Annealing temperature critically affects the deformation mechanisms and fracture behavior of laser powder bed fusion (LPBF) Ti-6Al-4V by governing microstructural evolution. In this study, we fabricated a series of LPBF specimens annealed at temperatures ranging from 650 degrees C to 1050 degrees C, and conducted quasi-static tensile tests along with microstructural and fractographic characterization and analysis. The results indicate that annealing temperature effectively regulates microstructure. Below the (3-transus, metastable alpha ' martensite decomposes into lamellar alpha+ (3, and the alpha laths coarsen with increasing temperature. Above the (3-transus (1050 degrees C), prior columnar (3 grains transform into equiaxed grains, which subsequently form alpha colonies upon cooling. A clear inverse relationship between strength and ductility is observed below the (3-transus, with the HT950 condition offering an optimal synergy of a yield strength of 821 MPa and an elongation of 18.40 %. Both yield strength and microhardness inversely correlate with alpha lath thickness. A progressive transition in the dominant deformation mechanism is observed with increasing annealing temperature, leading to a shift from coordinated dislocation slip and {1012} twinning in HT950 to a predominance of twinning in HT1050. Fractographic analysis confirms that the superior elongation of the HT950 specimen correlates with large dimples, whereas the activated {1012} twinning in HT1050 fails to promote intra-twin dislocation slip, leading to reduced ductility.

The fracture behavior of laser powder bed fusion (LPBF) fabricated Ti-6Al-4V components is significantly influenced by both manufacturing defects and microstructure. This study employed in-situ X-ray computed tomography (X-CT) to systematically characterize the distribution and evolution of manufacturing defects in LPBFproduced Ti-6Al-4V alloy during tensile loading. Combined with scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) analysis of microstructural characteristics and fracture surface morphology, this comprehensive approach reveals the coupled effects of manufacturing defects and microstructure on fracture behavior under tensile loading. The results demonstrate that defect evolution during the deformation process is sensitive to the defect type, with the morphological changes of lack of fusion (LOF) defects being more pronounced than those of gas pores and keyhole pores. Annealing treatment promotes the coarsening and globularization of alpha/alpha ' laths, which alters the deformation mechanism. Under as-built and 650 degrees C annealing conditions, microcracks tend to initiate at the boundaries of fine alpha ' laths, which, together with defect-induced local fracture, leads to a mixed ductile-brittle fracture. The coarsened alpha laths greatly enhance material toughness, effectively suppressing the adverse effects of manufacturing defects and promoting a fully ductile fracture. Notably, after annealing above the (3-transus temperature, the fracture behavior transitions to being microstructure-dominated, with alpha colony boundaries becoming preferential sites for crack nucleation, which promotes premature failure of the material, resulting in brittle fracture. These findings provide a theoretical basis for optimizing the post-processing of Ti-6Al-4V fabricated by LPBF.

Objective The integration of dissimilar titanium alloys via laser-directed energy deposition (L-DED) offers a promising avenue for fabricating advanced aerospace components with locally tailored properties. However, this integration is plagued by substantial challenges arising from interfacial property mismatches, which induce stress concentrations, strain localization, and premature failure under service conditions. These issues are primarily attributed to abrupt transitions in composition, microstructure, and mechanical properties across the interface. This study systematically investigates the efficacy of a multi-layer compositional gradient strategy in addressing these interfacial challenges for the high-temperature Ti65/TC25G titanium alloy system, with a particular focus on the mechanisms governing microstructural evolution and the resultant mechanical performance, in comparison to conventional direct deposition techniques. Methods The experimental methodology entails fabricating two distinct structural configurations on forged TC25G substrates via L-DED technology. For the first configuration, a 50 mm-thick layer of 100%Ti65 alloy is directly deposited onto the substrate, while the second features a meticulously engineered five-layer graded structure where the Ti65 mass fraction is incrementally elevated from 20% to 100% through precisely regulated compositional transitions, with each gradient layer designed to maintain a nominal thickness of 3 mm and topped with a final 10 mm-thick capping layer of pure Ti65 alloy. The L-DED process is conducted using a coaxial powder feeding system under a high-purity argon atmosphere with the oxygen volume fraction stringently controlled below 10(-3), and the key process parameters are optimized as follows-a laser power of 1100 W, a scanning speed of 8 mm.s(-1), a laser spot diameter of 3 mm, and a single-layer deposition thickness of 0.3 mm-with the powder feed rate meticulously calibrated for each targeted composition to ensure compositional accuracy. For comprehensive microstructural characterization, a scanning electron microscope (SEM) is employed to analyze the morphological features of the deposited layers, electron backscatter diffraction (EBSD) to determine the crystallographic orientation and phase constituents, and energy-dispersive X-ray spectroscopy (EDS) for elemental composition mapping across the interfacial regions, while the equivalent molybdenum mass fraction is calculated based on the experimentally measured compositions to quantitatively evaluate the variations in beta-phase stability within the graded structure. Mechanical performance assessments include Vickers microhardness mapping along the deposition direction with indentation spacing set at 200 mu m to capture spatial hardness distributions, tensile tests performed on specimens oriented perpendicular to the deposition direction (with the interfacial region intentionally positioned within the gauge length to evaluate interfacial bonding strength), and the integration of digital image correlation (DIC) to conduct in-situ full-field strain distribution measurements during tensile deformation, thereby enabling a detailed investigation of localized deformation behaviors and strain concentration phenomena. Results and Discussions Microstructural analysis reveals fundamentally distinct characteristics between the two deposition strategies. Direct deposition exhibits abrupt interfacial transitions, with localized clustering of lath alpha-phase in Ti65 deposits adjacent to the interface, accompanied by significant compositional fluctuations. EDS analysis demonstrates sharp gradients in critical beta-stabilizing elements-including Mo, Sn, Ta, and W-across the interface. The calculated equivalent molybdenum mass fraction profile shows a rapid decrease from approximately 9% in the substrate to 2.72% in the deposited layer, and abruptly crosses the stability range from alpha+beta to alpha-type. This microstructural and compositional heterogeneity directly manifests as mechanical incompatibility: microhardness profiles exhibit fluctuations within the Ti65 layer (averaging 377 HV), while tensile testing reveals pronounced strain localization (maximum local strain of 1.6%), leading to consistent fracture within the deposited material. In contrast, the graded structure facilitates continuous microstructural evolution, transitioning from fine acicular alpha/alpha' phases at the fusion line (aspect ratio of similar to 8.8) to coarse lath alpha-phase in pure Ti65 regions. Elemental distribution shows enhanced homogeneity, with the equivalent molybdenum mass fraction decreasing gradually from 9% to below 2.5% across a substantially wider transition zone. This controlled gradient promotes the steady evolution of the alpha/beta phase ratio, as confirmed by EBSD phase fraction maps. Mechanical performance is notably improved.The graded interface achieves a peak microhardness of 474 HV at the fusion zone, attributed to refinement strengthening from the fine acicular phases. Tensile properties exhibit moderate enhancement (ultimate tensile strength of 982 MPa, yield strength of 905 MPa,compared to 965 MPa and 892 MPa for direct deposition), while DIC analysis reveals fundamentally superior deformation behavior.Strain concentration occurs primarily in the TC25G substrate (maximum strain of similar to 1.9%), with well-defined strain gradients across the interface-indicating effective load transfer and coordinated deformation. This optimized stress distribution results in consistent "fracture mode transfer" to the base material, unequivocally demonstrating enhanced interfacial integrity. Conclusions This study demonstrates that a five-layer gradient deposition strategy successfully achieves continuous interfacial transitions in Ti65/TC25G dissimilar alloys and effectively mitigates the microstructural and compositional discontinuities inherent to direct deposition. The graded architecture not only enhances local hardness through microstructural refinement but also fundamentally modifies failure mechanisms by facilitating homogeneous load distribution and enabling the transition of fracture paths to the substrate.A Ti65 mass fraction range of 60%-80% is identified as particularly critical for balancing microstructural continuity with gradual mechanical property transitions. These findings provide a validated framework for the design and fabrication of high-integrity functionally graded titanium components via L-DED, and advance the integration of dissimilar materials in critical aerospace components requiring optimized performance and reliability. Furthermore, this work establishes a robust, experimentally validated framework for the design and manufacturing of high-integrity, functionally graded titanium alloy components using L-DED. It emphasizes the indispensable role of coordinated "composition-microstructure-property" control in overcoming interfacial incompatibility issues in dissimilar high-performance alloys, thereby paving the way for their successful application in demanding aerospace components-such as integrally bladed rotors (IBRs) and other critical aero engine structures.

VTiTa refractory multi-principal element alloys (MPEAs) are promising for irradiation environments, yet the role of local chemical order (LCO) in their radiation response remains to be clarified. We simulated collision cascades in VTiTa with random solid solution (RSS) and LCO states using molecular dynamics with a machine-learned potential. At the thermal-spike stage, LCO VTiTa lowers the peak number of Frenkel pairs (FPs) relative to RSS by about 35% at 10 keV, whereas the difference becomes much smaller at 50 keV. At the end of cascade simulation, however, RSS and LCO VTiTa retain comparable numbers of residual FPs, indicating that under single-cascade conditions LCO has only a limited effect on the final surviving point-defect population. Its main influence is instead manifested in defect morphology and clustering behaviors: relative to RSS VTiTa, LCO suppresses vacancy clustering and retains defects in a more dispersed form, and dislocation loop formation is noticeably weaker in both VTiTa structures than in pure V and VTa. These results show that the primary effect of LCO is to modify early-stage defect production and subsequent clustering behavior, and they provide atomistic guidance for the design of radiation-tolerant refractory MPEAs through control of chemical order.

The BSi-microalloyed CrCoNi medium entropy alloy (MEA) fabricated by circular oscillating laser directed energy deposition (COL-DED) shows excellent yield strength (YS) both in the as-printed and aged conditions. The as-printed CrCoNiB0.03Si0.03 MEA demonstrates an average ultimate tensile strength (UTS) and YS as high as 1014.7 MPa and 752.7 MPa, representing significant improvements of 78.9 % and 81.7 % compared to CrCoNi. After aging treatment, the UTS and fracture elongation of this alloy are further increased by 4.5 % and 25 % compared to the as-printed state. Microstructural analysis reveals that BSi microalloying induces a transformation of the matrix from a single-phase FCC to an FCC-BCT dual-phase structure, forming a lamellar BCTCr2B eutectic phase in the interdendritic regions. The incoherent interface between this phase and the FCC matrix creates a high-energy barrier, while the average grain size is refined from 94.8 mu m to 59.2 mu m. Aging treatment further promotes the proliferation of Cr2B phases. The synergistic effects of precipitation strengthening, grain boundary strengthening, and dislocation strengthening induced by the hard and brittle Cr2B phase in the matrix contribute to the enhanced mechanical performance of the MEA. This study elucidates the regulatory mechanism of BSi microalloying combined with aging treatment on the strengthening and toughening of MEAs.

To improve the tribological performance of TC18 alloy under harsh service conditions, we engineered TC4-based composite coatings reinforced by a multi-scale TiC architecture via laser cladding. Through systematic process optimization, dense and crack-free coatings with robust metallurgical bonding are successfully achieved. Microstructural characterization reveals a dual-phase alpha-Ti/beta-Ti matrix embedded with a hierarchical TiC reinforcement system: in-situ synthesized fine TiC precipitates are homogeneously dispersed to promote grain refinement, while coarse, ex-situ TiC particles act as an unyielding load-bearing macro-skeleton. This synergistic multi-scale TiC architecture increases the coating hardness to 589.83 HV0.3, about 1.7 times that of the substrate. Meanwhile, the coating exhibits significantly low friction coefficient and wear rate under both dry sliding (DS) and grease-lubricated (GL) conditions. The dominant wear mechanism fundamentally transitions from severe abrasive and adhesive wear of the substrate to mild abrasive wear of the coating. Notably, under GL conditions, the coating shows an extremely low wear rate of 3.65 & times; 10- 5 mm3/(N center dot m), which is a remarkable 92% reduction relative to the substrate (46.20 & times; 10-5 mm3/(N center dot m)). This exceptional wear resistance is primarily attributed to the synergistic effect of the multi-scale TiC architecture and grease-assisted boundary-lubrication state. These findings provide a robust design paradigm for developing advanced, wear-resistant coatings tailored for critical aerospace components.

Immiscible alloys hold great promise for industrial and electronic applications. The complexity of liquid-phase separation and the difficulty of in situ observation often necessitate numerical simulation. However, twodimensional models cannot capture genuine three-dimensional morphology or coupled multiphysics effects. To overcome these limitations, a three-dimensional phase-field model was developed for the Cu-Co binary system, coupled with systematic undercooling experiments to investigate the dynamic evolution mechanisms of phase separation. The results show that, under the combined effects of Marangoni motion and Ostwald ripening, Cu-Co alloys with different compositions undergo distinct microstructural evolutions, eventually forming coreshell structures with a Co-rich core and a Cu-rich shell. The phase with a lower volume fraction preferentially migrates and nucleates toward the interior of the melt, while differences in surface tension determine the final morphology of the core-shell structure. The simulation results show a high degree of consistency with the experimentally processed alloys morphologies, thereby validating the model and providing a reference for threedimensional modeling of alloy microstructural evolution under coupled multiphysics conditions.

The interactions between growing dendritic crystals and melt convection during pure substance solidification process ultimately determine the patterns of final microstructure. In the present study, a discrete kinetic scheme for dendrite growth in the presence of thermal convection is proposed. The scheme is derived from an anisotropic Boltzmann equation and utilizes the solution of characteristic lines to numerically compute fluxes at cell faces. An operator splitting method is used to address the anisotropic coefficient attached to the time-derivative term in the flux reconstruction step. Through Chapman-Enskog analysis, the scheme is shown to reproduce phase-field equation under certain conditions. This approach is straightforward and intuitive, allowing seamless integration into a unified kinetic computational framework, applicable to both uniform and non-structured meshes. The melting flow and heat transfer are modelled by Boltzmann-Shakhov equation, which is solved by discrete unified gas kinetic scheme. To test the discrete kinetic scheme, the growth of a single equiaxed dendrite of a pure substance in an undercooled melt with and without thermal convection were simulated and analyzed. Furthermore, the effects of the incoming flow velocity on the dendrite morphology and flow pattern are investigated. The results show that the proposed scheme has a good performance in predicting dynamic dendritic morphology. This method is expected to have some promising applications in simulating complex interface evolution during liquid-solid anisotropic phase transition.

Objective TA15 is a near-alpha titanium alloy with excellent high-temperature strength and creep resistance, and is widely used in aerospace components required to serve for long periods at 450-500 degrees C. Thin-walled structures, as typical characteristic structures in the aerospace field, can achieve an optimal balance between lightweight design and functional performance. Compared with traditional subtractive manufacturing, laser powder bed fusion (LPBF) enables the fabrication of components with complex geometric structures, lightweight design and optimized internal features. Thus, LPBF technology is revolutionizing the manufacturing methods of titanium alloy components. For titanium alloy components serving for long periods in high-temperature environments, their high-temperature creep and stress rupture properties directly determine the service life and reliability of the components. The creep performance of titanium alloys is highly dependent on their internal microstructure. Importantly, the unique forming process of LPBF means that variations in thickness, orientation and height all induce changes in the microstructural scale of the alloy, ultimately leading to differences in mechanical properties. Therefore, for TA15 alloy components serving for long periods in high-temperature environments, investigating the effects of thickness, height and orientation on their high-temperature stress rupture properties is particularly critical for ensuring the service reliability of such components. Methods TA15 alloy thin-walled structures with thicknesses ranging from 1 mm to 4 mm are fabricated by LPBF. Samples are taken from the same height positions of thin-walled structures with different thicknesses and from different height positions of thin-walled structures with a 2 mm thickness, respectively. First, the microstructure and defects of the thin-walled samples are characterized by means of optical microscopy (OM), laser scanning confocal microscopy (LSCM), and electron backscatter diffraction (EBSD), and then high-temperature stress rupture tests are conducted on the thin-walled samples with different thicknesses and heights. Furthermore, the evolution laws of the microstructure, defects and high-temperature stress rupture properties of the thin-walled structures with varying thickness and height are investigated. In addition, the high-temperature stress rupture properties of the samples along different loading orientations at the same height are compared to investigate the anisotropy of the thin-walled structures. Results and Discussions This research finds that the size of prior R grains decreases with increasing thickness and decreasing height from the substrate, while the width of alpha lamellae decreases with decreasing thickness and decreasing height from the substrate. The stress rupture properties of the alloy show obvious anisotropy, and the stress rupture life decreases with increasing thickness and decreasing height from the substrate. This is mainly because the sizes of prior R grains and alpha lamellae exert a significant influence on the creep resistance of the alloy: the larger the size of prior R grains and the smaller the width of alpha lamellae, the better the creep resistance of the alloy and the longer its stress rupture life. Conclusions The microstructure and high-temperature stress rupture properties of TA15 alloy thin-walled structures fabricated by LPBF are closely related to thickness, height and loading orientation. This research finds that with the reduction of thickness, the size of prior R grains increases nonlinearly with a sudden coarsening at a thickness of 1 mm, while the width of alpha lamellae decreases slightly; at this point, the stress rupture life of thin-walled samples increases with the reduction of thickness, and the stress rupture life of 1 mm thick thin-walled samples is 13.4% higher than that of 4 mm thick samples. With the decrease in height from the substrate, both the sizes of prior R grains and alpha lamellae decrease; at this point, the stress rupture life of thin-walled samples shows a decreasing trend as the height from the substrate decreases, and the stress rupture life of the samples at a distance of 25 mm from the substrate is 26.3% lower than that of the specimens at 65 mm. The stress rupture properties of thin-walled specimens show obvious anisotropy, and the stress rupture life for the loading direction parallel to the building direction is 30.5% higher than that for the direction perpendicular to the building direction. Analysis reveals that the alloy exhibits transgranular ductile fracture when the loading direction is parallel to the building direction, and at this point, the thinner the alpha lamellae and the larger the R grain size, the stronger the creep resistance of the alloy and the longer the stress rupture life. When the loading direction is perpendicular to the building direction, the alloy exhibits intergranular brittle fracture, and at this point, the R columnar grain boundaries bear Mode I opening tensile stress; the smaller the grain size and the higher the grain boundary content, the lower the stress rupture life.

The tribological properties and tribo-induced microstructural and chemical evolution of additive manufactured AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) at elevated temperatures are systematically investigated in this study. The AlCoCrFeNi2.1 EHEA consisting of FCC/BCC eutectic lamellae was produced by direct energy deposition. There is a distinctive monotonic decline in the coefficient of friction and wear rate from 0.58 and 1.97 x 10-4 mm3 N-1 m-1 to 0.4 and 1.97 x 10-5 mm3 N-1 m- 1 with increasing temperature from 25 degrees C to 1000 degrees C, accompanied by the transition of surface morphologies from loose debris accumulation to full coverage of oxide layer. The chemically stratified Cr2O3/Al2O3 bilayer in the topmost region provides self-lubricating and sustained protection. Coupled with the strain accommodation capability derived from the subsurface dynamic recrystallization microstructure, both factors synergistically contribute to superior wear resistance at 1000 degrees C. These findings offer valuable guidance for the future design of high-temperature wear-resistant materials.

In metals and alloys, solute segregation at grain boundaries typically undermines cohesion and ductility. Here, we overturn this paradigm by showing that solvent Fe atoms can preferentially enrich low-angle grain boundaries (LAGBs) in a ferrous alloy, dramatically enhancing ductility. Cold rolling and aging generate coherent nanoprecipitates, a high dislocation density, and abundant LAGBs in an austenitic matrix, yielding an ultrahigh tensile yield strength of similar to 1.74 GPa. Moreover, the solvent Fe enrichment at LAGBs lowers local stacking fault energy and activates austenite-to-martensite transformation under load. This transformation-induced plasticity effect stabilizes plastic flow, enabling a uniform elongation of similar to 26.2 % despite the alloy's exceptional strength. Our findings challenge conventional views of segregation and offer a new design strategy for ultra-strong, highly ductile alloys.

The magnetic field, along with temperature, significantly affects the mechanism of phase transformation, requiring detailed quantitative analysis. In this study, the influence of a magnetic field on the gamma-alpha (austeniteferrite) isokinetic phase transformation process of an Fe-1wt% Cu alloy was quantitatively analyzed through kinetics analysis by in-situ magnetization measurement. The kinetic calculation results demonstrate that the magnetic field accelerates the gamma-alpha phase transformation, leading to shorter transformation time, increased transformation rate, and grain refinement. Quantitative analysis of Avrami exponent, driving force, nucleation barrier and activation energy directly indicates that the magnetic field induces a shift from a site saturation nucleation mode to a continuous nucleation mode, increases the driving force of phase transformation, and reduces the nucleation barriers and activation energy, ultimately resulting in a higher nucleation rate, faster phase transformation rate, and more uniform and finer grain structure. Simultaneously, the magnetic field alters the impingement mode during isokinetic phase transformation, shifting it from anisotropic growth impingement to randomly dispersed nuclei impingement.

Rotary burrs made of WC-8Co cemented carbide are widely used in automated filing systems, yet rapid cutting-edge wear significantly limits their performance. For this purpose, coupled electromagnetic treatments were applied to the WC-8Co cemented carbide region of rotary burrs to enhance their cutting performance. Four key performance parameters were evaluated: average cutting-edge wear, cutting-head diameter wear, average machining depth, and material removal amount. The cutting performance and the resulting surface roughness of workpieces machined with treated and untreated burrs were compared. As a result, under optimal conditions (0.6 T magnetic field and 1.2 V electric field), coupled electromagnetic treatment reduced average cutting-edge wear and cutting-head diameter wear by 15.4% and 21.4%, respectively, increased average machining depth and material removal amount by 21.3% and 25.2%, respectively, and decreased the surface roughness of the machined workpieces by 36.2%. The study through experimental and numerical analysis confirmed that these enhancements in cutting performance are largely attributed to the increased thermal conductivity and hardness of the treated burrs, which result from reductions in magnetic domain walls and increases in crystal defects induced by the coupled electromagnetic treatment. Such changes collectively suppressed adhesion wear, oxidation wear, and abrasive wear, thereby enhancing the tool's cutting performance.

The mechanism of the influence of the gradient magnetic field on the dual FCC phase system was revealed using CoCrCuFeNi high-entropy alloy. Applying 75 T2/m GMF, the grain size of the alloy was refined from 58 mu m to 39 mu m, the proportion of Cu-lean FCC1 phase increased from 77.2 % to 97.5 %, and a regular orientation was formed. Such microstructure and phase transform have divergent effects on mechanical and magnetic properties. The hardness of CoCrCuFeNi high-entropy alloy increased from 305 HV to 389 HV, the increase in saturation magnetization was attributed to the dominance of the regularly oriented phase structure and the high concentration of ferromagnetic elements, and the grain refinement led to an increase in grain boundary density, which slightly increased the coercivity. This work provides ideas for analyzing the mechanical and magnetic evolution of high-entropy alloys caused by complex changes in microstructure and multiphases.

Continuous carbon fiber-reinforced polyether ether ketone (CCF/PEEK), a thermoplastic composite, holds significant promise for applications in aerospace and automotive manufacturing. However, challenges such as temperature gradients during printing and insufficient fiber impregnation result in weak interfacial properties, making internal defects and failure mechanisms key areas of research. This study employs high-resolution synchrotron x-ray computed tomography (SR-CT) and digital volume correlation (DVC) to investigate the failure modes, defect evolution, and internal three-dimensional strain distribution in CCF/PEEK samples during tensile testing. The analysis reveals that strain concentrates in regions with dense continuous fiber distribution before material failure, while post-failure strain localizes within interlaminar cracks. Furthermore, defect evolution analysis suggests that extensive fusion and growth of defects around fibers may serve as precursors to material failure. These findings indicate that weak bonding at the fiber/resin interface is the primary cause of tensile failure in CCF/PEEK, providing valuable insights for failure prediction and optimization of molding processes.Highlights Observation of CCF/PEEK failure modes using synchrotron radiation CT. Bulk cracks are concentrated in the interlaminar and fiber/resin interfaces. Significant difference in defect evolution before and after tensile failure. Strain concentration in the CCFs aggregation region predicts tensile failure.

Soft magnetic materials with tunable magnetization response are urgently needed for next-generation adaptive electromagnetic devices, yet conventional alloys face inherent limitations in balancing high saturation magnetization (M-s) and controllable magnetic sensitivity. Here, we propose CuFeCo immiscible alloys fabricated via directional solidification to overcome this challenge. By introducing immiscible Cu-rich phase into the FeCo-rich matrix, coupled with controlled pulling speeds (10-200 mu m/s), we achieve simultaneous enhancement of M-s and precise adjustment of the slope of the magnetization curve (dM/dH). The resulting alloy exhibits an exceptional M-s of 160.7 emu/g (at 200 mu m/s), while enabling a wide-range dM/dH adjustment from 38 to 83 kA/(mT). Our analysis reveals that changes in the directional solidification pulling speed induce a transition in the solidification microstructure from cellular dendrites to fibrous dendrites. A Cu-rich zone exists between FeCo-rich dendrites, and as the dendrites become progressively refined, the FeCo-rich phase fraction increases, leading to an enhancement in M-s. The < 001 > texture volume fraction of the FeCo-rich phase, dominated by preferential growth competition, increased from 32 % to 57 %, contributing to the enhancement of dM/dH. Magnetocrystalline anisotropy induces differential magnetization rates between the parallel and perpendicular orientations in the microstructure. Additionally, coercivity (H-c) exhibits an initial increase followed by a subsequent decrease, as FeCo-rich/Cu-rich phase boundaries gradually replace FeCo-rich dendrites grain boundaries, making the strip-like domains more continuous. Our work establishes a paradigm for designing property-programmable soft magnetic materials, bridging the gap in adaptive electromagnetic functionality.

A mesoscopic lattice Boltzmann model is proposed to investigate the dynamic evolution of solidstate structures during the hexagonal-to-orthorhombic transition, incorporating the micro-elastic theory. The model enables detailed observation of the morphology of both single- and multi- variant systems. The analytically recovered macroscopic governing equation is fully consistent with the kinetic theory, and the interactions between different domains are well characterized. The strategy opens up a vast range of solid-state phase transitions, particularly those involving multi-phase and multi-domain systems.

A high-Nb TiAl, Ti-47.5Al-7Nb-0.2W was fabricated by electron beam melting (EBM) with varying line offset. Defects, microstructure and tensile properties of as-built and hot isostatic pressing (HIP) materials were studied. For the first time to our knowledge, we reveal that the layered structure in EBM TiAl forms because of the preferential coarsening of γ grains in Al-rich regions during HIP. A smaller line offset leads to more Al evaporation, fewer coarsened grains and therefore higher strength, with yield strength reaching 776 MPa when line offset is 0.15 mm (HIP material). Dislocation glide and twinning are the main deformation modes; twin intersection and blocking of dislocation by twins are found to strengthen the alloy. The present alloy outperforms existing cast/EBM TiAl alloys (e.g., TiAl 4822) across temperatures (25–850 °C), demonstrating potential for high-temperature aerospace applications.

TiAlV-based alloys are ideal for designing lightweight materials; however, the addition of V does not mitigate the inherent brittleness of TiAl-based alloys. This paper presents a novel alloying strategy to enhance the room temperature ductility of TiAlV-based alloys produced via coaxial electron beam wire additive manufacturing. By leveraging the unique characteristics of the cold-cathode electron beam heat source, Cu was introduced into TiAlV-based alloys through in-situ dual-wire alloying process. The resulting Ti48Al2V alloy and Ti48Al2V1.27Cu alloy samples exhibited good appearance, free from microcracks and porosity, due to the stable dual-wire transition state, real-time layer height control, and closed-loop temperature control. A comprehensive comparison between the Ti48Al2V alloy and the Ti48Al2V1.27Cu alloy was conducted, focusing on grain morphology, chemical composition homogeneity, phase constitution, and mechanical properties. A multiphysics numerical model was developed to elucidate the feeding, melting, and mixing of dissimilar wires, as well as melt pool convection and the influence of phase transformations on the solidification behavior of TiAl-based alloys. The strengthening mechanism of the alloy's room temperature ductility was thoroughly explained. Results indicate that the selection of Cu, with its face-centered cubic structure, for the composition design of TiAlV-based alloys is justified based on thermodynamic calculations. A near-lamellar (NL) microstructure and enhanced room temperature ductility was achieved through precise process parameter control. The tensile strength at room temperature and 650 degrees C improved by 5.6 % and 4.5 %, respectively, while the elongation at room temperature and 650 degrees C increased by 39.3 % and 36.2 %, respectively. This study provides valuable insight for further low-cost insitu alloying methods to regulate the microstructure and enhance the room temperature ductility of TiAlV-based alloys.

The promising application potential of refractory high-entropy alloys (RHEAs) in high-temperature extreme environments is restricted by the difficulty in their preparation, especially for the components with complex shapes. Laser powder bed fusion (LPBF), as an advanced additive manufacturing technique, has been employed for fabricating RHEAs; however, their mechanical properties were still limited. In this study, different contents of B4C nano-ceramic particles were introduced to reinforce WMoTaTi refractory high-entropy alloys via LPBF, and the effects of B4C on the microstructure and mechanical properties of the alloys were systematically investigated. Room-temperature compression tests demonstrated that the yield strength of the alloy was markedly increased from 1062 MPa to 1558 MPa with the addition of 1.0 wt% B4C, while a high strength of 536 MPa was achieved at testing temperature of 1200 degrees C, indicating exceptional high-temperature properties. Through a comprehensive analysis, the multiple strengthening mechanisms were discussed to understand the strengthening effect of B4C particles. This study not only provides new experimental evidence for the strengthening of RHEAs by nano-ceramic particles but also expands the potential of LPBF technology for the fabrication of materials for extreme environments.