-MQL1, and nano-MQL2 environments, respectively. It was also observed that the coefficient of friction (CoF) and volume loss values decreased with pack boronizing in an MQL/nano-MQL environment. In a nano-MQL2 environment at 15 N load, volume losses for as-received and boron-coated Inconel 601 were determined as 0.288 mm3 and 0.249 mm3, respectively (13.54% decrease). The findings of this study demonstrate that pack boronizing and MQL and nano-MQL techniques enhance the tribological characteristics of Inconel 601 alloys. [ABSTRACT FROM AUTHOR]

As a crucial high-performance material, nickel-based superalloys inevitably generate residual stresses during processing, manufacturing, and usage. The mechanical properties of nickel-based superalloys are significantly reduced by residual stress, which becomes one of the important factors restricting material reliability. The systematic analysis of residual stresses in nickel-based superalloys throughout the entire manufacturing and usage processes is insufficient. The residual stress generation factors, measurement methods, prediction models, and control methods in nickel-based superalloys in recent years are summarized in this paper. The current challenge and future development trends in the research process of nickel-based superalloy residual stress are also presented. A theoretical reference for further research on residual stresses in nickel-based superalloys can be provided in this review. [ABSTRACT FROM AUTHOR]

New developments in nickel-based superalloys and production methods, such as the use of additive manufacturing (AM), can result in innovative designs for turbines. It is crucial to understand how the material behaves during the AM process to advance the industrial use of these techniques. An analytical model based on reaction–diffusion formalism is developed to better explain the solidification behavior of the material during laser metal deposition (LMD). The well-known Scheil–Gulliver theory has some drawbacks, such as the assumption of equilibrium at the solid–liquid interface, which is addressed by this method. The solidified fractions under the Scheil model and the pure equilibrium model are calculated using CALPHAD simulations. A differential scanning calorimeter is used to measure the heat flow during the solid–liquid phase transformation, the result of which is further converted to solidified fractions. The analytical model is compared with all the other models for validation. [ABSTRACT FROM AUTHOR]

As the turbine inlet temperatures of aero engines continue to rise, there is an urgent need to develop a new generation of single-crystal superalloys and their thermal protective coatings for turbine blades. In order to meet the stringent requirements for the comprehensive performance of high-temperature structural materials in the complex service environments of aero engines, the intelligent design research of single crystal superalloys and thermal protection coatings has been gradually carried out at home and abroad in recent years under the promotion of material integrated computational engineering and material informatics. This paper reviews the latest research progress in the design of novel single-crystal superalloys and thermal protective coatings by utilizing multi-scale computational simulations and machine learning methods. The findings confirm that multi-scale computational simulations offer robust theoretical support for understanding the strengthening and toughening mechanisms of single-crystal superalloys, as well as the oxidation resistance and diffusion protective mechanisms of thermal protective coatings. Additionally, the study highlights the reliability and significant potential of machine learning in constructing intrinsic "composition-structure-property" relationship for high-temperature structural materials. This approach paves an intelligent and efficient new pathway for the rapid development of next-generation high-temperature single-crystal superalloys and thermal protective coatings. [ABSTRACT FROM AUTHOR]

Refractory metals have increasingly attracted the attention of researchers due to their excellent high-temperature strength, thermal conductivity, radiation resistance, and biocompatibility for applications in extreme environments such as aerospace and nuclear industries. However, beyond traditional manufacturing processes, the complex post-treatment process, high cost, and difficulty in manufacturing complex geometry components limit its further application in modern industry. Compared to conventional manufacturing processes, selective laser melting (SLM) technology, an emerging technology, can significantly simplify the production process and has the advantage of manufacturing parts with complex geometry. Therefore, there is increasing research on manufacturing refractory metals using SLM technology. This article describes the current research progress of pure refractory metals manufactured by SLM regarding the preparation process, microstructure, metallurgical defects, and mechanical properties of refractory metals (tungsten, molybdenum, niobium, tantalum, etc.). Generally speaking, there are some technical difficulties in the fabrication of refractory alloys by SLM, summarized in this paper. Finally, the article presented the prospect of developing SLM refractory metals. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys, like Inconel 718, are very attractive metals for aerospace applications due to their excellent mechanical properties and thermal stability. However, these materials pose a significant challenge to the metal machining industry due to their very low machinability, especially in terms of reduced tool life because of the high heat generated during cutting. Nevertheless, it can be improved using high-performing tools that retain their hardness when exposed to high temperatures, such as ceramic tools. In this context, the study aims to compare the performance of two advanced ceramic tools, namely an alumina ceramic tool reinforced with SiC whiskers and a Bidemics™ one, when turning Inconel 718 at different cutting speeds, using as a baseline a conventional coated cemented carbide tool. First, the three inserts were characterized in terms of topography, thermal conductivity, and hot hardness to fully understand their operational behavior. Then, turning trials were conducted showing that both the ceramic tools outperform the coated carbide one in terms of tool life, with Bidemics™ demonstrating the best performance among all. This can be ascribed to its very high hardness maintained even at high temperatures, as well as its moderate thermal conductivity. [ABSTRACT FROM AUTHOR]

During the directional solidification (DS) of superalloys, the active alloy elements react with the ceramic mold, deteriorating the surface quality and affecting the dimensional accuracy of the alloys. It is important to investigate the interfacial reactions between the alloy melt and ceramic mold and to investigate the effect of the interfacial reactions on the structures of the alloy. Superalloy DZ40M was prepared by DS technology, the microstructures and element distributions of the alloy and the alloy-ceramic interface were observed by a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), and the interfacial reactions were analyzed from a thermodynamic perspective. Carbides are important strengthening phases in the alloy. Interfacial reactions between the carbides and the ceramic mold were further investigated. The results show that the alloy structure mainly contains Co (Cr/Ni/Zr/Al/W/Ti) solid solution columnar crystals (Coss), nearly continuously distributed Cr-enriched M7C3-type carbides as well as Ti/Zr/W-enriched MC-type carbides skeletal precipitates. The reactions between the Coss and the ceramic mold were mild, with a reaction layer of about 20–40 μm thickness, while the reaction between the grain boundary precipitates and the ceramic mold was severe because of a high content of Cr in the M7C3-type carbides and the presence of active elements Ti and Zr in the MC-type carbides, with a reaction layer of about 50 μm thickness. In addition, almost no obvious penetration of the mold refractory was observed in the interior of the alloy, showing that the ceramic mold has a relatively stable performance in investment casting of superalloy DZ40M. [ABSTRACT FROM AUTHOR]

To enhance the quality of vacuum arc remelting (VAR) ingots in enterprises, a remelting model and cracking criterion was developed based on simulation and a series of designed experiments to predict the segregation behavior, shrinkage cavity, thermal stress, and cracking tendency of VAR ingot. The remelting model was established by MeltFlow-VAR and Abaqus software. As MeltFlow-VAR cannot calculate the stress, through the secondary development program, the thermal stress of VAR ingot was calculated by introducing the temperature field of VAR process into Abaqus. This model was verified by longitudinal dissection of a 406 kg IN718 alloy VAR ingot. The simulated evolution of molten pool, shrinkage cavity, freckle formation probability and secondary dendrite arm spacing (SDAS) align consistently with the ingot microstructure and experimental results. Combined with thermal stress, the alloy strength at different temperature during cooling and solidification, and failure criterion, a crack criterion was constructed to predict the cracking tendency. Calculating the complete solidification time and cracking tendency of the VAR ingot after melting allows for the determination of the safe demolding time without cracks. This method can be used to explore the effect of different melting parameters, optimize VAR process and improve the quality of VAR production. [ABSTRACT FROM AUTHOR]

Oxygen, nitrogen and hydrogen elements in inorganic materials have attracted considerable attention. Based on more than 70 current Chinese standards and more than 40 journal papers in the past decade, the current status and development of inert gas fusion infrared absorption or thermal conductivity methods and standards for the determination of oxygen, nitrogen and hydrogen in inorganic material were reviewed, including steel and alloys, rare refractory metal alloys, light or heavy and precious non-ferrous metals, rare earth alloys, ferroalloys, non-ferrous intermediate alloys and inorganic non-metallic functional materials. The parameters in current standards were listed, including applicable objects, quantitative scope, sample mass, reference material and fluxes, as well as the main working conditions m methods from journals, such as analyte, element, instrument, crude, sample mass, fluxes, analytics power and reference material. Finally, the application prospects and development directions of gas analytics in inorganic materials were prospected. [ABSTRACT FROM AUTHOR]

Emulating the Ni-base superalloy γ + γ ′ microstructure in BCC–B2 refractory alloys is a promising design strategy to achieve high temperature strength and ductility. Ru-base B2 precipitates have shown exceptional thermal stability but can be difficult to solutionize, making high cooling rate solidification pathways like additive manufacturing (AM) a promising approach for synthesis of more homogeneous microstructures. Using single track laser experiments on aged bulk substrates, five representative refractory alloys with varying Ru-base B2 precipitates (AlRu, HfRu, TiRu) and matrix constituents (Mo, Nb) were investigated for their solidification behavior and defect susceptibility under laser melting conditions. Susceptibility to solidification cracking, solid-state cracking, and keyhole formation was found to be highly dependent on the matrix composition. Characterization of the melt pools by scanning and transmission electron microscopy shows evidence for disordered BCC upon solidification, enabling tailoring of the B2 precipitates that are thermodynamically stable above 1300 °C. The B2 precipitate morphologies in the melt tracks after aging treatments are influenced by the partitioning behavior of Ru from laser melting. Results from these single track experiments provide guidance toward design strategies for fabricable refractory BCC–B2 alloys. [ABSTRACT FROM AUTHOR]

The work focuses on characterizing the microstructure and selected properties of Al- (1.3 or 2.8 wt pct) and Ta-modified (2 or 3 or 4 wt pct) Alloy 740 Ni-based superalloy after heat treatment. The observations and analyses were conducted using thermodynamic simulations, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, steam oxidation, hardness, tensile, and stress rupture tests. The castings exhibit a typical dendritic structure, with the presence of fine γ′ precipitates, Nb-rich Laves phase precipitates, MC carbides, and MN nitrides are found in all modified castings. However, the presence of the η phase, G phase, and M23C6 is dependent on the superalloy's chemical composition. At room temperature, the reference cast superalloy had an ultimate tensile strength and yield strength of 655 MPa and 477 MPa, respectively. In modified castings, the ultimate tensile strength and YS are higher, respectively, 713–1046 MPa and 705–903 MPa. After steam oxidation at 760 °C/1000 h, the mass gain of the modified castings was in the range of 0.339–0.429 mg/cm2. The addition of tantalum resulted in decreased oxidation resistance and the formation of the TiTaO4 oxide at the Cr2O3/superalloy interface. [ABSTRACT FROM AUTHOR]

A critical issue in laser powder bed fusion (LPBF) additive manufacturing is the selective vaporization of alloying elements resulting in poor mechanical properties and corrosion resistance of parts. The process also alters the part's chemical composition compared to the feedstock. Here we present a novel multi-physics modeling framework, integrating heat and fluid flow simulations, thermodynamic calculations, and evaporation modeling to estimate and control the composition change during LPBF of nickel-based superalloys. Experimental validation confirms the accuracy of our model. Moreover, we quantify the relative vulnerabilities of different nickel-based superalloys to composition change quantitatively and we examine the effect of remelting due to the layer-by-layer deposition during the LPBF process. Spatial variations in evaporative flux and compositions for each element were determined, providing valuable insights into the LPBF process and product attributes. The results of this study can be used to optimize the LPBF process parameters such as laser power, scanning speed, and powder layer thickness to ensure the production of high-quality components with desired chemical compositions. [ABSTRACT FROM AUTHOR]

During the operation of the waste liquid incinerator, the alkali metal slag might adhere to the surface of the refractory material to form an inhomogeneous solid slag layer, causing the furnace lining to be simultaneously corroded by three phases of alkali metals: vapor, molten salt, and slag. This phenomenon intensifies the damage to the refractory material. Therefore, this paper investigates the mass transfer and permeation process, phase change process and corrosion rate of Na 2 CO 3 inside corundum refractory materials in three phases: Na vapor, molten Na 2 CO 3 and Na-slag. The results showed that alkali vapor penetrated the interior through the pores, and the NaAlO 2 and β-Al 2 O 3 generated by the reaction led to the volume expansion and microcracks. Na vapor continued to penetrate the interior along the cracks and eroded the sample, and the higher the temperature the greater Na vapor penetration. In vapor phase corrosion, the effect of corrosion time on the erosion resistance of corundum refractories is less than that of temperature, and the increase in corrosion time does not lead to the formation of additional new phases. In the molten salt corrosion experiments, it was found that the molten salt corrosion was accompanied by vapor phase corrosion at 1100 °C, and the amount of Na 2 CO 3 has a greater effect on the corroded mass than the temperature. Comparing the corrosion of refractory materials by the three phases of Na 2 CO 3 , the molten salt corrosion rate was the highest, followed by the vapor phase corrosion, and finally the slag corrosion. It is concluded that the slag layer can effectively prevent the corrosion of the refractory material by alkali metal molten salts and vapors, thus prolonging the service life of refractories. [ABSTRACT FROM AUTHOR]

This paper deals with the development and characterization of an Inconel 625 (IN625) reinforced with 2 wt.% of sub-micrometrical TiC particles produced by the laser powder bed fusion (LPBF) process. IN625 and IN625 2 wt.% TiC microstructural evolution was evaluated in the as-built, solution-annealed (2 h at 1150 °C), and prolonged heat-treated (2 h at 1150 °C + 100 h at 1000 °C) conditions. The IN625 and IN625 + TiC samples were successfully produced with low residual porosity (<0.15%). In the as-built conditions, both materials developed mainly columnar grains elongated to the building direction with melt pools, fine dendric structures, and small fractions of recrystallized grains. Some TiC segregations were observed in the composite, preferentially located at the melt pool boundaries. The heat treatments led to a different microstructural evolution between the base alloy and the composite. After solution annealing, the IN625 alloy was subjected to full recrystallization with a drastic reduction in hardness. Afterward, the prolonged thermal exposures for 100 h at 1000 °C provoked the formation of carbides, increasing the hardness. On the contrary, the composite retained the as-built microstructure with columnar grains in the solution-annealed and prolonged heat-treated conditions, revealing a limited formation and growth of carbides, thus resulting in a reduced hardness variation. The addition of TiC inside the IN625 enhanced the microstructural stability of the composite, preventing the recrystallization and the growth of phases occurring under prolonged thermal exposures. The current study therefore reported the effect of TiC particles on the microstructural stabilization of LPBFed IN625, with a peculiar focus on the prolonged thermal exposure at 1000 °C. [ABSTRACT FROM AUTHOR]

The mechanisms of stacking fault (SF) nucleation and extension, as well as its effect on improving plasticity of Co-Al-W-base superalloys were investigated in the present study. The characteristics of SF during the plastic deformation were systematically characterized using Transmission Electron Microscopy and High-Resolution Transmission Electron Microscopy. The results show that the elongation of Co-Al-W-base superalloy can be significantly improved by around 5% with the multiplication and extension of SF at 800 ˚C in comparison to that at 700 ˚C. The superlattice intrinsic stacking fault (SISF) can nucleate within the γ′ phase, which originals from the dissociation of an a/2 < 110 > dislocation within the γ′ phase. The trailing partial dislocation is pinned in the γ′ phase, and the leading partial dislocation slip in the γ′ phase, forming the extended SISF. The extended SISF can continually extend by the leading partial dislocation, even though encountering the a/2 < 110 > dislocation at the γ/γ′ interface. Therefore, the SFs can provide stable and continual plastic flow for the superalloy during plastic deformation, which facilities to relax the stress concentration around the MC carbides, retarding the microcrack propagation. It is considered as the key point for improving the intermediate-temperature plasticity of Co-Al-W-base superalloys. [ABSTRACT FROM AUTHOR]

Chondrules and Ca-Al-rich inclusions (CAIs) have been considered characteristic constituents of chondritic meteorites, although the outward transportation of CAIs has been theoretically pointed out. Stardust samples recovered by the Stardust mission from the 81P/Wild2 comet contained chondrule-like objects (CLOs) and refractory inclusions that include CAIs and amoeboid olivine aggregates (AOAs). However, it was not proven that the CLOs, AOAs, and CAIs coexist with fine-grained materials equivalent to chondritic porous interplanetary dust particles (CP IDPs) containing abundant glass with embedded metal and sulfides (GEMS). Here we report on two type II CLOs, containing <90 Mg# in ferromagnesian silicates, enclosed in GEMS-rich CP Antarctic micrometeorites (AMMs) (CP IDPs that reached the surface of the Earth) and one igneous object rich in kosmochloric (Ko-rich: NaCrSi 2 O 6 -rich) high-Ca pyroxene and Fe-bearing olivine (KOOL) that is enclosed in a CP IDP. KOOL grains have also been found in Stardust samples and CP IDPs. These three igneous objects are embedded in fine-grained matrices that do not show any evidence of aqueous alteration. The low Mg# and elevated Δ17O of olivine and pyroxene in these CLOs and the KOOL grain are consistent with previously studied CLOs from comet 81P/Wild 2 and a giant cluster IDP. These results support the view that CP IDP- and CP AMM-like materials constitute samples from comets or comet-like icy bodies. The CLOs were formed in oxidizing environment beyond the snow line and then transferred to the comet-forming region. In contrast, a spinel-hibonite (SHIB) fragment found in an AMM experienced aqueous alteration of its rim. The SHIB fragment contains ultrarefractory oxides and refractory metal nuggets and has a 26Mg excess like typical meteoritic CAIs. The mineralogy of the fine-grained matrix is very similar to CP IDPs and CP AMMs. However, because "GEMS" in the matrix of the SHIB fragment-bearing AMM lacks Fe-Ni metal and amorphous silicate in it contains Fe, it is clear that the matrix weakly experienced aqueous alteration. Olivine / (Olivine + low-Ca pyroxene) ratios in the matrices of the four samples range from 0.4 to 0.6, which are comparable with those of anhydrous CP IDPs and CP MMs (around 0.5), and those of P- and D-type asteroids and Jupiter-family comets (around 0.5). [ABSTRACT FROM AUTHOR]