Hot dip galvanized steel sheet developments continue to proceed at among the fastest rates compared to other industrial sectors. Factors influencing this rapid rate of progress include the unceasing demands of the automotive sector for steels with ever-increasing capabilities for mechanical performance, appearance, improved corrosion resistance and ease of production and assembly. Other sectors including construction and appliance benefit from these developments. In this review paper, recent developments related to the galvanizability of new steel grades will be described. Then two issues related to sustainable steelmaking will be summarized: First, the increased use of recycled steel that is essential for sustainable steelmaking has been shown to influence steel microstructures and the steel surfaces presented for galvanizing. Second, recent developments in reduced-carbon processing of continuous galvanized sheet.
This study investigates the combined effects of electromagnetic stirring (EMS) and chemical grain refinement (CGR) on solidification discontinuities in an Al-6wt%Si-2.5wt%Cu (Al6Si2.5Cu) alloy using 3D X-ray Computed Tomography. Results show that integrating EMS with an Al-5Ti-1B master alloy reduces the average grain size by 23.4% compared with CGR alone. This microstructural refinement produces a pronounced 57.95% reduction in total discontinuity volume and exhibits a near-cubic power-law dependence on grain size, with an exponent of 3.25. While the low-sphericity morphology characteristic of shrinkage cavities remains unchanged, the synergistic CGR + EMS treatment restricts the maximum defect size to below 0.4 mm, yielding a smaller, more homogeneously distributed defect population optimized for high-quality engineering components.
To address the problems of poor machinability of dual-metal network composites and unclear material removal mechanisms, this paper fabricated 316L stainless steel porous networks by selective laser melting technology, and prepared 316L network-reinforced ZA8 composites via squeeze casting process. The microstructure and dry milling performance were investigated. The composites formed dense three-dimensional interpenetrating structures, and an Al-enriched interfacial layer containing the Al 0 . 983 Cr 0 . 017 intermetallic compound was identified at the interface. The cutting force fluctuation amplitude of the composites was larger than that of pure ZA8 alloy, with an optimal cutting speed of 75 m/min. The surface roughness of the composite first decreased then increased but that of the ZA8 alloy continuesd to decrease with the increase of cutting speed. The cutting force and surface roughness of the composite increased with the increase of feed rate and depth of cut and machining defects were mainly concentrated at the interface.
Metal rubber is a key damping material in aerospace and other fields, whose fatigue damage is closely related to the vibration isolation effectiveness and safety of the system. This study investigates the influence of relative density and wire diameter on the wear evolution and performance degradation of metal rubber vibration isolators through accelerated fatigue experiments, vibration characteristic tests, and microscopic morphology observation, along with a neural network-based prediction model. The results indicate that increasing the wire diameter not only delays stiffness attenuation but also enhances performance stability under random and impact loads. In contrast, a higher relative density improves initial stiffness but accelerates performance degradation due to aggravated wear.
To verify the usability of FeCoNiCrTi high-entropy alloy coating on metallurgical copper components (blast furnace tuyere), the melting loss resistance of coating was investigated by our self-designed device. Due to the special preferential oxidation of Ti element, a dense oxide layer (thickness about 700 nm) mainly containing Ti oxide forms on the original coating surface. The oxide layer acts as a barrier, causing the coating not to be eroded by molten iron. Comparative experiment shows that the coating after removing the oxide layer is prone to metallurgical bonding with molten iron, causing a great risk of melting loss. Thus, the melting loss resistance of original FeCoNiCrTi high-entropy alloy coating is significantly improved by this titanium-rich oxide layer. In practical applications, the oxide layer is recommended to be retained to adapt to the harsh environment of blast furnace tuyere.
This study describes the development of a novel slag-free self-shielded metal-cored wire. Various concentrations (0 wt.%, 0.15 wt.%, and 0.3 wt.%) of graphene nanosheets (GNS) were included in the welding wire. In this study, a range of iron alloys, including boron and varying amounts of GNS, were synthesized by applying them to Q235 steel plates. The microstructure, microhardness, and wear resistance of the hardfacing alloy were then systematically investigated. The findings of the study indicate that the Fe 2 B phase is mostly seen at the interfaces between grains. When GNS are added to the hardfacing alloy, the morphology of the Fe 2 B phase changes. The structure changes from mainly fishbone-shaped to rod-shaped and granular forms. The Fe 2 B intergranular phase exhibits a progressive rise in percentage, with respective values of 40.3%, 41.9%, and 43.1% seen when GNS are not added, when 0.15 wt.% GNS is added, and when 0.30 wt.% GNS are introduced. The incorporation of GNS results in a consistent and progressive enhancement in the average microhardness. The hardness value was determined to be 454 HV in the absence of GNS, 513 HV with the addition of 0.15 wt.% GNS, and 520 HV with the addition of 0.30 wt.% GNS. The incorporation of GNS into the hardfacing alloy results in an enhancement of the matrix strength and a modification of the Fe 2 B phase, hence improving the wear resistance. The wear rate and friction coefficient demonstrate a declining pattern, with micro-cutting and fatigue wear identified as the primary wear processes.
The incorporation of low concentrations of silicon has been shown to have a significant effect on the oxidation behaviour of superalloys, but this effect has not been studied at low oxidation pressure. Silicon had a significant effect on the oxidation behavior of superalloys, but its positive role under low oxygen pressure has not been examined in detail. This study investigated the ultra-high temperature oxidation behavior of Co-20Re-25Cr ternary alloys with and without 3.0 at.% Si under 3.0 × 10 −5 Pa O 2 . The results showed that the Co-20Re-25Cr-3Si alloy exhibited enhanced oxidation resistance. This improvement was attributed to silicon, which promoted the rapid formation of a protective Cr 2 O 3 layer within a short period. The specific mechanism by which silicon affected the oxidation process was further analyzed and discussed. These findings were crucial for advancing the application of Co-Re-Cr-based alloys in aerospace.
This study investigates the single-crystal epitaxial growth behavior of nickel-based single-crystal superalloys during curved-path laser-directed energy deposition using a thermo-fluid-solid coupled numerical model. The results reveal that the core mechanism underlying the curvature-induced asymmetric epitaxial growth is the outward deflection of heat flow toward the outer side of the curved track.This deflection arises from the continuously changing scanning direction along the curved path, which creates a non-uniform radial distribution of laser energy input and cooling conditions. Consequently, the thermal gradient (G) and solidification rate (R) differ substantially between the inner and outer sides, leading to asymmetric epitaxial growth height, radial PDAS gradients, and altered columnar-to-equiaxed transition (CET) behavior. Under optimized low laser power (700 W) and high scanning speed (11 mm/s), a peak epitaxial growth fraction of 72.7% was achieved. Microstructural analysis confirms γ/γ′ phase consistency but reveals radial PDAS gradients and Al segregation in inter-dendritic zones due to cooling rate variations (10 3 –10 4 K/s). The model, validated against experimental melt-pool geometry, provides mechanistic insight into the asymmetric solidification behavior under curved scanning, laying a foundation for the precision repair of complex single-crystal components.
In response to the demand for tungsten (W) cathodes in high-power short-arc lamps, a powder metallurgy-swaging process was employed to fabricate thoriated W alloy rods with a diameter exceeding 30 mm. This approach successfully addressed issues related to the poor sintering performance and limited plastic deformation of large-diameter thoriated W rods. A comparative study was conducted on the microstructure and properties of thoriated W alloy with ThO 2 doping (WT20) and W alloy co-doped with thorium oxide, potassium, aluminum, and silicon (WKT20). The co-doping strategy significantly reduced the grain size in both the sintered and swaged states of the W alloy, increased the proportion of small-angle grain boundaries, and ensured the uniform distribution of submicron-sized thorium oxide particles in the matrix. Consequently, the service life of W cathodes for short-arc lamps was markedly extended, with the WKT20 cathode maintained stable operation for 950 h and showed only limited shallow microcracks at the cathode tip, in sharp contrast to the severe cracking and spalling observed in WT20 after 50 h.
The deformation mechanisms of heat-treated laser powder bed fused Ti-6Al-2Sn-4Zr-2Mo were investigated using tensile testing and transmission electron microscopy. Heat-treated conditions (solutionized and solutionized + aged) showed improved ductility and non-monotonic strain-hardening behavior compared to the as-built state. Transmission electron microscopy analysis revealed the formation of a metastable β phase (β m ) with a molybdenum equivalent content below 8 wt.%, which promotes stress-induced martensitic (α′) transformation during deformation. This transformation enhances strain hardening and delays necking. The solutionized + aged condition exhibited lower β-phase stability and a greater tendency for martensitic transformation. These results highlight the critical role of β-phase metastability in governing deformation and strength-ductility synergy.
Over the past three decades, research on aluminium (Al)-containing low-density steels (LDS) has accelerated due to their ∼8–15% lower density than conventional steels, increasing their demand in lightweight automotive applications, high-temperature applications and cryogenic uses such as storage tanks and spacecraft. This review focuses on Al-containing ferritic low-density steels (FLDS). It begins with a discussion of the formation of the κ-carbide and B2/DO 3 phases, the melting and casting route, followed by an overview of microstructural evolution. Furthermore, the elastic modulus, effects of microalloying elements on mechanical properties, deformation mechanisms and the influences of microstructure and strain-hardening behaviour on tensile properties are critically reviewed. Finally, future research directions for optimising the microstructure–mechanical property relationships in FLDS are discussed.
This study investigates the corrosion mechanism of TA2/304SS dissimilar laser welds with a Cu interlayer, with a focus on the synergistic effects of post-weld heat treatment (PWHT). While Cu interlayers are known to improve mechanical properties, their electrochemical role and the impact of PWHT on corrosion behavior remain unclear. The results show that PWHT at 700 degrees C for 30 min transforms dendritic structures into equiaxed grains, significantly reduces residual stress, and decreases the corrosion current density by nearly an order of magnitude. A unique reticulated Cu2O film forms, which seals micro-cracks and acts as a physical barrier. This work elucidates the synergistic sequence of "microstructural homogenization -> protective film formation -> self-sealing," offering a design strategy for durable Ti/steel joints in marine environments.
In order to enhance the photocatalytic performance of the Cu 2 ZnSnS 4 compound, an ionic substitution strategy was employed to partially and completely substitute Zn 2+ with Cr 3+ ions using the solvothermal method. The structural analysis reveals that partial substitution significantly improves the crystallite lattice order without disturbing the kesterite crystal structure, confirming the successful incorporation of chromium into the lattice. Morphological investigations imply the formation of spherically aggregated nanorods-like, which efficiently arise the lively surface area, at the same time as EDS analysis confirms a homogeneous elemental distribution without the formation of secondary phases. Upon comparing the photocatalytic performance of all synthesized compounds using methylene blue dye as a version pollutant, the Cu 2 Zn 0.5 Cr 0.5 SnS 4 compound showed the highest degradation efficiency of about 93% within 120 min in visible light irradiation. This more desirable overall performance is attributed to the synergistic outcomes of advanced crystallinity, changed morphology, and enhanced light absorption caused by partial Cr3 substitution. These consequences exhibit that managed ionic substitution represents an effective approach for tailoring the structural and photocatalytic residences of the Cu 2 ZnSnS 4 compound-primarily based substances for environmental remediation packages.
The inherent limitations of traditional stainless steels, particularly the inhomogeneity and instability of their passive films, may increase their susceptibility to corrosion under severe conditions. To break through the performance limits of corrosion-resistant materials, this study employed high-vacuum cold crucible suspension melting technology to prepare AlCo 0.2 Cr 1.7 FeNi 2.1 Mo 0.1 high-entropy alloy (HEA), and systematically investigated its corrosion behavior and passive film evolution in boiling HNO 3 solution compared with 321 stainless steel, thereby helping to elucidate the corrosion resistance mechanism of this HEA. Experimental results indicate that the AlCo 0.2 Cr 1.7 FeNi 2.1 Mo 0.1 HEA consists of BCC, B2, and σ phases. In boiling HNO 3 solution, its corrosion rate is significantly lower than that of 321 stainless steel, and this performance gap further widens over time. XPS results confirm that the AlCo 0.2 Cr 1.7 FeNi 2.1 Mo 0.1 HEA promotes surface oxidation through autocatalytic reduction in boiling HNO 3 , forming a hybrid passive film with Cr 2 O 3 as the matrix and Al 2 O 3 dispersed within it. This hybrid passive film structure demonstrates superior resistance to boiling HNO 3 corrosion compared to a single Cr 2 O 3 film. This study provides insights that extend beyond the corrosion resistance typically achieved by conventional materials by constructing a multi-component hybrid passive film and provides a highly promising candidate material for extreme environments such as nuclear fuel reprocessing.
An innovative approach for reinforcing 316L alloy with WC particles of different scales is proposed. WC/316L composite specimens featuring single- and multi-layer structures with different WC particle scales were produced through the laser-directed energy deposition (LDED) process. The incorporation of WC effectively promoted the formation of a passive film, significantly impeding the penetration of Cl- ions from the NaCl solution into the composite, thus preventing charge transfer and effectively suppressing further corrosion. Among the specimens, the fine WC/316L composite showed the highest corrosion resistance, achieving an 83.54% reduction in corrosion current and a 724.5% increase in polarization resistance. The average transverse tensile strengths for the four specimens-316L, 8 wt.% coarse WC/316L, 8 wt.% fine WC/316L, and a combination of 4 wt.% coarse WC and 4 wt.% fine WC/316L-were measured at 916 MPa, 959 MPa, 977 MPa, and 929 MPa, respectively, at three tensile rates. Compared to the pure 316L specimen, the tensile strengths of the other three materials improved by 4.7%, 6.7%, and 1.4%, respectively. These results demonstrate that the incorporation of WC significantly enhances the corrosion resistance and tensile properties of 316L alloy, offering an innovative solution to challenges like corrosion vulnerability and limited strength in aerospace, petroleum, and other applications.
This study systematically explored the effects of three dispersants on the stability of high solid content ceramic slurries, their printing performance and the properties of the ceramic parts obtained from them. The results show that although KH-570 can achieve a relatively low apparent viscosity of ceramic slurry through chemical bonding, its stability is poor and the sedimentation behavior is unfavorable for long term storage. BYK-110 significantly improves the stability of the slurry with its steric hindrance effect. It still maintains excellent dispersion at a solid content of 72 wt%, and the flexural strength of the sintered ceramic reaches 14.25 ± 0.39 MPa (1400°C), which is much higher than that provided by the KH-570 system at 5.60 ± 0.56 MPa (1400°C).
High-entropy alloys (HEAs), exemplified by the AlCoCrFeNi system, have garnered significant interest in materials science owing to their superior mechanical properties, including exceptional strength and hardness, characteristics that render them particularly well suited for wear-resistant applications. Recent developments have demonstrated that the incorporation of ceramic reinforcement phases into AlCoCrFeNi-based matrices represents an effective strategy for enhancing tribological performance via composite coating architectures. This review offers a comprehensive examination of coating systems, including reinforcement phase selection criteria and matrix functionality. A systematic analysis of matrix-strengthening approaches is provided, elucidating fundamental mechanisms and detailing how variations in alloying elements drive microstructural evolution and consequent improvements in wear resistance. Particular attention is devoted to interfacial optimization, offering a detailed discussion of interface characteristics and optimization strategies achieved through adjustments in elemental composition. Finally, the present limitations of AlCoCrFeNi composite coatings are reviewed, and prospective research avenues are suggested.
Laser cladding technology presents a promising method for fabricating multi-principal element alloy (MPEA) coatings, yet cracks remain one of the most prevalent defects in HEA laser cladding. In this study, FeCr0.5NiCu0.5 multi-principal element alloy coatings were produced on heat-resistant steel (12Cr1MoV) using laser cladding with varying scanning speeds. The study systematically examined the types and mechanisms of cracks within the multi-principal element alloy coatings and also summarized the effects of scanning speed on the coating's dilution rate and cooling rate. Results indicate that an increase in scanning speed significantly elevates the coating's dilution rate and the risk of cracking. With the increase in scanning speed, the cooling rate has risen from 2.68 & times; 103 K/s to 3.7 & times; 104 K/s, achieving an order of magnitude improvement. The secondary dendrite arm spacing (SDAS) has diminished from 4.02 & micro;m to 1.8 & micro;m, resulting in a significant refinement of the grains. Cracks within the coating are categorized into macrocracks and microcracks. Macrocracks originate at the interface between the coating and the substrate, induced by the substantial thermal expansion coefficient mismatch between the multi-principal element alloy and heat-resistant steel. Microcracks manifest as intergranular cracks due to the distribution of low-melting-point Cu elements along the grain boundaries, which increases the brittleness of the boundaries.
This review focuses on of the role of Ce in aluminum melt purification and aluminum matrix, its influence on the properties of aluminum and aluminum alloys, including both cast and wrought alloys. Ce exhibits excellent degassing and refining properties in aluminum melts, leading to improved metallurgical quality. In addition, Ce plays a significant role in aluminum matrices, including grain refinement, modification, alteration of solidification behaviour, and compound formation. Through these effects, Ce can have a substantial impact on the properties of aluminum and its alloys. This systematic review comprehensively elucidates the role and impact of Ce in aluminum and its alloys, providing a comprehensive understanding for materials researchers.
