Search Results (145)

Vanadium (V), molybdenum (Mo), and aluminum (Al) are important alloying elements in titanium alloys, typically introduced through master alloys such as V-Al and Mo-Al. Current preparation of these master alloys predominantly relies on the spontaneous reduction of V₂O₅ or MoO₃ by aluminum. However, separate production and addition of master alloys increase the cost of the titanium alloy. Insufficient understanding of the exothermic behavior and slag-forming process during the aluminothermic reaction often leads to low alloy yield and elevated impurity levels due to splashing and poor alloy–slag separation. This study focused on the controllable aluminothermic reaction of V₂O₅ and MoO₃ to produce high-quality and high-yield V/Al/Mo alloy. Thermodynamic calculations indicate that the reduction of MoO₃ to Mo by aluminum is more favorable than the reduction of V₂O₅ to V. Al% in the V-Al-Mo alloy is crucial for controlling reaction temperature. When the Al/O ratio in the raw materials exceeds 1.0, increasing aluminum reduces both the reaction exothermicity and theoretical reaction temperature. A combination of thermodynamic calculations and high-temperature experiments demonstrates that the heat generation and slag composition can be effectively controlled by Al/O ratio in raw materials. When the Al/O ratio in raw materials is 1.6–2.0, the yields of Mo and V exceed 99% and 95%, respectively. This study provides an effective approach to producing V/Al/Mo alloy under controllable conditions, which shows great potential for other aluminothermic reactions. Extensive solid solutions of V/Al/Mo also provide invaluable data for the optimization of the alloy database. Full article

One of the most effective methods of improving the properties of aluminium alloys is grain refining using Al-Ti-B master alloys. In contrast, zirconium is a key alloying element, used mainly in 2xxx and 7xxx series aluminium alloys, where it contributes to dispersion enhancement and reduces the rate of dynamic recrystallisation. However, even trace amounts of zirconium—just a few hundredths of ppm—significantly reduce the performance of Al-Ti-B grain refiners, a phenomenon known as ‘Zr poisoning’. This study investigates the impact of holding time and the level of Al-5Ti-1B addition on the microstructure and properties of an AlMgSi(Cu) alloy containing 0.15 wt.% Zr, cast as 7-inch DC billets. The structure and phase distribution were characterised using optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Grain size and morphology were evaluated through macrostructure analysis (etched cross-sections and polarised light microscopy), while chemical and elemental distributions were analysed via SEM-EDS and STEM-EDS mapping. Additionally, Brinell hardness measurements were conducted across the billet diameter to assess the correlation between grain size and mechanical properties. The results show that reducing holding time and increasing the Al-5Ti-1B addition improves grain refinement efficiency despite the presence of Zr. The finest grain structure (150–170 μm) and most homogeneous hardness distribution were achieved when the grain refiner was continuously fed during casting at 80 ppm B. These findings are supported by the literature and contribute to a deeper understanding of the Zr poisoning effect and its mitigation through optimized casting practice. Full article

This study systematically investigates the influence of grain refinement on the microstructural evolution and mechanical properties of recycled Al-7Si-0.3Mg-1Fe alloy through the addition of varying concentrations (0–1.25 wt.%) of Al-5Ti-2B master alloy. The synergistic effects of Al-5Ti-2B on the α-Al phase, eutectic Si, and Fe-rich intermetallics were characterized using metallographic analysis, XRD, SEM-BSE imaging, and EDS. In the unrefined alloy, the microstructure consisted of an α-Al solid solution with coarse plate-like eutectic Si, while Fe primarily formed needle-like β-Al₅FeSi phases that either surrounded or penetrated the eutectic Si. Increasing the Al-5Ti-2B addition refined both the α-Al dendrites and eutectic Si, while the β-Al₅FeSi phase transitioned from coarse to fine needles. The optimal refinement was achieved at a 1% Al-5Ti-2B addition, yielding a tensile strength of 149.4 MPa and elongation of 4.3%. However, excessive addition (1.25%) led to eutectic Si aggregation and β-Al₅FeSi coarsening, resulting in mechanical property deterioration and brittle fracture behavior. These findings provide insights into optimizing grain refinement for enhancing the performance of recycled Al-Si-Mg-Fe alloys. Full article

Secondary Al-Si alloys typically encompass several impurities that substantially influence the materials’ microstructure and mechanical performance. This study employed a composite addition of chlorinated salt fluxing and an aluminum–boron master alloy to reduce the levels of the impurity elements magnesium (Mg), titanium (Ti), and vanadium (V) in secondary Al-Si alloys. The investigation of the performance mechanism revealed that the distribution of alloys’ grain orientation and the ratio of small-angle grain boundaries were modified via synergistic purification, leading to the refined microstructure and mechanical performance of secondary Al-Si alloys. The removal rates of impurity elements under these optimal refining conditions were 89.9% for Mg, 68.9% for Ti, and 61.5% for V. The refined alloy exhibited a 45.5% decrease in grain size and a 28.7% improvement in tensile strength compared to the raw material. These findings demonstrate that fluxing can improve the extraction of Ti and V from secondary Al-Si alloy melts of aluminum–boron master alloys, providing a new cost-effective strategy for the removal of impurities and the optimization of the properties of secondary Al-Si alloys. Full article

Commercially pure aluminum (Al) was refined through the addition of the Al-5Ti-0.25C master alloy, resulting in the formation of Al₃Ti and TiC phases, which serve as refining agents. Open-cell metallic foams were successfully produced using the replication casting technique, with pore sizes ranging from 1.00 to 3.35 mm. For the infiltration process, refined aluminum was used, while unrefined aluminum served as a baseline reference. The resultant foams underwent multiple annealing cycles at 480 °C, with the most refined and homogeneous microstructure observed after 504 h. Comprehensive microstructural characterization was conducted utilizing scanning electron microscopy and optical microscopy. Additionally, uniaxial compression tests were performed to generate stress–strain profiles for the foams, facilitating an assessment of their energy absorption capacity. The findings indicated an enhancement in energy absorption capacity by a factor of 2.4 to 3, which can be attributed to the incorporation of Al-5Ti-0.25C and the subsequent annealing process. Full article

The tetragonal R_1−xZr_x(FeCo)₁₁Ti alloys, where R is a rare earth and Ti a transition metal, are promising candidates for permanent magnets. Sm_1−xZr_x(Fe_0.8Co_0.2)_12−yTi_y (x = 0 and 0.25; y = 1 and 0.7) master alloys were prepared by arc melting under argon atmosphere. Some of the samples were almost single-phase compounds at 1:12, with a very small amount of a-Fe(Co). Partially replacing Sm with Zr produced alloys with small amounts of Sm(FeCo)₂ Laves-type phases. The as-cast ingots were milled using high-energy ball milling (HEBM) for different times in an argon atmosphere and then annealed at 973 K–1173 K at different interval times (15–90 min). After annealing, the sample milled for 4 h contained a large variation of grain size from 2–4 μm to 20 μm or larger, while, after annealing, the other sampled milled for 8 h exhibited grains size in the range of 2–6 μm; therefore, their coercivity was higher, reaching a maximum value of 5.5 kOe for SmFe₉Co₂Ti annealed at 1123 K for 60 min. Coercivity was strongly affected by the annealing temperature and time. The microstructure evolution with emphasis on the particles size during annealing and their correlation with coercivity are herein discussed. Full article

This study explores the enhancement of antimicrobial and biomedical properties in Fe-based bulk metallic glasses (BMGs) through the addition of Ag. Fe_55-xCr₂₀Mo₅P₁₃C₇Ag_x (x = 0, 1, 2, 3 at.%) master alloy ingots were synthesized by the induction melting technique and industrial-grade raw materials, the master alloy ingots were prepared as bulk metallic glasses (referred to as Ag0, Ag1, Ag2, and Ag3) by the water-cooled copper-mold suction casting technique, and their glass-forming ability, corrosion resistance, biocompatibility, and antimicrobial properties were systematically investigated. The results indicate that the glass forming ability (GFA) decreased with increasing Ag content, reducing the critical diameter for fully amorphous formation from 2.0 mm for Ag0 to 1.0 mm for Ag3. Electrochemical tests in Hank’s solution revealed the superior corrosion resistance of the Fe-based BMGs as compared with conventional 316 L stainless steel (316L SS) and Ti6Al4V alloy (TC4), with Ag3 demonstrating the lowest corrosion current density and the most stable passivation. Biocompatibility assessments, including fibroblast cell viability and adhesion tests, showed enhanced cellular activity and morphology on Fe-based BMG surfaces as compared with 316L SS and TC4, with minimal harmful ion release. Antimicrobial tests against E. coli and S. aureus revealed significantly improved performance with the Ag addition, achieving bacterial inhibition rates of up to 87.5% and 86.7%, respectively, attributed to Ag⁺-induced reactive oxygen species (ROS) production. With their excellent corrosion resistance, biocompatibility, and antimicrobial activity, the present Ag-containing Fe-based BMGs, particularly Ag3, are promising candidates for next-generation biomedical implants. Full article

The Al-Ti-C alloy is the most widely used grain refiner for Al-7Si alloys. However, TiC particles in Al-7Si alloys tend to aggregate and settle, thereby reducing their refinement efficiency. In the present paper, a novel Al-3Ti-4.35La master alloy was developed, and its influence on the stability of TiC particles in Al-7Si alloys was investigated by XRD, SEM, and TEM. The results show that when the Al-TiC alloy is added to the Al-7Si alloy, TiC will accumulate and settle obviously after holding the alloy for a certain time (15 min, 30 min, and 60 min). When the Al-TiC alloy and the Al-3Ti-4.35La master alloy are added to the Al-7Si alloy, the aggregation and settlement of TiC are weakened under the same holding time. Additionally, the refinement effect of TiC is enhanced. The Ti and La elements dissolved by Ti₂Al₂₀La in the Al-3Ti-4.35La master alloy are absorbed on the surface of the TiC particles, which improves the wettability between the TiC particles and the aluminum melt, reduces the agglomeration and sedimentation of TiC particles in the aluminum melt, and improves its stability. Full article

This article presents studies on the effect of Sr and TiB on the crystallization process, mechanical properties, hardness, and density index of the Al-Si alloy from the EN AC-46000 group, with a narrowed chemical composition, produced by die-casting and HPDC (high-pressure die casting) technology. The research used the Box–Wilson method to design the experiment and stepwise multiple regression. To identify the optimal amount of Sr and Ti in the analyzed alloy that would simultaneously guarantee the maximization of UTS, YS, A_gt, and HBW and the minimization of the DI (density index), multi-criteria optimization was performed. The modifiers were added to the liquid alloy as AlSr10 and AlTi5B1 master alloys. It was found that for 0.02–0.04 wt.% Sr and 0.05–0.08 wt.% Ti in the die castings, the highest mechanical properties, such as UTS, YS, A_gt, and HBW (treated as stimulants in the experiment), can be obtained simultaneously with the lowest alloy gasification identified by DI (treated as a destimulant in the experiment). It was also confirmed that the same amount of the above-mentioned elements in HPDC castings caused an increase in UTS by approx. 14%, YS by approx. 6%, A by approx. 47%, and HBW by approx. 13%, with a relatively small increase in DI by approx. 5% compared to the unmodified alloy. Full article

Aiming at the high-value application of rare earth elements lanthanum (La), an Al-50% La alloy was selected and prepared in a vacuum medium-frequency induction furnace. The geometric characteristics of the Al-50% La alloy powders were compared and studied, with the powders prepared by two different methods: mechanical pulverization and gas atomization. The results showed that an Al-49.09% La master alloy was obtained, and the only intermediate phase containing La in the experimental alloy was Al₁₁La₃. From the perspectives of chemical and phase composition, La has a high yield. Additionally, an Al-La alloy with controllable rare earth intermediate phases can be obtained. The Al-La alloy powders prepared by the mechanical pulverization method are irregular in shape, but the particle size is relatively small, ranging from 0.25 to 66.9 μm. Submicron powders were obtained, with 4.38% of the powders having an equivalent particle size of less than 1 μm. Considering the characteristic of the selective laser melting (SLM) process forming micro-melt pools, a small amount of submicron Al-La alloy powders prepared by the mechanical pulverization method can be used as a trace additive for SLM preparation of CP-Ti. The powders prepared by gas atomization have good sphericity, with a particle size range of 1.65 to 76.0 μm. Among them, the powders with a size of 2–10 μm account for 75.52%, and this part of the powders can be used for the powder metallurgy preparation of composite materials. Full article

(1) In recent years, an increase in the available functionality of non-ferrous alloys has been observed based on the modification and optimization of their chemical composition. This study investigated the effect of Sr addition on the structure and properties of hypereutectic Zn–Al–Cu alloys. The objective was to determine how a modification with Al–Sr master alloy affects the crystallization kinetics, microstructure, hardness, and abrasive wear resistance and whether the modification of the phase composition reduces the corrosion resistance. (2) The total influence of strontium was determined based on the microstructure, phase composition, and derivative curve changes of the tested Zn–Al–Cu alloys with added Sr. Optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to analyze the influence of chemical and phase composition, and thermo-derivative analysis (TDA) was used to investigate the crystallization kinetics of zinc alloys with different chemical compositions. (3) Sr modification caused the formation of primary Al₂Sr phases in the Zn alloy and also secondary Zn₁₃Sr and Al₄Sr phases (depending on the melting temperature of the alloy). (4) The primary and secondary intermetallic phases with strontium increased the hardness by approx. 20% and the abrasion resistance by approx. 7.5%. Full article

This study aims to enhance the electrical conductivity of commercially pure aluminium by minimizing impurities and grain boundaries in its microstructure, ultimately improving the efficiency of electric motors constructed from rotors with squirrel cages made from this material. For this purpose, an aluminium–boron (AlB8) master alloy was added to aluminium with a purity of 99.7%, followed by the application of a grain-coarsening heat treatment to the rotors. To obtain commercially pure aluminium with boron additions of 0.05% and 0.1% by weight, specific amounts of the AlB8 master alloy were added into aluminium with a purity of 99.7%. Using these materials, squirrel cage components of rotors were produced via the high-pressure die-casting method. Subsequently, a grain-coarsening heat treatment of the rotors was performed at temperatures of 450 °C, 500 °C, and 550 °C, with holding times of 2, 6, and 10 h. The Box–Behnken design, which is based on statistical experimental design and response surface methodology, was employed to investigate the effects of adding boron and varying the heat treatment temperature and holding time on the electrical conductivity of commercially pure aluminium. The results showed that the synergistic effect of adding boron at 0.05 wt.% and applying the grain-coarsening heat treatment at a temperature of 550 °C for a holding time of 10 h significantly enhanced the electrical conductivity of commercially pure aluminium, increasing it from 60.62% IACS to 63.1% IACS. Correspondingly, the efficiency of the electric motor increased from 90.35% to 91.53%. These findings suggest that this hybrid method not only enhances the electrical conductivity of commercially pure aluminium but also has strong potential to improve its other properties, such as thermal conductivity. This will lead to products composed of components manufactured from the materials exhibiting better performance characteristics, such as increased efficiency and extended service life. Consequently, this innovative method will contribute economically and environmentally by facilitating the manufacture of high-performance products. Full article

The phase structure, grain refinement, and microalloying effect of the Al-5Er-Ti master alloy were analyzed by a refining experiment, microhardness test, OM, SEM, and XRD. The results show that when the Er/Ti atomic ratio is 2.7, the refining effect of the Al-5Er-0.5Ti master alloy is significantly better than Al-5Er, which is due to the Ti₂Al₂₀Er phase. There are three crystal orientations of Ti₂Al₂₀Er and α-Al that satisfy the E2E model, among which (620)_Ti2Al20Er<260>_Ti2Al20Er//(111)_Al<110>_Al is the least mismatched one. When the Er/Ti atomic ratio is reduced to below 1.3, the Ti-containing phase of the Al-5Er-Ti master alloy is composed of Ti₂Al₂₀Er and Al₃Ti. The primary phase size of the Al-5Er-1.5Ti master alloy decreases with the increase in cooling rate, and the grain refining effect improved more significantly. The optimum size of the Ti₂Al₂₀Er phase and Al₃Ti phase is 6.0 μm and 9.5 μm, respectively. The grain size of pure aluminum is reduced from 14,000 μm to 300 μm by Al-5Er-1.5Ti master alloy refinement, and the refinement rate is 97.9%. Direct aging of the refined sample did not have a precipitation strengthening effect. After the solution and aging treatment, the peak aging of the refined sample was reached in 15 min, and the microhardness increased by 41%. Full article

Nickel significantly increases the toughness of steel and makes it ideal for use in applications that require high impact and fracture resistance at low temperatures. These inherent advantages position nickel steel as indispensable material in various domains, with a pronounced presence in stationary Liquefied Natural Gas (LNG) tanks and in the shipbuilding industry, particularly for tanks in vessels intended for the transport of liquefied ethane and LNG. The presented study focuses on assessing the fracture toughness behaviour of nickel alloy steel 1.5662+QT640 under sub-zero and cryogenic temperatures. The fracture performance of the material was evaluated, specifically emphasizing the impact toughness and fracture toughness characteristics of the material. Moreover, it was discussed if the transferability of the experimental results to the well-known fracture mechanics-based concept of EN 1993-1-10, which relies on the master curve concept, is possible. The results show that the master curve concept is not applicable to the nickel alloy steel 1.5662+QT640 due to its exceptional fracture toughness behaviour at very low temperatures. Full article

To obtain high-quality grain refiner, a new Al-5Ti-1B-1RE master alloy grain refiner was synthesized by the melt-matching method. Its microstructure and refining effect, refining properties, and refining mechanism were analyzed. The experimental results show that the second-phase particles of Al-5Ti-1B-1RE master alloy are mainly TiB₂, Al₃Ti, Ti₂Al₂₀RE, etc. The magnitude of the free energy ΔG of the synthesis reaction is calculated to be ΔG_TiB2 < ΔG_Al3Ti < ΔG_Ti2Al20RE. The nucleation rate N mainly depends on the kinetic atomic diffusion activation energy Q and the thermodynamic nucleation work. The microstructure of commercial pure aluminum refined by the new grain refiner has almost transformed from coarse columnar crystals to fine equiaxed crystals, with an average grain size of 70.2 μm, which was 36.18% and 20.66% smaller than that refined by domestic and imported Al-Ti-B wire master alloy grain refiner, its mechanical properties of tensile strength σ_b were increased by 11.94% and 8.29%, and elongation δ was improved by 31.79% and 17.41%, respectively. The main refinement mechanism is the formation of TiAl₃ on TiB₂ particles and the release of RE atoms from the Ti₂Al₂₀RE phase, which in turn is partially transformed into the TiAl₃ phase, which promotes dual nucleation refinement. Full article