Search Results (2,581)

This study investigates the effect of sinusoidal arc oscillation frequency on bead geometry accuracy in Cold Metal Transfer-based Wire Arc Additive Manufacturing (CMT-WAAM) of the Al-4043 alloy. Single-pass depositions were performed at frequencies of 0–4 Hz (1.0 mm amplitude) and 0–5 Hz (1.5 mm amplitude), followed by multi-pass, multi-layer builds using optimal parameters. Cross-sectional analysis revealed that a 3–4 Hz frequency window minimizes wetting angle asymmetry and maximizes bead width-to-height ratio. At 4 Hz with 1.5 mm amplitude, the arc oscillation yielded a symmetric wetting angle deviation of only 1.22°. Multi-layer builds indicated that oscillation improved the effective cross-sectional area ratio from 75% (non-oscillating) to 82%, suggesting superior geometric efficiency and reduced material waste in post-machining. Full article

Traditional bone plates provide reliable fracture fixation; however, their high stiffness can cause stress shielding, thereby reducing mechanical stimulation of the bone tissue and slowing its regeneration. The biomechanical performance of a titanium plate with a localized porous structure for osteosynthesis of the radial shaft was investigated in this study. Three designs were considered: a solid plate and two plates with localized porous regions measuring 10 × 10 mm and 10 × 15 mm. The finite element analysis of the bone–plate system was performed using MSC Patran/Nastran, with rigid fixation of the proximal end of the bone and sequential application of an axial compressive load of 100 N, bending, and torsion with a moment of 1 N·m. Biomechanical performance was evaluated based on von Mises equivalent stress, fragment displacement (FD), interfragmentary movement (IFM), interfragmentary strain (IFS), and strain energy density (SED). To confirm the manufacturability of the design, the plate was fabricated from Ti–6Al–4V alloy using laser powder bed fusion (LPBF), and the geometry of the porous structure was verified by scanning electron microscopy. The results showed that the localized porous structure altered the load distribution between the plate and the bone, resulting in an increase in local stresses in the bone under the investigated loading conditions. These changes indicate an alteration in the mechanical environment within the bone, which may potentially affect conditions related to fracture healing. Among the investigated configurations, the plate with a 10 × 10 mm porous insert demonstrated the most balanced mechanical characteristics in terms of stresses in the implant, stress distribution in the bone, and structural stability. Full article

The structure, mechanical and electrical properties of Zr-based melt-spun Zr–(Al)–Ni–Cr–Ag alloys were investigated as a function of elemental composition. X-ray diffraction reveals the structural evolution from fully amorphous to nanocrystalline states, with the latter containing Zr₂Ni “big-cube” (space group Fd3̄m, cF96), fcc-Zr₂Ni, and β-Zr phases depending on the alloying ratio: Cr-rich compositions (≥15 at.%) stabilize β-Zr within the amorphous matrix, whereas Ag-enriched alloys promote “big-cube” phase formation. Ag atoms can replace both Zr and Ni sites in the “big-cube” lattice, yielding a (Zr,Ag)₂(Ni,Ag) solid solution and highlighting its role as a structural bridge between the amorphous and crystalline states. Nanoindentation measurements show that hardness increases from 6.5 GPa in fully amorphous ribbons to 10.12 GPa in three-phase nanocrystalline composites, with an H/E ratio of ~0.08 indicating predominantly covalent bonding, and the fracture strength of the amorphous alloys is ~2 GPa, exceeding literature values for related Zr-based systems. Electrical resistivity measurements over the 4–298 K range show that most alloys deviate from Matthiessen’s rule, exhibiting a negative temperature coefficient of resistivity consistent with the Mooij correlation; the presence of the icosahedrally ordered “big-cube” phase further increases resistivity relative to fully amorphous alloys. Full article

Cavitation erosion is a phenomenon that causes the degradation of engineering components operating in fluids under oscillating pressure, and it occurs through the repeated implosion of cavitation bubbles adjacent to the solid surface. This complex phenomenon involves both the hydrodynamic factors of the liquid and the properties of the material being eroded. Cavitation erosion tests were performed using a vibratory apparatus with piezoceramic crystals, in accordance with the ASTM G32-2016 standard. As a reference material, a wrought aluminum-based alloy in the hot-rolled condition, EN AW-6082, was selected. For both alloys, mass losses were measured and erosion rates were calculated. The eroded surfaces were examined by X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results indicate that the cavitation erosion resistance of the AZ 31B alloy in the hot-rolled condition is approximately 3.77 times lower than that of the reference material. This behavior is attributed to its lower hardness and heterogeneous microstructure, consisting of an α solid solution matrix with a hexagonal close-packed crystal structure and intermetallic particles of the Mg₁₇Al₁₂ type, which exhibit pronounced brittleness. Cavitation pits are observed mainly within the α-Mg solid solution grains and at the interfaces between the intermetallic phases and the α-Mg matrix. Full article

Ti-6Al-4V has seen widespread adoption in the aerospace industry due to its advantageous material properties, but the alloy is costly to produce with vulnerable supply chains. Repair and remanufacture offer economic and environmental benefits over scrapping components. Powder-based additive-manufacturing processes have been investigated; however, coaxial wire laser metal deposition (LMD) remains understudied in repair scenarios, and the transfer of planar process parameters to inclined geometries for complex repairs has not been established. This paper identifies a process window for 1.2 mm Ti-6Al-4V wire and applies the parameters to repair a trapezoidal groove. Tensile and fatigue properties are evaluated, and fractography is conducted using optical and scanning electron microscopy. Findings show the transfer from planar to inclined geometry induces evolving geometric and thermal boundary conditions, including underbuilding and thermal accumulation. Nonetheless, the repair exhibited a yield strength of 868.2 MPa, an ultimate tensile strength of 920.5 MPa, and an elongation of 8.9%. Moreover, UFT revealed a fatigue performance of the repairs that was consistent with heat-treated SLM materials. Fractographic analysis revealed triangular defects and feedstock contamination that contribute to reduced repair properties. As such, this paper demonstrated that coaxial wire-LMD can be used to deposit material into complex geometries, but a complete, defect free repair was not achieved. Full article

This study utilizes Omani limestone waste powder (CaCO₃) sourced from the mountain ranges of the Sultanate of Oman as an economical natural reinforcement for scrap-based aluminum matrix composites (AMCs) using stir casting. The recycling of aluminum alloy from end-of-life automotive engine cylinder blocks was strengthened with limestone at volume fractions of 2.5%, 5.0%, and 7.5%. Mechanical characterization was conducted in accordance with ASTM standards (E8/E8M, E18, E23). Statistical significance (p < 0.05) was calculated using one-way ANOVA. The optimum 5.0 vol.% reinforcing fraction showed tensile strength, Rockwell hardness and Charpy impact energy of 130.9 MPa (+16.9%), 91 HRF (+19.7%) and 7.2 J (+28.6%) compared to the unreinforced scrap alloy (112.0 MPa, 76 HRF, 5.6 J). The results of Scanning Electron Microscopy (SEM) research showed that the composite of 5.0 vol.% had a uniform distribution of CaCO₃ particles and very low porosity, while the composite of 7.5 vol.% had a significant porosity (2–8 μm), interconnected microcracks and particle agglomeration. The porosity was increased with the increase of the content of the reinforcement as shown by the density experiments based on Archimedes’ principle. The maximum deviation of the experimental density from the predicted one was at 7.5 vol. % reinforcement. X-ray diffraction (XRD) confirmed the stability of the aluminum matrix structure as well as stable CaCO₃ phases without any evidence of harmful interfacial reaction products (Al₄C₃ or CaAl₂O₄). The findings confirm the optimal reinforcement ratio of 5.0 vol.% of Omani limestone, tackling both the environmental load of limestone quarrying waste and the expensive synthetic reinforcements, in accordance with the circular economy goals of Oman Vision 2040. Full article

The Ti-6Al-4V alloy is widely used in aerospace and deep-sea applications due to its exceptional strength and corrosion resistance. However, its application is often constrained by high deformation resistance and a narrow hot-working temperature window, primarily attributed to its heat and mass transfer characteristics. To address these limitations, a novel Ti-6Al-1.3V-0.9Fe alloy was designed with an equivalent molybdenum content. In this study, Gleeble thermal simulation tests were conducted to investigate the impact of Fe on the hot deformation behavior under various conditions and to identify the optimal processing window for this alloy. The effects of deformation temperature and strain rate on the flow stress curves and peak stress were systematically analyzed, along with the role of Fe in microstructural evolution during hot deformation. The results demonstrate that the addition of Fe significantly refines the grain size of the Ti-6Al-1.3V-0.9Fe alloy. As expected, the flow stress decreases with increasing deformation temperature and increases at higher strain rates. Under high-temperature and low-strain-rate conditions, the alloy exhibits steady-state flow behavior, indicating improved hot workability. Based on the constitutive modeling, the apparent activation energy (Q) for hot deformation was calculated to be 503.81 kJ/mol. Finally, the optimal hot-working parameters for the Ti-6Al-1.3V-0.9Fe alloy were identified as a temperature range of 760 °C to 860 °C and a strain rate between 0.01 and 0.16 s⁻¹. Full article

This study investigates the evolution of microstructural, mechanical, and transport properties in AZ31 magnesium alloy surface composites reinforced with Ti₂AlC MAX-phase particles at volume fractions of 6, 9, and 12 vol.%, which were fabricated by solid-state friction stir processing (FSP). In contrast to conventional brittle ceramics, Ti₂AlC MAX-phase mitigates interfacial reactivity and thermal mismatch. FSP successfully fabricated a highly consolidated, macroscopically defect-free, dynamically recrystallized fine-grained stirred zone with homogeneous particle distribution and metallurgically clean interfaces. Mechanically, the addition of 12 vol.% Ti₂AlC significantly improved the elastic response, increasing the Young’s modulus from 51 GPa to 67 GPa. The microhardness of the stirred zone reached 60.14 HV, a 53.4% increase over the base metal. The controlled electron and phonon scattering, enabled by the introduction of heterogeneous Mg/Ti₂AlC interfaces, decreased the electrical and thermal conductivities from initial values of 1.15 × 10⁷ S/m and 86.0 W/m·K for the unreinforced matrix down to 7.8 × 10⁶ S/m and 76.0 W/m·K, respectively, and caused a significant reduction in the coefficient of thermal expansion. Theoretical analysis, utilizing the Wiedemann–Franz law and Maxwell–Eucken approximations, provided a supportive baseline indicating the dominance of electronic thermal transport and interfacial scattering mechanisms. These results outline a viable route for developing lightweight magnesium-based composites with tailored mechanical and thermal characteristics for advanced structural applications. Full article

The study investigates the effects of high-energy laser treatment on titanium-based alloys, TiAlV, TiNbZr, and TiNbSnTa, materials of high interest for medical applications such as implants and dental devices due to their exceptional strength-to-weight ratio, corrosion resistance, and biocompatibility. In this research, a unique high-energy laser was used for Ti-based surface activation. The laser exposure induced significant changes in both surface morphology and chemistry while preserving the bulk properties of the substrate. The modified surfaces were evaluated for their impact on cytocompatibility and antibacterial activity. It was found that viability of U-2 OS cells incubated with laser-treated Ti-based substrates was not negatively affected and was comparable to or slightly higher than that of control samples, indicating very good cytocompatibility of the prepared materials. Further, antibacterial evaluation against E. coli and S. epidermidis demonstrated that laser-treated samples had improved activity, especially against S. epidermidis, relative to untreated controls. Thus, these results demonstrate that high-energy laser treatment can simultaneously enhance the biocompatibility and antibacterial properties of titanium alloys, highlighting its potential as a versatile surface modification strategy for advanced biomedical devices. Full article

Additively manufactured AlSi10Mg aluminum alloy was investigated at two-layer build orientations: 0° and 90°. Impact-induced fractures were generated per the ASTM standard Charpy test. The resulting fracture surfaces were analyzed using the multi-image-based fractal analysis method. We used a digital microscope to analyze the fracture surface and examined compression, neutral, and tension zones on the surface. We found that the crack propagated symmetrically across the surface. The results showed that the compression zone has the lowest fractal dimension compared to the tension and neutral zones. The 0° orientation samples have a higher fractal dimension than the 90° orientation samples. Full article

At present, the detection methods for the microstructure and mechanical properties of aluminum alloys are mainly based on SEM, EBSD, TEM, tensile tests, and microhardness tests, which are time-consuming and destructive. In this paper, laser ultrasonic non-destructive detection is employed to obtain ultrasonic signals from Al-Cu-Mg aluminum alloy subjected to various heat treatment processes. The results reveal empirical correlations between the characteristic values of the ultrasonic signals and the material’s state. Specifically, the characteristic values exhibit an inverse correlation with the precipitated phase content. When both the precipitated phase content and the average grain size vary significantly, distinct deviations in the characteristic values are observed, which can serve as indicators of microstructural changes. The extracted ultrasonic eigenvalues also show promising, empirically derived correlations with mechanical properties, with frequency-domain attenuation coefficients demonstrating relatively higher sensitivity based on fitting analyses within the current dataset. These observed variations are tentatively discussed as plausible consequences of grain boundary scattering and changes in matrix solid solution strengthening associated with precipitate dissolution. Overall, the findings suggest the potential of laser ultrasonics as a rapid non-destructive evaluation tool, providing a preliminary scientific basis for further development of methods to assess the microstructure and mechanical properties of Al-Cu-Mg alloys within the tested parameter space. Full article

The interfacial reaction between solder and substrate is a critical factor governing joint reliability, making it essential to understand the formation and stability of interfacial reaction layers when developing new high-temperature lead-free solders. This study investigates the interfacial reaction layers formed in Zn-5Al-3Mg solder/Cu substrate joints soldered at 693 K under vacuum. With a binary Zn-Al solder, the Cu substrate is progressively consumed by Zn, and the intermediate phases CuZn₄, Cu₅Zn₈, and CuZn nucleate and grow concurrently at the solder interface. The addition of a minor amount of Mg to the Zn-Al alloy, however, fundamentally alters this reaction sequence. Transmission electron microscopy analyses, including scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy (STEM-EDS), energy-filtered TEM (EF-TEM), and electron diffraction, reveal three distinct interfacial layers: an outer Mg₂Zn₁₁ layer, a middle two-phase mixture of CuZn₄/Mg₂CuZn₃, and an inner Cu₅Zn₈ layer adjacent to the Cu substrate. The biphasic CuZn₄/Mg₂CuZn₃ mixture layer is shown to form via a quasi-peritectic reaction governed by sequential four-phase equilibria in the Zn-Mg-Cu ternary system. These findings demonstrate that minor Mg additions redirect the interfacial reaction pathway between Zn-Al-based solders and Cu substrates, providing new insight for the design of high-temperature Pb-free solder systems. Full article

This paper investigates the stress corrosion cracking (SCC) behavior under constant loading conditions and the early-stage grain-scale deformation mechanisms of a friction-stir-welded (FSW) joint of 7A52 aluminum alloy. The results show that when a constant load equivalent to 1.0 times the yield strength (439.43 MPa) of the base metal is applied, the joint fractures after 72 days of immersion in a 3.5 wt% NaCl solution, with the fracture located in the heat-affected zone on the advancing side (AS-HAZ). The fracture surface exhibits a mixed-mode morphology characterized by both brittle and ductile features. Observations suggest that cracks mainly initiate at the bottom of corrosion pits, at grain boundaries, and at the interfaces between precipitates (such as Mg-Si-rich, Al-Fe-rich, or Al-(FeMn)-rich) and the Al matrix. It is suggested that the initiation mechanisms are closely related to galvanic corrosion, interfacial weakening, and mechanical property mismatch. In situ tensile and EBSD results indicate that the AS-HAZ is the first region to undergo deformation. As the load increases from 400 N to 1500 N, the degree of strain localization intensifies, with high-strain regions preferentially concentrated at grain boundaries. Grain boundary damage is likely a key mechanism responsible for the initial failure on the advancing side of the FSW joint. Further in situ SEM observations reveal that during the early stage of tensile deformation, as the load increases from 300 N to 455 N, the grain surface in the AS-HAZ evolves from a flat morphology to a typical orange peel appearance. Meanwhile, grain boundaries change from clearly visible to blurred, slip traces increase, and multiple slip systems are activated within the grains. The continuous pile-up of dislocations at grain boundaries leads to a sharp increase in local stress concentration, ultimately inducing grain boundary instability and crack nucleation. Full article

Electron beam powder bed fusion (PBF-EB) of TiAl alloys exhibits different grain morphologies: equiaxed grains and columnar grains. However, the rule for controlling grain morphologies has not been found. In addition, the grain morphology is closely related to thermal gradient and growth velocity during PBF-EB. Here, thermal gradient and growth velocity are controlled by preheating temperature, beam current, and scanning speed. Based on the numerical simulation, the relationship between solidification parameters (thermal gradient and growth velocity) and process parameters (preheating temperature, beam current, and scanning speed) has been revealed. Meanwhile, the grain morphology of the topmost region of the PBF-EB-built Ti-48Al-2Cr-2Nb alloy can be controlled. In addition, the columnar-to-equiaxed transition is found in the PBF-EB-built Ti-48Al-2Cr-2Nb alloy. This is attributed to the PBF-EB technology belonging to the layer-by-layer stacking process, and the stacked layer reduces the thermal gradient and increases growth velocity in the remelting region. These findings will contribute to understanding the grain morphology evolution of TiAl alloys during PBF-EB, providing the principle for controlling the grain morphology of PBF-EB-built TiAl alloys. Full article

The Ti6Al7Nb alloy is increasingly applied as a vanadium-free alternative to Ti6Al4V for biomedical implants; however, implant performance is governed predominantly by the physicochemical properties of the surface layer. In this study, anodic oxidation was employed as a controlled surface engineering process to generate a functional oxide layer on Ti6Al7Nb alloy and to modify its structural, chemical, and electrochemical characteristics. The anodically formed surface layer was comprehensively characterized in terms of surface morphology, wettability, microhardness, crystallographic phase composition, electrochemical behavior, and surface chemistry combined with depth profiling analysis. In addition, the biological response of the modified surface was assessed using in vitro cytotoxicity tests. The results confirm the formation of a stable and chemically defined oxide layer with enhanced electrochemical stability and tailored surface properties. The modified surface exhibits improved corrosion resistance, controlled physicochemical parameters, and favorable cytocompatibility. These findings demonstrate that anodic oxidation enables precise engineering of the surface layer and highlight its key role as a functional interface controlling implant–environment interactions, confirming this approach as an effective strategy for the development of advanced Ti-based biomedical implant surfaces. Full article