Search Results (319)

Waste-to-hydrogen technology requires the involvement of new material development and performance evaluation for additive manufacturing (AM). Metal 3D printing is a very good possible alternative and is delivering results visible in the circular-economy environment. By using the AM technique, complex operations are avoided when combining the individual components, which is a typical disadvantage in obtaining composite materials; such samples are prepared with only one operation from the starting melt, which is chemically defined. Pyrolysis rotary kiln sealing rings are to be upgraded with several different microstructure coatings in order to improve the surface performance. The surface topology is aimed to be fine, dense and smooth. Also, the target characteristics are a low friction coefficient and a high hardness value, suggesting enhanced wear resistance. For elevated temperatures, 900 °C is selected for cobalt-based superalloy Stellite types with particle reinforcement. Two possibilities for advanced materials production are proposed with the Directed Energy Deposition Plasma Arc (DED-arc) and Laser Directed Energy Deposition (DED-LB). The shell of the rotary kiln sealing ring is made of stainless steel as the base, with the coating overlaid. Selected mixtures in powder form with defined composition are applied. For the DED-arc, commercially available Stellite 6 (Deloro Stellite^® 6) and 20 vol% WC particles with a grain size of 63–150 µm were employed. For the DED-LB, we employed TRIBALOY^® T-800 (Kennametal Stellite^TM) with 25 vol% TiC and a mesh size of −100/+325 (particle diameter between 45 and 150 µm). After the representative samples were metallurgically bonded with the base stainless steel, the relevant properties were obtained. Manufactured samples are compared in terms of microstructures and mechanical properties. Analysis of structure: Intermetallic carbides that formed on the cobalt basis make the composite harder and increase the plasticity in a defined direction. The hypoeutectic structures of Stellite 6 + 20% WC consist of dendrite and interdendrite eutectic. It is observed that with an increase in WC volume fraction, the size of the dendrites becomes finer, and the amount of eutectic structure is increased. For the TRIBALOY^® T-800 with TiC, we obtained relatively smaller grain sizes. The roughness values for the tested samples with WC were initially Ra = 0.8 µm, increasing up to Ra = 3.44 µm after the wear test, whereas for the TiC, they were slightly lower. Microhardness testing revealed increased values compared to the base stainless steels. Advanced sensor analysis with acoustic emission (AE) and electrical contact resistance (ECR) also showed the properties of the new materials. Customizable coatings with tailored properties were deposited by DED-arc and DED-LB. From the tests performed, a new technological procedure for the production of novel pyrolysis rotary kiln sealing rings is proposed. The microhardness, roughness, microstructure and abrasive wear-resistant response of the metallic composite material were examined in order to characterize the stable multiphase system. Full article

Brewer’s spent grain (BSG) is the primary by-product of the brewing industry and a low-cost lignocellulosic resource rich in phenolics, proteins, and arabinoxylans (AXs). Conventional recovery methods using acids, alkalis, and organic solvents often involve energy-intensive processes, generate hazardous waste, and limit food-grade applications. This review critically examines the evolution of extraction methodologies for BSG bioactives, highlighting the potential of deep eutectic solvents (DES) as sustainable alternatives. Key factors such as solvent chemistry (polarity, pH, and water content) influence bioactives’ recovery and selectivity. Process intensification techniques such as ultrasound, microwave, and pressurised liquid extraction enhance efficiency by reducing extraction time and temperature. The review assesses how various processes modify the structure–function properties of BSG bioactives, including antioxidant activity, protein functionality, and rheological behaviour. A significant finding is that DES research has primarily focused on single compounds, while integrated DES biorefineries for comprehensive valorisation remain underexplored. Future research should therefore prioritise integrated process design that balances recovery, structural preservation, functionality, and sustainability to support scalable, near-zero-waste BSG valorisation for food and nutraceutical applications. Full article

The effects of equimolar La/Ce co-doping (0–0.4 wt.% of each element) on the microstructure, mechanical properties, and electrical conductivity of the Al-0.5Fe (8176) conductor alloy were investigated in the as-cast, cold-drawn, and annealed (300 °C, 2 h) states. La/Ce additions refine the as-cast eutectic cells and modify the detrimental Al₁₃Fe₄ intermetallic from coarse plate-like to fine spheroidal particles. At 0.3 wt.% La + 0.3 wt.% Ce (0.3LC), the annealed wire reaches a peak elongation of 16.7% (+42.7% relative to the rare-earth-free alloy), while its electrical conductivity rises from 59.87 to 61.81% IACS. The conductivity increase is explained by a solute-scavenging mechanism: La and Ce bind Fe and Si impurities into stable Al-RE intermetallics, reducing solute-induced electron scattering in the α-Al matrix. At the same time, thermally stable Al-RE dispersoids pin subgrain boundaries during annealing, retard recrystallization, and preserve the fine-grained structure that benefits ductility. Both effects originate from the same RE addition. This coupled scavenging–pinning pathway breaks the usual trade-off between conductivity and ductility and defines an optimal composition range for high-performance Al-Fe conductor alloys. Full article

Hot-pressing densification is an effective method to improve the physical and mechanical properties of fast-growing wood, but it typically faces challenges such as moisture-induced rebound and brittle fracture of cell walls. This work proposed a strategy for preparing densified Chinese fir (DCF) via deep eutectic solvent (DES) pretreatment. The effects of pretreatment conditions (i.e., DES concentration, treatment temperature, and treatment time) and physical compression ratio on the dimensional stability, mechanical properties, and microstructure of DCF were systematically investigated. The results demonstrated that under the best-performing conditions within the investigated range conditions (10 wt% DES concentration, treatment at 100 °C for 8 h, and 50% compression ratio), the modified fir (viz., DCF) exhibited substantial improvements compared to NW in terms of modulus of rupture (147.8 MPa, a 163.5% increase), modulus of elasticity (8622 MPa, a 71.1% increase), compressive strength along the grain (81.8 MPa, a 138.5% increase), and Shore D hardness (70.6, an increase of 83.9%). Furthermore, the moisture-induced rebound rate was reduced to 0.77%, indicating that the dimensional stability of DCF was effectively enhanced. Microstructural and chemical characterization revealed that DES partially degraded part of the amorphous hemicelluloses, thereby plasticizing the cell wall and enabling cells to undergo flexible folding and dense closure during the hot-pressing process while largely retaining the main cellulose crystalline skeleton. The present work provides a feasible route for converting fast-growing plantation wood into structural materials. Full article

Sn-3Ag-0.5Cu-xBi alloys (SAC305-xBi) represent promising lead-free alternatives for low-temperature soldering. Low Bi concentrations can strengthen SAC-based solders through solid-solution strengthening, refining β–Sn grains and transforming needle-like Ag₃Sn phases into equiaxed morphologies. However, excessive Bi alloying may induce precipitation of brittle Bi particles, cause microstructural instability and interfacial degradation, thereby weakening the solder joint performance. As such, the concentration of Bi in the SAC305 alloys should be carefully controlled. In this work, the microstructure and corrosion behavior of Sn-3Ag-0.5Cu-xBi solder alloys (SAC305-xBi, where x = 0, 1, 2 and 4 wt. %) were investigated. Attention has been paid to the influence of low Bi concentration on the microstructure, morphology, and chemical composition of the phases present in the solder alloys before and after corrosion exposure. The alloys were prepared by induction melting of Sn, Ag, Cu and Bi lumps under Ar gas. The microstructure of the SAC305 and SAC305-1Bi alloys represented a hypoeutectic microstructure with dendritic (Sn) grains and the ternary eutectic, consisting of (Sn), Cu₆Sn₅ and Ag₃Sn, located in inter-dendritic regions. In the SAC305-2Bi and SAC305-4Bi alloys, a segregation of (Bi) particles was observed in addition to dendritic (Sn) and ternary eutectic. The (Bi) particles were located at the (Sn)Ag₃Sn interface in the inter-dendritic spaces of the (Sn) solid solution. The corrosion resistance of the as-cast alloys was studied in aqueous NaCl electrolyte (3.5 wt. %) using electrochemical methods. Open circuit potentials of the alloys were found to increase with increasing concentration of Bi. The highest corrosion current was found for the SAC305-1Bi alloy. It was observed that micro-galvanic cells at the Sn-Ag₃Sn interface were the initiating factors of corrosion in the SAC305-1Bi alloy. The corrosion activity of the SAC305-1Bi alloy is related to the high density of fine Ag₃Sn particles. The higher fraction of Ag₃Sn particles provided a dense network of local galvanic interaction sites, leading to the acceleration of the corrosion rate. The presence of discrete Bi precipitates in the SAC305-2Bi and SAC305-4Bi alloys, on the other hand, partially reduced the risk of galvanic corrosion. Since Bi has a higher standard electrode potential compared to Sn, the Bi/Ag₃Sn and Bi/Cu₆Sn₅ couples were less prone to corrosion. The corrosion mechanism of the SAC305-xBi alloys is discussed, and results are compared to previously studied SAC-Bi alloys. Full article

Aluminum alloy capsules play a critical role in shape control, heat transfer, and pressure transmission during the PM-HIP sintering of Al-based powders. As the weakest part of the capsule, the reliability of the welded joint is crucial for the safe operation of the HIP process and the quality of the final product. This study investigated the effects of two typical HIP temperatures on the evolution of second phases and texture. The results show that: (1) At 400 °C, suppressed Si diffusion retains a continuous, low-melting-point Al-Si eutectic network and needle-like secondary phases in the weld zone, thereby impeding residual stress relief. Compositional segregation in the heat-affected zone weakens grain boundary stability. The texture undergoes only limited recovery, with a strong <100> orientation retained and micro-strain not effectively relieved, restricting joint ductility. (2) At 510 °C, Si is sufficiently spheroidized, forming a bead-like structure. Needle-like second phases transform into globular/short-rod morphologies, disrupting the continuity of the brittle phases. Simultaneously, complete recrystallization is induced, resulting in a randomized texture and significant release of micro-strain, thereby improving microstructural homogeneity and plastic deformation capacity. This study suggests that the internal stress concentration arising from the low-melting-point eutectic phase and strong texture poses a failure risk for the capsule. Therefore, employing the 510 °C HIP process to achieve second-phase spheroidization and texture weakening can significantly mitigate this failure risk. Full article

High-strength Mg alloys always contain heavy RE solutes, which leads to the high cost of Mg alloys preventing commercial use. In this work, we developed a new high-performance Mg–3Nd–1Yb–0.6Zn–0.4Zr alloy with low RE content and investigated the effects of heat treatment on the microstructure and mechanical properties. The results show that the main secondary phase in the as-cast alloy is the eutectic Mg₁₂RE phase at grain boundaries. The average grain size is measured to be 24.6 μm. After solution treatment, the grain-boundary eutectic Mg₁₂RE phase is completely dissolved into the matrix, without obvious grain growth. The alloy exhibits an obvious age-hardening effect during aging at 200 °C, and its hardness reaches a peak at 15 h, with a hardness increment of ~31 HV. A high-density prismatic β′ phase is formed in the matrix after peak aging. The peak-aged alloy presents optimal mechanical properties, with ultimate tensile strength, yield strength and elongation of 282 MPa, 202 MPa and 6.8%, respectively, which are remarkably superior to those of typical alloys such as EV31A and WE43. Quantitative calculation of strengthening mechanisms indicates that age hardening is the dominant strengthening mechanism of the peak-aged alloy, and the precipitation strengthening contribution of prismatic β′ phase is 158 MPa, accounting for approximately 78% of the yield strength. Full article

Aluminum alloys are widely used in the automotive and aerospace industries due to their low density and very high specific strength, and high-pressure die casting (HPDC) allows us to mass-produce complex components despite porosity and microstructural heterogeneity. In this study, we examine the individual and combined effect of grain refinement (AlTi5B1), chemical modification (AlSr15), and T6 heat treatment on the microstructure, mechanical properties, and corrosion of ENAC 46000 alloy produced in cold-chamber HPDC. The material characteristics were assessed through hardness, tensile, fatigue, and corrosion testing as well as optical microscopy, SEM, and EDS measurements. The microstructural characteristics were found to be fine α-Al grains, and Sr modification transformed eutectic Si into a fibrous structure. T6 treatment dissolved coarse Al₂Cu phases into fine coherent precipitates. T6 heat treatment was the primary strengthening process and produced an increase in hardness of 59% (to 143 HB) compared to non-T6 conditions, while the fatigue resistance was still excellent in the as-cast state (1.16 × 10⁶ cycles). Moreover, the modified and T6-treated condition exhibited the lowest corrosion rate (15.3 × 10⁻³ mm/year). Therefore, because no single processing route is the best way to maximize all performance characteristics (as well as process efficiency), a multi-property evaluation should be performed to tailor treatment to the engineering service requirements. Full article

In hybrid wire arc additive manufacturing with interlayer friction stir processing (UAMFSP), refined microstructures are produced in aluminum alloy builds; however, the thermal parameters governing layer-resolved defect evolution remain poorly understood. In this study, a correlative mechanistic framework is presented in which post-peak cooling rate is identified as a plausible controlling factor for porosity evolution in UAMFSP Al 4043 three-layer walls. A multi-scale characterization is performed by employing infrared thermography, quantitative optical grain morphology analysis (N  =  10,346 grains, Layers 1–3), scanning electron microscopy from 250× to 35,000×, and image-based porosity quantification from calibrated SEM fields. This primary quantitative comparison is established between L1 and L3 only; Layer 2 is excluded from the 250× quantitative analysis owing to its thermally distinct cooling regime and is treated separately. A counterintuitive layer-dependent porosity gradient is reported, wherein the upper layer (L3) exhibited 80% higher porosity (2.90 ± 1.18%) and 107% higher pore density (4283  ±  900 pores/mm²) than the bottom layer (L1), despite recording a 26% lower peak FSP surface temperature (195.1 vs. 263.2 °C) (n = three fields per layer; Cohen’s d ≈ 1.7). Based on these results, the post-peak cooling rate, rather than peak temperature, is identified as a plausible controlling factor for void consolidation quality, as evidenced by the observation that L3 cools at −12.3 °C/s versus −16.2 °C/s for L1, which is consistent with prolonged high-temperature dwell and reduced plastic-flow-assisted pore closure in the upper layer. The anomalously rapid cooling of L2 (−46.9 °C/s), attributed to a bilateral thermal gradient between the substrate and the air-cooled free surface, places it in a thermally distinct regime; accordingly, L2 is utilized exclusively for high-magnification SEM characterization in this study. High-magnification SEM imaging (12,000×–35,000×) revealed a frequent spatial co-location of sub-micron pores with fragmented Al–Si eutectic particles, which is consistent with preferential void persistence near particle–matrix interfaces. Grain morphology also exhibits non-monotonic evolution with build height, with mean circularity following the order L3 (0.645) > L1 (0.621) > L2 (0.569), and the equiaxed grain fraction ranging from 25.5% (L2) to 36.1% (L3) (ANOVA: F = 56.2, p = 5.15 × 10⁻²⁵), while the mean equivalent grain diameter remained below 3.4 μm across all layers. Overall, the outcomes of this study establish post-peak cooling rate, rather than peak temperature, as a plausible controlling factor for void consolidation quality in UAMFSP builds, with the caveat that complete causal isolation requires controlled single-variable experiments. These outcomes are presented as a first mechanistic framework for this class of hybrid process and are intended to motivate targeted controlled experiments, subsurface thermal characterization, and expanded porosity sampling in future investigations of multi-layer additive–deformation manufacturing of Al-based alloys. Full article

xAl₃Zr/Al-5Cu-0.6Mn-0.15Ti composites were fabricated via an in situ reaction method, and the influence of Al₃Zr content on the microstructure and mechanical properties in both as-cast and T6-treated conditions was systematically investigated. The results reveal that the D0₂₃-Al₃Zr content increases in proportion to the K₂ZrF₆ addition level. Following T6 heat treatment, finely dispersed θ′-Al₂Cu precipitates were formed within the matrix, and the α-Al + θ-Al₂Cu eutectic network dissolved. The blocky Al₃Zr particles underwent spheroidization and could continuously exert a grain boundary pinning effect to suppress grain coarsening. After T6 heat treatment, the 4.5 wt.% Al₃Zr composite exhibited average ultimate tensile strengths of 324.44 MPa at room temperature and 123.38 MPa at 350 °C, corresponding to improvements of 8.56% and 23.31%, respectively, relative to the unreinforced base alloy. Following thermal exposure at 350 °C for 24 h, the composite exhibited less pronounced coarsening of the θ′-Al₂Cu precipitates compared with the base alloy, while the Al₃Zr particles retained their morphological and dimensional stability. Consequently, the reductions in both tensile strength and hardness were smaller than those observed for the base alloy. Analysis indicates that Al₃Zr particles significantly refine the α-Al grains and enhance the alloy’s thermal stability. The superior property retention is attributed primarily to the high thermal stability of the Al₃Zr particles, which preserve their dispersion-strengthening contribution at 350 °C, with the reduced θ′ coarsening as a contributing factor. The overall strengthening of the composite arises from the combined and largely independent contributions of Al₃Zr particle strengthening and θ′-Al₂Cu precipitation strengthening. Full article

Hot cracking in welding is a very complex phenomenon. It can happen in the weld metal zone during solidification but also in the heat-affected zone (HAZ). Hot cracking defects are material decohesion that occur at high temperatures along grain boundaries when the strain and strain rate exceed a certain level. The cracks can be internal or open to the surface in the weld bead. During a welding operation, different types of hot cracks can appear, such as hot cracking due to solidification, hot cracking due to liquation, hot cracking due to loss of ductility. The main factors favoring hot solidification cracking include the presence of residual elements and impurities, leading to the formation of a low-melting eutectic; the solidification mode; and mechanical restraints. This review paper gives an introduction to solidification cracking in stainless-steel welds, the weldability of the austenite grades, and the causes of solidification cracking occurrence. The main methods with which to detect and inspect cracks are investigated. Particular focus is placed on TIG (tungsten inert gas), also known as Gas Tungsten Arc Welding (GTAW). A review of the literature reveals that considerable progress has been made in terms of the improvement in the properties of the weld joint through the application of mitigation means and strategies. The effort made by researchers in understanding solidification cracking phenomena has been key to enhancing cracking resistance and ensuring the integrity of structures. Full article

This paper aims to analyse the microstructure and properties of the titanium- and boron-alloyed high-carbon medium-manganese 140Mn6Cr3TiB steel deposit before and after high-frequency mechanical impact (HFMI) treatment. XRD, SED, and EDS analyses were applied to evaluate the microstructural peculiarities of the studied deposit. Nanoindentation and scratch/sliding tests respectively revealed distinct correlations between the phase composition and the deformation/wear behaviour. HFMI results in the formation of the strain-induced ε- and α’-martensites (~66% and 3–6%, respectively), a significant grains/crystallites refinement (down to 31–54 nm), and dislocation density, which support essential hardening (by ~50%). The HFMI regime (load = 100 N, amplitude = 10 µm, and time = 60 s) was found to be the best, which led to the enhanced wear resistance (decreased wear volume) by ~4 times. The heterogeneous nature of the steel deposit creates a “shield-and-buffer” effect, where the hard eutectic framework resists penetration and tough matrix prevents brittle failure, maintaining a high tolerance to abrasion damage. The HFMI-hardening changed the wear mechanism from the ‘wedge/pile-up’ formation to ploughing. Thus, the HFMI shows a good efficiency in finishing the protective medium-manganese steel deposits of enhanced wear resistance to prolong the operation life of responsible parts. Full article

The work is a continuation of studies , focused on the development of fundamental principles of aluminum activation by low-melting metals forming eutectic alloys with fine-grained structure and limited solid solubility. The aim of this work is to investigate the mechanism and kinetics of the interaction of aluminum-based eutectic alloys with water and aqueous electrolytes. Analysis of phase diagrams of binary systems (Al–Ga, Al–In, In–Ga, Al–Sn, Sn–Ga, Al–Zn, Zn–Ga) shows that alloy composition governs surface heterogeneity and reactivity. Ternary and quaternary systems (Al–In–Ga, Al–Sn–Ga, Al–In–Sn–Ga) exhibit enhanced interaction with water due to increased heterogeneity, leading to the formation of numerous microgalvanic couples and accelerated aluminum dissolution. The process is characterized by the stationary potential of aluminum and involves coupled chemical, electrochemical, and topochemical stages described by the Avrami–Erofeev equation, with n ≈ 1.27–2.07. An increase in the In–Ga or In–Sn–Ga fraction reduces the activation energy: 9.1 kcal/mol (82% Al–9% Ga–9% Sn), 11.4 kcal/mol (92% Al–4% Ga–4% In), and 15.5 kcal/mol (91% Al–3% Ga–3% In–3% Sn). Full article

To address the demand for lightweight, high-performance Al-Si-Mg alloys in aerospace and automotive industries, this work proposes a novel synergistic strengthening strategy by combining rare-earth Y microalloying and in situ synthesized ZrB₂ nanoparticles to construct a hybrid reinforcement architecture. The effects of Y-ZrB₂ additions on the microstructure, crystallographic orientation evolution, and mechanical properties of Al-Si-Mg alloys were systematically investigated via XRD, SEM, EBSD, and tensile/hardness tests. Results show that compared with the base alloy and single-modified alloys, the co-addition of Y and ZrB₂ simultaneously enhances mechanical properties and optimizes grain structure. The optimal comprehensive performance is achieved at 0.3 wt.% Y + 2 wt.% ZrB₂ after T6 heat treatment, with ultimate tensile strength of 332.87 MPa, yield strength of 271.35 MPa, elongation of 16.24%, and Vickers hardness of 153.9 HV. Phase analysis and SEM-EDS confirm a synergistic coupling relationship between Y-rich phases and ZrB₂ nanoparticles. EBSD characterization reveals that Y-ZrB₂ modification has negligible effect on the morphology and crystallographic orientation stability of primary α-Al grains, but effectively regulates the lattice rotation, texture redistribution, and growth behavior of eutectic Si. At the optimal composition, the fraction of high-angle grain boundaries (HAGBs) reaches a maximum of 34.3%. Furthermore, the synergistic effect significantly increases the geometrically necessary dislocation (GND) density and reduces the Schmid factor of the dominant {111}⟨110⟩ slip system, thus enhancing dislocation strengthening and plastic deformation resistance. This work clarifies the intrinsic strength-ductility synergy mechanism of Y-ZrB₂ co-modified Al-Si-Mg alloys, paving a new pathway for the development of advanced lightweight aluminum alloys. Full article

Lead-based alloy has received widespread attention as a coolant in nuclear reactors. However, there is limited research on pure lead after solidification. In this study, a systematic investigation was conducted on the long-term evolution of the microstructure and physical properties of pure lead samples solidified under different cooling rates, with a comparative analysis against of lead–bismuth eutectic (LBE). Microscopic detection (using optical and electron microscopes), density measurement, and compressive mechanical testing were carried out. The study results show that during the long-term evolution process after solidification (at room temperature of 27 °C), pure lead samples spontaneously undergo recovery and recrystallization, with larger grain size and more uniform microstructure. The density of samples remains within a stable range. The yield strength of samples after solidification will gradually decrease over time. For example, after 180 days of evolution, the yield strength of the rapidly cooled sample (10 K/min) decreased from 4.879 MPa to 3.766 MPa. Full article