Search Results (3,560)

A primary challenge in successfully manufacturing reactive materials for laser metal deposition (LMD) is to prevent oxidization. To address the oxidation susceptibility of titanium alloys in open environments, a local atmosphere protection model was developed. Using Ansys Fluent 2023R1 software, the effective protective atmosphere range provided by the local shielding device under varying shielding gas flow rates was investigated in detail, and a mathematical model for the effective protection area was obtained through quadratic polynomial fitting. A quadratic regression model linking process parameters with the length of high-temperature zones was established using central composite design (CCD). By integrating these two models, a local shielding gas model for LMD titanium alloys in an open environment was formulated. Validation experiments demonstrated excellent morphology of the single layers with shiny silver. The local shielding atmosphere can effectively protect the high-temperature region. These findings provide a basis for the deposition of active materials in an open environment and the selection of appropriate shielding gas flow rates. Full article

Ultrathin titanium alloy foils are attractive for engineering components requiring flexural compliance and mechanical support, yet their recoverable deformation behavior at the foil scale remains insufficiently characterized. This study evaluates 30 μm Ti–24Nb–4Zr–8Sn (wt.%, Ti2448) foils in the as-rolled and solution-treated states and compares their tensile loading–unloading response with same-thickness CP Ti and Ti–6Al–4V reference foils. The Ti2448 foils exhibit a larger recoverable-deformation window and a lower apparent loading modulus than the reference foils under the same testing protocol. The highest recoverable strain is obtained in the solution-treated longitudinal condition, indicating that the recoverable deformation is sensitive to both processing state and loading direction. These results suggest Ti2448 foils as potential candidates for flexure-related applications requiring large recoverable deformation. Full article

Chromate-free conversion coatings are increasingly investigated as environmentally acceptable alternatives to conventional chromate conversion coatings for corrosion protection of aluminum alloys. In the present study, the electrochemical behaviour and long-term corrosion stability of several commercial conversion coating systems based on trivalent chromium (TCP), zirconium (ZrCC) and zirconium/titanium (Zr/TiCC) were systematically evaluated on AA3003 aluminum alloy and compared to chromate conversion coating (CCC) CR614. Three TCP coatings (ST650, MC1300 and B30002), two ZrCC (MC1700 and MC160/161), and one Zr/TiCC (B2040) were investigated. Coatings were prepared at pre-selected pH and concentration, but at varying conversion times. The protective performance of the coating was then tested across various exposure conditions using potentiodynamic polarization measurements: (i) after 24 h of exposure to air, (ii) after 24 h of immersion in 3.5 wt.% NaCl solution and (iii) simulated acid rain solution, and (iv) after exposure in a salt spray chamber for 500 h. The protective performance strongly depended on both the conversion conditions and the exposure environment. The optimal conversion times ranged between 40 s and 18 min, depending on the coating type. Differences between the investigated systems remained relatively limited when investigated after exposure to air and immersion in the simulated acid rain solution. However, in chloride-containing environments, substantially greater differentiation between the coatings was observed. Among the investigated systems, TCP coatings exhibited the most favourable overall corrosion performance, particularly after prolonged salt spray exposure, where ST650 and B30002 polarization resistance values were approximately 8800 and 5300 kΩ cm², respectively, together with corrosion current densities as low as 0.0004 and 0.001 μA cm⁻². ZrCC systems MC1700 and MC160/161 also provided significant corrosion protection, achieving polarization resistance values around 2700 and 2400 kΩ cm² after 500 h of salt spray exposure, whereas the Zr/TiCC coating B2040 exhibited poorer long-term performance. The results further demonstrated that prolonged salt spray exposure provides considerably more realistic evaluation of long-term coating protectiveness than short-term electrochemical measurements alone. Overall, optimized TCP and ZrCC systems provided corrosion protection under chloride-containing conditions comparable to or superior to the investigated conventional chromate conversion coating CR614 deposited on AA3003 alloy. Full article

The presence of openings in spherical pressure hulls compromises the structural integrity and induces stress concentrations at the opening area. The strength assessment of shell openings remains a challenge in shell strength theory, even if using an approximated algorithm. While finite element analysis (FEA) is commonly employed, it is computationally prohibitive for iterative design. To address this gap, this study proposes a novel theoretical framework to calculate the Stress Concentration Factor (SCF) for spherical hulls with complex opening reinforcements under external pressure. A geometric transformation method based on the Equal Area Criterion (EAC) is established to convert complex reinforcement geometries into analytical forms. The accuracy is validated through comprehensive FEA and full-scale hydrostatic pressure tests on titanium-alloy manned hulls. The results demonstrate that the proposed method has high accuracy and exhibits excellent applicability, with deviations from experimental data generally within 5%. This study establishes a rapid assessment framework with high accuracy, providing a valuable engineering tool for deep-sea structural design. Full article

Precise segmentation of high-magnification titanium alloy micrographs under few-shot scenarios remains a non-trivial task, primarily owing to the intricate morphology, heterogeneous discrete distribution, and weak phase boundaries of the primary α phase. To address these issues, this paper presents MaterialAlphaSAM, a lightweight domain-adaptive segmentation framework built upon the Segment Anything Model (SAM). Leveraging SAM’s powerful global context modeling capability, the proposed method incorporates two key modules: a Geometry-Constrained Prompt Prior (GCPP) module and a Domain-Adaptation Adapter (DAA) module. The GCPP module explicitly embeds geometric and morphological priors to generate semantically guided prompts, effectively alleviating prompt redundancy and noise sensitivity. The DAA module performs cross-domain alignment of the encoder features, reducing the domain discrepancy between natural images and metallic microstructures. Extensive experiments demonstrate that both modules consistently boost segmentation performance. On the titanium alloy dataset, MaterialAlphaSAM achieves 89.53% IoU and a 94.40% F1-score, outperforming FCN, UNet, DeepLabV3, PSPNet and the vanilla SAM. It exhibits superior robustness to weak boundaries, fine-scale α phases, and complex background interference. Full article

Aerospace load-bearing components require materials that exhibit high specific strength, excellent fatigue resistance, and superior environmental adaptability. Titanium alloys are indispensable for aerospace applications because of their exceptional mechanical properties, particularly their outstanding high specific strength, and their peak mechanical strength is typically achieved through solution heat treatment followed by artificial aging. This review systematically summarizes recent advances in the compositional design, microstructural evolution, and critical microstructure–property relationships of aerospace titanium alloys. It further highlights intrinsic effects of alloying elements on phase stability, dislocation behavior, and phase transformation pathways, and analyzes how lamellar, equiaxed, and bimodal microstructures regulate dislocation transfer, local strain partitioning, and damage evolution. The interactions and competition among deformation and phase-transformation mechanisms, including slip anisotropy, deformation twinning, stress-induced phase transformations, and ω-related processes, are critically assessed. However, unresolved challenges remain in quantitatively characterizing multi-mechanism coupling and local heterogeneity. To address these challenges, this review elucidates the transition rules of dominant mechanisms across different microstructures and proposes a high-precision digital composition–microstructure–property mapping framework to facilitate predictive and service-oriented alloy design. Full article

Superplastic forming (SPF) of titanium alloys exhibits strong deformation path dependence because microstructural evolution, damage development, and material response are influenced by prior loading history. However, constitutive models for SPF are often evaluated primarily by fitting accuracy rather than their ability to represent deformation history. This review examines path-dependent constitutive modeling from a memory-architecture perspective. The relevant literature was identified through a structured review of titanium-alloy SPF studies, which were supplemented by selected high-temperature forming studies from other metallic systems when they provided transferable constitutive frameworks. Existing constitutive models were classified into four categories according to how deformation history is retained and represented: stateless models, implicit or projected memory models, reduced-order memory models, and high-dimensional or explicit memory models. The analysis shows that many conventional formulations achieve acceptable accuracy within calibrated monotonic regimes by strongly compressing deformation history, thereby limiting their ability to distinguish complex loading paths. Internal-state-variable models provide a practical balance between path representation, interpretability, and implementation, whereas high-dimensional memory models offer stronger sequence sensitivity at the cost of greater data and calibration requirements. This memory-architecture framework clarifies the limitations and applicability of existing constitutive models and provides guidance for model selection in SPF process simulation. Full article

This paper presents a systematic parametric study of how incremental titanium additions (0.1, 0.2, and 0.3 wt.%) alter the thermal conductivity, grain morphology, hardness, and tensile behaviour of Al6061 alloy intended for electronic heat sink service. Unlike prior investigations focused primarily on the Al6063–Ti system or on ceramic-phase reinforced aluminium composites, the present work isolates the grain-refinement and intermetallic-formation pathways in the 6xxx series with lower alloying additions (≤0.3 wt.%), manufactures specimens via stir casting followed by controlled homogenisation and T6-equivalent ageing, and evaluates performance against a thermal resistance index (TRI) to enable direct cross-study comparison. Thermal conductivity measurements were conducted according to ASTM E1225 across a 27–500 °C window. The results confirm a monotonic rise in conductivity from a baseline of 181 W/mK (undoped alloy) to 221.42 W/mK at 0.2 wt.% Ti—a 22.3% improvement—driven by quantifiable grain refinement (grain size reduced from 85 μm to 48 μm) and the associated redistribution of Mg and Si solute atoms. Brinell hardness increased from 98 to 120 BHN and ultimate tensile strength climbed from 250 MPa to 285 MPa across the same composition range, confirming thermal–mechanical co-enhancement. The study defines a composition window of 0.2–0.3 wt.% Ti as optimal for heat sink grade Al6061 and provides quantitative benchmarks against published Ti-doped aluminium alloy. Full article

Background: Degenerative joint diseases are a major cause of disability and drive the increasing demand for joint arthroplasty. Long-term prosthesis success depends on rapid and stable bone–implant integration, which is influenced by the osteo-inductive and osteo-conductive properties of implant materials. Chromium–cobalt (CrCo) and titanium (Ti) alloys are widely used in reconstructive orthopedics, but direct comparative data on their biological performance, particularly for trabecular titanium (T-Ti), remain limited. This study aimed to directly compare the biocompatibility and osteogenic potential of CrCo and T-Ti using human mesenchymal stromal cells (MSCs). Methods: Human MSCs were characterized by immunophenotyping and cultured on CrCo and T-Ti scaffolds under control and osteogenic conditions for up to 28 days. Cell adhesion and morphology were assessed by scanning electron microscopy. Proliferation and viability were quantified, and osteogenic differentiation was evaluated using alkaline phosphatase activity, calcium deposition assays, and gene expression profiling of osteogenic markers. Results: Both materials supported MSC adhesion and proliferation, confirming cytocompatibility. Under control conditions, T-Ti significantly increased alkaline phosphatase activity and osteogenic gene expression. Under osteogenic stimulation, T-Ti accelerated differentiation and mineralized matrix deposition. CrCo exhibited limited stimulation of the osteogenic-supportive microenvironment and delayed differentiation responses. Conclusions: Trabecular titanium, in terms of morphology and topology, provides a biologically active scaffold that both induces and conducts osteogenic differentiation of human MSCs, whereas CrCo acts primarily as a mechanically optimized but biologically passive material. These findings support the use of trabecular titanium at bone-contact interfaces in joint prostheses to enhance osteointegration and potentially improve long-term implant stability. Full article

This paper establishes a multi-scale nested sub-modeling finite element simulation framework for the deformation and damage analysis of large-scale structures under complex loading conditions. By sequentially transferring displacement solutions from the global model to local sub-models, the framework enables progressive high-resolution analysis from the macroscopic scale (>10 m) down to the microscopic scale (~1 μm), thereby significantly improving solution accuracy in critical regions while maintaining computational efficiency. The proposed approach is validated on a shell structure subjected to hydrostatic pressure and on a plate with a central crack. The results show that the relative errors of stress and strain along specified paths in the shell structure are within 5%, while the relative errors of the stress intensity factor along the crack front in the cracked plate are also below 5%. Furthermore, the framework is integrated with the crystal plasticity finite element method, and a fatigue indicator parameter model based on the accumulated equivalent plastic strain is established to predict the shear fatigue life of Ti-6Al-4V ELI titanium alloy. The predicted fatigue lives are in good agreement with experimental data, with all errors below 10%. This study demonstrates that the proposed sub-modeling method can accurately transfer multi-scale mechanical responses and achieve localized refinement analysis of large-scale structures and can be effectively used for crystal plasticity simulations and fatigue life assessment. Full article

Metal additive manufacturing (AM) enables components with high geometric complexity and functional integration; however, these advantages are realized only when topology optimization (TO) aligns with AM-specific constraints. This review examines TO strategies for metal AM, with emphasis on laser powder bed fusion (LPBF) as the most established industrial route. It categorizes and assesses density-based methods, level-set approaches, and lattice or architected-material optimization, focusing on how each captures manufacturability (overhang limits, minimum feature size, surface roughness), physics (residual stress, thermal distortion), and AM-induced anisotropy. It further distinguishes algorithms that embed constraints directly into the TO loop from workflows that rely on post-optimization repair. It discusses implications for robustness and transferability across machines and alloys. Experimental and numerical evidence for titanium alloys, aluminum alloys, nickel-based superalloys, and stainless steels is synthesized to relate design decisions and processing conditions to reported gains in stiffness-to-weight ratio, strength, fatigue performance, and buy-to-fly efficiency. Persistent gaps include validation under realistic load spectra, uncertainty quantification, standardized benchmarks, microstructure-informed objectives, and sustainability metrics. Beyond synthesizing existing TO formulations and constraints, this review contributes a criteria-based decision structure linking TO method selection, constraint strategy, and process-physics coupling and identifies four inherent paradoxes defining the field’s open challenges. Full article

This paper aims to analyse the microstructure and properties of the titanium- and boron-alloyed high-carbon medium-manganese 140Mn6Cr3TiB steel deposit before and after high-frequency mechanical impact (HFMI) treatment. XRD, SED, and EDS analyses were applied to evaluate the microstructural peculiarities of the studied deposit. Nanoindentation and scratch/sliding tests respectively revealed distinct correlations between the phase composition and the deformation/wear behaviour. HFMI results in the formation of the strain-induced ε- and α’-martensites (~66% and 3–6%, respectively), a significant grains/crystallites refinement (down to 31–54 nm), and dislocation density, which support essential hardening (by ~50%). The HFMI regime (load = 100 N, amplitude = 10 µm, and time = 60 s) was found to be the best, which led to the enhanced wear resistance (decreased wear volume) by ~4 times. The heterogeneous nature of the steel deposit creates a “shield-and-buffer” effect, where the hard eutectic framework resists penetration and tough matrix prevents brittle failure, maintaining a high tolerance to abrasion damage. The HFMI-hardening changed the wear mechanism from the ‘wedge/pile-up’ formation to ploughing. Thus, the HFMI shows a good efficiency in finishing the protective medium-manganese steel deposits of enhanced wear resistance to prolong the operation life of responsible parts. Full article

Plasma electrolytic oxidation (PEO) has emerged as a leading surface engineering technology for improving the tribological and corrosion performance of lightweight structural alloys, including aluminum, magnesium, titanium, and zirconium. Unlike conventional anodizing or line-of-sight deposition processes, PEO forms thick, multiphase ceramic oxide coatings metallurgically bonded to the substrate through plasma-assisted in situ oxidation, enabling treatment of complex and internal geometries that competing technologies cannot reach. The tribological performance of PEO coatings is governed by coupled interactions among electrolyte chemistry, electrical discharge behavior, phase evolution, porosity development, and residual stress state. This review critically evaluates the friction, wear, and tribo-corrosion behavior of PEO coatings under dry sliding, lubricated, high-temperature, marine, and vacuum environments, and systematically examines the influence of processing parameters, microstructural evolution, transfer layer formation, and counterface interactions on coating performance. Hybrid and duplex systems incorporating solid lubricants, polymer impregnation, sol–gel sealing, and multilayer architectures are discussed as strategies to overcome limitations associated with brittleness and surface porosity. Current research challenges, including fatigue degradation, coating defect control, limited cross-study standardization, and incomplete mechanistic understanding of process–microstructure, tribological relationships, are critically assessed. Emerging directions encompassing self-lubricating adaptive coatings, AI-guided process optimization, and multifunctional hybrid architectures are highlighted as pathways toward next-generation surface systems. This review provides a mechanism-based framework for understanding tribological behavior in PEO coatings and identifies critical opportunities for future industrial implementation in aerospace, automotive, marine, biomedical, and energy applications. Full article

Friction stir processing (FSP) is an advanced solid-state surface modification technique for biomedical titanium alloys. This study presents a computational investigation of FSP applied to Ti-6Al-4V alloy through three-dimensional finite element modeling and Taguchi-based statistical optimization. A Taguchi L9 orthogonal array evaluated rotational speed (400–1000 rpm), traverse speed (50–100 mm/min), shoulder diameter (6–18 mm), and pin diameter (2–6 mm), reducing the required simulations from 81 (full factorial) to nine (88.9% reduction). A calibrated friction model (μ = 0.35/0.25/0.20 for 400/800/1000 rpm, F = 6000 N) yielded maximum temperatures of 870–1384 °C; all predicted temperatures remained below the melting point of Ti-6Al-4V (1660 °C). These values are consistent with experimentally reported ranges for FSW/FSP of Ti-6Al-4V. Traverse speed is the dominant parameter (ANOVA contribution: 63.1%, F = 10.44), followed by rotational speed (26.7%) and shoulder diameter (4.1%). Simulation 3 (400 rpm, 100 mm/min, Ds = 18 mm, T_max = 870 °C) appears to be the most promising thermal condition for preserving the fine-grained α + β microstructure, as it remains below the β-transus temperature (980 °C) throughout the processed zone. Full article

TA15 titanium alloy fabricated by Laser Powder Bed Fusion (L-PBF) exhibits high strength but poor ductility due to its fine acicular α′ martensitic microstructure. This study systematically investigates the effects of post-annealing treatments (800–950 °C for 0.5–4 h) on the microstructural evolution and mechanical performance of L-PBF-built TA15. Results show that with increasing temperature and time, the metastable α′ martensite decomposes into a progressively coarser lamellar (α + β) structure. This transformation leads to a decrease in strength and hardness but a significant improvement in ductility, with elongation increasing from (8.5 ± 0.5)% (as-built) to (19.4 ± 1.1)% (900 °C/2 h) as the ultimate tensile strength (UTS) decreased from (1100 ± 29) to (895 ± 37) MPa. However, annealing at 950 °C, which approaches the β-transus temperature, induces a coarse Widmanstätten structure in the alloy. Although this structure yields a relatively high elongation (23.8 ± 3)%, it also leads to excessive strength loss, with an ultimate tensile strength of only (833 ± 23) MPa, rendering it less desirable for structural applications requiring high load-bearing capacity. Moreover, such coarse lamellar structures are generally associated with poor fatigue resistance, as cracks tend to propagate along prior β grain boundaries. An optimal strength-ductility synergy is achieved by annealing at 900 °C for 0.5 h, yielding an ultimate tensile strength of (951 ± 13) MPa and an elongation of (18.8 ± 1.7)%. These findings provide crucial guidance for tailoring the mechanical properties of L-PBF-fabricated TA15 alloy through post-processing heat treatments. Full article