Search Results (114)

The incorporation of recycled metallurgical slags into refractory materials constitutes a promising approach to enhancing sustainability in the refractory industry. This study investigates the effect of vanadium-bearing slag aggregates as partial replacements for tabular alumina in castables and compares their behaviour with high-alumina and bauxite-based castables. Two vanadium-bearing slags with different mineralogical compositions were introduced in the 1–3 mm aggregate fraction with substitution up to 25 wt.%. Their effects on microstructure, thermo-mechanical performance, and corrosion resistance were evaluated. The introduction of vanadium-bearing slag significantly alters the microstructure of the castables, affecting their performance. Both slags displayed grains with higher porosity, microcracking, and heterogeneity compared with tabular alumina, but showed similarities to bauxite grains. Slag 1, enriched in calcium aluminate phases, provides limited mechanical strength but improved corrosion resistance due to improved bonding with the matrix. Slag 2, containing a higher spinel content, enhances mechanical strength, showing behaviour comparable with bauxite-based castables, particularly at 10 wt.% replacement. Vanadium is mainly present in metallic form and as Mg(Al,V)₂O₄ spinels in both slags. Upon firing, vanadium migrates toward the grain boundaries and reacts with the surrounding calcium aluminate phases to be incorporated in Ca(Al,V)₂O₄ and Ca(Al,V)₄O₇, while the spinel phase remains stable. Full article

Ag and Cu in biodegradable Zn alloys have been the focus of research due to their biocompatible corrosion products, as well as their ability to improve the mechanical properties of the alloy. In this research, the impact of Ag and Cu on the fluidity of biodegradable Zn alloys was evaluated through the spiral fluidity test. Zn–xAg and Zn–xCu alloys containing Ag or Cu in pure Zn at proportions of 0.5, 1, 2, and 3 wt.% were prepared. In the first stage of the study, the casting temperature to be used in the fluidity tests of the alloys was determined by casting pure Zn at different temperatures. Spiral castings of the alloys were then produced and the fluidity lengths in the spiral channel were measured. Test results showed that the mold filling distances decreased with increasing amounts of Ag and Cu, with Cu causing a stronger reduction than Ag at comparable addition levels. When the Ag content in Zn was raised from 0.5 wt.% to 1 wt.%, a significant reduction in fluidity was observed. Formation of CuZn₅ and ε–AgZn₃ phases in the microstructures was identified as the main factor limiting melt flow. These findings provide insights into how Ag and Cu additions influence the castability of Zn alloys, offering guidance for optimizing alloy composition for biodegradable implant applications. Full article

Al–Zn–Ca alloys are good candidates for industrial electronics and electric vehicles due to their high thermal conductivity, castability, and corrosion resistance, but their strength requires improvement. This study investigates how Sc and Zr additions affect the microstructure, thermal, mechanical, and corrosion properties of an Al–3 wt% Zn–3 wt% Ca base alloy. Microstructural analysis showed that substituting Sc with Zr did not drastically alter the phase composition but changed the elemental distribution: Sc was uniform, while Zr segregated to center of dendritic cell. Zr addition also refined the grain size from 488 to 338 μm. An optimal aging treatment at 300 °C for 3 h was established, which enhanced hardness for all alloys via precipitation of Al₃Sc/Al₃(Sc,Zr) particles. However, this Zr substitution reduced thermal conductivity (from 184.7 to 168.0 W/mK) and ultimate tensile strength (from 269 to 206 MPa), though it improved elongation at fracture (from 4.6 to 7.1%). All aged alloys exhibited high corrosion resistance in 5.7% NaCl + 0.3% H₂O₂ water solution, with Zr-containing variants showing a lower corrosion rate and better pitting resistance. The study confirms the potential of tuning Sc/Zr ratios in Al–Zn–Ca alloys to achieve a favorable balance of strength, ductility, thermal conductivity, and corrosion resistance. Full article

Metal casting industries generate substantial quantities of spent foundry sand (SFS), a silica- and alumina-rich by-product that remains underutilized, with recycling rates below 30%. This study explores the incorporation of aluminum SFS as a secondary raw material in aluminosilicate refractory castables to promote sustainable waste valorization and circular economy practices. Refractory mixtures were prepared with bauxite, kyanite, calcium aluminate cement, microsilica, and flint clay, where fine flint clay was partially replaced by aluminum SFS at 0, 5, 10, and 15 wt.%. Samples were dried at 120 °C and sintered at 850, 1050, and 1400 °C for 4 h. Bulk density, apparent porosity, cold crushing strength, and modulus of rupture were measured, while phase and microstructural evolution were examined by XRD and SEM. The 5 wt.% SFS-containing castable exhibited comparable strength and density to the reference formulation, attributed to the formation of secondary mullite and anorthite that improved matrix cohesion. Higher SFS contents (10–15 wt.%) increased porosity and reduced strength due to excess SiO₂ and silica polymorphism. These results demonstrate the technical feasibility of using aluminum SFS in refractory castables, contributing to resource conservation, waste reduction, and the development of environmentally sustainable refractory materials for high-temperature applications. Full article

This study investigates the use of steel and cast iron for producing cast furnace rolls to replace welded rolls, which often fail from cracks and limited durability. Casting had not been previously considered by the manufacturer, but rising demands for durability and quality make it a promising alternative. Material selection focused on mechanical properties, wear resistance, and production costs. To ensure casting quality, Magmasoft 6.0 software was applied for detailed simulation of casting, solidification, and cooling. Results showed that steel alloys (GS-34CrMo4 and GS-20Mn5) are prone to shrinkage and porosity, which cannot be fully avoided even with feeders. In contrast, GJS-500-7 cast iron exhibited low shrinkage tendency and minimal defects, proving suitable for production while reducing costs. It also offers lower weight and efficient metal use, improving cost-effectiveness. Detected defects were concentrated in the central casting area, where they have little impact on functionality. Based on sixteen simulations, GJS-500-7 cast iron emerged as the most suitable material for furnace rolls thanks to its thermal resistance, castability, low porosity, and ability to meet required specifications. This process optimization represents an efficient, cost-effective choice, improving final product quality and creating new opportunities for the manufacturer. Full article

The aluminum casting alloy AlSi7Mg0.6 (A357) is extensively used in the automotive industry due to its favorable balance of mechanical properties, castability, lightweight characteristics, and corrosion resistance. Castings made from this alloy are often subjected to harsh service environments, where surface degradation and microstructural variability can significantly impact fatigue performance. This study investigates the combined effects of surface corrosion damage and higher Fe content on the fatigue life of the AlSi7Mg0.6 alloy, using a rotating bending fatigue test under simultaneous corrosion exposure in a 3.5 wt. % NaCl solution. The effect of corrosion and Fe content on fatigue life was then investigated and analyzed using Wöhler curves and scanning electron microscopy (SEM). The results demonstrate that the corrosion-fatigue interaction accelerated the kinetics of the fatigue process, while the fracture mechanism and crack initiation places are not fundamentally altered compared to alloys in the state without corrosion damage. A comparison of the fatigue lifetime of samples in an air environment and a corrosive environment shows that the corrosive environment (3.5% NaCl) reduces the fatigue lifetime of alloys without T6 by an average of 7.5 MPa and alloys after T6 by 6 MPa. The results are probably due to the penetration of chloride ions into casting defects located on the surface of the samples. Surface pits formed during corrosion act as stress concentrators, increasing the likelihood of stress-induced failure. Microstructural feature morphology, especially Fe-rich intermetallic phases, influences crack propagation mechanisms. Full article

Hypoeutectic Al-Si-Mg alloys are among the most widely used casting materials in the automotive and aerospace industries due to their low density, high strength-to-weight ratio, corrosion resistance, and good castability. A critical challenge during solidification is shrinkage porosity, which arises from insufficient feeding and significantly reduces casting reliability. While the role of silicon in altering the phase diagram of Al-Si-Mg alloys is well-understood, its direct impact on feeding behavior has not been previously quantified in detail. In this study, the influence of silicon content (5–9 wt.%) on feeding ability was systematically investigated using thermal analysis (TA). By analyzing cooling curves, first derivatives, and ΔT curves, key solidification temperatures, including the liquidus, dendrite coherency, rigidity, and solidus, were precisely identified. For the first time, these data were used to quantitatively define all five feeding regions (liquid, mass, interdendritic, burst, and solid feeding) as a function of silicon content. The results demonstrate that increasing the Si content decreases the liquidus and dendrite coherency temperatures, raises the rigidity and solidus temperatures, and shortens the overall feeding ranges, particularly the interdendritic region (~32 °C reduction). This novel TA-based quantification of feeding regions provides insights that extend beyond classical phase diagram interpretation. The findings confirm that higher Si contents improve feeding ability by narrowing the freezing range and reducing the risk of porosity, while also providing a unique dataset for validating casting simulation software. The results also confirm that increasing the silicon content enhances feeding ability and improves castability by narrowing the freezing range and promoting more uniform solidification in Al-Si-Mg alloys. The study therefore bridges fundamental solidification science with industrial practice, supporting improved alloy design and defect control in Al-Si-Mg castings. Full article

The global reliance on coal-fired power generation continues to produce vast quantities of fly ash, exceeding 500 million tons annually, with limited recycling rates. Given its high silica (SiO₂) and alumina (Al₂O₃) contents, fly ash represents a promising alternative raw material for sustainable refractory production. In this study, four aluminosilicate refractory castables were formulated using bauxite, calcined flint clay, kyanite, calcium aluminate cement, and microsilica, in which the fine fraction of flint clay was partially replaced by 0, 5, 10, and 15 wt.% fly ash. The specimens were dried at 120 °C and sintered at 850, 1050, and 1400 °C for 4 h. Their physical and mechanical properties were systematically evaluated, while phase evolution and microstructural development were analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results revealed that the incorporation of 10 wt.% fly ash (10FAC) provided the optimal balance between densification and strength, achieving compressive strengths of 45.0 MPa and 65.3 MPa after sintering at 1050 °C and 1400 °C, respectively. This improvement is attributed to the formation of a SiO₂-rich liquid phase derived from fly ash impurities, which promoted the in-situ crystallization of acicular secondary mullite and enhanced interparticle bonding among corundum grains. The 10FAC castable also exhibited only a slight increase in apparent porosity (26.39%) compared with the reference (25.74%), indicating effective sintering without excessive vitrification. Overall, the study demonstrates the technical viability of using fly ash as a sustainable substitute for flint clay in refractory castables. The findings contribute to advancing circular economy principles by promoting industrial waste valorization and resource conservation, offering a low-carbon pathway for the development of high-performance refractory materials for structural and thermal applications in energy-intensive industries. Full article

Developing sustainable ceramic formulations that integrate industrial by-products addresses the high energy and raw material demands of refractory manufacturing while advancing circular economy goals. This study investigates the recycling of chamotte waste from rejected fired electrical porcelain as a partial substitute (5 and 10 wt.%) for flint clay in aluminosilicate refractory castables. Samples were fired at 110, 815, 1050, and 1400 °C and evaluated for bulk density, apparent porosity, cold crushing strength, and flexural strength. Microstructural and mineralogical changes were analyzed by SEM and XRD. Incorporating 10 wt.% chamotte waste fostered an in situ mullite-reinforced microstructure, enhancing mechanical strength (58 MPa—CCS, 18.8 MPa—MOR) and lowering porosity (24.4%), demonstrating chamotte’s dual role as recycled raw material and reinforcement phase for densification and durability. These properties matched or surpassed those of the conventional formulation, with strength improvements of up to 44%. The findings demonstrate that high-temperature industrial waste can be effectively valorized in advanced refractories, reducing reliance on virgin raw materials, diverting waste from landfills, and promoting industrial symbiosis within the ceramics and metallurgical sectors. Full article

B is considered a valuable additive for TiAl alloys, because it is believed to improve their properties by refining their microstructures. However, the effects of B on the practical properties of TiAl alloys for jet engine blades and the optimal addition amount for achieving balanced properties remain unclear. Specifically, there have been very few studies to date in which the practical properties of alloys have been evaluated across a wide range of B addition levels. Therefore, we evaluated various reliability, cost, and performance properties of jet engine blade materials using cast Ti-45,47Al-2Nb-2Mn (the same as XD alloys), with varying B addition levels. The results showed that, in some cases, low B addition levels (0.1–0.2 at.%) could enhance the impact resistance and high-cycle fatigue performance. However, even low B addition levels negatively impacted the machinability, castability, and creep strength. Further, adding 0.4 B or more significantly reduced most practical properties. Compared to XD alloys, TiAl4822 exhibited a superior balance, which is attributed to the higher B content (1 at.%) in XD alloys and the greater effectiveness of Cr relative to Mn in improving the alloy’s high-temperature impact resistance. Full article

Heat sinks with thin and tall fins made from pure aluminum using die casting are in demand due to the higher thermal conductivity of pure aluminum compared to aluminum alloys. However, die casting of thin and tall fins using pure aluminum is considered difficult because of the poor castability of pure aluminum. Casting conditions suitable for pure aluminum heat sinks with tall and thin fins were identified from flow length tests using a narrow-gap spiral die. Based on these findings, casting of pure aluminum heat sinks with thin and tall fins was attempted. The casting conditions that extended the flow length of pure aluminum were different from the conventional theoretical conditions for aluminum alloy die casting. Discovery of this unique result was very useful for the production of pure aluminum heat sinks using die casting. Specifically, using the appropriate plunger speed and die temperature to extend the flow length was effective for filling the thin fins with molten metal. As a result, it was clarified that pure aluminum heat sinks with thin and tall fins, having a height of 50 mm, a draft angle of 0.5°, and a fin top thickness of 0.5 mm, could be successfully produced using die casting. The heat dissipation properties of the pure aluminum heat sink with thin and tall fins were also evaluated. Full article

Research on raw materials for Al₂O₃-SiC-C refractory castables used in blast furnace troughs is relatively well established. However, gaps remain in both laboratory and industrial trials concerning the performance of castables incorporating SiC-modified flake graphite and alternative carbon sources. This study investigated the sintering behavior, mechanical properties, and service performance of Al₂O₃-SiC-C castables utilizing varying contents of modified flake graphite, pitch, and carbon black as carbon sources. Samples were characterized using SEM, XRD, and EDS for phase composition and microstructural morphology analysis. Key findings revealed that the thermal expansion mismatch between the SiC coating and flake graphite in SiC-modified graphite generated a microcrack-toughening effect. This effect, combined with the synergistic reinforcement from both components, enhanced the mechanical properties. The SiC modification layer improved the wettability and oxidation resistance of the flake graphite. This modified graphite further contributed to enhanced erosion resistance through mechanisms of matrix pinning and crack deflection within the microstructure. However, the microcracks induced by thermal mismatch concurrently reduced erosion resistance, resulting in an overall limited net improvement in erosion resistance attributable to the modified graphite. Specimens containing 1 wt.% modified flake graphite exhibited the optimal overall performance. During industrial trials, this formulation unexpectedly demonstrated a water reduction mechanism requiring further investigation. Full article

This article presents a review of the composition optimization progress of nickel-based single crystal (SC) superalloy design in recent years in order to obtain better high-temperature performance for the development of the aviation industry. The influence of alloying elements on the creep resistance, microstructure characteristics, oxidation resistance, castability, density, and cost of superalloys is analyzed and discussed. In order to obtain better high-temperature performance, the content of refractory elements (Ta + Re + W + Mo) and Co was increased gradually. The addition of Ru was added in the fourth-generation nickel-based SC superalloy to stabilize the microstructures and suppress the precipitation of the topologically close-packed (TCP) phase. However, the content of the antioxidant element Cr significantly decreased, while the synergistic effect of Al, Cr, and Ta received more attention. Therefore, synergistic effects should also receive more attention to meet the practical needs of reducing the content of refractory elements to reduce costs and density in future single crystal alloy designs without compromising critical performance. Full article

The problems associated with TNT necessitate the development of novel melt-castable compounds with melting points between 70 and 120 °C, a crucial endeavor in the field of energetic materials. This study introduces a promising melt-castable explosive based on nitropyrazole, whose melt-castable properties were achieved by the introduction of methyl groups. The synthesis of 3,5-dinitro-4-methylnitramino-1-methylpyrazole involves a three-step process starting from 3,5-dinitro-4-chloropyrazole, including substitution, nitration, and methylation reactions. Additionally, two alternative synthesis routes and six energetic salts were examined. Structural elucidation was conducted using conventional methods such as NMR, IR, and X-ray, while the energetic properties of the compound, including thermal behavior, sensitivities, and theoretical performance, were investigated. Also, compatibility with common explosives was investigated, the experimental enthalpy of formation by bomb calorimetry was determined, and an SSRT test was performed. Furthermore, the melt-cast explosive underwent an Ames test in order to assess its toxicity. Full article

High-chromium cast irons (HCCIs) have emerged as preferred materials for critical wear-resistant components operating under extreme conditions, owing to their excellent wear resistance, low cost, and good castability. They are widely used in metallurgy, energy, and mechanical engineering industries. The evolution of solidification microstructure directly governs the final properties of HCCIs, making the in-depth investigation of their solidification behavior of great significance. This paper provides a comprehensive review of recent experimental and simulation-based advances in understanding the solidification microstructure evolution of HCCIs. The effects of alloy composition, cooling rate, and inoculation treatments on microstructure development and phase distribution during solidification are critically analyzed. Furthermore, the application of simulation techniques—including thermodynamic modeling, phase-field method, cellular automata, and finite element analysis—is discussed in detail, highlighting their roles in revealing the mechanisms of microstructural evolution. Finally, the current challenges and potential future research directions in the study of the solidification behavior of high-chromium cast irons are outlined. Full article