Matrix microstructural degradation during long-term high-temperature oxidation limits the service life of Ni-based single-crystal superalloys. Regulating this evolution through trace rare earth addition is a critical optimization strategy. In this work, the effects of yttrium (Y) addition (0, 0.011, and 0.033 wt.%) on the oxidation performance and matrix microstructural evolution of the typical Ni-based single-crystal superalloy oxidized at 1100 °C for 200 h in air were systematically investigated by experiments combined with density functional theory calculations. The results show that the present form of Y in the alloy matrix depends on the addition amount. Isolated Y atoms stabilize Al-containing local configurations, lower the energetic cost for Al detachment, and enhance the thermodynamic driving force for Al2O3 formation. These combined effects promote rapid formation of a protective Al2O3 layer at 0.011 wt.% Y addition, thereby inhibiting outward diffusion of γ′-forming elements and suppressing matrix degradation, which greatly reduces the thickness of the γ′-free and γ′-reduced layers. However, excessive Y (0.033 wt.%) promotes the formation of Y-Y atomic clusters, which weaken these beneficial effects and delay Al2O3 formation to a certain degree. Based on these findings, a schematic diagram illustrating the evolution of elemental diffusion and matrix microstructure with different Y additions is proposed.

During the slag-matte separation in low nickel matte smelting, one of the vital reasons for valuable metals losses is the entrainment of molten matte into slag by floating SO2 bubbles. The density functional theory (DFT) based on first principles was adopted to investigate the interfacial adsorption behavior of low nickel matte main components FeS, Ni3S2, Cu2S and SO2, and analyze their adsorption energy, electron transfer and microscopic mechanism. Calculation results indicate that the adsorption energy of SO2 on hexagonal FeS-001 is − 1.35 eV, with a weak covalent interaction present at the interface. The adsorption energy of Ni3S2 toward SO2-110 is − 7.22 eV, exhibiting the strongest interaction, hybridization occurs between O atoms in SO2 and S atoms on the surface of Ni3S2. For cubic Cu2S, the adsorption energy of SO2 is − 1.77 eV, and strong interactions are established between O atoms in SO2 and Cu on the Cu2S surface. Adsorptions of three sulfides with SO2 are all chemical adsorption. Among these, SO2 exhibits significantly higher adsorption energy on Ni3S2 than FeS and Cu2S, facilitating the entrainment of Ni3S2 into slag by SO2 bubbles and thus, causing nickel loss. These findings offer a theoretical foundation for reducing valuable metal losses and optimizing smelting processes.

In this study, interlayer remelting strategies were utilized to optimize the microstructure and properties of laser powder bed fused (L-PBF) 17-4 PH stainless steel (SS). Parallel remelting reduced retained austenite (RA) from 34.9% to 25.6%, promoted uniform RA distribution, and significantly enhanced yield strength (from 825 MPa to 1020 MPa) and hardness (from 379 HV0.1 to 402 HV0.1), though at the cost of ductility (from 14.6% to 10.7%) and corrosion resistance in 5 wt% HCl (corrosion rate increased by similar to 3.9 times). In contrast, orthogonal remelting further reduced RA to 12.3%, induced RA grain coarsening (4.3 mu m) with a pronounced <101>//Z texture, and transformed the columnar martensitic matrix into a coarser blocky morphology (6.4 mu m). This strategy achieved a more balanced combination of properties, with yield strength of 917 MPa, hardness of 390 HV0.1, preserved ductility (13.6%), and a >30% reduction in corrosion rate in 5 wt% HCl, attributed to the more localized RA distribution. However, no significant improvement in corrosion resistance was observed in concentrated 15 wt% HCl, where the intrinsic material properties dominated. These results demonstrate that interlayer remelting provides a versatile approach to precisely control the microstructure, optimizing both mechanical and corrosion properties in L-PBF fabricated 17-4 PH SS for a range of service conditions.

High-stability crucible is of vital importance for the purity control of Ni-based single crystal superalloy during vacuum induction melting process, especially when the active elements are added into the alloy. In this study, a novel kind of C(2)M(2)A(14) ceramic is developed as the substrate to investigate its interfacial wettability and reaction with Hf-containing alloys. Thermodynamic calculations and molecular dynamics simulations reveal that C(2)M(2)A(14) exhibits optimal thermodynamic stability and the poorest wettability to the alloy melt compared with conventional Al2O3 and MgO substrates. Experiments show that the wetting angles of both Al2O3 and MgO substrates decrease with Hf addition increasing on the alloy melt. By comparison, the wetting angle of C(2)M(2)A(14) substrate exhibit a slight change. In addition, the thickness of the reaction layer for alloy/C(2)M(2)A(14)substrate interface is only 0.5 similar to 1 mu m, while those for Al2O3 and MgO are much thicker, i.e., 0.5 similar to 2.2 mu m and 20 similar to 30 mu m, respectively. The wettability and reaction mechanism between different substrates and Hf-containing alloys are elucidated.

This study presents a systematic investigation into the evolution of non-metallic inclusions during the industrial continuous casting production of high-carbon chromium bearing steel. Conventional 2D characterization techniques and X-ray-based Micro-CT were employed to compare the number, type, size, and spatial distribution of inclusions throughout the LF-RH double-refining process. The results show that Al2O3 and MgO center dot Al2O3 are the dominant inclusion types formed during melting and refining, with MgO center dot Al2O3 exhibiting a strong thermodynamic tendency for formation. Due to differences in the resolution of the two characterization methods and variations in inclusion characteristics among the samples, inclusions with an equivalent diameter larger than 5 mu m show better consistency between the results obtained from the two techniques. This finding revises the assumption that X-ray-based CT techniques inherently yield larger equivalent inclusion diameters. The spatial distribution and morphological characteristics of inclusions are identified as key influencing factors. In ultraclean bearing steel characterized by non-uniform inclusion distribution and predominantly spherical oxide inclusions, when only inclusions larger than the critical equivalent diameter of 5 mu m are considered, the equivalent diameters obtained from 3D characterization are significantly smaller than those derived from 2D methods. This study provides vital industrial data for the future development of precise multidimensional characterization of inclusions in ultra-clean special steels. It also supports the establishment of a reliable 2D-3D conversion model that incorporates characteristic parameters.

The precipitate and texture are key factors in the crystallographic evolution, recrystallization behavior, and grain orientation distribution of the grain-oriented (GO) silicon steels. The retained precipitates and texture evolution of Bi dosage GO silicon steel during the hot rolling, normalization, cold rolling, and decarburization have been systematically studied with 0- to 25-ppm Bi content. The results show that the Bi dosage leads to the precipitation of fine AlN and the possible formation of (Bi-MnS)s, with a Bi-MnS pre-composite structure potentially forming. The precipitate size in the 12-ppm sample is the smallest, and the thermal stability is high. The 114<841> grains rotate around the ND axis to form a nearly 110 crystal nucleus, which is then consumed by Goss grains and undergoes selective abnormal growth. The γ fiber texture, (ND//<111>), is prone to undergo geometric softening during the cold rolling, resulting in concentrated local plastic deformation and the formation of high-density shear bands, which have high stored energy and significant lattice distortion, providing preferred nucleation sites for Goss grains. Finally, the magnetic induction B8 is achieved at 1.78 T, and the iron loss is 1.31 W/kg. There results provide guidance for achieving dual control between precipitation pinning and texture evolution with the Bi dosage.

Sliding wear tests were conducted on carburized G13Cr4Mo4Ni4V steel under grease-lubricated condition at varying loads and temperatures using an SRV-4 tribometer. The results indicate that the wear mechanism transitions from pitting abrasive wear or adhesive wear to oxidative wear and severe abrasive wear as the load and temperature increase to 180 N and 315 degrees C. Wear behavior is closely associated with matrix softening, carbide characteristics and tribolayer formation. The fracture of aggregated carbides leads to adhesive peeling of the matrix. While, dislodged carbides act as abrasives, damaging both the matrix and the tribolayer. Compared to easily fractured long-strip M2C carbides, the spherical M2C and MC carbides provide better resistance to adhesive wear by reducing the contact area between friction pairs. The subsurface microstructure exhibits wear influenced layers (-V) approximately 25-30 mu m thick. This wear influenced layer comprises various combinations of the damaged layer (IV), the plastic deformation layer (III), the recrystallized layer (II) and the tribolayer (I), depending on the test conditions. The formation of the tribolayer with a thickness of 1-2 mu m is influenced more significantly by temperature (315 degrees C) than by load (180 N). Furthermore, it contributes to a reduction in the coefficient of friction (COF) and wear rate.

The growing demand for advanced sodium-ion batteries (SIBs) necessitates the development of high-rate and durable anode materials. However, conventional ZnS-based anodes often suffer from sluggish ion transport kinetics and structural instability during cycling. Herein, a hierarchical ZnS/MoS3 composite with a carbon matrix (ZSCM) was synthesized through a MOF-derived carbonization-sulfurization route followed by an amorphous MoS3 surface modification. This unique architecture combines a conductive 3D carbon framework, abundant heterointerfaces, and multiphase synergy, which significantly enhance charge transport and interfacial reaction kinetics. As a result, the ZSCM anode delivers a high reversible capacity of 559.3 mAh·g-1 at 0.1 A·g-1 and maintains 370.8 mAh·g-1 even at 10 A·g-1. Structural and spectroscopic analyses reveal a multistep sodium storage mechanism involving the irreversible conversion and partial alloying of ZnS, along with the stepwise reduction and partial reoxidation of MoS3. Moreover, the ZnS/MoS3 heterointerface induces a built-in electric field due to interfacial work function differences, which facilitates charge redistribution and accelerates ion/electron migration. The assembled full cell with Na3V2(PO4)3 as the cathode further confirms the practical applicability of this design. This work offers mechanistic insights and an effective strategy for constructing ZnS-based anodes toward high-performance, multistep sodium storage.

The additive manufacturing (AM) of tool and mold components is increasingly adopted for its design flexibility and rapid prototyping advantages. Nevertheless, the broader application of is challenged by process-induced imperfections such as residual stresses, micro-defects, and retained austenite, which can compromise mechanical performance. This study investigates the role of energy input in regulating quality and microstructure of H13 steel fabricated via electron beam powder bed fusion (EB-PBF). Results indicate that the relative density first increases with energy input, reaching a peaking of 99.3 % at 40 J/mm3, beyond which it declines due to excessive evaporation and resultant porosity. The microstructure consists of martensite and nanoscale carbides, exhibits excellent mechanical properties, achieving a tensile strength of 1681.2 ± 34.4 MPa and an elongation of 7.2 ± 0.3 %. With increasing energy input, microstructural evolution involves grain coarsening and enhanced carbide precipitation. Moreover, the crystallographic texture transitions from a strong [110]<001> cubic orientation aligned with the build direction to a more randomized state. This microstructural response is attributed to the sustained high-temperature environment in EB-PBF, which mitigates thermal gradients during solidification and reduces the energy barrier for phase transformations driven by fluctuations in energy input. These findings offer valuable insights for microstructural control and process optimization in the pursuit of high-performance H13 steel components via EB-PBF.

The microstructure evolution, reversed austenite stability, and fracture mechanism were studied in the multiphase austenite steel (Fe-0.2C-12Mn-3Al-2.0Cu-3.0Ni, wt.%) with the pre-strain control, targeting an improved strength-ductility synergy. The two-step intercritical annealing and pre-strain control effectively improves austenite stability, increases dislocation density, refines grain structure, and increases martensite fraction, and then leading to simultaneous enhancements in ultimate tensile strength (UTS) and total elongation (TEL). The 10% pre-strain control results in UTS of 1341.4 MPa and uniform TEL of 18.7%. The overall improvements in mechanical properties are attributed primarily to the staged TRIP effect, synergized with dislocation strengthening and grain refinement. The staged transformation from austenite to martensite, strategically triggered by pre-strain control, enables a sustained work hardening capability.

In nickel flash smelting, the adhesion of Fe3O4 to low-nickel matte results in the physical entrapment loss of valuable metals in slag, posing a critical barrier to improving copper and nickel recovery rates. In this study, the interfacial adhesion behaviors between Fe3O4 and representative sulfides in low-nickel matte, including FeS, Ni3S2, and Cu2S, were systematically investigated using first-principles density functional theory (DFT) calculations to elucidate the underlying adhesion mechanisms. The calculated adsorption energies of the (111) crystal plane of Fe3O4 with FeS, Ni3S2, and Cu2S are −13.74, −5.91, and −13.19 eV, respectively, substantially higher than those associated with SO2 and other matte constituents. This indicates that interfacial adhesion dominates the separation process between slag and matte at the interface. Electronic structure analysis reveals there exists significant charge transfer and covalent bonding between FeS, Cu2S with Fe3O4, as evidenced by distinct hybridization peaks in the density of states (DOS) near −4.23 and −4.60 eV. In contrast, Ni3S2 exhibits weaker interfacial polarization and lower binding strength. Based on these findings, strategies such as reducing the Fe/SiO2 ratio, raising the smelting temperature, and minimizing oxygen partial pressure and Fe3O4 content are proposed to enhance fluidity and interfacial tension between low-nickel matte and slag, which accordingly mitigate the adhesion effect between the Fe3O4 and low nickel matte, thereby offering theoretical guidance for improving the recovery efficiency of valuable metals during matte smelting.

The characteristics of alternating current (AC) arc play a crucial role in the heating efficiency of ladle furnaces that use arc as a heat source. In this paper, a model of stirring by blowing argon gas at the bottom of the ladle, a model of gas component transport in the cavity, and an AC arc model are established to study the distribution of slag eyes, cavity gas distribution, and AC arc characteristics in ladle furnaces. The influence of electrical operation on the AC arc characteristics of ladle furnaces is also analyzed. The research found that when the bottom-blowing gas flow rate of a single hole is 400 L/min, the average mass fraction of argon gas around the three-phase electrodes is 13.7 pct. Considering the fluctuation of cathode spots, the average temperature and average velocity of the arc column are identically distributed in the radial direction during the period, while the temperature and velocity distributions only change in the axial direction. The temperature is higher in the areas near the surface of the molten pool and the bottom of the electrode. At the same power and rated power, when the gear is increased from 4th gear to 8th gear, the area of the high-temperature zone in the arc continues to expand, the highest temperature occurs near the surface of the molten pool, and the average surface heat flux of the molten steel increases by 4.95 × 106 and 3.29 × 106 W/m2, respectively.

Heat treatments utilizing varying quenching temperatures were applied to G13Cr4Mo4Ni4V martensitic steel. The investigation focused on the microstructural evolution and its influence on the strength and toughness under different heat treatments of the steel using scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). An analysis of the underlying strengthening and toughening mechanisms was conducted. The results demonstrate that the steel can achieve superior overall properties when quenched at 1100 degrees C. The prior austenite grain size, martensitic packet size and block width all increase with the increasing quenching temperature. In contrast, the width of the martensitic laths remains largely unaffected. Among the contributing strengthening mechanisms, solid solution strengthening accounts for the highest proportion. Second phase strengthening is most significant at the quenching temperature of 1100 degrees C correlating with the peak yield strength. The yield strength and impact toughness show stronger correlation with characteristic sizes of the martensitic block and packet, respectively. Furthermore, the heterogeneous distribution of aggregated nano-sized carbides induces local strain concentration leading to a reduction in impact energy. The formation of ferrite slightly enhances strength due to strain hardening but drastically diminishes impact energy. This embrittlement is attributed to microcracks initiation at the ferrite-matrix interfaces.

The effect of 1 wt% Cu on oxide-scale heterogeneity and subsurface microstructural evolution was studied in Fe–0.2C–8Mn–3Al–3.5Ni medium-Mn steel exposed to static air at 700–800 °C for 2 h. Both Cu-free and Cu-bearing steels formed stratified scales. The scales consisted of Fe- and Mn-rich external oxides and an Al-enriched inner oxidation region. Thus, Cu did not change the basic scale architecture. Its main effect was on the inner oxidation front. In the Cu-bearing steel, localized Cu–Ni-rich particles and island-like regions appeared near the inner oxide and the substrate. Similar regions were also found within the inner oxidation region. Their discontinuous distribution differed from that of a continuous protective layer. Their spatial association with Al–O-rich regions is consistent with rejection of relatively noble Cu and Ni from the growing oxides. It also suggests a local link between Cu–Ni enrichment and Al-rich internal oxidation. Root-like oxidation fronts and the more continuous distribution of Al–O-rich oxides along grain boundaries indicate grain-boundary-associated internal oxidation. EBSD results showed lower local misorientation and a higher high-angle grain-boundary fraction in the air-exposed peripheral region of the Cu-bearing steel than in the Ar-treated reference. These EBSD characteristics indicate recovery-dominated orientation evolution near the oxidized surface. The results identify Cu-associated chemical heterogeneity at the oxidation front and an atmosphere-dependent subsurface orientation response.

The effects of He ion irradiation on the microstructural evolution, hardness and corrosion resistance of additively manufactured (AM) stainless steels were examined. Irradiation induces the formation of alpha' phase with positive correlation with the dose. The hardness of & ouml;+ sigma phase is enhanced by the generation of alpha' phase and the enrichment of dislocations ( from 4.28 +/- 0.01 GPa to 8.75 +/- 0.57 GPa). The decrease of Fe/Ni content of & ouml;+ sigma phase triggers the inversion of the & ouml;+ sigma phase potential (anodic -> cathodic) after irradiation. He bubbles form a composite defect structure with dislocations at supercritical concentration in the peak damage zone. Interfacial analysis shows that He bubble aggregation at the inclusions/substrate interface triggers atomic spacing expansion (from 2.1 to 2.4 & Aring;), inducing interfacial expansion and stress concentration. Passive film analysis showed that irradiation led to an increase in Fe, Ni(OH)2 content, and MoOS -> MoOS conversion in the passive film accelerated the decomposition of the passive film.

Optimizing the foaming characteristics of tundish fluxes is crucial for effectively enhancing plasma-heating efficiency, necessitating a systematic investigation into the evolution of these fluxes under plasma-heating conditions. In this study, the foaming process of slags was observed, and the influence of plasma heating on slag structure was analyzed using DSC, high-speed camera imaging, XRD, Raman spectroscopy, and 27Al MAS-NMR. The results indicate that, during plasma heating, the gas source for slag foaming primarily originates from carrier gas entrainment and CO2 released from carbonate pyrolysis. Under a fixed addition level of 5 wt%, the foaming duration of the K2CO3, Na2CO3, Rb2CO3, Cs2CO3, and Li2CO3 systems decreased sequentially from 136 to 111 s, among which the N-K system exhibited the most stable foaming behavior. The N-K system was characterized by the highest BO/Si ratio (3.804) and an appropriate AlO4 fraction (66%), forming a moderately polymerized bridging-oxygen network. This structure reduced surface tension while maintaining suitable viscosity, thereby lowering the energy required for foam formation and extending foam lifetime. In contrast, Li+ led to an excessively dense network, whereas Cs+ resulted in an overly loose structure, both of which were unfavorable for foam stability. Further analysis revealed that the ultra-high-temperature and electric field environment under plasma heating promoted structural evolution of all slag systems toward more defined types, with silicate and aluminate units transforming into species and AlO4 units, respectively. These findings suggest that high temperature provides the energetic basis for structural reconstruction, while the electric field and the size effect of alkali metal ions synergistically govern the pathway and extent of structural evolution. Collectively, these results provide a theoretical foundation for compositional optimization of tundish fluxes under high-efficiency plasma-heating conditions and offer data support for subsequent industrial applications.

A quantitative study of inclusions in an industrial superalloy ingot produced by vacuum arc remelting (VAR) was conducted, and the characteristics as well as the formation mechanism of non-metallic inclusion clusters were discussed. Results showed that inclusions within the VAR ingot primarily consisted of individual nitrides and composite inclusions such as oxide-nitrides. The quantity density of individual inclusions increases radially from the center to the edge of the ingot, while decreasing axially from the top to the bottom, with the average size gradually decreasing in both radial and axial directions. Clustered inclusions were identified in the subsurface regions (2-10 mm in depth) and sidewall surfaces of the ingot. The formation mechanism and distribution characteristics of clustered inclusions during the VAR process were studied by combining in-situ high-temperature laser confocal microscopy observation and numerical analysis. In-situ observations confirm that larger inclusions lead to reduced critical aggregation distance, while smaller spacing enhances attraction and promotes cluster formation. The cavity bridge force between inclusions is significantly greater than the capillary force and van der Waals force, serving as the primary force responsible for the aggregation of inclusions. Numerical analysis reveals that inclusions within the VAR melt pool exhibit typical flow-following behavior and size effects, with their trajectory leading to preferential accumulation patterns along both the sidewall and subsurface regions, thereby facilitating cluster formation through particle agglomeration.

The recycling and reuse of superalloy scrap constitutes a critical approach to reducing engine component costs, necessitating guaranteed material performance. This study investigates the effects of recycled processing scrap on the cleanliness, microstructure, and mechanical properties of GH4738 nickel-based superalloy through vacuum induction melting (VIM) combined with vacuum arc remelting (VAR). Results demonstrate that, compared with the 100

A new type of superconducting wire with high critical current density, fine filament, ultra-low loss experimental NbTi/Cu5Ni/Cu has been developed in this paper for the miniaturized heavy ion therapy device of China. The wire uses Cu-5%Ni alloy instead of conventional high-purity OFC as the matrix, which could prevent the coupling between filaments at low temperature and reduce the eddy current loss effectively. Meanwhile, the Cu5Ni matrix and NbTi filament are separated by high-purity Nb. Nb, as a barrier layer, could isolate the diffusion reaction between Cu and Ti in the process of high-temperature and long-time aging heat treatment. In order to reduce the hysteresis loss of the wire, the filament inside the wire is increased to 75276. The filament diameter is reduced to 1.9 mu m under wire diameter of Phi 0.8 mm. Due to large number of filaments of the wire, filament breakage and wire breakage phenomena occur during processing of the wire. The J(c) (4.2 K, 5 T) of the wire is only 2410 A/mm(2), and the "n" value is only 17.9. The hysteresis loss (4.2 K, +/- 3 T) of the wire is 19.9 mJ/cm(3), which reached a new higher level in history.

In the converter steelmaking process, the flow dynamics is closely related to the refractory lining structure of the bath, such as hearth height-to-diameter (H/D) ratio and lining erosion at different campaign stages. The step of pre-processing in computational fluid dynamics (CFD) simulation is time-consuming for different lining structures, and usually takes around a week per case using the traditional direct modeling method. A parametric modeling tool has been developed to quickly generate various converter structures with quality structured grids within seconds, based on Python and OpenFOAM software. CFD simulations were established and validated using hydraulic modeling to investigate the flow dynamics and lining erosion characteristics in a 100 t top-bottom combined blowing converter under different H/D ratios and campaign stages (initial, middle, and late). The results show that the average molten bath velocity is positively correlated with bath depth. An increase in bath depth extends the path length for kinetic energy transfer of combined blowing gas streams. Excessively large bath depth or diameter will deteriorate the flow pattern and result into corresponding dead zones. Furnace wall and bottom erosion intensifies at higher H/D ratios but decreases in the late campaign stages. The H/D ratio of 1.67 is recommended in the initial design stage considering the flow characteristics. In the late campaign stage, increasing the bottom-blowing flow rate and carrying out furnace maintenance operations are recommended to maintain metallurgical efficiency and lining safety.