Search Results (3,097)

The 6xxx-series Al alloys have been used for decades because of their favorable strength-to-weight ratio, corrosion resistance, and fatigue performance. However, conventional welding techniques often induce localized weakening, as thermal effects modify the microstructure and compromise structural integrity. For nearly 70 years, AA4043 welding wire has been the primary choice for joining 6xxx-series Al alloys. Nevertheless, microstructural and mechanical property mismatches between the base metal and weld region remain key factors contributing to premature failure, while welding-induced defects further increase rupture susceptibility. Microalloying has emerged as an effective strategy for enhancing both the mechanical and thermal properties of aluminum alloys. In this study, rare-earth (RE) elements La and Ce were introduced into the AA4043 system to exploit their grain refining and mechanical strengthening capabilities. In addition, the effects of Sr modification were examined and compared with La-Ce addition. This work aims to elucidate the strengthening mechanisms associated with La-Ce-Ti microalloying in AA4043 welding wire, a topic that has rarely been systematically investigated. With 0.019Ti-0.02La-0.03Ce additions, the modified wire exhibited significant performance improvements, achieving an UTS of 204 MPa and a YS of 191 MPa—representing increases of 10.3% and 18.6%, respectively. Full article

Rubber components filled with carbon black are widely used in vehicles for sealing, preventing water ingress, and reducing vibration and aerodynamic noise. However, carbon particles increase the electrical conductivity of rubber. When a carbon-filled rubber part comes into contact with the metal car body, it may act as a cathode, accelerating metal corrosion via galvanic coupling. This study combined volume resistivity and zero-resistance ammeter (ZRA) measurements, resistometric corrosion monitoring, and accelerated corrosion testing to assess the effect of rubber conductivity on the corrosion degradation of painted car body panels in defects. More conductive rubber induced a higher galvanic current and accelerated paint delamination from defects. Real-time monitoring confirmed an earlier onset of corrosion and higher corrosion rates for steel coupled with conductive rubber. These findings emphasize the importance of using low-conductive rubber with resistivity from 10⁴ Ω·m to minimize the risk of galvanic corrosion of the car body. Full article

During the drilling operations of a shale gas well in Central China, a severe failure occurred in the pressure-resistant cylinder of the measurement while drilling (MWD) tool, with numerous microcracks observed on the outer surface of the cylinder. This significantly compromised the safety of the MWD tool and the reliability of the logging data. To determine the cause of the failure, macroscopic morphology analysis and physicochemical performance tests were conducted on the failed pressure-resistant cylinder, which is made of Cr20Ni11 (UNS 308) austenitic stainless steel. Additionally, scanning electron microscopy, X-ray energy dispersive spectroscopy, white light interferometry, and X-ray photoelectron spectroscopy were employed to analyze the morphology and chemical composition of the corrosion products and cracks, thereby identifying the cause of the corrosion failure. It is demonstrated that the physicochemical properties of the pressure-resistant cylinder comply with the specifications of relevant standards. Nevertheless, the size of non-metallic inclusions in the material reaches 100 μm, which significantly enhances the material’s susceptibility to stress corrosion cracking (SCC). Meanwhile, solid particles and high-concentration Cl⁻ present in the drilling fluid deteriorate the passive film formed on the substrate surface. EDS analysis reveals that the Cl⁻ content is measured to be 4.09 wt%, which induces pitting on the substrate with a maximum pitting depth of 13.5556 μm. Under the synergistic effect of stress and corrosion, the pressure-resistant cylinder experiences SCC failure initiated by Cl⁻; specifically, cracks nucleate at the bottom of the pitting pits and propagate along the radial direction. Full article

Stainless steels are commonly used in coastal structures and in seawater desalination and treatment systems, so understanding their corrosion behaviour under different salinity conditions is important to ensure the durability and reliability of the material. In this study, the behaviour of AISI 304L, AISI 316L, and 2205 duplex stainless steels (DSS) was tested in three media with different salinities: brackish water (BSW), seawater (SW), and concentrated seawater bittern (CSW). Testing was conducted using classical electrochemical methods (open circuit potential, linear, and potentiodynamic polarization) supplemented by surface analyses (optical microscopy, SEM/EDS, and optical profilometry). Corrosion resistance increased in the order AISI 304L < AISI 316L < 2205 DSS. Duplex steel 2205 performed best in all media: it exhibited the most positive open circuit potential, the highest polarization resistance, the lowest corrosion current density, and the widest passive range. Unexpectedly, CSW showed improved corrosion resistance compared to SW, which is explained by the reduced chloride content characteristic of seawater bittern after NaCl crystallisation and the presence of magnesium, calcium, and sulphate ions that promote the formation of protective deposits on the metal surface. Pronounced pitting was observed on AISI 304L steel in seawater, while surface degradation in brackish and concentrated seawater was significantly less, and 2205 DSS remained almost unchanged. The results obtained can serve as guidelines for the design and selection of materials for equipment and structures in industries operating in aggressive marine and coastal environments, such as desalination plants, shipbuilding, and energy systems. Full article

Grey cast iron brake discs are widely used in automotive applications due to their excellent thermal and mechanical properties. However, stricter environmental regulations such as Euro 7 demand improved surface durability to reduce particulate emissions and corrosion-related failures. This study evaluates multilayer coatings fabricated by Laser Metal Deposition (LMD) as a potential solution. Two multi-layer systems were investigated: 316L + (316L + WC) and 316L + (430L + TiC), which were primarily reinforced with ceramic additives to increase wear resistance, with their influence on corrosion being critically evaluated. Electrochemical tests in 5 wt.% NaCl solution (DIN 17475) revealed that the 316L + (316L + WC) coating exhibited the lowest corrosion current density and most stable passive behavior, consistent with the inherent passivation of the austenitic 316L matrix. In contrast, the 316L + (430L + TiC) system showed localized corrosion associated with micro-galvanic interactions, despite the chemical stability of TiC particles. Post-corrosion SEM and EDS confirmed chromium depletion and chloride accumulation at corroded sites, while WC particles exhibited partial dissolution. These findings highlight that ceramic reinforcements do not inherently improve corrosion resistance and may introduce localized degradation mechanisms. Nevertheless, LMD-fabricated multilayer coatings demonstrate potential for extending brake disc service life, provided that matrix–reinforcement interactions are carefully optimized. Full article

Octachlorinated metal phthalocyanines (MPcCl₈, M = Co, Zn, VO) represent an underexplored class of functional materials with promising potential for chemiresistive sensing applications. This work is the first to determine the structure of single crystals of CoPcCl₈, revealing a triclinic (P-1) packing motif with cofacial molecular stacks and an interplanar distance of 3.381 Å. Powder XRD, vibrational spectroscopy, and elemental analysis confirm phase purity and isostructurality between CoPcCl₈ and ZnPcCl₈, while VOPcCl₈ adopts a tetragonal arrangement similar to its tetrachlorinated analogue. Thin films were fabricated via physical vapor deposition (PVD) and spin-coating (SC), with SC yielding highly crystalline films and PVD resulting in poorly crystalline or amorphous layers. Electrical measurements demonstrate that SC films exhibit n-type semiconducting behavior with conductivities 2–3 orders of magnitude higher than PVD films. Density functional theory (DFT) calculations corroborate the experimental findings, predicting band gaps of 1.19 eV (Co), 1.11 eV (Zn), and 0.78 eV (VO), with Fermi levels positioned near the conduction band, which is consistent with n-type character. Chemiresistive sensing tests reveal that SC-deposited MPcCl₈ films respond reversibly and selectively to ammonia (NH₃) and hydrogen sulfide (H₂S) at room temperature. ZnPcCl₈ shows the highest NH₃ response (45.3% to 10 ppm), while CoPcCl₈ exhibits superior sensitivity to H₂S (LOD = 0.3 ppm). These results suggest that the films of octachlorinated phthalocyanines produced by the SC method are highly sensitive materials for gas sensors designed to detect toxic and corrosive gases. Full article

Titanium-based bulk metallic glasses (BMGs) offer high strength, lower stiffness than Ti-6Al-4V, and superior corrosion resistance, but conventional Ti glass-forming systems often contain toxic Ni, Be, or Cu. This work investigates five novel Ti-based alloys free of these elements—Ti₄₂Zr₃₅Si₅Co_12.5Sn_2.5Ta₃, Ti₄₂Zr₄₀Ta₃Si₁₅, Ti₆₀Nb₁₅Zr₁₀Si₁₅, Ti₃₉Zr₃₂Si₂₉, and Ti_65.5Fe_22.5Si₁₂—synthesized by arc melting and suction casting. Single-track laser remelting using a selective laser melting (SLM) system was performed to simulate additive manufacturing and examine microstructural evolution, cracking behavior, mechanical properties, and cytocompatibility. All alloys solidified into fully crystalline α/β-Ti matrices with Ti/Zr silicides; no amorphous structures were obtained. Laser remelting refined the microstructure but did not induce glass formation, consistent with the known limited glass-forming ability of Cu/Ni/Be-free Ti systems. Cracking was observed at low laser energies but crack density decreased as laser energy increased. Cracks were eliminated above ~0.4 J/mm for most alloys. Ti₄₂Zr₃₅Si₅Co_12.5Sn_2.5Ta₃ exhibited the lowest stiffness (~125 GPa), while Ti₆₀Nb₁₅Zr₁₀Si₁₅ showed the highest due to silicide precipitation. Cytotoxicity tests (ISO 10993-5) confirmed all alloys to be non-toxic, with some extracts even enhancing fibroblast proliferation. This rapid laser-remelting approach enables cost-effective screening of Ti-based glass-forming alloys for additive manufacturing. Ti–Zr–Ta–Si systems demonstrated the most promising properties for further testing using the powder bed method. Full article

Pipeline steels under cyclic loading in corrosive environments are prone to wear and corrosion–wear synergy. Low-dilution, high-reliability Ni-based Cold Metal Transfer (CMT) overlays are therefore required to ensure structural integrity. In this work, three overlay architectures were deposited on L415QS pipeline steel: a single-layer ERNiFeCr-1 coating, a double-layer ERNiFeCr-1/ERNiFeCr-1 coating, and an ERNiCrMo-3 interlayer plus ERNiFeCr-1 working layer. The microstructure, interfacial composition gradients, and dry sliding wear behavior were systematically characterized to clarify the role of interlayer design. The single-layer ERNiFeCr-1 coating shows a graded transition from epitaxial columnar grains to cellular/dendritic and fine equiaxed grains, with smooth Fe dilution, Ni–Cr enrichment, and a high fraction of high-angle grain boundaries, resulting in sound metallurgical bonding and good crack resistance. The double-layer ERNiFeCr-1 coating contains coarse, strongly textured columnar grains and pronounced interdendritic segregation in the upper layer, which promotes adhesive fatigue and brittle spalling and degrades wear resistance and friction stability. The ERNiCrMo-3 interlayer introduces continuous Fe-decreasing and Ni-Cr/Mo-increasing gradients, refines grains, suppresses continuous brittle phases, and generates dispersed second phases that assist crack deflection and load redistribution. Under dry sliding, the tribological performance ranks as follows: interlayer + overlay > single-layer > double-layer. The ERNiCrMo-3 interlayer system maintains the lowest and most stable friction coefficient due to the formation of a dense tribo-oxidative glaze layer. These results demonstrate an effective hierarchical alloy-process design strategy for optimizing Ni-based CMT overlays on pipeline steels. Full article

Mild steel readily corrodes in acidic environments, and most industrial corrosion inhibitors are synthetic, often toxic, and environmentally harmful. In this study, electrocatalytically active Cd–Cs mixed oxide nanocomposites were synthesized via a green route using an aqueous extract of Trachyspermum ammi (ajwain) seeds as a natural reducing, stabilizing, and capping agent. This eco-friendly method eliminates harsh chemicals while producing nanomaterials with active surfaces capable of facilitating electron transfer and scavenging free radicals. Incorporation of cesium introduces basic, electron-rich sites on the Cd–Cs oxide surface, serving as inhibition promoters that enhance charge transfer at the metal/electrolyte interface and assist in the formation of an adsorbed protective film on steel. The nanocomposites were optimized by adjusting precursor ratios, pH, temperature, and reaction time, and were characterized by UV–Vis, FTIR, XRD, SEM–EDS, HR-TEM EDS, BET, DLS, XPS, and zeta potential analyses. Strong antioxidant activity in ABTS and DPPH assays confirmed efficient catalytic quenching of reactive radicals. Corrosion inhibition potential, evaluated by using potentiodynamic polarization, electrochemical impedance spectroscopy, and gravimetric analysis in 0.5 M HCl, shows an inhibition efficiency of 90–91%. This performance is associated with an electrocatalytically active, adsorbed barrier layer that suppresses both anodic dissolution and cathodic hydrogen evolution, which depicts mixed-type inhibition. Overall, the biosynthesized Cd–Cs mixed oxide nanocomposites function as promising green synthesized nanomaterial with dual antioxidant and corrosion-inhibiting functions, underscoring their potential for advanced surface engineering and corrosion protection. Full article

Metallic implants used in orthopedics, such as titanium alloys, possess excellent mechanical strength but suffer from corrosion and poor bio-integration, often necessitating revision surgeries. Bioactive coatings, particularly hydroxyapatite, can enhance implant osteoconductivity, but high-purity synthetic hydroxyapatite is costly. This study investigates the development and characterization of a low-cost, biocompatible coating using hydroxyapatite derived from an unconventional natural source dromedary bone applied onto a titanium substrate via plasma spraying. Hydroxyapatite powder was synthesized from dromedary femurs through a thermal treatment process at 1000 °C. The resulting powder was then deposited onto a sandblasted titanium dioxide substrate using an atmospheric plasma spray technique. The physicochemical, structural, and morphological properties of both the source powder and the final coating were comprehensively analyzed using Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray Diffraction, and Fourier-Transform Infrared Spectroscopy. Characterization of the powder confirmed the successful synthesis of pure, crystalline hydroxyapatite, with Fourier-Transform Infrared Spectroscopy analysis verifying the complete removal of organic matter. The plasma-sprayed coating exhibited good adhesion and a homogenous, lamellar microstructure typical of thermal spray processes, with an average thickness of approximately 95 μm. X-ray Diffraction analysis of the coating revealed that while hydroxyapatite remained the primary phase, partial decomposition occurred during spraying, leading to the formation of secondary phases, including tricalcium phosphate and calcium oxide. Scanning Electron Microscopy imaging showed a porous surface composed of fully and partially melted particles, a feature potentially beneficial for bone integration. The findings demonstrate that dromedary bone is a viable and low-cost precursor for producing bioactive hydroxyapatite coatings for orthopedic implants. The plasma spray method successfully creates a well-adhered, porous coating, though process-induced phase changes must be considered for biomedical applications. Full article

Mg alloys show great potential in biomedical fields due to superior biocompatibility and biodegradability. Additive manufacturing (AM) provides opportunities in fabricating metallic implants with complex geometries while inherent defects during AM limit its further applications. In this work, laser shock peening (LSP) was employed as a post-processing technique to tailor the surface integrity and corrosion resistance of additively manufactured AZ91 Mg alloy by selective laser melting (SLM). The surface morphology, microstructure and porosity, surface hardness and residual stress, and corrosion resistance of the SLMed alloy before and after LSP were examined. The results show that a gradient structure is formed along the depth direction after LSP and high-density dislocations and high-fraction low-angle grain boundaries are induced. The porosity is gradually reduced in number and size and the highest density of 1.794 g/cm³ is obtained after two impacts of LSP. The surface hardness and residual compressive stress both increase with LSP number and the highest values of 135.26 HV and 40.13 MPa after four impacts, respectively. All of the SLMed alloy samples show improved corrosion resistance after LSP. This work provides a promising route for enhancing the performance of additively manufactured Mg alloys through laser materials surface modification. Full article

In this paper, three quinoline-based quaternary ammonium salts were successfully synthesized, with quinoline, 8-hydroxyquinoline, and 8-methoxyquinoline used as raw materials, and benzyl chloride as a quaternization reagent. The as-synthesized quaternary ammonium salts showed excellent corrosion inhibition performance in the acidic environment based on the derivative’s cationic activity, heteroatom electron effect, and conjugated aromatic system. Specifically, the methoxy-containing product exhibited the highest corrosion inhibition efficiency of 96.92%. The quantitative calculation analysis demonstrated that the addition of methoxy and hydroxyl groups facilitated the quaternization reaction and enhanced the adsorption of the quaternary ammonium salts on the metal surface. The molecular dynamics study indicated that the three corrosion inhibitors adsorbed on the metal surface in a parallel orientation. This study has a certain reference significance for the research and development of quaternary ammonium salt as corrosion inhibitors in an acidic environment. Full article

Titanium alloys are widely employed for biomedical implants due to their high strength, biocompatibility, and corrosion resistance, yet their lack of intrinsic antibacterial activity remains a major limitation. Incorporating copper, an antibacterial and β-stabilising element, offers a promising strategy to enhance implant performance. This study investigates Ti-6Al-7Nb modified with 1–9 wt.% Cu via in situ alloying during metal-based laser powder bed fusion (PBF-LB/M), with the aim of assessing processability, microstructural evolution, and mechanical properties. Highly dense samples (>99.9%) were produced across all Cu levels, though chemical homogeneity strongly depended on processing parameters. Increasing Cu content promoted β-phase stabilisation, Ti₂Cu precipitation, and pronounced grain refinement. Hardness and yield strength increased nearly linearly with Cu addition, while ductility decreased sharply at ≥5 wt.% Cu due to intermetallic formation, hot cracking, and brittle fracture. These results illustrate both the opportunities and constraints of rapid alloy screening via PBF-LB/M. Overall, moderate Cu additions of 1–3 wt.% provide the most favourable balance between mechanical performance, manufacturability, and potential antibacterial functionality. These findings provide a clear guideline for the design of Cu-functionalised titanium implants and demonstrate the efficiency of in situ alloy screening for accelerated materials development. Full article

This study systematically investigates the catalytic degradation performance and reaction mechanism of Fe₈₀P₁₃C₇ Metal Glass (MG) in a Fenton-like system for the removal of Methylene Blue (MB). Kinetic experiments on degradation reveal that under acidic conditions (pH = 3), Fe₈₀P₁₃C₇ MG exhibits exceptional catalytic activity, achieving complete degradation of a 50 mg/L MB solution within 12 min. Its degradation rate significantly surpasses that of Fe₇₈Si₉B₁₃ MG and commercially available ZVI powder. Key parameters such as catalyst dosage, H₂O₂ concentration, solution pH, and initial dye concentration were systematically examined to determine the optimal reaction conditions. The characterization results indicate that Fe₈₀P₁₃C₇ MG maintains high activity even after multiple cycles of use, attributed to surface selective corrosion and crack formation during the reaction process. This “self-renewal” mechanism continuously exposes fresh active sites. Mechanistic studies confirm that the degradation process is driven by an efficient redox cycle between Fe²⁺/Fe³⁺ within the material, ensuring sustained and stable generation of •OH, which ultimately leads to the complete mineralization of MB molecules. This research provides solid experimental and theoretical foundations for the application of Fe₈₀P₁₃C₇ MG in dye wastewater treatment. Full article

The present study assesses the effectiveness of the indole-type alkaloid Yohimbine (YHB) as a green corrosion inhibitor for OLC52 carbon steel and Al in 0.25/0.25 mol L⁻¹ acetic acid/potassium acetate solutions relevant for de-icing applications. Electrochemical techniques, including cyclic and linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy have been combined with the evaluation of adsorption isotherms and molecular modeling calculations. YHB significantly decreases the corrosion rate for both metals, attaining inhibitory efficiencies of up to 95% for OLC52 and 91% for Al at 298 K, while maintaining high protection efficiency even at higher temperatures. The Langmuir adsorption model and the values of $∆G_{ads}^o$ between −31 and −41 kJ mol⁻¹ indicate a spontaneous adsorption process defined by a mixed physicochemical mechanism, resulting in the formation of a compact protective film. Quantum molecular descriptors support the ability of YHB molecules to interact with metal surfaces via donor–acceptor interactions and electrostatic interactions. The findings demonstrate the potential of YHB as an environmentally friendly inhibitor for the protection of ferrous and non-ferrous alloys in mildly acidic acetic/acetate media used in de-icing solutions. Full article