The limited corrosion resistance of Magnesium alloys, arising from their inherently high electrochemical activity, significantly restricts their applications in sweat-contacting scenarios such as wearable electronic housings and biomedical devices. Monolayer coatings produced by magnetron sputtering often contain intrinsic defects, failing to achieve sufficient protection. To address this, ceramic composite coatings were deposited on ZK61M magnesium alloy via magnetron sputtering and subsequently modified with fluorosilane solution. The resulting TiAlN/Si3N4/PFOTES composite coating exhibited an impedance value 14 times greater than that of the uncoated magnesium alloy and a water contact angle of this coating could be as high as 145°, demonstrating superior hydrophobicity. In simulated sweat immersion tests, coated specimens demonstrated a corrosion rate reduction of approximately 55% compared to bare ZK61M magnesium alloy. Furthermore, a corrosion kinetics model was constructed to elucidate the corrosion mechanism in depth. The synergistic effect between chemical hydrophobicity and physical barrier provides a new perspective for designing innovative composite coatings.

Two heats of M2 high-speed steel with different rare-earth (Ce) contents were produced by a domestic steel plant using the following process route: electric arc furnace (EAF) smelting → ladle furnace (LF) refining → vacuum degassing (VD) → electroslag remelting (ESR) → forging → rolling. Optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and high-temperature confocal microscopy were used to investigate the effects of Ce on the inclusions and carbides in M2 high-speed steel. The results indicated that the addition of Ce reduced the oxygen and sulfur contents in the electroslag ingot. The inclusions were completely modified, with large irregular Al2O3 inclusions becoming small globular CeAlO3 inclusions. Meanwhile, their number density and average size decreased. Although the number density only decreased by 12%, from 450 to 396, the average size decreased by 43.1%, from 1.81 to 1.03 μm. The cleanliness of the molten steel was significantly improved. Thermodynamic calculations indicated that CeAlO3 inclusions had the lowest Gibbs free energy and were therefore the most likely to form in the electroslag ingot. The eutectic carbides found in the as-cast structure of an electroslag ingot with the Ce addition exhibited a finer size, smaller quantity, and partial fragmentation of the network structure. A high-temperature confocal laser scanning microscope was used for in-situ observations of the solidification processes of the two groups of test steels, and the degree of mismatch was calculated. The results showed that the degree of mismatch between (001) CeAlO3 and (100) γ-Fe was 4.49%, indicating that CeAlO3 inclusions could serve as effective heterogeneous nucleation cores for γ-Fe. This promoted an increase in nucleation sites during the solidification of molten steel, which greatly compressed the growth space of eutectic carbides, and thereby inhibited the precipitation of eutectic carbides. This was consistent with the observation results from the high-temperature confocal microscopy. In both groups of annealed wire rods, the carbides were M6C, MC, and M7C3. The addition of Ce did not change the type of carbides in the wire rod. The microstructure of the annealed wire rod consisted of coarse primary carbides and smaller spheroidized pearlitic carbides. The addition of Ce decreased the amount of large carbides while increasing the proportion of fine pearlitic carbides. The statistical results for the carbides in a longitudinal section of the wire rod showed that after the addition of Ce, the number of carbides increased from 733 to 1145 in the same area (1000 μm2), representing a 56.21% increase. Meanwhile, the area fraction of carbides decreased from 12.87% to 8.06%, a reduction of 37.37%. The influence of Ce on the inclusions and carbides improved the properties of the M2 high-speed steel. The research results provide theoretical support for the production of high-quality M2 high-speed steel.

To give insights into the role of pouring zone structure in tundish fluid flow and product quality, a combined approach of physical modeling, numerical simulation, and industrial trials was employed to investigate the effects of varying pouring zone structures on fluid flow, refractory stress distribution, temperature distribution, and inclusion removal in a six-strand tundish for tire cord steel production. The optimized structure, incorporating a cylindrical turbulence inhibitor and a larger upward inclination angle of symmetric deflector holes, reduces the dead zone ratio by 7.3 pct and increases the average residence time by 9.1 pct. Furthermore, the high-stress region shrinks, and the shear stress acting on the bottom and sidewall of the pouring zone is significantly reduced. The optimized structure shows a neglectable influence on the outlet temperature of all strands. The pouring zone exhibits the highest inclusion removal ratio for different inclusion sizes and reaches a stable removal state in the shortest time. The removal ratio in the pouring zone and the overall inclusion removal ratio increases by approximately 8 and 10 pct, respectively, after the optimized pouring zone structure is applied. Industrial trials further verified the modeling results with a decrease of 8.3 to 63.6 pct in number density, average equivalent circle diameter, and average width of inclusions, and the decrease of inclusion proportion (> 7 μm) from 6.6 pct to less than 1.8 pct.

Traditional cold heading steel is limited by several issues, including heterogeneous microstructures in hot-rolled products that lead to cold heading cracks, lengthy spheroidizing annealing cycles, and high energy consumption. These issues collectively impair both product quality and production efficiency. This study conducted industrial-scale experiments to produce 40Cr cold heading steel with varying rare earth (La) additions. The influence of La on the microstructure and mechanical properties of cold heading steel, as well as the mechanism underlying cold heading failure behavior analysis were systematically investigated through an integrated approach that combined industrial production, laboratory annealing, microstructural characterization, and mechanical testing. The findings demonstrate that La effectively refines the austenitic grain structure by improving the solidification process. The addition of La increases the ferrite fraction in hot-rolled wire rods while reducing the spacing between pearlite, significantly enhancing the strength and toughness of the hot-rolled wire rod. After the spheroidizing annealing process, La enhances the spheroidization degree of cementite, significantly reducing the spheroidizing annealing time. Furthermore, La transformed the morphology of inclusions from ellipsoidal Al2O3 center dot CaO center dot CaS to spherical LaAlO3 center dot CaO center dot CaS and significantly reduced the quantity of lamellar pearlite structure, significantly mitigating cracking issues associated with inclusions during cold heading and enhancing compressive properties. This research revealed the mechanism by which rare earth microalloying improved the microstructure and cold heading failure behavior of cold heading steel. The findings provide valuable technical and theoretical support for the industrial fabrication of high-strength, high-toughness rare earth-containing cold heading steels.

316L and DSS 2205 suffer from pitting corrosion in a denitrification agent, NaClO2 solution, despite their excellent corrosion resistance and widespread utilization in plants. Herein, nitric acid passivation was successfully employed to enhance the corrosion resistance of 316L and DSS 2205 in 3% NaClO2 solution. The 3% NaClO2 solution, in which 316L and DSS showed the lowest corrosion rate, was chosen by electrochemically studying the effect of NaClO2 concentration on the steel's corrosion from a series of solutions containing 1%, 3%, 6%, and 10% NaClO2. The passive films with and without nitric passivation were investigated by chemical composition, electrochemical property, semiconductor behavior, and morphology observation analyses. The enhanced corrosion resistance of both 316L and DSS 2205 after nitric passivation was attributed to the Cr enrichment and decreased active area on the steel surface. The semiconductor property test and point defect model showed that both the reduced doping density and the decreased diffusivity contributed better resistance against ClO2- and Cl-. The passivated 316L showed better corrosion resistance according to electrochemical tests and potentially is an option to replace high-cost DSS 2205.

Rare earth La was introduced into 40Cr steel in industrial experiments to achieve the purpose of modifying inclusions. The impact of La on the inclusion modification was studied, and its influence on the solidification structure was further investigated. With adding 0.0023

Invar alloy is widely recognized as an ideal functional material due to its excellent thermal expansion properties. However, its limited strength restricts its application as a structural material. Current research focuses on enhancing strength while maintaining its low coefficient of thermal expansion (CTE). In this paper, a cold deformation-aging method was employed to promote the precipitation of V (C, N) phases for strength improvement. Various cold deformation ratios were introduced into the invar alloy, and their effects on microstructure evolution, thermal expansion behavior, and mechanical performance were investigated. Experimental results demonstrated that the aged alloy at a 40 % reduction achieved a tensile strength of 844 MPa, representing a 45 % enhancement compared to non-deformed aged alloy, while maintaining a low CTE value. Microstructural analysis revealed that increased dislocation density from higher cold rolling reduction provided abundant nucleation sites for V (C, N) precipitation. Simultaneously, these precipitates effectively pinned dislocations and facilitated dislocation multiplication, so that the strength of the aged alloy remained at a high level. These results establish fundamental guidelines for developing high-strength invar alloy with low-CTE, while offering practical insights for optimizing deformation parameters in industrial processing.

The removal of residual elements in the scrap steel recycling process has emerged as a significant challenge for the contemporary metallurgical industry. The current production methods cannot effectively eliminate the adverse effects of residual elements. Consequently, a novel strategy is proposed to enhance hot workability by adding Ce to an invar alloy containing Sn. In this study, after adding 500 ppm Sn, the reduction in area decreases markedly from 75 to 40% at 1050 °C. After adding 44 and 120 ppm Ce, the reduction in area remarkably increases to 80 and 76%, respectively. The Sn‐containing sample hot ductility improves at 1150 °C, and the sample containing Ce still maintains a high level. After adding Sn and Ce, the typical inclusions transformation process is as follows: MnS → MnS + Ni 3 Sn 2 → Ce 2 O 2 S and Ni 3 Sn 2 ·Ce 2 O 2 → Ce 2 O 2 S, Ce 2 O 3 , Ni 3 Sn 2 ·Ce 2 O 2 S and Ni 3 Sn 2 ·Ce 2 O 3 . The lattice mismatch of Ce 2 O 2 S and Ni 3 Sn 2 , Ce 2 O 3 and Ni 3 Sn 2 is 1.96 and 3.26%, respectively. The rare‐earth inclusions act as a heterogeneous nucleation core, which attract Ni 3 Sn 2 to nucleate. Two kinetic models are developed to elucidate the Sn and Ce nonequilibrium segregation and the inclusion transformation process. The beneficial transformation of inclusions and the preferential segregation of Ce enhanced the hot ductility of the invar alloy.

Invar alloy is widely used for manufacturing precision instruments owing to its exceptionally low thermal expansion property. Nevertheless, conventional invar alloys usually lack the sufficient strength required for engineering applications, so there is an urgent need for innovative approaches to enhance the strength. In this study, the possibility of elevating the strength and preserving the low coefficient of thermal expansion (CTE) of invar alloy is investigated by combining deformation strengthening with the V (C, N) precipitation strengthening mechanism. The increase in dislocation density resulting from deformation treatment promotes the V (C, N) precipitation. This leads to a significant enhancement in the strength of alloys after cold-rolling aging compared to direct aged counterparts, while preserving the low CTE. After a cold-rolling deformation with a 40% reduction and subsequent aging at 650 °C for 3 h, the V-N invar alloy exhibits a tensile strength of 907 MPa and an elongation of 6.9%, demonstrating the optimal mechanical properties. In addition, the CTE value maintains a low value of 1.31 × 10−6/°C within the temperature range of 20 to 100 °C. These findings are vital for developing high-strength, low-CTE invar alloys.

Invar steels possess excellent thermal expansion properties, making them suitable as materials for manufacturing precision instruments. However, conventional invar steels lack sufficient strength for engineering applications, and various strengthening methods are urgently needed to enhance their strength. In this work, the possibility of enhancing the strength and maintaining low coefficient of thermal expansion (CTE) of the steel through mechanical heat treatment and the introduction of vanadium carbonitride is demonstrated. V–N microalloying and various heat treatment processes enable invar steel to enhance its strength while maintaining low thermal expansion properties. The strength of low-nitrogen addition invar steel measured 593 MPa during direct aging, representing a 44.6

Corrosion is an unavoidable issue that steel encounters during service; however, the generic methods employed for corrosion prevention often need high cost or preparation conditions. In this study, a facile chemical replacement deposition method was proposed to realize an anticorrosion superhydrophobic coating on a X80 steel surface. The growth mechanism of the rough structure and its impact on the wettability of the superhydrophobic coating were analyzed. The superhydrophobic coating, deposited for 50 s and modified for 30 min, achieved optimal electrochemical properties and a maximum water contact angle. The immersion test, in the saturated CO2 oilfield produced water, demonstrated the better corrosion resistance of superhydrophobic coating than X80 steel. Correspondingly, a kinetic corrosion model was established to analyze the anticorrosion mechanism. In summary, this method significantly improves the corrosion resistance of X80 steel and is attractive for other industrial fields.

Nb-microalloyed steels are widely used in construction engineering fields due to their excellent mechanical properties, but they face serious corrosion problems in service environments. Pitting corrosion is the severest form of corrosion, and the types of inclusions are the leading cause to induce pitting corrosion. A new strategy is proposed to enhance the corrosion resistance of steels by achieving a beneficial transformation of inclusions with Ce treatment. In this paper, two types of Nb-microalloyed steels (0% Ce and 0.0058% Ce steel) were prepared to study the modification effect on inclusions in industrial production. The spherical CaS center dot C(12)A(7) inclusions were modified to smaller ellipsoidal Ce2O2S inclusions, and the proportion of inclusions (0-2 mu m) increased significantly from 27 to 66%, while large inclusions (>6 mu m) disappeared. A kinetic model of inclusion evolution was established. The results of electrochemical tests indicated that the corrosion potential was positively shifted, and the corrosion current was reduced after Ce treatment. Additionally, the number of defects in the passivation film was decreased, and the corrosion resistance of the steel was significantly improved. The addition of Ce changed the types of inclusions and reduced the number of pitting nucleation points, which led to a remarkable reduction in the number and size of pitting pits. The mechanism of pitting corrosion induced by different types of inclusions was further investigated, and a pitting corrosion model was modeled based on the immersion experiments. Research results provide theoretical support for enhancing the corrosion resistance of steel.

Low alloy steel faces localized corrosion issues in service environments, primarily due to pitting corrosion induced by inclusions. Conventional protective measures cannot significantly improve the corrosion resistance of the steel. In this study, an effective industrial approach was proposed to enhance the corrosion resistance of low alloy steels. Cerium (Ce) was added during the refining process to modify inclusions and alter the mechanism of inclusion-induced localized corrosion, thereby improving the substrate's ability to inhibit pitting corrosion. The effect of Ce treatment on the cleanliness of molten steel was investigated, and a kinetic model of inclusion evolution was established based on thermodynamic calculations. The pitting corrosion induced by CaS·C12A7 and CeAlO3 inclusions was studied through immersion experiments over different durations. The degree of corrosion after being soaked for 20 min was significantly different. The size and depth of pitting pits induced by CeAlO3 inclusions were much smaller than those induced by CaS·C12A7 inclusions. The electron back scatter diffraction tests confirmed that CaS·C12A7 inclusions exhibited a higher corrosion sensitivity compared to CeAlO3, thus promoting the initiation of pitting. Electrochemical tests demonstrated a positive shift in the corrosion potential and a reduction in current density. This implies that CeAlO3 inclusions can significantly inhibit pitting occurrences. Based on the dissolution behaviors of CaS·C12A7 and CeAlO3 inclusions, a kinetic model was established to describe the initiation and propagation of pitting induced by these inclusions.

Industrialized tests are conducted to produce 20MnTiB cold heading steel with varying Ce contents.A Vickers hardness tester,tensile tester,impact tester,optical microscope,and scanning electron microscope are used to study the deterioration of inclusions in the steel and observe the changes in microstructure and mechanical properties of the hot-rolled wire rod after Ce addition.The application mechanism of Ce is also analyzed.The results show that the S content in the molten steel decreases,and the cleanliness is significantly improved after the addition of 0.0025％Ce.The inclusions in the wire rod transform from large-sized and elongated Al2O3·MgO·CaO·CaS composite inclusions to small-sized and spherical CeAlO3·MgO·CaO·CaS composite inclusions.Concurrently,the long strips of MnS inclusions disappear.Thermodynamic calculations indicate that at 1839 K,the order of precipitation of different Ce inclusions is as follows:CeAlO3＞Ce2O3＞Ce2O2S＞CeO2＞Ce3S4＞Ce2S3＞CeS.This suggests that with a Ce mass fraction of 0.0025％,the most probable inclusions are CeAlO3.Considering that 20MnTiB cold heading steel contains B,Ti,and other hardenability elements,improper process control during hot rolling can easily lead to the formation of a bainite structure in the wire rod.This causes the mechanical strength of the wire rod to be higher than desired,leading to occasional cracking during late cold heading and significant wear on the cold heading mold.After the addition of Ce,the microstructure of the wire rod is refined,with an increased proportion of ferrite and a reduction in both the presence and size of granular bainite.Ferrite is a soft and tough phase,while bainite is a reinforcing phase.The reduction in granular bainite and the increase in ferrite contribute to a decrease in strength and hardness.Lower hardness and strength are beneficial for improving the cold heading performance of the wire rod.After Ce addition,the cold heading performance of the wire rod is improved to a certain extent.Additionally,the ambient-temperature impact toughness of the wire rod significantly increases from 31.7 to 52.3 J with the addition of Ce,an increase of 65.0％.This substantial increase in impact performance further enhances the cold heading performance of the wire rod.The reduction in hardness and mechanical strength,combined with the significant increase in impact properties,makes the rare-earth microalloyed hot-rolled wire rod more suitable for cold heading applications.These research results provide technical and theoretical support for the further development of new rare-earth microalloyed cold heading steels.

Invar alloys that combine high strength with a low coefficient of thermal expansion (CTE) are urgently required for industrial applications. Based on the lower coarsening rate during aging and the CTE values of carbonitrides, a novel strategy is proposed to prepare carbonitrides by reducing carbon and increasing nitrogen to design high-strength and low-thermal-expansion invar alloys. The V(C, N) nanoprecipitate was introduced into the invar alloy, and its effects on the microstructure, thermal expansion behavior, and mechanical properties were investigated. The direct-aged alloy exhibited an enhanced tensile strength of 525MPa and a ductility of 47.6%. The cold-deformation aging alloy achieved an enhanced tensile strength of 815MPa while retaining 7.4% ductility and a low CTE value of 1.23×10-6 /°C. The V(C, N) nanoprecipitates effectively immobilized dislocations and grain boundaries, leading to a high dislocation density and small grain size in the alloy. The contributions of each strengthening mechanism were calculated, and the precipitation and dislocation strengthening were found to be the main mechanisms of strength enhancement. These results provide a novel approach for preparing high-strength and low-CTE invar alloys.

As the leading technology for producing bismuth ingots from bismuth sulfide concentrate, pyrometallurgical smelting has the shortcomings of high energy consumption, gas pollution, and dust emissions. Hydrometallurgical treatment has been widely regarded because of its low carbon, energy efficiency, and eco-friendly characteristics. In this paper, metallic bismuth is prepared through "transformation pretreatment-methanesulfonic acid (MSA) leaching-bismuth electrodeposition" from a bismuth-based acid-leaching residue, and the separation of bismuth from associated minerals such as pyrite and molybdenite is realized. First, Bi2O(OH)2SO4 of bismuth-containing acid-leaching residue is transformed to acid-soluble Bi2O3 in NaOH solution. The transformed product is leached in MSA solution, and the obtained bismuth methanesulfonate-leaching solution is electrodeposited to generate bismuth metal. Under the optimal parameters, the total recovery ratio of bismuth from a bismuth-based acid-leaching residue to bismuth metal can reach 97%. The final-leaching residue is mainly composed of elemental sulfur and sulfide ores (pyrite, molybdenite, etc.), which can be separated and recovered by the flotation process. The purity of bismuth metal from electrodeposition is higher than 99.96%, and the waste electrolyte can be recycled to the acid-leaching procedure as the leaching agent. The proposed technology in this work can also be applied to treating bismuth-containing secondary materials and low-grade complex sulfide ores. It is expected to have bright application prospects in bismuth hydrometallurgy and sustainable metallurgy.

Magnesium-based biodegradable metal bone implants exhibit superior mechanical properties compared to biodegradable polymers for orthopedic and cardiovascular stents. In this study, MgZZC-x (x = 1, 1.2) alloys were screened by in vitro biocompatibility tests in three simulated body fluids under nontoxic conditions. The MgZZC-1 alloys with better biocompatibility were selected to predict the days required for complete degradation. The evolution of degradation products was analyzed, and the mechanism of formation of the product film was inferred. A degradation kinetic model was established to investigate the effect of MEM components on the degradation of the alloys. The results demonstrate that the proteins in MEM can greatly retard the degradation progress by attaching to the surface of MgZZC-1 alloys, which are predicted to degrade completely within 341 days. The carbonate and phosphate buffers were adjusted to pH in MEM solution, delaying the degradation of magnesium alloys. This process in MEM more accurately reflects the actual degradation in the body and is superior to that in Hanks and SBF solutions. This study will promote the application of biodegradable materials in clinical medicine.

Alloy 800H is commonly used in high temperatures and corrosive environments due to its exceptional strength and resistance to high temperatures, but the ingots are prone to longitudinal cracking during the hot working process because of its coarse solidification structure. Based on the heterogeneous nucleation effect of rare earth inclusions, a strategy is proposed to refine the solidification structure of alloy 800H by La treatment to solve the crack problem. In this study, four kinds of alloy 800H ingots (0, 120, 260 and 470 ppm La) were prepared to investigate the effect of La on the solidification structure. After adding La, the types of inclusion were changed, and the modification path of inclusions was Al2O3 (0 ppm La) -> LaAlO3 (120 ppm La) -> LaAlO3La2O2S and La2O2S (260 ppm La) -> La2O2S and La2O3 (470 ppm La). After adding La, the inclusion morphology tended to be more spherical and the average size smaller. The lattice misfit calculation indicated that La-containing inclusions can serve as heterogeneous nucleation cores, and the number of effective heterogeneous nucleation also increased with La content increased. The columnar to equiaxed transition occurred early with La treatment, the ratio of the equiaxed zone increased from 2.1% to 36.5%, and the average equiaxed grain size decreased from 2.56 to 0.43 mu m with La content increased from 0 to 470 ppm. The solidification structure of alloy 800H was significantly refined by adding La, and can thus provide a new strategy to solve the crack problem.

IGC mechanisms and/or corresponding IGC resistance mechanisms of 304 and 304L ASSs by adjusting carbon contents were systematically investigated by microstructure characterization, electrochemical and IGC tests. The results reveal that a maximum IGC degree of 304 ASS is observed at an aging temperature of 660 degrees C for 10 h based on a continuous precipitation of Cr-carbides along grain boundaries. The roles of precipitated Cr-carbides are concluded as two aspects, involving an occurrence of Cr-depleted regions and a destruction of film stability along grain boundaries. However, this IGC behavior is not linearly relevant with precipitation behavior of Cr-carbides, and a co-segregation mechanism of Cr and C atoms before a nucleation of carbides plays a decisive role in this current study. In comparison, 304L ASS (by adjusting carbon contents) exhibits a superior IGC resistance after a long-term aging treatment, which is mainly attributed to simultaneously restricting a precipitation of Cr-carbides and ensuring a continuous supply of Cr atoms toward Cr-depleted regions. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The corrosion behavior of rare earth (RE) low-alloy steel in soil simulation solution was investigated by immersion test, electrochemical experiment, scanning electron microscopy, and X-ray diffraction, compared with Q450 weathering steel. The kinetics model of all steels in soil simulation solution was established. The pitting corrosion mechanism of nonmetallic and RE inclusions was discussed. The results revealed that the RE improved the corrosion resistance of low-alloy steel by modifying inclusions and promoting the formation of a dense protective film. The steel containing 0.0047% RE achieved the best corrosion resistance. The corrosion product layers were mainly composed of gamma-FeOOH, alpha-FeOOH, Fe3O4, and Fe(OH)(3). The results of the kinetic model showed that the dissolution of the anode was the restricted link of the whole process. The lowest apparent corrosion rate constant k of the sample containing 0.0047% RE was 2.359 x 10(-4) mu m/h in the soil simulation solution. The kinetic model could serve as a method to predict the service life of steel parts.