Four high entropy alloys (FeMnCrNi system HEAs) with different Al and Ti contents were fabricated via vacuum induction melting using low-cost ferroalloys and pure metals. The influence of Al and Ti on inclusion characteristics was analyzed using an electrolytic extraction process in combination with scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) characterization. The obtained results showed that in Ti-free (Fe50Mn30Cr10Ni10(S1) and Fe44Mn30Cr10Ni10Al6 (S2)) HEAs, the main inclusions were MnS, Al2O3, and Al2O3-MnS, which were irrelevant of Al content. In Ti-containing HEAs, aggregated Ti(CxN1−x) inclusions were formed, along with Al2O3-Ti(CxN1−x) and Al2O3-TixOy-Ti(CxN1−x) complex inclusions regardless of Ti content. Non-equilibrium thermodynamic calculations revealed that Ti, C, and N segregated at the solidification front, driving the precipitation of Ti(CxN1−x), and the composition of Ti(CxN1−x) in Fe44Mn30Cr10Ni10Ti6(S3) and Fe44Mn30Cr10Ni10Ti2Al4(S4) was very similar to that of TiC. Inclusion growth modeling indicated that faster cooling rates produced smaller inclusions, while higher Ti content led to larger sizes. Due to aggregation effects, the experimentally observed inclusion sizes exceeded those predicted by theoretical models. Collision and aggregation modeling further revealed that the S3 alloy exhibited a higher number density of Ti(CxN1−x) inclusions, which increased the collision frequency among inclusions and consequently promoted the aggregation process. Reducing Ti content could suppress Ti(CxN1–x) inclusion growth during solidification, and also could decrease their number density, collision frequency, and aggregation. The obtained results of this study provide a theoretical basis for controlling the inclusions in Al-Ti containing high entropy alloys manufactured by low-cost feedstocks

The agglomeration of inclusions in continuous casting blooms destroys the continuity and compactness of the steel matrix, which seriously restricts the fatigue life and corrosion resistance of the steel. A novel traceability method for the distribution of inclusions was introduced to reveal the evolution of inclusion agglomeration. This method demonstrated the position evolution of inclusions when they passed through different planes by assigning colors for inclusions. In this study, a mathematical model coupled with electromagnetic field, flow, heat transfer, solidification, and non-metallic inclusion movement was developed to study the agglomeration behavior of inclusions under dual-mode electromagnetic field control modes (edge-to-center flow mode and the coupled mode of center-to-edge flow and edge-to-center flow). Numerical simulation revealed that the coupled mode significantly enhanced inclusion distribution uniformity in the solidified shell, with a 63.7 % reduction of the number in the localized agglomeration zone compared to the edge-to-center flow mode. Experimental measurements demonstrated a 46.7 % decrease in inclusion number density near the quarter position of the loose side under coupled mode compared to edge-to-center flow mode. Under coupled mode, the flow of molten steel at the center and the edge of the mold with the opposite directions helped to disperse the inclusions and promote the uniform distribution of inclusions in the cross-section. This study provides a new strategy to suppress inclusion agglomeration in continuous casting blooms by electromagnetic metallurgy technology.

The passivation, oxidation stratified architecture, and mechanical behavior of Al-doped fcc + hcp dual-phase cobalt-based multi-principal element alloys (MPEAs) Co(47.5-x)Cr30Fe7.5Ni7.5Mn7.5Alx (x = 0, 0.5, 1.0, 1.5, 2.0 at.%) at elevated temperatures were studied comprehensively in the present work. The evolution of the surface morphology, specific oxide growth processes, and elemental distributions were analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), and X-ray Photoelectron Spectroscopy (XPS). The analyses show that the oxidation kinetics of the Al-doped MPEAs follow the parabolic or near-parabolic law at 600, 800, and 1000 °C. The alloys generally undergo different oxidation stages: for instance, (1) surface reaction between O2– ions and metal ions, (2) surface thickening via oxygen chemisorption, (3) oxide flaking induced by thermal expansion coefficients mismatches. However, no spallation was observed for the present alloys during the 100 h oxidation experiment. The experimental results indicate that the oxide layers have a triple-layer stratified architecture: the outer layer Mn3O4, the intermediate layer (Mn,Cr)xO4, and the inner layer Cr2O3 + Al2O3. CanA2 (Co47Cr30Fe7.5Ni7.5Mn7.5Al0.5) exhibits optimal high-temperature oxidation resistance and demonstrates high strength-ductility at room and elevated temperatures in different processes. The pre-formed Al2O3/Cr2O3 in passive film at room temperature serves as a critical diffusion barrier at high temperature, reducing oxidation rate by 63 % at 1000 °C. This work proposes a surface engineering strategy for designing promising materials with a barrier layer for aerospace engines.

A novel methodology to control the size and chemistry of TiN particle in an inclusion-engineered steel is manufactured using spark plasma sintering (SPS) in combination of post heat treatment. The chemical composition of TiN particles keeps being stable after sintering with metallic Fe-C-Mn particles, and a very slight deviation of TiN size could be observed. In addition, an attempt to further classify the particle size in different narrow ranges has been presented here for future work. This feasibility study paves the way for a further development of the fabrication methodology for the next generation inclusion-engineered steels with a homogenous distribution of desired phase of particles.

Complex phase steels (CP steels) exhibit an excellent hole expansion performance due to the subtle hardness difference between different kinds of microstructures, in which the high-hardness martensite-austenite (MA) constituents are the critical structure type. The present study aims to improve the hole expansion property by constructing the continuously distributed MA constituents along the rolling direction at the thickness center. Microstructures and hole expansion behavior were investigated using laser confocal microscopy, scanning electron microscopy (SEM), electron backscattering diffraction (EBSD), and hole expansion tests. Microstructure characterization results indicate that after improvements, the MA constituents were aggregated at the thickness center in a continuous distribution along the rolling direction with a long axis of approximately 1.25 mu m, and an average distance of less than 1.0 mu m. Hole expansion behavior analysis reveals that the fracture initiated at the edge of the base steel, shown in a mixed ductile-quasi-cleavage fracture. The fracture mode changes to pronounced necking ductile fracture induced by void aggregation at the thickness center of the advanced steel. Micro-hardness quantification of the plastic damage on the punching edge shows that the advanced steel exhibits the highest hardening at the thickness center with a 41% hardness increase over the pre-punching, higher than the 31% hardening in the maximum hardening burr zone of the base steel. The hole expansion ratio of the advanced steel suffering serious punching damage was approximately 43%, higher than that of the base steel (34%). Quasi-in-situ interrupted hole expansion test indicates that on the thickness center of the advanced steel, the circumferential cracks formed through the multiple void interaction mechanism which promotes the stress release. In the matrix, pit-like damage is in a void coalescence mechanism. Both mechanisms lead to mechanical instability and eventual failure. The position of the damaged particles at the hole edge had a decisive impact on the fracture mode.

Stainless steels have undergone more than a century of continuous development, during which various advanced grades—such as lean duplex, super austenitic, and high-nitrogen stainless steels—have been introduced. Despite remarkable progress, the manufacturing of stainless steel remains a complex process that spans multiple critical stages, including stainless steelmaking, solidification and casting, continuous casting, heat treatment, electroslag and vacuum arc remelting, as well as both hot and cold rolling operations. Ensuring excellent corrosion resistance and mechanical performance of the final products continues to be a central focus of research and production. The current Special Issue (SI) entitled ‘Advanced Stainless Steel—from Making, Shaping, Treating to Products’ has collected eight research papers focusing on various aspects of steel production, e.g., inclusions in steelmaking and continuous casting processes, continuous casting processes and the quality of stainless steel casting, heat treatment, corrosion of steels, and fatigue of steels. This summary aims to contribute to the state-of-the-art of the development of steel production.

Cobalt-based entropic alloys doped with Ti/Zr/Hf have been investigated in the present work. Thermodynamic calculations have been conducted to predict the phase evolution. The effect of two types of processes (homogenization and cryogenic treatment) on microstructures and properties have been comprehensively analyzed. The compositions and microstructures of the designed alloys in different states have been investigated using multiple techniques. Electrochemical corrosion behaviors at room temperature, high-temperature oxidation behaviors at 600 °C, 800 °C, and 1000 °C, as well as the hardness and compression tests, have been systematically performed. The Ti-doped cobalt-based entropic alloy demonstrated excellent overall properties, including strong electrochemical corrosion resistance, high-temperature oxidation resistance, and a combination of high strength and ductility. The phase map from electron backscatter diffraction (EBSD) indicated that Ti has weaker stability for the formation of the C14-Laves phase compared to the alloying effects of Zr and Hf. The characterization results align with the thermodynamic calculations. This work paves a way for establishing material design strategies to develop advanced alloys with superior performance.

Rare earth can modify inclusions in non-oriented silicon steel which is harmful to magnetic properties. This study focused on the 3.1% Si non-oriented silicon steel under industrial production conditions. Samples were taken during the stages before and after addition of rare earth ferrosilicon alloy in Ruhrstahl-Heraeus (RH) unit, different pouring time in tundish, and continuous casting slab. This study systematically examined the morphology, composition, and size distribution of inclusions throughout the smelting process of non-oriented silicon steel by scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), and thermodynamic analysis at liquid steel temperature and thermodynamic analysis of equilibrium solidification. The research results demonstrated that the rare earth treatment ultimately modifies the original Al₂O₃ inclusions in the non-oriented silicon steel into REAlO₃ and RE₂O₂S inclusions, while also aggregating AlN inclusions to form composite inclusions. After rare earth modification, the average size of the inclusions decreases. In the RH treatment process, the inclusions before the addition of rare earth ferrosilicon alloy are mainly AlN and Al₂O₃. After the addition of rare earth ferrosilicon alloy, the inclusions are mainly RES and REAlO₃. In the tundish and continuous casting, the rare earth content decreased, and the rare earth inclusions transform into RE₂O₂S and REAlO₃. For the size of inclusions, after adding rare earth ferrosilicon alloy, the average size of inclusions rapidly decreased from 16.15 μm to 2.65 μm and reach its minimum size 2.16 μm at the end of RH treatment. When the molten steel entered the tundish, the average size of inclusions increased slightly and gradually decreased with the progress of pouring. The average size of inclusions in the slab is 5.79 μm. Phase stability diagram calculation indicates the most stable rare earth inclusion is Ce₂O₂S in molten steel. Thermodynamic calculations indicated that Al₂O₃, Ce₂O₂, Ce₂S₃, AlN, and MnS precipitate sequentially during the equilibrium solidification process of molten steel.

Unwanted ice accumulation can lead to catastrophic disasters or economic losses. Photothermal superhydrophobic surfaces show promise for anti-/de-icing applications, but their effectiveness depends critically on precise micro-nano hierarchical structure design and functionalization. Current approaches face significant limitations: lithography enables ordered patterns but becomes cost-prohibitive for nanoscale features, while disordered micro-nano structures suffer from poor performance tunability and inconsistency. This study develops a high-performance structured micro/nano-crystal array photothermal superhydrophobic metamaterial (SMNA-PSM) for anti-/de-icing. The structured crystal array features abundant micro-nano surfaces, transforming deposited Metal-insulator-Metal (MIM) structures into heterogeneous resonators. These heterogeneous resonators with varying sizes, angles, and thicknesses possess more electromagnetic wave response sites and scattering surfaces, converting the separated absorption peaks of the uniform MIM structure into a continuous absorption band, achieving 96% solar spectrum absorptivity. Moreover, by simply adjusting the deposition material, the surface morphology of the crystal array can be tuned from smooth to rough, thereby enabling a switch from hydrophobicity to superhydrophobicity. Unlike conventional micro-nano hierarchical structures, structured micro-nano crystal arrays can be integrated with film stacked architectures, inheriting film-based advantages: tunable performance, uniformity, substrate-friendliness, and scalability. This approach demonstrates broad application potential in micro-nano structure fabrication, broadband wave absorption, wettability control, photothermal conversion and anti-/de-icing.

Spectrally selective absorbers garner significant attention across diverse domains owing to their pivotal roles in electromagnetic stealth technologies, solar-thermal photovoltaics, and related applications. However, enhancing the absorption properties frequently necessitates the augmentation of the metamaterial patterned layer complexity. This introduces a paradox in application, where the increased intricacy of structural patterning adversely intersects with fabrication processes, thereby exacerbating the practical applicability challenges due to manufacturing constraints. Therefore, this study leverages a design methodology that combines artificial intelligence (AI) with finite element simulation. This approach propels the realization of broadband selective absorption based on a simple biomimetic metamaterial structure, achieving broadband absorption without increasing structural complexity or reducing fabrication efficiency. The spectrally selective absorbing metamaterial designed with AI achieves broadband absorption unaffected by polarization in the 5-8 mu m range. With electromagnetic waves impinging perpendicularly, the average absorptance exceeds 0.9, proving valuable for radiation cooling compatible with infrared stealth. Furthermore, the design method elucidated in this study exhibits remarkable robustness and transferability, significantly improving the design efficiency of complex spectral metamaterials. This innovative approach heralds a design paradigm shift, facilitating the creation of stealth-compatible and other advanced multiband spectrally selective absorbing materials.