Metals, Volume 14, Issue 1 (January 2024) – 132 articles

This study investigates the influence of different sinter-HIP temperatures and binder saturation levels on the microstructure and properties of WC–12Co cemented carbide, produced using binder jetting. The sinter-HIP process was performed at 1400 °C, 1460 °C, and 1500 °C and binder saturation levels of 60% and 75% were selected during printing. The binder saturation proved to affect the repeatability of the manufacturing process and the sturdiness of the green models. The increase of the sintering temperature from 1400 °C to 1460 °C is correlated with an increase in the density. Nonetheless, a further raise in temperature to 1500 °C leads to significant grain coarsening without clear advantages in terms of porosity reduction. Both the transverse rupture strength and Vickers hardness increase when the sinter-HIP temperature rises from 1400 °C to 1460 °C, where the typical results for traditionally manufactured WC–12Co are met, with a comparable grain size. The transverse rupture strength and Vickers hardness then decrease for samples treated at 1500 °C. Finally, potential issues in the manufacturing process are identified and correlated with the defects in the final components. Full article

This paper presents the results of research focused on increasing the lifespan of HPDC moulds for casting aluminium alloys by applying duplex PVD coatings in combination with laser texturing the base material before the coatings’ deposition. This article describes the HPDC process and the degradation mechanisms of the moulds that arose during this process. The PVD nanostructured coatings utilised, the methods of their deposition, and the evaluation of their wear resistance are defined in this paper. The surface texturing process is described alongside the description of the analysis of the wear of the functional parts of the mould after decommissioning, which was carried out by visual inspection and optical and light microscopy. Three types of PVD duplex coatings were analysed during our study. The coatings were deposited using the LARC technology method (lateral rotating cathode). Subsequently, the procedure of laser texturing in the form of dimple textures using a laser was proposed. The quality of the coatings was evaluated under tribological conditions by means of the “Ball on disc” method. Based on the experimental results, recommendations for practice are established. Full article

Additive manufacturing, particularly the laser powder bed fusion (LPBF) technique, has ushered in a new era of intricate metallic component fabrication, leveraging the exceptional performance of the Ti6Al4V alloy. However, the intricate mechanical behavior of additively manufactured Ti6Al4V, particularly its anisotropic attributes stemming from non-equilibrium microstructures, presents a formidable challenge. In this study, we embark on a comprehensive exploration of the anisotropic mechanical properties exhibited by LPBFed Ti6Al4V alloy. The interplay between microstructure and tensile response is unraveled by integrating experimental investigations with crystal plasticity finite element (CPFE) simulations. The acquired empirical data with CPFE model predictions are harmonized through systematic tensile tests along distinct processing orientations. The results unveil the genesis of plastic anisotropy within the LPBFed Ti6Al4V alloy, ascribed to the emergence of columnar grains meticulously aligned along the building direction, despite the intricate material microstructure inherent to additive manufacturing. These findings collectively furnish a holistic comprehension of the intricate nexus between material attributes and the mechanical manifestations intrinsic to metal components realized through additive manufacturing modalities. Full article

This article uses scanning electron microscopy (SEM) and electron back-scattering diffraction (EBSD) to study the effect of C and Mn segregation on the microstructure and mechanical properties of high-strength steel with 20 mm thickness used for wind power before and after simulated welding. A Gleeble-3500 (GTC, Dynamic Systems Inc., Poestenkill, NY, USA) was used to study the microstructure evolution of the simulated coarse-grained heat-affected zone (CGHAZ) of experimental steel under different welding heat inputs (10, 14, 20, 30 and 50 kJ/cm) and its relationship with low-temperature impact toughness (−60 °C). The results indicate that alloy element segregation, especially Mn segregation, significantly affects the impact toughness scatter of the steel matrix, as it induces the formation of low-temperature martensite or hard phase, such as M/A (martensite/austenite) constituent. In addition, segregation also reduces the low-temperature impact toughness of the simulated welding samples and increases the fluctuation range. For high-strength steel with yield strength higher than 460 MPa used for wind power generation, there is an optimal welding heat input (~20 kJ/cm), which enables the simulated coarse-grained heat-affected zone (CGHAZ) to obtain the highest impact toughness due to the formation of lath bainite (LB) and the finest crystallographic block units. Excessive or insufficient heat input can induce the formation of coarse granular bainite (GB) or lath martensite (LM), leading to a larger size of crystallographic block units, reducing the hindering effect of brittle crack propagation and deteriorating low-temperature impact toughness. Full article

In this study, static shoulder friction stir welding (SSFSW) is innovatively employed to join Al6061 and Ti6Al4V, aiming to minimize material mixing and intermetallic formation, significantly influencing the interfacial microstructure and joint strength. The results revealed that SSFSW reduced the intermetallic layer thickness at the interface, improving joint quality. The mutual interdiffusion of Al and Ti at the interface was influenced by an exothermic chemical reaction, forming an Al₅Ti₂–Al₃Ti sequence due to the diffusion of Al into the Ti matrix. The microstructural analysis demonstrated better interfacial microstructural homogeneity in SSFSW joints than conventional FSW (CFSW), with finer titanium particle distribution. The larger particles resulted in coarser grains in CFSW, affecting the mobility of dislocations, which potentially led to the inhomogeneous concentration of dislocations at the interface. Recrystallization mechanisms varied between CFSW and SSFSW, with the Ti interface showing equiaxed and recrystallized grains due to the dynamic recovery driven by adiabatic shear bands. The tensile testing results of SSFSW exhibited a joint efficiency of 88%, demonstrating a 20.2% increase compared to CFSW, which can be attributed to differences in fracture modes. This study contributes to an understanding of dissimilar Al-Ti joining and provides insights for industries seeking to leverage the benefits of such combinations in lightweight and high-performance structures. Full article

At present, blast furnace (BF) ironmaking is still the main process for producing hot metal in China and around the world. Under the constraint of the global goal of “double carbon”, it is urgent to carry out hydrogen metallurgical innovation for the existing BF ironmaking process with higher carbon emissions. In recent years, BF technology with hydrogen enrichment and pure oxygen has made some progress, effectively reducing carbon emissions of hot metal per tons, but it is still unable to break through the technical bottleneck of emission reduction of more than 30%. In view of this, the authors put forward an ironmaking technology of a reduction smelting furnace (RSF) that is hydrogen-rich and utilizes pure oxygen and carbon recycle (Hy-O-CR), which breaks through the technical defect of traditional BF emission reduction of less than 30% by reshaping the furnace. Firstly, the construction process of the mass and energy balance model for two main unit modules in the new process (RSF with Hy-O-CR and top gas cycle) is introduced, and then the parameter optimization under specific scenario conditions is analyzed, and the influence mechanism of several key variables on the parameters in the furnace is obtained. Finally, the emission of CO₂ in the whole process is explored in the case of two typical operating parameters. The results show that after using CCUS technology, the minimum value of direct CO₂ emission is 215.93 kg/tHM, which is as high as 84.58% compared with the traditional BF process. Even if the removed CO₂ is counted in carbon emissions, the minimum value of direct or indirect carbon emissions is 729.85 kg/tHM, and the proportion of emission reduction can reach 47.87%. The research results show that the reconstruction of Hy-O-CR technology can change the ratio of direct reduction and indirect reduction, which greatly breaks through the emission limit of the traditional BF and provides a new reference for hydrogen metallurgy technology and a basis for further study of the optimization of RSF size. Full article

Mg₈₀Ni_16−xAl_xY₄ (x = 2, 4, 8) alloys were prepared by induction levitation melting, and the effect of substitution of Al for Ni on the microstructure and hydrogen storage properties was studied in the present work. The results illustrated that the solidification path, phase constitution, and grain size were significantly altered by Al addition. Appropriate Al addition improved abundance and grain refinement of the Mg, Mg₂Ni, and Mg₁₅NiY ternary eutectic. But as Al further increased, Mg solidified independently rather than in the formation of the ternary eutectic. More Al favored the formation of Al₃Ni₂Y but suppressed Mg₂Ni and YMgNi₄. Although the hydrogen absorption activation and the kinetic property deteriorated, the thermodynamic stability of hydrides was enhanced by adding Al. Hydrogen absorption ability under low pressure was improved, and the Mg₈₀Ni₈Al₈Y₄ alloy could absorb nearly 3.5 wt% hydrogen under 1 bar hydrogen at 250 °C. Full article

In order to explore the hot deformation behaviors of the as-cast 7005 aluminum alloy, a number of hot tensile tests with four temperatures (100, 200, 300, and 400 °C) and three strain rates (0.001, 0.01, and 0.1 s⁻¹) were performed. The Johnson–Cook model was used to express the relationship between stress, strain, strain rate, and temperature. Scanning electron microscopy (SEM), optical microscopy (OM), and transmission electron microscopy (TEM) were selected to reveal fracture features and microstructure evolution of the studied alloy. The results indicate that the flow stress level of the alloy reduces with increases in the deformation temperature and decreases in the strain rate. The established Johnson–Cook model can be employed to characterize the thermal flow behavior of the experimental alloy. The grains near the fracture surface were elongated, and a certain number of holes were found after deformation at 400 °C. The alloy exhibits obvious ductile fracture features. The dimple is deep with high quantity. Due to the plastic deformation, a high-density dislocation structure is found in the material. High-temperature conditions promote the annihilation of dislocation, and, as a result, the dislocation density decreases gradually with the increase in temperature. In addition, a certain number of precipitates were found in the alloy after high-temperature tension. Full article

Ni-base superalloys are employed to produce parts of aeronautic engines, space vehicles and power plants. During the production process or lifetime of components, cracks may occur which affect their performance. Reliable repairs can be carried out through high-energy density welding techniques. This work investigated laser welding of the directionally solidified IN792 DS superalloy. The characteristics of the original material and their evolution in the base metal, heat-affected zone and melt zone after laser welding in different conditions and post-welding heat treatment were investigated through micro-hardness tests, light and scanning electron microscopy observations. The study allowed to optimize the process parameters and post-welding heat treatment, obtaining joints without macro-defects, such as cracks and pores, and with properties and microstructures of the melt zone like those of base metal. Full article

Titanium alloy pressure spherical–cylindrical shells enable the effective utilization of the strength of spherical and cylindrical pressure-resistant shell components. In this study, a numerical simulation of the residual stress of a titanium alloy butt-welding plate was conducted by employing sequential coupling and a temperature heat source model. The results of welding residual stress analysis agreed well with the experimental results reported in the literature. Subsequently, the welding residual stress of a titanium alloy pressure spherical–cylindrical shell was calculated and analyzed using the same method. Finally, the influence of residual stress on the ultimate bearing capacity of the shell was assessed. On the inner surface of the shell, the horizontal welding residual tensile stress, perpendicular to the weld path, exhibited a bimodal distribution. The longitudinal welding residual tensile stresses were higher than the horizontal welding residual stress. Near the weld on the outer shell surface, higher longitudinal welding residual tensile stresses existed, whereas the horizontal welding residual stress was compressive. Both the inner and outer shell surfaces exhibited significant longitudinal residual tensile stresses along the weld path, though residual compressive stresses existed on both surfaces. The influence of welding residual stress on the ultimate load-bearing capacity of the shell was minimal. Full article

β-titanium (β-Ti) alloys are used in various biomedical applications, especially for orthopedic implants, due to their superior biocompatibility, excellent corrosion resistance, and enhanced mechanical properties. However, the inferior tribological properties of β-Ti alloys lead to fretting wear and a strong tendency to seize, which is a major concern in orthopedic applications involving continuous friction. This work aims to address this issue by incorporating biocompatible nitrides in Ti-Nb-Zr-Ta (TNZT) β-Ti alloys. TNZT composites comprising 2 wt.% of biocompatible nitrides (TiN, NbN, ZrN, and TaN) were prepared using high-energy ball milling followed by spark plasma sintering. All the nitrides improved the hardness and wear resistance of TNZT alloys and showed excellent biocompatibility. TNZT-2 wt.% TiN showed the average highest hardness of 311.8 HV and the lowest coefficient of friction of 0.659, suggesting the highest efficiency of TiN in improving the tribological performance of TNZT alloys. The underlying mechanisms behind the superior performance of nitride-reinforced TNZT composites are discussed in detail. The effect of TiN concentration was also studied by preparing TNZT composites with 5 and 10 wt.% TiN, which showcased a higher hardness of 388.5 HV and 444.3 HV, respectively. This work will aid in producing superior β-Ti alloys for advanced orthopedic applications. Full article

This study investigates the cold formability of twin-roll cast and rolled magnesium strips, specifically focusing on AZ31 and ZAX210 alloys. The aim is to assess the suitability of these alloys for various forming processes. The mechanical properties and formability characteristics of the strips were thoroughly examined to provide insights into their potential applications in transportation industries such as automotive and aerospace. The AZ31 and ZAX210 alloys were subjected to twin-roll casting and rolling processes to produce thin strips. The resulting strips were then evaluated for their cold formability. The results indicate that both alloys exhibit favourable cold formability. The ZAX210 alloy, in particular, demonstrates medium strengths with an average tensile strength of approximately 240 MPa at room temperature. The 0.2% proof stress values range between 136 MPa and 159 MPa, depending on the sampling direction. The total elongation values vary from 28% in the transverse direction to 32% at a 45° angle, indicating excellent ductility. Comparing the two alloys, the AZ31 alloy shows higher strengths due to its higher aluminium content. However, it also exhibits a more pronounced directional dependence of mechanical properties due to the formation of a strong basal texture during hot rolling. The transverse direction experiences reduced total elongation compared to the rolling direction, achieving only about 50% of the total elongation. The average Erichsen Index recorded for AZ31 and ZAX210 strips were 4.9 mm and 7.1 mm, respectively. The ZAX210 strip displays superior formability, which can be attributed to the fine-grained microstructure and the texture softening resulting from the weakening of the basal texture intensity and the splitting of the basal pole towards the rolling direction. In conclusion, the investigated twin-roll cast, rolled and annealed AZ31 and ZAX210 magnesium strips exhibit promising cold formability characteristics. The findings of this study contribute to the understanding of their mechanical behaviour and can guide the selection and optimisation of these alloys for various forming applications. Full article

The powder metallurgy (PM) route for the production of closed-cell metallic foams has recently received a significant amount of attention. One of the major issues is the non-uniform and non-spherical nature of the cells produced, which can negatively affect the mechanical behavior. The current paper uses the PM route to process metallic foams for the first time using novel Al-TiH₂ foamable precursor “particles” (FPPs). The effect of FPP content (0–10 wt.%) on the developed foam structure of aluminum and its mechanical properties is investigated. An increase in FPP content results in a decline in product density by forming uniform and near-spherical cells. The main advantage of the FPPs is the localization of the blowing agent TiH₂ particle content within Al-TiH₂ composite particles (i.e., giving rise to a higher local TiH₂ content), which has led to the production of pores with relatively high circularities even at very low overall TiH₂ contents. The foams produced displayed energy absorption capacities of 10–25 MJ/m³ at 50% strain, and maximum energy absorption efficiencies ranging from 0.6–0.7 (for 40–60% closed cell content) Full article

The efficient fabrication of titanium components using laser direct metal deposition (DMD) is gaining significant importance in the aerospace and medical sectors. The DMD process must be appropriately designed to address the issue of oxidation, as titanium exhibits a high affinity for oxygen. The carrier gas flow and shield gas flow, which have been considered secondary factors so far, are shown to exert a substantial influence on the gas dynamics of the DMD process. By varying these parameters, it is possible to identify the influence of the gas volume flows on the oxidation behavior exhibited during the DMD process. To quantify the oxygen uptake in titanium structures during buildup, hot carrier gas extraction is employed. Experiments are conducted using both a three-jet and a coaxial nozzle to assess the influence of nozzle geometry. Additionally, the experiments are conducted within a shielding gas chamber to demonstrate the benefits of such a chamber in mitigating oxidation. Finally, the study reveals that by appropriately combining the parameters of carrier gas volume flow, shield gas volume, and travel speed, it is possible to fabricate titanium components, which fulfill the requirements regarding oxygen content of aerospace and medical applications even without the utilization of a shielding gas chamber. Full article

This work explores technical feasibility in hot isostatic pressing (HIP) manufacturing of an integral bimetallic component using steel and Ni alloy powder for supercritical carbon dioxide (sCO₂) turbomachinery. Lab-scale bimetallic HIP specimens using HAYNES^® 282^® and SS316L or SS415 powder are investigated in powder configuration, heat treatment, microstructure, and tensile properties up to 400 °C. Interdiffusion profiles at dissimilar alloy interfaces caused by HIP cycle is predicted by DICTRA simulations and validated by electron probe microanalysis (EPMA). The interdiffusion distance of most elements is around 100 μm, while C and N have a higher interdiffusion distance. Dense distribution of Ti-rich carbonitrides and alumina particles are found to decorate prior particle boundaries near joining interface on the 282 side, affecting tensile strength across interface as well as tensile failure location. A higher amount of excessive carbonitride formation near interface is observed in SS316L/282 than in SS415/282, which is consistent with the predicted greater degree of interdiffusion effect in SS316L/282. Typical HAYNES^® 282^® heat treatment condition is applicable to 282/SS316L and 282/SS415 combinations, resulting in a higher strength than cast CF8M and CA6NM. A pilot-scale bimetallic SS415/282 pipe is then demonstrated to show the promise of scaleup. Full article

Soft magnetic Fe-Al alloys have been a subject of research in the past. However, they never saw the same reception in technical applications as the Fe-Si or Fe-Ni alloys, which is, to some extent, due to a low ductility level and difficulties in manufacturing. Additive manufacturing (AM) technology could be a way to avoid issues in conventional manufacturing and produce soft magnetic components from these alloys, as has already been shown with similarly brittle Fe-Si alloys. While AM has already been applied to certain Fe-Al alloys, no magnetic properties of AM Fe-Al alloys have been reported in the literature so far. Therefore, in this work, a Fe-12Al alloy was additively manufactured through laser powder bed fusion (L-PBF) and characterized regarding its microstructure and magnetic properties. A comparison was made with the materials produced by casting and rolling, prepared from melts with an identical chemical composition. In order to improve the magnetic properties, a heat treatment at a higher temperature (1300 °C) than typically applied for conventionally manufactured materials (850–1150 °C) is proposed for the AM material. The specially heat-treated AM material reached values (H_C: 11.3 A/m; µ_max: 13.1 × 10³) that were close to the heat-treated cast material (H_C: 12.4 A/m; µ_max: 20.3 × 10³). While the DC magnetic values of hot- and cold-rolled materials (H_C: 3.2 to 4.1 A/m; µ_max: 36.6 to 40.4 × 10³) were not met, the AM material actually showed fewer losses than the rolled material under AC conditions. One explanation for this effect can be domain refinement effects. This study shows that it is possible to additively manufacture Fe-Al alloys with good soft magnetic behavior. With optimized manufacturing and post-processing, further improvements of the magnetic properties of AM L-PBF Fe-12Al may still be possible. Full article

Pellet ore is an important raw material for blast furnace ironmaking, and its reduction and expansion performance directly affects the smooth operation and smelting indicators of the blast furnace. This paper quantitatively studied the effects of magnesium minerals such as dolomite and serpentinite on the pellet-forming performance, the microstructure after roasting, compressive strength, and the reduction expansion performance of Baiyun Ebo iron concentrate. The optimal ratio of dolomite and serpentinite to add was determined when preparing pellets using Baiyun Ebo iron concentrate powder. The results showed that the drop strength and compressive strength of the green pellet after adding serpentine were relatively higher than those after adding dolomite, indicating that controlling the MgO content in the green pellet at 2.5% using serpentine was beneficial for improving the drop strength and compressive strength. Under the condition of adding dolomite, when the MgO content was 2.5%, the compressive strength of the roasted pellet was the highest, which was 2192.6 N, and the volume expansion rate was 12.32%. Under the condition of adding serpentine, when the MgO content was 2.5%, the compressive strength of the roasted pellet was 2622.2 N, and the volume expansion rate was 9.71%. Compared with dolomite as a magnesium additive, when the reduction expansion rate of Baiyun Ebo iron concentrate was controlled within 20%, serpentine only needed to have a MgO content of about 1.5% in the pellets, while dolomite needed to have a MgO content of about 2.5%. Therefore, under the condition that the MgO contents of dolomite and serpentine were equivalent, the amount of serpentine used was lower. Full article

Brazing technology is widely used in modern industrial systems as an important connection method. The brazing joints are the weakest zone in the whole structure and directly determine the working efficiency and life of the entire system. However, the research on the connection mechanism and fracture behavior of brazing joints is still unclear. In this study, the peeling force and displacement curves during the peeling process are tested by using T-type specimens. Based on the cohesive zone model, the peeling energy of each part during the whole peeling process is calculated and analyzed. The results show that the whole peeling process can be divided into three stages, including the initial stage, crack propagation stage, and stable peeling stage. The peeling energy of each stage can be calculated experimentally. The larger the peeling energy, the better the joint performance. Then, a simplified calculation method for peeling energy is developed for T-type joints and is verified as accurate using experimental data. It is also observed that the increase in the base material thickness can effectively improve the peeling performance of the joints. This provides a feasible and effective method for peel strength calculation and evaluation in brazing joints. Full article

The microstructure developed in a low-alloy steel during friction stir welding and post-weld tempering was studied. The quenched steel samples were subjected to tempering at 650 °C for 1 h, followed by warm rolling to a total strain of 1.5 at the same temperature. The processed steel samples were characterized by an ultrafine-grained microstructure of the lamellar type with a transverse grain size of 360 nm and exhibited an yield strength of about 1200 MPa and a total elongation of 13%. Then, the steel plates were joined by friction stir welding. The yield strength of the weld joint was about 1170 MPa, although the total elongation decreased to 1.5%. The martensite microstructure, with a high-angle grain boundary spacing of about 800 nm, was developed in the stir zone. This martensite in the stir zone originated from the ultrafine-grained prior austenite, resulting in an almost two-fold increase in hardness as compared to the base material. Tempering of the welded sample at 650 °C for 1 h resulted in a decrease in the hardness of the weld joint to the level of the base material. Nevertheless, the fracture of the welded and tempered sample occurred in the base material. The yield strength of the welded sample after tempering was 930 MPa, with a total elongation of 13%. Full article

A newly developed medium-carbon carbide-free bainitic steel was fabricated for the first time utilizing the laser powder bed fusion (L-PBF) technique. Process parameters were optimized, and a high density of 99.8% was achieved. The impact of austempering heat treatment on the bainite morphology and transformation kinetics was investigated by high-resolution microstructural analysis (SEM, TEM, and EDS) and dilatometric analysis, and results were compared with conventionally produced counterparts. Faster kinetics and finer microstructures in the L-PBF specimens were found as a consequence of the as-built microstructure, characterized by fine grains and high dislocation density. However, a bimodal distribution of bainitic ferrite plate thickness (average value 60 nm and 200 nm, respectively) was found at prior melt pool boundaries resulting from carbon depletion at such sites. Full article

Near-full density and crack-free AISI H13 hot-work tool steel was fabricated using laser-directed energy deposition (L-DED). Two different heat-treatment scenarios, i.e., direct tempering (ABT) from the as-built (AB) condition and systematization and quenching prior to tempering (QT), were investigated, and their effect on the microstructure, hardness, fracture toughness (K_app), and tempering resistance of the L-DED H13 is reported. For this purpose, the optimal austenitization schedule was identified, and tempering curves were produced. At a similar hardness level (500 HV1), QT parts showed higher K_app (89 MPa√m) than ABT (70 MPa√m) levels. However, the fracture toughness values obtained for both parts were comparable to those of wrought H13. The slightly larger K_app in the QT counterpart was discussed considering the microstructural homogenization and recrystallization taking place during high-temperature austenitization. The tempering resistance of the ABT material at 600 °C was slightly improved compared with that of the QT material, but for longer holding times (up to 40 h) and higher temperatures (650 °C), ABT showed superior resistance to thermal softening due to a finer martensite substructure (i.e., block size), a finer secondary carbide size, and a larger volume fraction of secondary V(C,N) carbides. Full article

This paper aims to perform a comparative investigation on the corrosion protection of steel in the simulated pore solutions of alkali-activated slag (SH) by NO₃⁻ and NO₂⁻ intercalated Mg-Al layered double hydroxides (MAL) which were fabricated by the calcination rehydration method. The corrosion potential, electrochemical impedance spectroscopy, potentiodynamic polarization and corrosion condition of steel were measured. Furthermore, changes in the microstructures of NO₃⁻ intercalated MAL (MAL-N3) and NO₂⁻ intercalated MAL (MAL-N2) before and after the adsorption of chloride ion were observed by X-ray diffraction and Fourier transform infrared spectroscopy. The results show that compared to the simulated concrete pore solution (OPCH), MAL-N3 and MAL-N2 exhibit lower chloride adsorption capacities and better corrosion inhibition effects in SH. The chloride adsorption capacity of MAL-N2 is lower compared with that of MAL-N3 due to the different volumes of intercalated anions. In contrast, MAL-N2 presents superior corrosion inhibition than MAL-N3. Furthermore, the decreases in [OH⁻] in SH due to the additions of MAL-N3 and MAL-N2 are more prominent than those in OPCH. The different synergistic effects due to the competitive anion-exchanges in the interlayers of NO₃⁻ and NO₂⁻ intercalated MAL in the two solutions contribute to the above effects. Full article

Mechanical components often experience fatigue loading from various waveform conditions during their operational lifespan. However, the underlying mechanisms through which variations in loading waveform affect the fatigue life of components remain unclear. Thus, this study conducted tension–compression fatigue experiments on 34CrNi3MoVA steel specimens under the same stress amplitude with different waveforms (cosine, triangular, sawtooth, and reverse sawtooth) to investigate the effects of loading waveform variations on the cyclic strain hardening behaviors, the fatigue fracture failure, and the fatigue life. The results indicated that specimens under different waveforms all exhibited cyclic strain hardening. The fatigue cyclic hardening level progressively increased in the order of cosine, triangular, and sawtooth waveforms, resulting in a continuous increase in cyclic saturation strain amplitude. The analysis of fatigue fractures demonstrated a consistent increase in both the initiation and propagation zone areas in the order of cosine, triangular, and sawtooth waveforms, and the boundary between the propagation and final fracture zones gradually shifted from a straight to a curved shape. The influence mechanisms of cyclic loading waveforms on the fatigue life of specimens were analyzed based on the energy dissipation, leading to the development of a universal fatigue life prediction model applicable to different waveform conditions, the model was then verified with the reverse sawtooth wave specimens and resulted in a prediction error less than 15%. The study is expected to serve as a significant guide for predicting and evaluating the fatigue life of mechanical components under various fatigue loading conditions. Full article

This paper deals with the separate electrochemical recovery of transition metals from battery black liquor. In a first approach, the authors investigated a model waste electrolyte mainly consisting of Cu, Co, Ni, and Mn in an acidic solvent, using citric acid as a complexing agent. An open porous Inconel^® foam had been included as an electrode to benefit from the increased active surface area. Under the selected operation conditions, Cu was completely recovered, presenting almost 100% purity, while, in the case of Co, the purity was 96%, and a remanent concentration of about 1.2 g L⁻¹ could still be determined. Full article

The thermodynamic properties of the CaO-Al₂O₃-VO_x slag system are of great significance to the direct alloying of vanadium in the smelting process of vanadium steel. In this paper, the phase equilibrium relationship of the CaO-Al₂O₃-VO_x system under argon atmosphere at 1500 °C was studied with a high-temperature phase equilibrium experiment. Combined with SEM-EDS, XRD, and XPS, the types and compositions of each phase of the equilibrium slag samples and the content of different valence states of the vanadium element were determined. The result shows that under argon atmosphere (p(O₂) = 10⁻³ atm) at 1500 °C, the CaO-Al₂O₃-VO_x slag system contains four three-phase regions, seven two-phase regions, and a single-phase region (glass phase). The phase equilibrium results were plotted in a CaO-Al₂O₃-V₂O₅-VO₂ spatial phase diagram, and the phase equilibrium results were projected on the CaO-Al₂O₃-V₂O₅ and CaO-Al₂O₃-VO₂ pseudo-ternary phase diagrams, respectively. In the end, the rationality of projecting the phase equilibrium results to the pseudo-ternary phase diagram was quantitatively evaluated. Full article

Ball-milled Fe-Si-Al soft magnetic powder cores with the particle compositions away from the classical Sendust point were prepared in this work. The influences of alloy composition on the metallographic structure, density, hardness, and resistivity of Fe-Si-Al alloy, as well as the frequency-dependent permeability, loss, and the anti-saturation performance of Fe-Si-Al powder cores, were investigated systematically. It was found that the hardness of Fe-Si-Al alloy increases with the Si mass ratio and the saturation magnetization (M_s) increases with the Fe mass ratio. The alloy hardness affects the particle size after the ball-milling process and, thus, influences the porosity of the powder core. Together with adjusting the demagnetization field by controlling the particle size and the core’s porosity, changing the alloy composition to drive K and λ deviating from zero can effectively improve the anti-saturation performance of Fe-Si-Al powder cores at the expense of hysteresis loss, to some extent. In this work, good comprehensive magnetic properties were obtained in the Fe_85.5-Si₁₂-Al_2.5 powder core. Its effective permeability percentage at 100 Oe and M_s were 59.12% and 132.23 emu/g, respectively, which are higher than those of the classical Sendust core. This work provides a feasible idea for optimizing the overall performance of the high-power magnetic device. Full article

This study investigates the influence of molten nitrate salt exposure on the intergranular corrosion (IGC) behavior of three grades of austenitic stainless steel (namely, AISI 304, AISI 304H, and AISI 321H). Two electrochemical techniques, double loop electrochemical potentiokinetic reactivation and potentiodynamic polarization methods, are applied after stainless steel is exposed to 600 °C molten nitrate salt, 60% NaNO₃, and 40% KNO₃ for varying immersion durations. Corrosion morphology is examined using optical microscopy and scanning electron microscopy images to assess susceptibility to IGC. IGC is prompted by the presence of chromium carbides at grain boundaries, which leads to chromium depletion around these carbides. The findings of the experiments reveal distinct IGC behavior among stainless steel grades. For AISI 304, the degree of sensitization (DOS) increases as exposure time progresses. However, AISI 304H and AISI 321H stainless steel exhibit diminishing DOS after 100 and 10 h of exposure, respectively. This trend is attributed to desensitization or the healing effect when stainless steel is exposed to molten salt for a prolonged time. The depletion and recovery of Cr near grain boundaries are confirmed by the inverse relationship to DOS of pitting potential. Full article

In this work, the interaction of an additively produced Ti-₄Al-₃V titanium alloy with a nickel superalloy tool and the features of the stir zone formation during friction stir processing have been studied. The stop-action technique was used to produce the samples to be studied using optical and scanning electron microscopy methods, as well as microhardness measurements. As a result, it was revealed that the tool, when moving, forms a pre-deformed area in front of it, which is characterized by a fine-grained structure. The presence of an interface layer between the workpiece material and primary fragmentation by the tool was revealed. It was demonstrated that the transfer of titanium alloy material occurs periodically following the ratio of feeding speed to tool rotation rate. Metal flow around the tool can occur in both laminar and vortex modes, as indicated by the tool material stirred into the transfer layer and used as a marker. Full article

The TiNbZr/(Ti, Nb)B metal matrix composite with 2.5 vol.% of borides was produced by vacuum arc melting. The composite was then cold-rolled to thickness strains of 10, 20, 50, or 80%. In the initial condition, the composite had a network-like microstructure consisting of the soft TiNbZr matrix (dendrites) and the rigid (Ti, Nb)B shell (interdendritic space). In comparison with the as-cast condition, cold rolling increased strength by 17–35%, depending on the thickness strain. After the maximum thickness strain of 80%, yield strength and ultimate tensile strength of the composite achieved 865 and 1080 MPa, respectively, while total elongation was found to be 5%. Microstructural analysis revealed that cold rolling to 50% resulted in the formation of crossing shear bands caused by the considerable difference in deformation behavior of the matrix and reinforcements. Cold rolling to 80% led to the formation of a lamellar-like microstructure comprising the interlayers of the (Ti, Nb)B phase between the TiNbZr laths. The maximum strain (80% cold rolling) shortened the (Ti, Nb)B fibers into nearly equiaxed particles, with a length to diameter ratio of ~2. Full article

Since steel cleanness comes to the fore of steel producers worldwide, it is necessary to understand the formation mechanism and modification of non-metallic inclusions (NMIs) in more detail. One central point is the identification of the source of especially interfering NMIs to prevent their evolution in the future. The present study applies two approaches to determine the source of NMIs in Ti-stabilized ultra-low carbon (ULC) steels—the active and the passive tracing. Both approaches are applied to an industrial experiment. The active tracing technique is focused on investigating the clogging layer formation in submerged entry nozzles and, hence, the origin of alumina particles. This method adds rare earth elements (REEs) directly to the melt to mark pre-existing deoxidation products at a certain point of the steelmaking process. The main concern of the passive method, the so-called REE fingerprint, is the determination of the source of mesoscopic NMIs. For the REE fingerprint, the pre-existing concentration of REEs in different potential sources and the investigated NMIs are measured by using an inductively coupled plasma mass spectrometer (ICP-MS). The resulting patterns are compared after normalizing the contents to chondrites, and the NMIs’ origins are identified. Concerning the EDS analysis and the resulting patterns from the REE fingerprint, the mold slag and, respectively, the casting powder were the sources of the investigated NMIs. Full article