Search Results (222)

To optimize the laser drilling process and reduce the processing time, this study investigates picosecond laser trepan drilling on the titanium alloy TC4, analyzing the effects of laser parameters on micro-hole diameter, taper, and roundness. Four independent variables were selected: laser power, defocusing distance, scanning speed, and the number of scans. An L₂₅ (5⁶) orthogonal array was employed for experimental design. The mean response and range analyses evaluated parameter impacts on micro-hole quality, revealing the influence mechanisms of these variables at different levels. The results indicate the following: (1) the scanning speed and laser power significantly affect entrance and exit micro-hole diameters; (2) the defocusing distance substantially influences micro-hole taper; (3) the laser power most critically impacts inlet roundness; (4) the defocusing distance, scanning speed, and laser power directly correlate with outlet roundness; (5) the number of scans exhibits weaker relationships with inlet/outlet diameters, taper, and roundness. A comprehensive balance method applied to orthogonal test results for process optimization yielded the following optimal parameters: 90% laser power (30 W total), −0.2 mm defocus, a 27 mm/s scanning speed, and 15 scans. Full article

This study develops an optimized femtosecond laser welding process for joining quartz glass and TC4 titanium alloy (Ti-6Al-4V) under non-optical contact conditions, specifically addressing the manufacturing needs of specialized photoelectric effect research containers. The joint primarily consists of parallel laser-welded zones (WZ) interspersed with base material. The defocus distance of the femtosecond laser predominantly influences the depth and phase composition of the WZ, while the weld spacing influences the crack distribution in the joint region. The maximum shear strength of 14.4 MPa was achieved at a defocusing distance of +0.1 mm (below the interface) and a weld spacing of 40 μm. The XRD stress measurements indicate that the defocusing distance mainly affects the stress along the direction of laser impact (DLI), whereas the weld spacing primarily influences the stress along the direction of spacing (DS). GPA results demonstrate that when the spacing is less than 30 μm, the non-uniform shrinkage inside the WZ induces tensile stress in the joint, leading to significant fluctuations in DS residual stress and consequently affecting the joint’s shear strength. This study investigates the effects of process parameters on the mechanical properties of dissimilar joints and, for the first time, analyzes the relationship between joint residual strain and femtosecond laser weld spacing, providing valuable insights for optimizing femtosecond laser welding processes. Full article

Low-surface-energy and wettability-based antifouling coatings have garnered increasing attention in marine applications owing to their environmentally friendly characteristics. However, their limited functionality often results in suboptimal long-term antifouling performance, particularly under dynamic marine conditions. To address these limitations, a polydimethylsiloxane (PDMS)-based slippery (PSL) coating was fabricated on TC4 titanium alloy by integrating surface silanization via (3-Aminopropyl)triethoxysilane (APTES), antimicrobial Ag-TiO₂ nanoparticles, laser-induced hierarchical microtextures, and silicone oil infusion. The resulting PSL coating exhibited excellent oil retention and stable interfacial slipperiness even after thermal aging. Compared with bare TC4, low-surface-energy Ag-containing coatings, Ag-containing superhydrophobic coatings, and conventional slippery liquid-infused porous surfaces (SLIPS), the PSL coating demonstrated markedly superior resistance to protein adsorption, bacterial attachment, and diatom settlement, indicating an enhanced synergistic antifouling effect. Furthermore, it significantly reduced the diatom concentration in the surrounding medium without complete eradication, underscoring its eco-friendly and non-disruptive antifouling mechanism. This study offers a scalable, durable, and environmentally benign antifouling strategy for marine surface protection. Full article

Traditional narrow gap welding of thick titanium alloy plates easily produces dynamic molten pool flow instability, poor sidewall fusion, and excessive residual stress after welding, which leads to defects such as pores, cracks, and large welding deformations. In view of the above problems, this study takes 16-mm-thick TC4 titanium alloy as the research object, uses low-power pulsed laser-GTA flexible heat source welding technology, and uses the flexible regulation of space between the laser, arc, and wire to promote good fusion of the molten pool and side wall metal. By implementing instant ultrasonic impact treatment on the weld surface, the residual stress of the welded specimen is controlled within a certain range to reduce deformation after welding. The results show that the new welding process makes the joint stable, the side wall is well fused, and there are no defects such as pores and cracks. The weld zone is composed of a large number of α′ martensites interlaced with each other to form a basketweave structure. The tensile fracture of the joint occurs at the base metal. The joint tensile strength is 870 MPa, and the elongation after fracture can reach 17.1%, which is 92.4% of that of the base metal. The impact toughness at the weld is 35 J/cm², reaching 81.8% of that of the base metal. After applying ultrasound, the average residual stress decreased by 96% and the peak residual stress decreased by 94.8% within 10 mm from the weld toe. The average residual stress decreased by 95% and the peak residual stress decreased by 95.5% within 10 mm from the weld root. The residual stress on the surface of the whole welded test plate could be controlled within 200 MPa. Finally, a high-performance thick Ti-alloy plate welded joint with good forming and low residual stress was obtained. Full article

Laser–MIG hybrid welding–brazing was performed to join TC4 titanium alloy and 5083 aluminum alloy with ER5356, ER4043 and ER2319 filler wires. The effects of the different filler wires on the microstructural features and mechanical properties of Ti/Al welded–brazed butt joints were investigated in detail. The wetting and spreading effect of the ER4043 filler wire was the best, especially on the weld’s rear surface. Serrated-shaped and rod-like IMCs were generated at the top region of the interface of the joint with ER4043 filler wire, but rod-like IMCs did not appear at the joints with the other filler wires. Only serrated-shaped IMCs appeared in the middle and bottom regions for the three filler wires. The phase compositions of all the IMCs were inferred as being made up of TiAl₃. The average thickness of the IMC layer of joints with the ER5356 and ER2319 filler wires was almost the same and thinner than that of the joint with the ER4043 filler wire. The average thickness was largest in the middle region and smallest in the bottom region for all the joints with the three filler wires. The average microhardness in the weld metal of ER5356, ER4043 and ER2319 filler wires could reach up to 77.7 HV, 91.2 HV and 85.4 HV, respectively. The average tensile strength of joints with the ER5356, ER4043 and ER2319 filler wires was 106 MPa, 238 MPa and 192 MPa, respectively. The tensile samples all fractured at the IMC interface and showed a mixed brittle–ductile fracture feature. These research results could help confirm the appropriate filler wire for the laser–MIG hybrid welding–brazing of Ti/Al dissimilar butt joints. Full article

The residual stress induced during the processing of titanium alloy materials can significantly influence the deformation control of precision-machined workpieces, especially for workpieces characterized by low stiffness and high-precision requirements. In this study, TC18 titanium alloy forgings with a dense structure were manufactured via forging. By conducting turning and heat treatment experiments on the workpiece, the distribution and evolution of residual stress and the deformation characteristics of TC18 titanium alloy on slender shafts were systematically investigated under different turning and heat treatment conditions. Based on the experimental results, the effects of the turning parameters, including feed rate, cutting speed, cutting depth, and axial thrust force of machine tool center, on workpiece deformation were quantitatively analyzed, and an optimal heat treatment strategy was proposed. The findings indicate that between-centers turning is recommended to control workpiece deformation. Optimal turning parameters include a cutting speed of 640–800 r/min, a feed rate of 0.05–0.1 mm/r, a cutting depth of 0.1 mm, and a thrust force of the center set to 10% of the rated value, resulting in minimal deformation and superior surface quality. In addition, during the heat treatment annealing of slender shaft titanium alloys, residual stress is effectively eliminated at temperatures ranging from 640 to 680 °C with a holding time of 1–3 h. Furthermore, the vertically fixed placement method during heat treatment reduced deformation by approximately 50% compared to free placement. These results provide valuable insights for optimizing machining and heat treatment processes to enhance the dimensional stability of titanium alloy components. Full article

Medical titanium alloy Ti-6Al-4V (TC4) is widely used as a surgical implant material in biomedical fields owing to its superior biocompatibility, corrosion resistance, and mechanical performance, particularly for osseous integration applications. However, long-term contact of medical titanium-based implants with human soft tissues may induce infection and inflammation. To address these limitations, a drug-loading gel was designed to be synthesized on a TC4 surface to improve biointegration. Considering the critical regulatory roles of temperature and pH in physiological environments, this study synthesized a dual-responsive hydrogel using the temperature-sensitive monomers 2-(2-methoxyethoxy)ethyl methacrylate (MEO₂MA) and oligoethylene glycol methacrylate (OEGMA) and the pH-sensitive monomer diethylaminoethyl methacrylate (DEAEMA), employing stereocomplexed polylactic acid as a physical crosslinker and N,N′-methylenebisacrylamide (MBA) as a chemical crosslinker. A polydopamine-based initiator was synthesized via dopamine functionalization with 2-bromoisobutyryl bromide (BIBB). The amphiphilic co-network hydrogel was grafted onto a modified TC4 surface through atom transfer radical polymerization (ATRP). Integration of the drug-loading gel and TC4 gives the implant an “active therapeutic” function by localized drug release. The results demonstrated that the energy storage modulus of the double-crosslinked gel matched that of human soft tissues. The gels exhibited efficient drug release. Full article

TC4 titanium alloy and 5083 aluminum alloy with different groove shapes were joined by laser-MIG hybrid welding–brazing using ER4043 filler wire. The effects of groove shape on the weld formation, intermetallic compounds and tensile property of the Ti/Al butt joints were investigated. The welds without obvious defects could be obtained with grooves of I-shape and V-shape on Ti side, while welds quality with grooves of V-shape on Al side and V-shape on both sides were slightly worse. The interfacial intermetallic compounds (IMCs) on the brazing interface were homogeneous in the joints with groove of V-shape on Ti side, and V-shape on both sides, which had similar thickness and were both composed of TiAl₃. Unlike the IMCs mainly composed of TiAl₃ at the I-shape groove interface, TiAl₃, TiAl, and Ti₃Al constituted the IMCs at the V-shape on Al side interface. The average tensile strength of Ti/Al joints with groove of I-shape was the highest at 238 MPa, and was lowest at 140 MPa with groove of V-shape on Al side. The tensile samples mainly fractured at IMCs interface and the fractured surfaces all exhibited mixed brittle–ductile fracture mode. Based on the above research results, I-shape groove was recommended for laser-arc hybrid welding–brazing of 4 mm thick Ti/Al dissimilar butt joints. Full article

The torsional behavior during the deformation process of the axial closed die rolling the axial closed rolling (ACDR) forming is studied in this paper using a numerical simulation technique on TC11 titanium alloy. The axial and radial pinch angles, as well as the degree of specimen torsion, increased with the amount of deformation. The orientation distribution function (ODF) maps of the α-phase and β-phase were obtained by Electron Back Scatter Diffraction (EBSD) treatment of the TC11 titanium alloy. It can be noticed that there were different types of texture with different strengths in the ACDR samples, and in the xz and yz planes, textures in the direction of the column were predominantly of {0001} <2$\overline{1}\overline{1}$0> and {01$\overline{1}$0} <2$\overline{1}\overline{1}$0>; the weaker the texture was, the closer to the edge of the sample. In the xy plane, the texture structure was mainly distributed along the cone direction, and the textures were {$\overline{1}$2$\overline{1}$0} <10$\overline{1}$0> and {01$\overline{1}$0} <2$\overline{1}\overline{1}$0>. However, the closer to the edge position of the specimen, the higher the intensity of the texture, and the texture was {1$\overline{2}$1$\overline{2}$} <1$\overline{2}$16>. The β-phase is mainly distributed as {001} <100>, {110} <1$\overline{1}$0>, and {110} <001> textures within the specimen, and the texture strength is about 8.5 times. However, owing to the small proportion of the β-phase content in the specimen, the distribution pattern of its texture has a weak impact on the texture distribution of the overall specimen. A high degree of isotropy in the radial and tangential tensile properties, with a strength isotropy of over 99 percent and a plasticity isotropy of over 95 percent, resulted from the distribution of texture types with varying strengths and orientations within the ACDR specimens, which weakened the TC11 discs’ overall orientation. Full article

The dual-pole magnetic abrasive finishing (DMAF) method was proposed to achieve a smooth surface on TC4 titanium alloy. Firstly, both the distribution of the magnetic field and the intensity of magnetic induction produced by nine combinations of magnetic poles of different shapes were simulated using Ansys Maxwell software (2024R2). According to the results of the simulation, the optimal combination of magnetic poles was determined. Then, the machining parameters of multi-stage DMAF were optimized through comparative experiments on major single factors. Finally, combinations of the mixed magnetic abrasive in three polishing stages were obtained as follows: #100 electrolytic iron powder (Fe₃O₄) + #2000 white abrasive (WA), #200 Fe₃O₄ + #8000 WA, and #450Fe₃O₄ + #w1 diamond (DMD). The gap between the upper and lower magnetic poles was set to 5 mm, the rotational speed of the magnetic pole was set to 300 rpm, and the quality ratio of the abrasive was 2:1. The experiments indicated that the average surface roughness Ra was reduced from an initial value of 0.433 μm to 8 nm after 30 min of multi-stage DMAF, and a nano-level mirror polishing effect was essentially achieved in the polishing zone. Full article

Electron backscatter diffraction and scanning electron microscopy were performed herein to in situ investigate the influence of texture on the anisotropic deformation mechanism of TC11 forged components. The in situ tensile specimen was cut from the TC11 ring forging, and the tensile force–displacement curve was recorded while the slip lines in the specimen surface detected was traced during the in situ tensile test. The tensile results show that the yield and ultimate tensile strengths decreased in the order of transverse-direction (TD) > rolling-direction (RD) > normal-direction (ND) samples. The anisotropy of the tensile strength was related to the differences in the activated slip systems of the ND, TD, and RD samples. The slip lines results show that in the yielding stage, the ND, TD, and RD samples were dominated by Prismatic <a>, Pyramidal <c + a>, and Pyramidal <a> slips, respectively. In order to further analyze the relationship between the slip system and the yield strength, an anisotropy coefficient was determined to evaluate the differences in resistances for different activated slip systems, providing a good explanation of the variations in the tensile strength anisotropy. The ratios of the critical resolved shear stress (CRSS) of the basal, Prismatic <a>, primary Pyramidal <c + a>, and secondary Pyramidal <c + a> slip systems in the α phase were estimated to be 0.93:1:1.18:1.05 based on the type, number, orientation of slip activations, and Schmid factor. Moreover, the Prismatic <a> slips primarily occurred in the axial and radial (ND and RD) samples with [0001] and [$\stackrel{\mathrm{-}}{1}2\stackrel{\mathrm{-}}{1}2$] textures, whereas the Pyramidal <c + a> slip system was dominant in the TD samples with [11$\stackrel{\mathrm{-}}{2}2$] and [10$\stackrel{\mathrm{-}}{1}$2] textures. Overall, this research demonstrates that the activation of the α-phase slip depends on the grain orientation, SF, and the CRSS, promoting strong strength anisotropy. Full article

To address the challenges of high labeling costs and insufficient cross-condition generalization in training cutting tool wear state prediction models, this paper proposes a model optimization method based on knowledge distillation. By constructing a teacher model using a Bidirectional Gated Recurrent Unit (BiGRU-GRU) and a student model utilizing a Transformer architecture, we jointly employ KL divergence distillation, feature Euclidean distance distillation, and cross-entropy supervised training. A multi-objective joint loss function is designed to facilitate knowledge transfer. Using a self-collected dataset of aerospace TC18 titanium alloy cutting tools and the publicly available PHM2010 dataset, we conduct comparative experiments based on two different data partitioning strategies: tool grouping and mixed grouping. The results indicate that knowledge distillation significantly enhances the performance of the student model. The Transformer-BiGRU model is more robust to knowledge distillation. Positive results were obtained for the Transformer-BiGRU model in both tool grouping and mix grouping experiments. Additionally, comparative experiments show that the proposed method outperforms traditional methods (such as GS-XGBoost and Attention-CNN) in both grouping types, validating the effectiveness of knowledge distillation in transferring knowledge related to tool wear discrimination and addressing the issue of insufficient training data. The research demonstrates that combining knowledge distillation with the Transformer architecture can effectively enhance model generalization capabilities, providing theoretical support for monitoring the state of aerospace titanium alloy machining tools. However, the misclassification issue during the severe wear stage still requires further optimization based on physical principles. Full article

Laser shock peening (LSP) is an effective method to improve the fatigue property of metallic materials, and a thorough understanding of its strengthening mechanism is crucial for technology application. In this study, the LSP and fatigue tests of TC4 titanium alloy have been carried out. Combined with the structural characterization and the crystal plasticity finite element (CPFE) simulation, the relationship of stress distribution, microstructure evolution and fatigue performance caused by LSP is revealed. The results indicate that the material’s fatigue life initially increases and subsequently declines with the rising pulse energy. At the optimal pulse energy condition, the laser-shocked specimen demonstrates a 126% increase in fatigue life relative to the untreated specimen, which is accompanied by the higher residual compressive stress along the depth. Meanwhile, the grains become more refined with a uniform size change gradient, and the β phase content drops from 4.1% to 2.2%. Notably, regions with <$\stackrel{-}{1}$2$\stackrel{\mathrm{-}}{1}$0> crystal orientation can be selectively achieved. With the favorable <$\stackrel{\mathrm{-}}{1}$2$\stackrel{\mathrm{-}}{1}$0> slip direction orthogonal to the applied fatigue loading axis, the generation and propagation of dislocations are effectively constrained, thereby significantly enhancing the material’s fatigue performance. The stress distribution and fatigue life in models with different grain sizes and phase contents are further analyzed by the CPFE method, showing good consistency with the experimental results. Theoretically, the excessively high pulse energy causes the transient temperature (1769 °C) to surpass the melting point (1660 °C), which can affect the recrystallization structure and stress distribution. Full article

This study aims to enhance the wear resistance of MAO/MoS₂ composite coatings fabricated on TC4 titanium alloy substrates through a composite process of microarc oxidation (MAO) and hydrothermal synthesis. The MAO treatment experiments were designed according to the L16 (4⁵) orthogonal array to optimize the NaAlO₂ concentration and electrical parameters (oxidation voltage, frequency, duty ratio, and treating time), with four levels for each factor. The optimized MAO process parameters were identified as a NaAlO₂ concentration of 10 g/L, an oxidation voltage of 500 V, a frequency of 200 Hz, a duty ratio of 20%, and a treating time of 30 min. The experimental results indicated a notable reduction in porosity, from 4.45% to 0.30%, in the optimized composite coating. Concurrently, there was a 43.2% increase in microhardness and a 327.9% increase in adhesive strength. Furthermore, the average coefficient of friction (CoF) of the composite coating was observed to be 0.13 at a high load of 20 N and a wear time of 20 min, representing a significant reduction of 68.5% compared to the CoF of the single MAO coating. Full article

WMoTaNbV refractory high-entropy alloys (RHEAs) have received widespread attention due to their excellent low-temperature toughness, hardness, and wear resistance. In recent years, the rapid development of surface modification technology represented by laser cladding has provided a new technological path for RHEA surface forming, and at the same time put forward higher requirements for raw material powder. In this study, WMoTaNbV RHEA spherical powder was prepared by radiofrequency plasma spheronization, and then WMoTaNbV RHEA coating was prepared on the surface of Ti6Al4V (TC4) alloy by laser cladding technique. The experimental results show that the prepared alloy powders have very high sphericity and are almost free of agglomeration and oxidation. Coatings with laser powers of 3.1–3.9 kW (gradient setting of 2 kW) were tested, with the 3.3, 3.5, and 3.7 kW coatings showing the best of the abrasion resistance. The microhardness of the 3.3 kW, 3.5 kW, and 3.7 kW coatings was 1.72, 1.97, and 1.76 times higher than that of the substrate, and the wear resistance was 1.83, 3.42, and 2.13 times higher than that of the TC4 substrate, respectively. This experimental result shows that the surface hardness and wear resistance of WNbMoTaV RHEA coating can be effectively improved by precisely regulating the laser power, thus improving the surface hardness and friction and wear properties of TC4 titanium alloy. Full article