Abstract:The effects of different aluminum ratios on the preparation of titanium-based alloys via aluminothermic reduction of high-titanium slag were investigated. Titanium-based alloys were prepared by self-propagating aluminothermic reduction using high-titanium slag, aluminum powder, KClO₃, and CaO as raw materials. The thermodynamics and kinetics of the aluminothermic reduction of high-titanium slag were calculated. The results show that high-titanium slag can be used to prepare titanium-based alloys via aluminothermic reduction. The main reaction is the reduction of TiO₂ by Al. The activation energy of the reaction is 274.4 kJ/mol, and the reaction order is 1.04. With the increase in aluminum ratio, the mass fraction of Ti element in the titanium-based alloy gradually decreases, and that of Al element gradually increases. At the same time, there are small amounts of alloying elements such as Fe, Mn, and Si in the titanium-based alloy. Phase analysis shows that under a low aluminum ratio, the main phase is Ti₃Al; under a high aluminum ratio, it is TiAl. The results of chemical composition analysis show that the prepared titanium-based alloy has a composition of 51.6wt% Ti, 40.6wt% Al, 7.6wt% Fe, 3.4wt% Mn, and 1.3wt% Si under the experimental conditions of aluminum ratio as 1.0. The microstructural analysis shows that the prepared titanium alloy consists of a base-phase region, an iron-rich phase region, and a silicon-rich phase region.

Abstract:Accurate prediction of hot deformation behavior is critical for numerical simulation and intelligent manufacturing of titanium alloy forgings. The high-temperature deformation characteristics of TC18 titanium alloy were investigated using isothermal compression tests on a Gleeble-3800 thermal simulator over the temperature range of 720–840 °C and strain rate range of 0.001–1 s^–1. To precisely describe the flow behavior, three strain-compensated Arrhenius (SCA) constitutive models were developed and evaluated: a linear regression-fitted SCA (LR-SCA) model, a genetic algorithm-optimized SCA (GA-SCA) model, and a response surface-modified SCA (RS-SCA) model. The results demonstrate that genetic algorithm optimization effectively identifies global optimal parameters, while the response surface modification successfully accounts for the coupling effects of temperature and strain rate. Statistical evaluation reveals that the RS-SCA model achieves superior predictive capability, with a correlation coefficient (R) of 0.9980 and a mean absolute relative error of 2.16%, a significant improvement over the LR-SCA model's 7.01%. The reliability of the established RS-SCA model is further validated through its secondary development in DEFORM-3D, where finite-element simulations under stable processing conditions show excellent agreement with experimental load-displacement curves. This robust constitutive model provides a solid foundation for finite element simulation and process optimization of TC18 alloy components in thermomechanical processing applications.

Abstract:The microstructural features of high-temperature titanium alloy Ti650 and their effects on mechanical properties were investigated. Results indicate that the S2-type (Ti,Zr)₆Si₃ silicide precipitates in the alloy exhibit no specific crystallographic orientation relationship with the matrix. Their morphology and distribution strongly depend on the microstructure type: in fine-lamellar Widmanst?tten structure, fine elliptical particles (20–60 nm) precipitate along the α/β interface; while in equiaxed, dual-phase, or coarse-lamellar Widmanst?tten structures, blocky silicides (approximately 200 nm) form within α grains. Room-temperature tensile tests reveal that equiaxed and dual-phase microstructures achieve the optimal strength-ductility balance (tensile strength of approximately 1100 MPa, elongation of approximately 13%). The fine-lamellar structure exhibits outstanding creep resistance at 650 °C and 100 MPa, with a steady-state creep rate nearly one order of magnitude lower than that of the equiaxed structure. Further mechanism analysis indicates that in the equiaxed structure, dislocations can traverse coarse silicide grains within the crystal via bypass mechanisms, allowing the creep process to persist. In contrast, fine spherical silicides are uniformly distributed within the lamellae and at grain boundaries. These silicides synergistically strengthen the lamellar structure, significantly increasing the energy barrier to dislocation motion and thereby conferring superior creep resistance on this microstructure.

Abstract:To address nodular protrusions on titanium alloy-closed impellers caused by gas entrapment during gelcasting of integrated Y₂O₃ (yttria) ceramic molds, this work established a predictive and control framework that couples a Carreau non-Newtonian viscosity model with a transient two-phase volume-of-fluid filling solver. Rheological experiments were fitted to obtain the Carreau parameters for the yttria slurry (relative error < 5%), enabling time-space reconstruction of bubble generation-migration-entrapment throughout filling. Results show that the simulated entrapment locations exhibit strong spatial correspondence with computed-tomography voids in ceramic molds and nodular defects on Ti alloy castings at both the impeller and bottom regions. Parametric studies indicate that a moderate filling velocity of 0.05 m·s^–1 markedly reduces trapped-gas volume; a bottom-fill configuration essentially eliminates entrapment in the impeller region; on this basis, applying horizontal vibration (50 Hz, 1 mm) during and after filling removes the remaining bubbles. Ceramic molds fabricated with the optimized parameters were verified by scanning, confirming the disappearance of gas entrapment within the impeller. The study provides a reusable framework for defect prediction and active process control in gelcasting of complex Ti alloy components.

Abstract:To address the failure caused by surface corrosion fatigue of titanium alloy structural components and to extend the service life of titanium alloys used in aircraft structures, supersonic fine particle bombardment (SFPB) technology was applied to the hot-rolled Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy with varying impact durations. This process created a gradient nanostructure on the surface of the samples, and various instruments and equipment were used to study the effects on the microstructure, microscopic morphology, and mechanical properties after different treatment time. Results show that when the SFPB treatment time is 60 s, the surface average nanocrystal grain size of the hot-rolled structure is minimized, measuring 30.4 nm. The surface roughness of the treated samples increases compared to the original ones, and the minimum surface roughness is obtained after treatment for 60 s. However, longer impact times leads to the formation of microcracks on the sample surface. The SFPB treatment introduces high compressive residual stress on the sample surface, resulting in a significant increase in microhardness. After the SFPB treatment, the strength increases, with a slight decrease in elongation before stabilizing. With treatment time of 60 s, the best combination of strength and plasticity is achieved. The corrosion fatigue life of the SFPB-treated sample is improved by 12.7 times compared to the untreated sample. The SFPB treatment is able to generate a gradient nanolayer near the surface of the TA15 titanium alloy, significantly enhancing its tensile properties and corrosion fatigue life.

Abstract:The dynamic globularization behavior, law, mechanism, globularization kinetic curve and model of TA15 titanium alloy lamellar structure were studied by pulse current assisted compression test and quantitative analysis of metallographic structure. The results indicate that the increase in current density further aggravates the flow softening phenomenon. The globularization rate increases with the increase in current density and deformation. Based on the Avrami equation, a dynamic electro-induced globularization kinetics model for TA15 alloy is established. The model predicts that the ranges of the critical strain ε_c for dynamic spheroidization and the strain ε_f for completing dynamic spheroidization are 0.090–0.187 and 5.02–6.31, respectively, and both decrease with the increase in current density. The globularization kinetics rate increases first and then decreases with the increase in strain and current density. In addition, the higher the current density, the greater the peak value of the spheroidization kinetics rate and the smaller the strain corresponding to the peak value.

Abstract:A numerical model was established using the finite volume method to establish a corresponding relationship between the simulated temperature with flow fields and the actual solidification structure of the ingot. The grain growth direction and grain morphology transformation of the industrial-scale Ti-1023 alloy ingot were investigated. The results indicate that the predicted grain growth direction (angle) of columnar grain at the bottom and edges of the ingot agrees with the actual one with coincidence degree more than 90% through temperature gradient components and . The temperature gradient-solidification rate (G-R) diagram was plotted. There is an obvious boundary between equiaxed and columnar grains, and the critical parameter G* for columnar-equiaxed crystal transformation varies under different melting processes.

Abstract:The influence of trace amounts of rare earth element Y on the high-temperature oxidation resistance was investigated for low-cost and easily deformable Ti44Al3Mn0.4W0.4Mo0.1B0.1C(TMMW) alloy at 800 °C. The microstructure and oxide film of the alloy were analyzed using EPMA, XRD, and TEM, and the underlying mechanisms of element Y affecting the high-temperature oxidation resistance of the alloy were explored. Results indicate that the addition of a trace amount of Y exerts a certain impact on the microstructure of the alloy. After identical heat treatment, the Y-free alloy primarily consists of γ, α₂, and β_o phases, whereas the Y-containing alloy not only contains these phases but also exhibits precipitation of the YAl₂ phase at lamellar boundaries and within the matrix, with minimal formation of Y₂O₃. Cyclic oxidation kinetics tests reveal that the oxide film formed on both alloys comprises a three-layer composite structure: TiO₂/Al₂O₃/TiO₂+Al₂O₃, with the transition layer mainly composed of TiMn₂-Laves phase and a small quantity of Mo- and W-rich β_o phase. The addition of 0.3at%Y effectively reduces oxidation mass gain, enhances spallation resistance of the oxide scale, and significantly decreases the βo phase content in the transition layer.

Abstract:To further enhance low-temperature toughness and clarify the low-temperature fracture failure mechanisms of titanium alloys, a TC4-0.55Fe alloy was prepared by micro-alloying with Fe, and its impact performance and fracture behavior were systematically investigated over the temperature range 20 ℃ to –196 ℃. The alloy exhibits a Charpy impact toughness of 66.8 J·cm^–2 at 20 ℃, which remains unchanged as the temperature drops to –20 ℃. When the temperature drops to –70 ℃, the low-temperature toughness decreases to 46.8 J ·cm^–2. When the temperature drops to –196 ℃, the toughness still retains 25.1 J·cm^–2, which is 23.8% higher than that of TC4 alloy. SEM image of fracture confirms that –196 ℃ is still above ductile-brittle transition temperature. of the alloy EBSD characterization reveals abundant deformation twinning in the vicinity of the crack at all test temperatures, with twin density increasing markedly as temperature decreases. The outstanding impact toughness of the TC4-0.55Fe alloy is attributed to the synergistic effects of fine-grain strengthening, the dispersion of fine acicular α_s precipitates within the β matrix, and a significant increase in twin density at low temperature, which jointly promote crack-path deflection and significantly enhance resistance to fracture.

Abstract:Carbon (C), as a crucial trace element in nickel-based superalloys, exerts a significant influence on mechanical properties even with minor variations in content. This study investigated the effect of C content on the microstructure and mechanical properties of a novel nickel-based superalloy GH4750. The results demonstrate that with increasing C content from 0.024wt% to 0.042wt% and then to 0.082wt%, the quantity and average size of M_C carbides increase. These carbides can effectively pin grain boundaries, resulting in a progressive reduction in grain size from approximately 35 μm to approximately 31 μm and ultimately to approximately 22 μm. Both the room-temperature and 750 °C tensile strengths initially increase and then decrease as the C content increases. Conversely, the elongation displays the opposite trend. The differences in tensile properties are closely related to the carbide characteristics. An appropriate increase in carbide content can inhibit the formation and coalescence of microvoids, effectively pin grain boundaries, and prevent grain boundary slip at elevated temperatures. Excessive carbides act as preferential sites for microcrack initiation. The stress-rupture life decreases with increasing C content, attributed to the larger grain size. Based on comprehensive consideration, the optimal C content for the novel nickel-based superalloy GH4750 is determined to be 0.042wt%.

Abstract:To tackle the segmentation challenges arising from the complex morphology, significant size variations, blurred boundaries, and tight interconnections of superalloy grains, this research presents a grain segmentation network integrated with a joint suppression attention mechanism that fuses channel and spatial information. The proposed network combines the global modeling capacity of Swin Transformer and the local detail restoration capability of a convolutional neural network (CNN), and embeds the aforementioned joint suppression attention mechanism, which integrates channel and spatial information, into the decoder. Results show that this mechanism effectively suppresses noise and texture interference, enhances the abilities of feature screening and generalization, and reinforces the fusion of shallow and deep features, thereby markedly improving the continuity of grain boundaries. Experimental results demonstrate that the proposed algorithm achieves an IoU of 67.34% and an F1-score of 78.62% on the self-constructed metallographic dataset, with all metrics outperforming those of mainstream grain segmentation algorithms for superalloys.

Abstract:Degradation behavior of the microstructure and mechanical properties of a long time serviced GTD111 DS superalloy turbine blade was investigated. Rejuvenation heat treatment was subsequently applied using a treatment of hot isostatic pressing (HIP) followed by solution and double-aging treatments. The results demonstrate that during service, pore density increases significantly from blade tip to root; MC carbides decompose into M₂₃C₆ carbides and η phase; secondary γ′ precipitates undergo severe spheroidization and rafting, accompanied by the dissolution of tertiary γ′ precipitates. The overall microstructural degradation pattern along the blade longitudinal axis follows the order: tip>central region>root>tenon. Along the transverse axis, it follows the order: trailing edge>leading edge>suction side>pressure side. The microstructure degradation directly leads to a progressive reduction in ultimate tensile strength at 25 and 980 °C and stress rupture life at 980 °C/220 MPa from the tenon to the blade tip. After rejuvenation heat treatment, the microstructure and mechanical properties are markedly improved. Area fraction of microporosity at the blade tip is reduced, MC carbides are partially restored, and the sizes of secondary and tertiary γ′ precipitates decrease to approximately 0.5 μm and 59 nm, respectively. Ultimate tensile strength of the blade tip increases from 810 MPa to 1122 MPa at room temperature and from 388 MPa to 468 MPa at 980 °C; the stress rupture life (980 °C/220 MPa) is prolonged from 1.95 h to 11.31 h. After rejuvenation, all mechanical properties at the blade tip exceed those of the tenon region.

Abstract:The effects of Co and C on microstructural characteristics and stability during long-term aging at 1000 °C in a novel hot-corrosion- resistant Ni-based single-crystal superalloy were investigated. Four single-crystal alloys with varying Co and C contents were prepared via directional solidification and characterized by SEM, EDS, EPMA, and TEM. The results show that C suppresses solidification micropores and reduces γ/γ′ eutectic fraction by promoting the precipitation of MC-type carbides, such as TaC. Co enhances the solid solubility of the γ-matrix, effectively inhibiting the segregation of Re, W, Ta, and Al, while carbides reduce the homogenization efficiency. Co lowers the γ′ solvus temperature and refines the size of γ′ precipitates, while C increases the solvus temperature and promotes γ′ coarsening due to the release of γ′-forming elements during carbide dissolution. During long-term aging, γ′ coarsening follows Lifshitz-Slyozov-Wagner (LSW) kinetics. Both Co and C reduce the absolute value of the γ/γ′ lattice misfit and increase the effective diffusion coefficient (D_eff). Co reduces the γ′ coarsening rates, while C accelerates it. The misfit dominates coarsening at fixed C content, whereas D_eff governs it at fixed Co content. Predictions from three models for topologically close-packed (TCP) phase precipitation show discrepancies with experimental data: Co promotes TCP formation, while C inhibits it through consuming MC carbides consisting of Mo and W.

Abstract:A novel core-shell nanocomposite was prepared by coating carbon onto aluminum nanoparticles (ANPs). As a typical energetic material, this nanocomposite absorbs the heat energy prior to ignition and combustion. Molecular dynamics simulations were used to elucidate the phase-transition mechanism of the nanocomposite upon heating and to analyze migration at the core-shell boundary. The results show that the critical melting point of carbon-coated ANPs (8 nm in diameter), at which the material transitions from solid to liquid, is approximately 1050 K. The interatomic potential energy of nanocomposites is lower than that of aluminum cores. Therefore, upon injection of thermal energy, the initial amorphous phase transforms into the liquid phase, which then diffuses from the surface to the core. Low interatomic potential energy leads to an earlier transition to the liquid phase. Furthermore, the core-shell ratio is the main factor affecting the critical melting point. The higher the core-shell ratio, that is, the thinner the carbon coating, the lower the melting point. Therefore, effectively controlling this parameter is an important indicator of ignition efficiency.

Abstract:La₂Sn₂O₇ powder was synthesized via chemical co-precipitation, and the Ag/ZnO/La₂Sn₂O₇ composites were prepared by hot-pressed sintering. The arc-erosion behavior and mechanisms of the composites were investigated at a constant voltage of 7 kV in CO₂, N₂, CO₂/c-C₄F₈, and N₂/c-C₄F₈ mixtures. The results show that the difference in arc breakdown current is very small across different atmospheres, while the erosion area, arc energy, and arc duration in mixed gas are clearly smaller than those in CO₂ and N₂. As the content of c-C₄F₈ rises, the breakdown strength in mixed gas increases gradually and is higher than that in CO₂ and N₂. The optical images of the arc show that the arc volume in mixed gas is obviously smaller than that in single-gas CO₂ or N₂, and the arc volume decreases gradually with the increase in c-C₄F₈ content. The erosion morphology analysis indicates that more pores, spattered particles, and cracks are present in the composites after arc-erosion in CO₂ and N₂. In the gas mixture, the erosion area is the smallest in the N₂/c-C₄F₈ (80/20) mixture, and particles and pores are significantly reduced. The low arc energy observed in N₂/c-C₄F₈ mixtures significantly reduces arc volume and erosion area. X-ray photoelectron spectroscopy results reveal partial decomposition of La₂Sn₂O₇ into La₂O₃ and SnO₂, while AgF and CF_x compounds are identified on eroded surfaces in c-C₄F₈ containing mixtures.

Abstract:The influence of ultrasonic treatment on the microstructure and tensile properties of as-cast Mg-12Gd-0.5Zr alloys was examined. The results indicate that ultrasonic treatment markedly refines the α-Mg grain structure, with the finest grains observed at an input power of 1500 W. This grain refinement is attributed to the combined effects of cavitation and acoustic streaming, which promote heterogeneous nucleation. Furthermore, the treatment reduces the size and number of the secondary Mg₅Gd phase while enhancing its spatial uniformity. A considerable dissolution of Gd atoms into the α-Mg matrix is also observed, likely due to the suppression of Gd segregation by acoustic streaming. Correspondingly, ultrasonic treatment yields notable improvements in ultimate tensile strength, yield strength, and elongation at room temperature. These improvements are primarily attributed to the refined microstructure and the increased solid solubility of Gd within the matrix.

Abstract:To overcome the limitations of poor room-temperature ductility and significant anisotropy in AZ91 magnesium alloy, a constant-strain-rate backward extrusion (CSR-BE) process was introduced to enhance deformation homogeneity through synergistic regulation of die curvature and strain rate. The methodology employs axisymmetric slip-line theory, combined with volume constancy principles, to derive a die profile equation that enables precise control of strain rates throughout deformation. Comprehensive DEFORM-3D simulations reveal that CSR-BE achieves a 9.3% reduction in extrusion force compared to conventional backward extrusion, accompanied by substantial improvements in deformation uniformity: a 99.96% decrease in flow velocity variance, an 85.2% reduction in stress field variation, and an 81.6% mitigation of temperature distribution fluctuations. Mechanistic analysis demonstrates that the optimized die geometry shifts the material flow dominance from radial shear to axial stretching, characterized by a decrease in the slip-line orientation angle from 36.27° at the inlet to 11.3° at the outlet. The engineered hydrostatic pressure gradient effectively alleviates localized stress concentrations, eliminates friction-induced dead zones, and suppresses strain-rate variations. Quantitative stress and flow-rate calculations confirm that this approach fundamentally addresses the microstructural heterogeneity inherent to traditional extrusion methods. CSR-BE process establishes a theoretically grounded manufacturing strategy for producing high-performance magnesium alloy rods with enhanced isotropy, demonstrating significant potential for industrial-scale applications through its combined efficiency and microstructural control advantages.

Abstract:Thermal management in electronic packaging is one of the important technical bottlenecks hindering the development of integrated circuits. Diamond/copper composites have excellent performance in the field of thermal management, but the difficulty in their complex structure formation leads to applications restricted in the field of water cooling in electronic packaging. In this research, the sintering performance between the green body and the composite plate was enhanced by employing a silver doping strategy, thereby addressing the thermal management challenges in electronic packaging. Composite base plates and pin-fin type composite base plates were prepared, and their application benefits were evaluated in both indirect and direct water cooling scenarios. Results demonstrate that the silver-doped copper billet achieves good sintering performance when combined with tungsten-coated diamond/copper composite plates. The composite base plate and the pin-fin type composite base plate effectively reduce the temperature of the heating sheet by 5–6 °C and 4–5 °C during water-cooling tests respectively. The numerical simulation results are in good agreement with the experimental data, confirming the excellent thermal uniformity of the composite structures. This research successfully overcomes the limitations associated with the low thermal conductivity of traditional packaging components and the challenges in fabricating complex structures using diamond/copper composite materials.

Abstract:To investigate the influence of solution and aging parameters on the strengthening and toughening mechanisms of 2195 Al-Li alloy, orthogonal experiments combined with range analysis were conducted. The regulatory rules of heat treatment regimes on the mechanical properties and microstructure of the alloy were illustrated. The results indicate that during solution treatment process, the 2195 Al-Li alloy exhibits significantly higher sensitivity to solution temperature than to solution time. Thus, to design the solution process, the appropriate solution temperature should be given priority consideration, followed by optimization of the corresponding holding time based on this temperature. In the aging stage, the strengthening effect of the 2195 Al-Li alloy is primarily dominated by the T₁ phase, and its precipitation behavior is strictly regulated by aging temperature and time. Under natural aging (under-aged state), the precipitated phases are predominantly δ′ phases, resulting in a relatively limited strengthening effect. At the peak aging stage, the T₁ phases exhibit characteristics of fine size, dispersion, and high density, and at this time, the strength of the alloy achieves its maximum value. Upon entering the over-aged stage, the coarsening of T₁ and δ′ phases lead to a decrease in alloy strength. Consequently, precise control of aging parameters provides an effective means of tailoring the type, size, and spatial distribution of strengthening precipitates, thereby optimizing the comprehensive mechanical properties of the 2195 Al-Li alloy to meet the requirements of its forming processes and structural applications.

Abstract:In this study, wear-resistant and corrosion-resistant cobalt-based Stellite 6 coating were fabricated on 17-4PH steel by laser cladding with varying Y₂O₃ content (0wt%, 0.3wt%, 0.6wt%, and 0.9wt%). The effects of Y₂O₃ addition on the microstructure, microhardness, wear resistance, and corrosion resistance of the laser-cladded Stellite 6 samples were investigated. The results indicate that the addition of Y₂O₃ changes the grain structure from coarse columnar grains to fine, uniform equiaxed grains. The sample with 0.6wt% of Y₂O₃ exhibits an average grain size of 54.6 μm, representing a maximum grain refinement of 66.0% compared to the sample without of Y₂O₃ addition. Furthermore, Y₂O₃ particles are mainly dispersed in the interdendritic regions of the Stellite 6 alloy samples, forming a particle layer in front of the dendrite grains, which inhibits grain movement and solute atom diffusion. The sample with 0.6wt% of Y₂O₃ addition shows the highest microhardness, with an average value of 532 HV. Due to the smallest grain size and spacing between Y₂O₃ particles, it also demonstrates the best wear resistance and corrosion resistance performance. Compared to the sample without Y₂O₃ addition, the maximum microhardness increases by 22.6%, the wear rate decreases by 72.2%, the corrosion potential increases by 25.6%, and the corrosion current density decreases by 39.8%.

Abstract:Lanthanum hexaboride (LaB₆) is an excellent high-temperature ceramic material for thermionic cathodes. However, the high brittleness of LaB₆ makes it difficult to process, limiting the further engineering application. In this study, Barium hexaboride (BaB₆) with low work function and Vanadium diboride (VB₂) with high elastic modulus were added into LaB₆. (La_0.5Ba_0.5)B₆-VB₂ composite with the high relative density of 98.57%, whose matrix is a single-phase solid solution, was prepared by spark plasma sintering (SPS) under the conditions of 1900 ℃, 40 MPa, and 5 min. As the sintering temperature increases from 1500 ℃ to 1900 ℃, the average grain size of the composite increases from 2.68±1.44 μm to 7.21±1.37 μm, Vickers hardness increases from 16.57±0.88 GPa to 24.89±1.26 GPa, fracture toughness increases from 1.95±0.16 MPa·m^1/2 to 3.81±0.28 MPa·m^1/2, and the maximum bending strength reaches 376.32 MPa. Crack deflection and branching are identified as the primary toughening mechanisms in the composite. (La_0.5Ba_0.5)B₆-VB₂ composite exhibits the maximum current density of 7.56 A/cm² and the minimum work function of 2.97 eV.

Abstract:TiZr-based refractory high-entropy alloys (RHEAs), known for their high hardness, compressive strength, and thermal phase stability, have garnered attention due to their potential application in armor-piercing warheads. This study introduced a machine learning (ML)-assisted approach to alloy design, aiming to uncover the complex relationships between composition and performance and to improve design efficiency. To address the critical requirement for hardness in armor-piercing applications, a 15-dimensional feature dataset was constructed from 157 experimental hardness data points, incorporating component molar fractions and five key descriptors. Eight ML models, including random forest, K-nearest neighbors, and support vector machines were trained, and XGBoost was identified as the most accurate through hyperparameter tuning via grid search and cross-validation. The SHAP (Shapley additive explanations) framework was applied to interpret feature contributions. Results indicate that the XGBoost model achieves the highest predictive performance (R2=0.73, and the average absolute percentage error is 14.0%). The most influential factors affecting alloy hardness are mixing enthalpy (), Nb content, and atomic size mismatch (). Effective hardness control relies on the synergistic regulation of thermodynamic stability, electronic structure, and geometric dimensions, where inter-feature compensation plays a critical role in optimizing overall performance.

Abstract:Discontinuous yielding of metal materials during room-temperature deformation is a critical scientific issue that significantly affects their mechanical properties and application safety. This review summarized recent research advancements in this field, with a focus on the characteristics, influencing factors, and underlying mechanisms of discontinuous yielding. The discontinuous yielding phenomenon was mainly characterized by a yield drop and a stress plateau on the stress-strain curve. Results show that microstructural characteristics such as alloy composition, degree of recrystallization, grain size and morphology, as well as phase composition and stability, serve as primary factors influencing discontinuous yielding. These factors affect the yielding behavior by regulating dislocation movement and deformation mechanisms. Furthermore, the intrinsic relationship among discontinuous yielding, room-temperature deformation mechanism, and the work hardening behavior in metallic materials was explored. Based on current research, future studies should focus on the microstructure regulation, alloy design, deformation mechanisms, and the development of constitutive models to deepen the understanding of discontinuous yielding and to provide a foundation for optimizing material properties.

Abstract:Laser cladding is widely employed for surface strengthening of titanium alloys and other metals owing to its advantageous metallurgical bonding and narrow heat-affected zones. Among various strengthening materials, WC is used as a superhard ceramic phase. Through its synergistic effect with Co, the hardness and wear resistance of the cladding layer can be effectively enhanced. However, research has demonstrated that laser power exerts a significant influence on cladding layer quality. When excessive power is applied, excessive dissolution of WC particles occurs, facilitating crack initiation and pore formation. Conversely, insufficient power commonly leads to defects, such as unmelted particles and porosity. This review focused on the influence of laser power on WC grain size and growth mechanisms within the coating, and summarized the wear resistance mechanisms of the coating. Furthermore, the main limitations currently encountered in the preparation of WC-Co coatings were analyzed, along with corresponding improvement strategies. Finally, existing challenges and future development trends were discussed.

Abstract:Nickel-based superalloys are widely used in critical hot-section components of high-end equipment such as aero-engines and gas turbines due to their excellent mechanical properties and oxidation resistance at elevated temperatures. As an advanced manufacturing method, laser directed energy deposition (L-DED) has demonstrated great potential in the repair of complex components, owing to its advantages such as mold-free near-net shaping, controllable energy input, small heat-affected zone, and dense microstructure in the deposited layer. However, during L-DED repair process, nickel-based superalloys undergo complex rapid melting and solidification, as well as repeated thermal cycling, resulting in unique microstructural features and a high tendency to develop typical metallurgical defects, such as pores, cracks, stray grains, and microstructure degradation, which can significantly degrade their mechanical performance. The typical defects and their control methods, as well as microstructural evolution characteristics were reviewed, and the key mechanical properties, including room-temperature tensile strength, high-temperature creep resistance, and fatigue performance, between directly deposited and repaired nickel-based superalloys were compared. Furthermore, based on existing theoretical models, the mechanisms of defect formation and microstructural evolution were analyzed, highlighting the current technical challenges and limitations in this field. This review provides a theoretical foundation and direction for the process optimization, microstructural control, and performance enhancement of L-DED-repaired or L-DED-formed nickel-based superalloys.

Abstract:Laser additive manufacturing, as an advanced digital forming technology, is widely used in the research of superalloy preparation. GH3536, as a solid solution strengthened nickel-based superalloy, is suitable for the preparation of components for combustion chambers of aero-engines due to its excellent mechanical properties. The control of metallurgical defects, microstructure modulation and mechanical property strengthening mechanism of laser additive manufacturing of GH3536 alloy were reviewed. The current research status and progress of laser additive manufacturing for GH3536 alloy were analyzed, and the research on the influence mechanism of its tensile and creep properties and other research was expected. It is hoped to provide reference for the research and development of laser additive manufacturing for GH3536 alloy.