This study investigates the flexural behavior and failure mechanisms of fused filament fabrication (FFF) beams manufactured from pure ABS, pure PLA, and three-layer hybrid configurations (ABS/PLA/ABS and PLA/ABS/PLA). Three-point bending tests were conducted to obtain force–deflection and corresponding stress–strain responses, followed by scanning electron microscopy (SEM) analysis of fracture surfaces to elucidate the governing microstructural damage mechanisms. The results indicate that pure PLA specimens exhibit the highest flexural stiffness and peak load capacity but fail in a predominantly brittle manner, whereas pure ABS specimens display enhanced ductility and deformation capacity at the expense of reduced strength. The multilayer beams exhibited mechanical responses intermediate between those of the monolithic PLA and ABS specimens, with their performance strongly influenced by the stacking sequence. The PLA/ABS/PLA configuration exhibited higher load-bearing capacity, which can be associated with the presence of the stiffer PLA outer layers, while the central ABS material region contributed to a more gradual deformation response. In contrast, the ABS/PLA/ABS configuration showed lower load-bearing capacity but greater deformation before final failure, consistent with the more ductile behavior of the ABS outer layers. SEM observations revealed that failure in multilayer specimens is governed by interfacial debonding, porosity, and void formation, whereas interlayer voids and filament necking dominate fracture in monolithic materials. Finite element analysis (FEA) performed in ANSYS accurately captured the experimental load–deflection trends and stress distributions, showing strong agreement with the measured results. The combined experimental, microstructural, and numerical evaluations demonstrate that tailored multilayer material constructions can efficiently balance strength and ductility in FFF-printed structures.
Carbon fiber-reinforced plastic (CFRP) composites are widely used in the aerospace and automotive industries, where high-quality micro-holes are essential for mechanical fastening and assembly. This study investigates static-water-assisted nanosecond infrared laser trepan micro-drilling of 1 mm-thick CFRP laminates and compares its performance with conventional open-air drilling. The effects of pulse width (9, 13, and 17 ns) and scan speed (40, 50, and 60 mm/s) on hole diameter, ovality, apparent taper angle, and heat-affected zone (HAZ) are evaluated. Compared with open-air drilling, static-water assistance reduces the entry- and exit-side HAZ by approximately 92–93% and 70–78%, respectively, and decreases the mean entry and exit ovality from 8.63% to 4.68% and from 40.48% to 27.45%, respectively. Confocal and scanning electron microscopy (SEM) further reveal reduced fiber pull-out, fiber breakage, and fiber-matrix debonding under static-water conditions. However, static-water drilling also produces greater entry overcut relative to the 500 µm target diameter (mean entry diameter of 747 µm versus 602 µm in open air), a higher mean apparent taper angle (10.34° versus 8.40°), localized redeposited and thermally degraded epoxy around the hole periphery. The increased taper is attributed to the larger entry-side material removal combined with progressive attenuation and scattering of the laser beam by cavitation bubbles and ablation debris in the stagnant water as drilling proceeds through the laminate. Overall, static-water assistance substantially suppresses thermal damage and improves hole circularity, although these benefits are accompanied by reduced entry-side dimensional accuracy and increased apparent taper.
This study investigates the dissimilar welding of Hastelloy C-2000 and Monel 400 using Laser Beam Welding (LBW). Owing to the differences in their chemical, thermal, and metallurgical characteristics, joining these alloys can lead to elemental segregation, undesirable phase formation, residual stresses, and reduced joint performance. Hence, a low-heat-input and precisely controllable process is required to minimize metallurgical degradation and thermal distortion. This study evaluates the metallurgical and mechanical characteristics of dissimilar joints to assess the suitability of LBW for high-performance alloy applications. Detailed microstructural analysis was performed using Optical Microscopy, Scanning Electron Microscopy, and X-ray Diffraction, revealing finer dendritic structures and minimal intermetallic phase formation. Residual stress measurements indicated lower tensile stress magnitudes in the LBW welds, which was attributed to the rapid thermal cycle and reduced heat input. Mechanical characterization through tensile, Charpy impact, and hardness testing showed that the LBW joints exhibited 12–15% higher ultimate tensile strength and up to 20% greater impact toughness. The hardness distribution across the weld zone was more uniform, indicating better metallurgical bonding and lower thermal distortion. Moreover, LBW resulted in a narrower heat-affected zone and reduced the weld bead width, thereby enhancing the joint quality. The key findings revealed that LBW produced high-aspect-ratio welds with narrow HAZs, refined dendritic microstructures, and minimal elemental segregation. XRD analysis confirmed a predominantly single-phase FCC Ni–Cu solid solution with minor carbide formation and no harmful intermetallic compounds. The fusion zone exhibited a hardness of approximately 244–251 HV, confirming the high mechanical integrity of the welded joint.
Machining titanium alloys is challenged by high friction and temperature at the tool–workpiece interface, leading to rapid tool wear and poor surface integrity. While cutting fluids during machining have been used to avert this, they have been observed to induce irreversible chemical reactions with the machined surfaces, while also presenting manufacturers with additional cutting fluid purchase, use, and disposal costs, in addition to environmental and health concerns. This has motivated a shift towards dry machining. This study investigates the performance of MoS 2 -alloyed TiAlSiN thin film coatings (referred to as n :MoS 2 ) deposited by magnetron sputtering on tungsten carbide cutting tools for dry rough turning of Ti-6Al-4V alloy. After deposition, the MoS 2 -alloyed coatings maintained mechanical properties comparable to the TiAlSiN thin films (H ∼ 10 GPa and H/E ∼ 0.06), while significantly improving the tribological behaviour of the coated tools (coefficient of friction: TiAlSiN ∼ 0.16 and n :MoS 2 ∼ 0.13). Moreover, the n : MoS 2 -coated tools exhibited reduced and steady cutting temperatures, smoother chip flow, and the lowest flank wear, VB B (∼0.191 mm), corresponding to wear reductions of approximately 71% compared to the as-manufactured (VB B = 0.651 mm) and 20% relative to TiAlSiN-only coated tools (VB B = 0.239 mm). The enhanced performance was attributed to the effective self-lubrication and improved heat dissipation at the cutting interface. These results demonstrate the strong potential of MoS 2 -alloyed TiAlSiN coatings for enabling high-performance, environmentally sustainable dry machining of titanium alloys.
Micro-arc oxidation (MAO) technology was employed to fabricate composite ceramic coatings on a 6061 aluminum alloy substrate. TiO2 nanoparticles were introduced into a silicate-based electrolyte to investigate their effects on the microstructure and properties of the MAO coatings. The results revealed that the TiO2-containing coating exhibited a smoother and denser surface with reduced pore size, as well as increased thickness and significantly improved corrosion resistance compared with the additive-free MAO coating and the 6061 aluminum alloy substrate. Furthermore, the corrosion current density of the MAO/TiO2 coating decreased by three orders of magnitude, while the corrosion potential shifted in the positive direction by 0.94 V. The impedance arc radius was also considerably larger than that of the 6061 aluminum alloy. In addition, salt spray testing revealed no visible signs of corrosion after 720 h of exposure, demonstrating the excellent corrosion resistance of the MAO/TiO2 coating. These findings provide insights into the formation and corrosion protection mechanisms of TiO2-doped ceramic coatings, extending the potential application of MAO technology to a broader range of metallic materials and providing a theoretical foundation and technical support for improving the surface protection of metallic alloys in industrial corrosion protection applications.
