Search Results (304)

This Special Issue presents recent advances in the production, modelling, processing, and characterization of advanced industrial materials, highlighting the diversity and sophistication of contemporary research discussing metallic, polymeric, composite, and nano-structured systems. The collected contributions address key challenges in materials science, ranging from surface quality control, the development of novel machining and fabrication tools, and optimization of thermoplastic composite consolidation, to provide fundamental insights into additive manufacturing, rheology, and constitutive modelling. The showcased studies introduce innovative approaches to metrology, including advanced optical, fluorescence, and X-ray scattering techniques for characterizing nano-particles, microstructures, and thermal properties. The presented research also features investigations into the welding of dissimilar steels, binder jetting of stainless steel, and the influence of heat treatment on functional steel performance, alongside environmentally oriented research on natural-fibre energy devices and bio-based polymer composites. Further research topics include defect structures in doped crystals, low-temperature synthesis of oxide films, and mechanical behaviour of steels under extreme conditions. Collectively, these articles demonstrate the strong synergy between experimental methods, computational modelling, and industrial applications, underscoring the continued progress in materials reliability, surface engineering, and advanced manufacturing technologies. This Special Issue therefore provides a comprehensive overview of current trends and emerging directions, offering valuable methodological and conceptual insights in the field. Full article

The future of reinforcing steel bars (rebar) is being shaped by technological advancements, sustainability initiatives, and evolving construction practices. Welding of rebar has a significant and evolving influence on construction practices, particularly with trends emphasizing speed, precision, and prefabrication. On the other hand, the variability in mechanical response depends not only on the chemical composition but also on the manufacturing and welding process. This study analyzed five commercial brands of ASTM A706 reinforcing steel rods available in the Ecuadorian market with different diameters (12, 14, 16, and 18 mm) subjected to tensile and bending tests. A total of 228 specimens were analyzed, and 114 samples were welded by shielded metal arc welding process using an E8018-C3 electrode, preparing the joint with a simple V-bevel at 45°. The tensile tests results allow for a comparison between the welded and unwelded steel bars, where it is identified that the welding process generates a slight decrease in the mechanical properties and increases the variability in the results, although it is emphasized that these variations do not affect compliance with the standards, since all the samples meet the mechanical strength requirements by being within the limits established by the ASTM A706/A706M standard. Full article

The 2000 series aluminium alloys are an attractive option for lightweight structures, but solidification cracking in fusion welding remains an issue in additive manufacturing technologies. Al-Cu-Li alloys, in particular, have gained considerable attention due to their excellent strength-to-weight ratio and corrosion and fatigue resistance, making them highly suitable for aerospace components. Nevertheless, their narrow solidification range makes them highly susceptible to cracking, porosity formation, and elemental evaporation during fusion-based AM processes. These challenges underscore the necessity for advanced processing technologies and the development of suitable feedstock materials to ensure weld integrity and optimal performance. Although Al–Cu–Li alloys are highly valued in the aerospace sector, the application of wire arc additive manufacturing (WAAM) is currently limited by the lack of commercially available wire compositions. This study focuses on the use of powder metallurgy Al-Cu-Li wires in wire arc additive manufacturing, specifically using plasma metal deposition technology, to explore welding characteristics. This research demonstrates the development of an alternative wire using powder metallurgy for WAAM. Powder metallurgy wires were deposited on 5053 and 7075 aluminium substrates, and their microstructure, chemical composition, and mechanical properties were analysed. Key findings include significant elemental losses of Li and Cu during deposition—approximately 55% and 25%, respectively—as well as noticeable variations in microstructure, porosity, and grain morphology, depending on the substrate. Deposits on the 5083 aluminium exhibited more equiaxed grains and a higher chemical homogeneity compared to those on the 7075 substrate. This work establishes a link between material design and additive manufacturing by demonstrating that powder metallurgy Al–Cu–Li wires can be effectively processed by WAAM, achieving controlled elemental losses and a uniform microstructure that enhances weld integrity in aerospace components. Full article

Air suspension components are critical elements of automotive chassis and are commonly fabricated by welding 6061-T6 aluminum using 4043 filler wire with the cold metal transfer (CMT) process. Variations in vehicle architecture necessitate different groove angles and matching parameter windows. This study aims to elucidate how groove angle and heat input govern weld quality to inform process optimization. Two groove angles (120° and 90°) were investigated under distinct heat-input conditions (denoted 120-H and 90-L). Characterization covered chemical composition, macroscopic morphology, porosity, microstructure, hardness, and mechanical properties. The key novelty lies in elucidating the relationship between liquation cracking and metal flow lines, which jointly govern crack propagation. Integrating evidence from porosity measurements, crack characterization, and numerical simulations indicates that the 120-H parameter set requires further optimization. Overall, the results underscore the pivotal roles of groove angle and heat input in CMT welding of 6061-T6 aluminum and provide a basis for process parameter optimization in air suspension manufacturing. Full article

In this study, two types of submerged arc welding (SAW) wires were prepared—one without cerium (Ce) and another containing 0.14 wt.% Ce. Deposition experiments were carried out on corrosion-resistant crude oil storage tank steel plates using a multi-layer, multi-pass welding process. Through a combination of microstructural characterization techniques, including optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM), along with mechanical property testing, a systematic investigation was conducted to evaluate the influence of Ce on the weld metal microstructure and its impact toughness at −20 °C. The results reveal that Ce introduced via the welding wire into the weld seam refines and disperses inclusions, leading to the formation of composite inclusions primarily composed of Ce₂O₃, Ce₂O₂S, and CeS. These Ce-enriched inclusions serve as heterogeneous nucleation sites, increasing the area fraction of acicular ferrite (AF) within the weld columnar grain region from 52% to 83%, and within the heat-affected zone from 20% to 37%. Correspondingly, the proportions of blocky and polygonal ferrite decrease, while the size of martensite/austenite (M/A) constituents is reduced. The addition of Ce thus diminishes the size of hard phase inclusions and M/A constituents in the weld metal, enhancing the critical fracture stress and increasing the energy required for crack initiation. Meanwhile, the higher proportion of AF elevates the density of high-angle grain boundaries, thereby improving crack propagation resistance. These combined effects raise the −20 °C impact energy of the weld metal from 117 J to 197 J. Full article

Joining dissimilar metals, such as aluminum and steel, presents an attractive option for creating lightweight yet durable structures. However, challenges arise from the formation of brittle intermetallic compounds (IMCs) at the interface of dissimilar joints, which significantly impact joint strength under load and often lead to brittle failure. This research elaborates on how an S-shaped Al/Steel interface made by a modified friction stir welding (FSW) process mitigates the detrimental effect of IMC thickening on joint strength. This study aims to explore the effects of various post-weld heat treatments on steel and aluminum joints produced through FSW (100–400 °C for 30–90 min). Al/steel FSW joints were characterized by SEM/EDS for interface microstructure and composition, microhardness mapping, tensile testing, and fractography. Any post-weld heat treatment above the temperature of 100 °C caused a drop in joint strength from 2400 N to 1800 N due to the elimination of protrusions in the IMC layer. Further post-weld heat treatment had a negligible effect on the joint strength due to an S-shaped interface. A finite element simulation using a cohesive model for the joint interface is used to study the fracture mechanism of the joint. Both experimental observations and simulation results suggest that the portion of the S-shaped interface perpendicular to the loading direction acts as an initiation site of fracture and fails in a brittle manner. The top and bottom of the interface, which are inclined to the loading direction, fail in a ductile manner with noticeable plastic deformation in the steel adjacent to the interface. The proposed method for FSW of aluminum to steel significantly improves joint durability at elevated temperatures, particularly up to 400 °C. Full article

This paper presents results from an extensive study on laminated timber beams manufactured without adhesives or metal fasteners. The use of such elements enables the implementation of the 4R principles in construction (Reduce, Reuse, Recycle, Repair). Prior to the testing of beam elements, tests were conducted on embedment strength of wooden dowels in comparison with conventional steel ones. The specimens varied in dowel diameter and in the angle of applied load relative to the grain direction. In addition to mechanically inserted dowels, an innovative dowel-welding method was examined. Welding enhances the bonding between lamellas, thereby improving overall mechanical performance. Further investigations involved beams with lamellas joined by dowels of different diameters, spacing, orientation, and installation methods. Experimental results were compared with analytical models for composite beams. The study showed that, except through the entire height of the beam section, it is possible to use dowels that connect only two lamellas, which is important for production. Dowels placed at 45° in relation to the lamella fibers showed approximately 20% greater capacity. It is also important to mention that study shows how welded dowels are only useful when they have larger diameters because then they achieve a significant level of cohesion. Full article

Thermoplastic composites are growing in popularity in the aerospace and automotive industries; they enable weldable and recyclable structures. Resistance welded hybrid thermoplastic and metal joints are attractive for rapid assembly, but the thermal mismatch between metals and polymers introduces residual stresses, which can drive edge debonding and compromise durability. This study presents fabricated single-lap PC/CF–Al7075 coupons with measured mid-span bow resulting from welding, evaluated bond quality by step-heating thermography, and an evaluated framework for residual stress prediction using Ansys complemented by a bimetal analytical check. Three thermal cycles were examined with different temperature gradients (200, 220, 240 °C): the measured bow was 16.5 mm and remained constant, whereas analytical calculation increased with ΔT similarly to the FEM prediction. The current FEM under predicted the bow (Mean Absolute Percentage Error is 21%), showing stress contours that decay with distance from the bond and revealing pronounced peaks in both σ_xx and σ_zz components at weld edges, consistent with shear-lag theory. FEM returned edge-peaked peel rising from 43 to −64 MPa and σ_xx was up to 12% more compressive than analytical calculation; an effective CF/PC CTE of 1.5 × 10⁻⁶ K⁻¹ reconciled curvature with test better than catalogue values. The temperature insensitive bow is attributed to polycarbonate flow/viscoelastic relaxation above Tg and hot relaxation in aluminum, with effects not represented in the elastic models. Edge peel and shear govern initiation risk. Full article

Friction stir additive manufacturing (FSAM) is a promising solid-state technique for fabricating high-strength aluminum alloys, such as Al-7075, which are difficult to process using conventional melting-based additive manufacturing (AM) methods. This study investigates the mechanical properties and tool wear behavior of seven-layered Al-7075 multi-layered composites reinforced with silicon carbide (SiC) and titanium carbide (TiC) fabricated via FSAM. Microstructural analysis confirmed defect-free multi-layered composites with a homogeneous distribution of SiC and TiC reinforcements in the nugget zone (NZ), although particle agglomeration was observed at the bottom of the pin-driven zone (PDZ). The TiC-reinforced composite exhibited finer grains than the SiC-reinforced composite in both as-welded and post-weld heat-treated (PWHT) conditions, achieving a minimum grain size of 1.25 µm, corresponding to a 95% reduction compared to the base metal. The TiC-reinforced multi-layered composite demonstrated superior mechanical properties, attaining a microhardness of 93.7 HV and a UTS of 263.02 MPa in the as-welded condition, compared to 88.6 HV and 236.34 MPa for the SiC-reinforced composite. After PWHT, the TiC-reinforced composite further improved to 159.12 HV and 313.46 MPa UTS, along with a higher elongation of 11.14% compared to 7.5% for the SiC-reinforced composite. Tool wear analysis revealed that SiC reinforcement led to greater tool degradation, resulting in a 1.17% weight loss. These findings highlight the advantages of TiC reinforcement in FSAM, offering enhanced mechanical performance with reduced tool wear in multi-layered Al-7075 composites. Full article

This study investigates two-sided pulsed-periodic laser welding of three-layer metal–polymer–metal (MPM) composite sheets composed of galvanized dual-phase steel (DPK 30/50+ZE) as outer layers and a polypropylene–polyethylene (PP–PE) core. Welding was performed using a Rofin StarWeld Performance pulsed Nd:YAG laser with controlled parameters: pulse energy (30–32 J), duration (6–8 ms), and frequency (up to 1 Hz). High-quality welds were achieved with penetration depths reaching 70% of the outer metal layer thickness and minimal defects. Microscopic analysis revealed distinct fusion and heat-affected zones (HAZ) with no evidence of cracks or porosity, indicating stable thermal conditions. Mechanical testing showed that the welded joints attained a tensile strength of approximately 470 MPa, about 80% of the ultimate tensile strength of the base metal, with an average elongation of 0.6 mm. These results confirm the structural integrity of the joints. The observed weld morphology and microstructural features suggest that thermal conditions during welding significantly affect joint quality and HAZ formation. The study demonstrates that strong, defect-free joints can be produced using basic beam-shaping optics and outlines a pathway for further improvement through the integration of diffractive optical elements (DOEs) to enhance spatial-energy control in multilayer structures. Full article

The article presents a study of the possibilities for restoring the working surfaces of molds for high-pressure casting of non-ferrous metals by laser surfacing using a filler material. Test specimens with parameters of real forming elements were manufactured. The influence of nitriding on welded layers and basic material was studied in comparison with one without nitriding. The X-ray diffraction method was used to obtain the phase composition of the surface of the samples in areas submitted to nitriding. Scanning electron microscopy (SEM) was used to determine the microstructure of the nitriding layers, welded layers and bulk material. Energy-dispersive X-ray spectrometry (EDX) was applied to investigate the chemical composition in the welded and nitrided zone. Mechanical property means of microhardness measurements were studied. Four zones were identified after nitriding in the weld area. The first zone closest to the surface with a thickness of 0.025 mm is characterized by a higher microhardness, which reaches 700 HV. The second zone, which is part of the diffusion zone, is 0.1 mm thick, and it is characterized by the same size grains with a similar shape and microhardness, which reaches 600 HV. The microhardness measured in the welded zone after nitriding is 50% greater than that without nitriding. The thickness of the diffusion zone in 1.2343 steel reaches about 0.15 mm, and the microhardness is about 900 HV near the edge, but quickly decreases to 400 HV. Full article

Part segmentation can be used to overcome limitations of additive manufacturing (AM) processes such as Direct Energy Deposition of Metals (DED). In this case subparts of soft martensitic steel 1.4313 produced by conventional manufacturing (CM) and AM are joined by laser welding. This paper reports the difference in thermal conductivity of conventional and additive manufactured parts. The thermal conductivity was calculated from the thermal diffusivity, the specific heat, and the bulk density. Furthermore, the temperature was measured during welding and the microstructure analyzed. The far field temperature was measured using eight K-type thermocouples and the microstructure was analyzed by metallography and light microscopy. The results showed that the thermal conductivity of AM material is 8% lower and therefore the heating rate 5% lower compared to CM material. The lower thermal conductivity is explained in the literature by its higher dislocation density, unfavorable alloying element distribution and a lower rest austenite content. AM introduces structural complexity that hampers electron and phonon transport, thereby reducing the thermal conductivity despite similar base chemical compositions. The heat-affected zone is only clearly visible on the CM side due to carbide formation. In DED parts, it comes to different phases in non-equilibrium states, which complicates the identification of carbides and the HAZ. The findings are important for the design of hybrid components to improve the the joint integrity and functionality of hybrid parts. Full article

In high-altitude corrosive environments, weathering steel is widely applied due to its excellent corrosion resistance. However, the welded joint regions, where the chemical composition and microstructure undergo changes, are susceptible to the corrosion-induced degradation of mechanical properties. This study investigates the corrosion–mechanical synergistic degradation behavior of a 16 mm thick Q500 qENH base metal and its V-type and Y-type welded joint specimens. Periodic immersion corrosion tests were conducted to simulate plateau atmospheric conditions, followed by mechanical performance evaluations. Corrosion metrics—including corrosion rate, cross-sectional loss, penetration depth, and corrosion progression speed—were analyzed in relation to mechanical indicators such as the fracture location, yield load, ultimate load, yield strength, and tensile strength at varying exposure durations. The results indicate that the corrosion process exhibits distinct layering, with a two-stage characteristic of rapid initial corrosion followed by slower progression. Welded joints consistently exhibit higher corrosion rates than the base metal, with the rate difference evolving nonlinearly in an “increase–decrease–stabilization” trend. After corrosion, the mechanical performance degradation of welded joint specimens is more severe than that of base metal specimens. Full article

Ship repair is hazardous, often presenting unsuitable working areas and risks due to the ship’s configuration. Welding tasks are particularly dangerous due to the high temperatures generated, high enough to melt the metal in structural elements, bulkheads, linings, and tanks. This study investigates the consequences of temperature distribution during the welding of naval plates and proposes some accident prevention measures. Industry working conditions were reproduced, including the materials, procedures, and tools used, as well as the certified personnel employed. DH 36-grade naval steel, with a composition of C max. 0.18%, Mn 0.90–1.60%, P 0.035%, S 0.04%, Si 0.10–0.50%, Ni max 0.4%, Cr max 0.25%, Mo 0.08%, Cu max 0.35%, Cb (Nb) 0.05%, and V 0.1%, was welded via FCAW-G (Gas-Shielded Flux-Cored Arc Welding), selected for this study because it is one of the most widely practiced in the naval industry. The main sensor used in the experiments was an FLIR model E50 thermographic camera, and thermal waxes were employed. The results for each thickness case are presented in both graphical and tabular form to provide accurate and actionable guidelines, prioritizing safety. After studying the butt jointing of naval plates of various thicknesses (8, 10, and 15 mm), safe distances to maintain were proposed to avoid risks in the most unfavorable cases: 350 mm from the welding seam to avoid burn injuries to unprotected areas of the body and 250 mm from the welding seam to avoid producing flammable gases. These numbers are less accurate but easier to remember, which prevents errors in the face of hazards throughout a long working day. Full article

This paper describes the development of a new hybrid composite for the metal joints of aluminium and glass fibre composite adherents. The aluminium adherend is manufactured using friction stir-formed studs that are inserted into the composite adherend in the through-thickness direction during the composite manufacturing process, where the dry fibres are displaced to accommodate the studs before the resin infusion process. The materials used were AA6082-T6 aluminium and plain-woven E-glass fabric reinforced epoxy, with primary applications in naval vessels. This joining approach offers a cost-effective solution that does not require complicated onsite welding. The joint design was developed based on a simulation test program with finite element analysis, followed by experimental characterisation and validation. The design solution was analysed in terms of the force displacement response, sequence of load transfer, and characterisation of the joint failure modes. Full article