Search Results (482)

The magmatic Ni-Co-Cu mineralization in the Iken deposit in the central part of the Kun-Manie complex, Amur Oblast, Russia, hosted by an olivine-bearing websterite, is of a low-sulfide type. The fine-grained disseminations of base metal sulfides (BMS), dominantly pyrrhotite, pentlandite (a major source of Ni of industrial importance), and chalcopyrite, are followed by a scarce Pd-Pt-Ag mineralization. Elevated contents of Al in orthopyroxene (mean 2.78 wt.% Al₂O₃) along with Al–Na enrichment in clinopyroxene (diopside; mean 5.10 wt.% Al₂O₃) are associated with highly aluminous compositions of low-chromium members of the spinel–hercynite series. High levels of TiO₂ in kaersutite and titanian phlogopite also reflect a pronounced degree of fractionation of the ore-forming melt. Minor portions of sulfide melt are distributed evenly as a result of immiscibility at advanced stages of orthopyroxene crystallization, after the formation of olivine. Differentiated grains of droplet-like BMS largely settled in situ close to grain boundaries of orthopyroxene or occupied interstitial spaces of pyroxenes and olivine in association with spinel–hercynite and fluorapatite. A combination of late saturation in S with relatively quick cooling rates of the hypabyssal body prevented the effective settlement and accumulation of sulfide droplets in the ore zone. The well-developed lamellae of troilite (Fe₅₀S₅₀) exsolved from the host pyrrhotite Fe₄₈S₅₂ during subsolidus cooling, as a consequence of a low-temperature reaction triggered by a sudden drop in fO₂. An influx of mantle-derived fluid bearing CO₂, CO, and CH₄ with the rising magma could be the primary cause of the fO₂ reduction. Also, graphite-bearing metasedimentary rocks could have been assimilated. Tiny grains of minerals of noble metals (moncheite and merenskyite with essential amounts of melonite component, sperrylite, hessite, alloy Au_63.2Ag_36.8, and argentopentlandite) deposited late in a fluid-enriched medium under submagmatic conditions. Full article

CoCrFeNi-based high-entropy alloys (HEAs) have shown great potential for widespread applications in aerospace, chemical, and medical equipment fields due to their high strength, wear resistance, corrosion resistance, and thermal stability. In the present study, a series of Ni₂CoCrFeV_xCu_y alloys were designed to obtain a ductile FCC matrix suitable for ceramic-particle reinforcement. Subsequently, two representative reinforcement strategies, namely, in situ TiC formation and direct TiN nanoparticle addition, were employed to investigate their effects on the microstructure and mechanical properties of the alloy. The results showed that Ni₂CoCrFeV_0.5Cu_0.2 exhibited the best strength–ductility balance, with a tensile elongation of 51.8% among the designed alloys. Besides, the comprehensive performance of high-entropy alloys can be effectively enhanced by in situ generation of TiC and addition of TiN particles. The in situ synthesized TiC exhibited a finer and more uniform distribution than the directly added TiN particles, resulting in a more favorable strength–ductility balance under the present processing conditions. Full article

Heat-treatable aluminum alloys are widely used in aerospace and automotive industries for high-performance structural applications. However, their processing through conventional fusion-based additive manufacturing is limited by solidification-related defects, such as hot cracking, porosity, and elemental segregation. To overcome these limitations, friction-based additive manufacturing (FBAM) has emerged as a promising solid-state alternative. FBAM primarily includes friction stir additive manufacturing (FSAM), additive friction stir deposition (AFSD), friction screw extrusion additive manufacturing (FSEAM), and friction rolling additive manufacturing (FRAM), which differ in feedstock form and process configuration. In these processes, feed material is consolidated through frictional heat generated below the melting temperature, enabling the formation of refined equiaxed microstructures while minimizing solidification defects. Despite these advantages, significant challenges persist in processing heat-treatable aluminum alloys, particularly the 2xxx, 6xxx, and 7xxx series. These include non-uniform microstructure and mechanical properties along the build direction; precipitation instability; process-induced defects, such as tunnel formation; and mechanical properties that are often inferior to those of the corresponding base materials (BMs). Reported FBAM builds generally exhibit equiaxed ultrafine grains below 1 μm; however, the strength and microhardness of heat-treated alloy builds commonly remain around 70–75% of the corresponding BM. Following post-heat treatment, microhardness can be nearly fully recovered, whereas UTS typically reaches about 80–85% of BMs, often with an associated ductility reduction of nearly 50%. This review critically analyzes research reported over the past decade on FBAM processing of heat-treatable aluminum alloys, covering FSAM, AFSD, FSEAM, and FRAM. The key challenges related to microstructural evolution and mechanical performance are systematically discussed for each alloy series. Furthermore, mitigation strategies proposed in the literature, including process parameter optimization, in-process cooling, post-heat treatment, and nanoparticle reinforcement (e.g., SiC, TiC, Ni and ZrO₂), are evaluated. Finally, existing research gaps are identified, and future directions are proposed to support the development of robust, scalable, and high-performance FBAM processes for heat-treatable aluminum alloys. Full article

The coupled effects of Ni and Ti additions on amorphization, spark plasma sintering (SPS) response, and hardness evolution were investigated in Al-rich Al–Fe–Nb-based metastable alloys. Mechanically alloyed Al₈₂Fe₁₄Nb₂Ni₂, Al₈₂Fe₁₄Nb₂Ti₂, and Al₈₂Fe₁₂Nb₂Ni₂Ti₂ powders showed progressive loss of long-range order, with the quinary alloy exhibiting the strongest amorphization tendency, consistent with its higher configurational entropy (5.420 J·mol⁻¹·K⁻¹) and more negative mixing enthalpy (−9.36 kJ·mol⁻¹). SPS displacement analysis revealed that primary displacement contribution occurs during heating and is progressively limited by crystallization-induced stiffening. Consolidation at 500 °C produced amorphous–nanocrystalline composites containing Al₁₃Fe₄ and Al₃Nb, whereas increasing the temperature to 550 °C promoted further devitrification. The highest hardness, 445.4 HV, was obtained for Al₈₂Fe₁₄Nb₂Ni₂, despite its lower amorphous-forming ability than the quinary alloy. This demonstrates that hardness is controlled not by maximum amorphization, but by the kinetic balance between amorphous retention, fine intermetallic precipitation, and densification efficiency. The results identify SPS as a coupled densification–transformation route for designing high-strength Al-based amorphous–nanocrystalline alloys. Full article

Bone staples that are in fixation of fractures or arthrodesis are mostly fabricated using Nitinol. While the attractiveness of this type of staple is widely recognized, concerns have been raised about the suitability of these staples in patients who are allergic to nickel. In this paper, current studies on bone staples are discussed and have found that existing bone staples are mostly Nitinol-based and are inapplicable to some patients who are allergic to Nitinol. The concept of digital triad (DT-II) is introduced to model, verify and validate bone staples with the consideration of installing parameters in an inserting process. A design study is defined to investigate the impact of two main inserting parameters on clamping forces of a staple. The study leads to the conclusions that with an appropriate adjustment on inserting parameters, new Ni-free β-Ti Alloy can be used to produce bone staples with clamping forces equivalent to those that are made from Nitinol-based materials. These findings may guide orthopedic surgeons in the selection of bone staples for use in a given fracture fixation or arthrodesis case. Full article

Solar-driven NiTi alloy wire rotary engines are promising for lightweight actuation, but their performance is often restricted by insufficient light absorption of the alloy wire and unstable wheel–wire transmission. In this work, a collaborative surface-modification strategy was developed by combining a CNT/PDA-based photothermal coating on the NiTi alloy wire with a CNT/PDMS-based coating on the wheel surface. To establish a controllable wire-coating process, electrophoretic deposition parameters were first screened on titanium plates using an orthogonal design involving voltage, duty ratio, water content, treatment time, and electrode distance. Among the tested conditions, an electrode distance of 10 mm provided the most favorable balance between coating thickness and microstructural uniformity, while water content and electrode distance were identified as the main factors affecting coating variation. After transfer to the alloy wire, the coating greatly reduced reflectance in the 300–1400 nm range and significantly enhanced photothermal heating, increasing the maximum irradiation temperature by about 30 °C. On the wheel side, PDMS-based surface modification further improved rotational output, and the 1.5 wt% + 10 wt% formulation showed the best performance. In coupled rotation tests, the system with simultaneous wire and wheel modification exhibited the fastest startup and the highest angular velocity, reaching about five times that of the slowest rotating modified group. These results demonstrate that coordinated surface modification of the alloy wire and wheel is an effective route to improving the photothermal response and rotational performance of NiTi alloy wire rotary engines. Full article

Metallic biomaterials are frequently exposed to chemically aggressive environments that may compromise surface integrity and corrosion resistance. Acidic media containing organic acids represent a relevant challenge for metallic systems, as they can destabilize passive oxide layers and promote surface degradation processes. The present in vitro study investigated acid-induced surface alterations in four commercially relevant orthodontic alloys—nickel–titanium (NiTi), copper–nickel–titanium (CuNiTi), titanium–molybdenum alloy (TMA), and stainless steel—as representative metallic biomaterials. Specimens were exposed to two commercially available acidic beverages with distinct pH conditions, followed by analysis of surface morphology, roughness, and elemental composition using atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results demonstrated pronounced alloy-dependent differences in degradation behavior. Stainless steel and TMAs exhibited significant increases in surface roughness and morphological alterations, whereas NiTi-based alloys showed comparatively stable surface characteristics. Elemental analysis revealed material-specific compositional variations, suggesting selective surface modification processes under acidic exposure. These differences can be attributed to variations in alloy composition, microstructure, and the stability of passive oxide layers, which collectively govern corrosion resistance in metallic systems. The findings provide insight into acid-induced degradation mechanisms in metallic biomaterials and highlight the importance of material-dependent corrosion behavior under chemically aggressive conditions. These observations may have implications for surface-mediated biological responses and long-term functional performance of metallic biomaterials. Full article

Cable wires provide a viable technical pathway for the laser additive manufacturing of high-entropy alloys (HEAs). However, the complex interplay of structural and material parameters of cable wires leads to significant variations in molten pool dynamics, which poses challenges to the fabrication of high-quality HEA coatings. To clarify the effects of these key factors on molten pool behavior, a multi-physics numerical model for the laser cladding of Al₅₀Si₆Ti₈Cr₁₂Cu₁₂Ni₁₂ cable wires was established in this study. A dedicated physical model for cable wires was developed, and the Level Set Method was employed to track fluid interfaces throughout the cladding process. Based on the proposed model, the temperature distribution, stress fields, and elemental homogeneity within the molten pool were systematically investigated. The results reveal that chromium (Cr) addition induces a viscosity reduction, and a torsional pitch of ≤4 mm is critical for achieving defect-free, compositionally uniform HEA coatings, which provides novel insights for process optimization and alloy design of cable-wire laser cladding. Full article

Laser cladding has attracted considerable attention for titanium alloy surface modification owing to its high energy density, rapid cooling rate, and excellent metallurgical bonding capability. To investigate the effect of Nb content on the microstructure and properties of NiTi-based coatings, composite coatings containing 10–40 wt% Nb were fabricated on a titanium alloy substrate via laser cladding. The effects of Nb content on phase constitution, microstructure evolution, mechanical properties, tribological performance, residual stress, and surface topography were systematically characterized using XRD, SEM, EDS, microhardness testing, wear testing, digital image correlation, and atomic force microscopy. The results show that increasing Nb content significantly affected the solidification behavior and phase evolution of the coatings. With increasing Nb addition, the dominant phase gradually evolved from NiTi to a coexistence structure of NbTi₄ and NiTi, while Ti dilution and elemental segregation became increasingly pronounced. The crystallite size increased from 19.63 nm to 25.91 nm, accompanied by intensified dendritic segregation and surface roughening. Among all samples, the coating containing 10 wt% Nb exhibited the best overall performance, characterized by the finest microstructure, the lowest surface roughness, the lowest residual stress, and the best wear resistance. The superior performance of the low-Nb coating was mainly associated with its finer and more homogeneous microstructure, reduced elemental segregation, lower stress concentration, and enhanced grain-boundary strengthening effect. Excessive Nb addition intensified Ti dilution, grain coarsening, residual stress accumulation, and microstructural heterogeneity, thereby degrading the overall coating performance. More importantly, this study reveals that Nb-regulated Ti dilution behavior governs the synergistic evolution of elemental segregation, surface roughening, residual stress accumulation, and tribological degradation during laser cladding. This work provides new insight into the process–structure–property relationship of NiTi-based composite coatings and offers theoretical guidance for the composition optimization and engineering application of high-performance laser-clad coatings on titanium alloys. Full article

Additive manufacturing of NiTi shape memory alloys is challenging due to their sensitivity to composition and thermal history. The gap between high-resolution powder-based AM and high-productivity wire-based processes for NiTi remains a challenge. This study investigates the technical feasibility of depositing Ni-rich NiTi (56 wt.% Ni) using a micro gas metal arc-based directed energy deposition (µ-GMA-DED) process with a 300 µm wire. The investigation was conducted on a single-bead, single-layer geometry deposited onto a titanium substrate. The deposited layer exhibited a heterogeneous microstructure with dendritic and eutectic-like regions, where phase analysis revealed a mixture of NiTi and Ni₃Ti intermetallics. Differential scanning calorimetry showed suppression of the martensitic transformation in the as-deposited condition, likely due to the high fraction of non-transformable Ni₃Ti, compositional redistribution during rapid solidification, and potential substrate dilution. The nanoindentation results reflected this heterogeneity, with Young’s modulus ranging from 64 to 151 GPa. While post-deposition heat treatment partially restored the martensitic transformation, these results demonstrate the preliminary feasibility of the µ-GMA-DED process, noting that strict control over chemistry and dilution is required before the route can be applied to functional components. Full article

Heat-assisted metal spinning comprises incremental forming routes, conventional spinning, shear spinning and flow forming, performed at elevated temperature to increase formability. This review consolidates the main advances of the last fifteen years. It outlines spinning mechanics and the rationale for heating (higher ductility, lower forming forces and microstructure control), then compares global and local heating strategies (furnace, flame, induction, laser and hot-gas convection) in terms of temperature uniformity, industrial practicality, energy efficiency and cost. Key process parameters (spindle speed, feed rate and thickness reduction) are discussed with respect to defect formation, and representative windows for defect mitigation are reported. Progress in modeling is reviewed, including coupled thermo-mechanical finite element simulations, damage/formability prediction and emerging data-driven optimization. The review also summarizes microstructural evolution under heat-assisted conditions, phase transformation, dynamic recrystallisation and grain growth, and its impact on final properties. Across more than 100 studies, evidence shows that robust thermal management can roughly double achievable deformation before failure and enables property tailoring in difficult-to-form alloys (Ni-based alloys, high-strength steels, Al, Mg and Ti). Remaining challenges include reliable in situ temperature measurement/control and improved predictive fidelity of simulations. Future opportunities include digital twins, real-time sensing and adaptive, machine-learning-assisted control. Full article

Machine learning interatomic potentials (MLIPs) are typically developed for globally ordered homogeneous systems (GOHomS), which exhibit only minor local deviations from equilibrium configurations. Consequently, most existing MLIPs trained on GOHomS often perform inadequately when applied to locally ordered heterogeneous systems (LOHetS), e.g., substitutional alloying elements in multicomponent alloys. To describe doping alloy systems, we develop a fine-tuned MLIP based on the MACE foundation model, specifically tailored for Mo-based dilute alloys containing one or two out of 20 substitutional elements: Cr, Fe, Mn, Nb, Re, Ta, Ti, V, W, Y, Zr, Al, Zn, Cu, Ag, Au, Hg, Co, Ni, and Hf. The model is built on more than 7000 equilibrium and non-equilibrium structures derived from first-principles density functional theory (DFT) calculations. The optimized large-scale fine-tuned model attains state-of-the-art accuracy, with a mean absolute error (MAE) and root-mean-square error (RMSE) of 2.27 meV/atom and 3.79 meV/atom for energy predictions, and 13.83 meV/Å and 24.26 meV/Å for force predictions, respectively. Systematic evaluation under different data-splitting protocols shows that unknown element extrapolation remains challenging under strict dopant hold-out, whereas substantially improved accuracy can be achieved in partial-exposure transfer settings. The fine-tuned models reduce the MAE by approximately 7–10 times compared to models trained from scratch, and by 10–20 times relative to zero-shot foundation models. This performance gain remains consistent across varying dataset sizes (equilibrium vs. non-equilibrium structures) and model scales. Our work illustrates the efficacy of transfer learning from globally ordered homogeneous systems to locally ordered heterogeneous multicomponent alloy environments. However, direct transfer to entirely unknown elements remains challenging, especially when proxy embeddings are employed without fine-tuning. Thus, to achieve high accuracy without incurring additional cost, it is essential to include unknown elements in the training dataset while minimizing the number of configurations containing known elements. Moreover, the current findings are primarily validated for dilute Mo-based alloy systems. Extending this approach to more compositionally complex alloy spaces may necessitate additional data and further fine-tuning. Full article

This study investigates the influence of design factors and key process parameters—including explosive welding (EXW), rolling, and laser processing—on the formation, microstructure, and tribological properties of Ti–Cu–Ni intermetallic coatings. A combined manufacturing approach was employed, starting with the EXW of an MN19 cupronickel alloy to a VT1-0 titanium substrate, followed by multi-pass rolling to achieve a cladding thickness of approximately 0.3 mm. Subsequently, laser surface remelting was performed to facilitate controlled mass transfer and homogenization within the reaction zone. Numerical simulation using COMSOL Multiphysics v. 5.4 was utilized to optimize the thermal cycles and determine the ideal energy density (42 J/mm²) for phase formation. The results demonstrate that the primary structural components of the coatings produced under optimal conditions are solid solutions based on the ternary-modified titanium cuprides Ti₂Cu(Ni) and TiCu(Ni). The transition from a layered bimetal to a finely dispersed intermetallic structure significantly enhances the surface characteristics. This specific phase composition provides a sustained microhardness of ~5 GPa across the coating cross-section. Comparative wear tests against fixed abrasive revealed that the wear resistance of the Ti–Cu–Ni coatings is 2.5 times higher at room temperature and 1.5 times higher at 600 °C than that of the base VT1-0 titanium. Full article

Three Ni-based composite coatings with varying TiCN/h-BN contents were fabricated on the surface of Ti-6Al-4V (TC4) alloy by laser cladding. The coatings were formulated with a fixed 15% TiCN and 0%, 2% and 5% h-BN, corresponding to L1–L3 coatings. The microstructure and phase composition were fully characterized and investigated. In addition, the microhardness and wear resistance of the coating were evaluated too. The analysis revealed that the L1–L3 coatings primarily consisted of Ti, TiNi, Ti(C, N) and TiAl₃ phases. Microstructural analysis indicated that the top region of the coating was predominantly composed of granular crystals, while the middle and bonding regions featured a combination of dendrites and white granular crystals. The average microhardness values for the L1–L3 coatings were measured at 1203.8, 1216.8 and 1235.5 HV_0.2, respectively, while the corresponding wear volumes were 0.098, 0.094 and 0.086 mm³. As the h-BN content increased, the microstructure of the Ni-based composite coating became finer and finer. Some TiB particles were also generated in the coating, which made the average microhardness and wear resistance increase gradually. Notably, the coating with 5% h-BN demonstrated the highest average microhardness and optimal wear resistance. Compared with the substrate, 5% h-BN increased the wear resistance of the substrate by 47.6%. The primary wear mechanism observed was abrasive wear. Full article

The recovery of oxygen-affine elements such as tantalum (Ta) using pyrometallurgical routes is difficult because this element cannot easily be enriched in a metal alloy, as is the case with battery recycling for the more noble metals Co, Ni, and Cu. A promising procedure, on the other hand, is to enrich this element in simple oxide compounds formed in a silicate melt. This enrichment in tailored mineral compounds is also known as the “Engineered Artificial Minerals” (EnAM) approach. Currently, the Technological Readiness Level (TRL) of this approach is relatively low and limited to understanding the mechanisms involved in the incorporation of target elements and the search for suitable compounds with a high enrichment factor, favorable morphology, and early crystallization during solidification in order to achieve maximum recovery yield of the selected compound (element). Due to its high ion charge (high field strength) and small ion radius for a heavy element, it is plausible that Ta behaves similarly to the abundant element titanium (Ti), whose chemistry is much better known. Ti minerals such as ulvospinel, perovskite, ilmenite, and pseudobrookite are therefore suitable candidates in the search for a suitable tantalum EnAM. A comparison of the solidification of synthetic silicate melts dominated by iron and calcium with Ti as an additive show that Ta is not incorporated into ulvospinel formed in olivine-containing Fe-rich silicate melts (base composition with 57 wt.% FeO). In contrast, the perovskites formed in silicate melts dominated by calcium-alumosilicate (max. 10 wt.% FeO addition) do incorporate Ta. Crystal size and Ta content increase with increasing iron content (up to a maximum of about 10 wt.%). The results indicate a possible solid solution with the well-known compounds CaTiO₃ and FeTiO₃ and the virtual compounds Ca_0.8TiO₃ and Fe_0.8TiO₃. Full article