The effects of adding 1at% early transition metals (M=Ti, V, Cr, Zr, Nb, Mo) on the melt-spun structure, crystallized microstructure, and magnetic properties of Fe84.5B13Cu1.5M1 alloys were investigated. The mechanisms of different M elements in regulating the alloy structure and magnetic performance were also discussed. Results show that except for the M=Zr alloy presenting fully amorphous state in the as-spun condition, other alloys all contain pre-existing alpha-Fe grains dispersed in amorphous matrix with average grain sizes (d(alpha)(-Fe)) smaller than 10 nm and high numerical density (N-d). M doping can reduce both N-d and d(alpha)(-Fe) of pre-existing alpha-Fe phases to varying degrees, with reduction effectiveness following the sequence: CrM elements. M doping significantly influences the alpha-Fe phase/amorphous-nanocrystalline composite structure and magnetic properties after heat treatment. Compared with Fe85.5B13Cu1.5 alloy, alloys with M=V/Cr/Nb/Mo exhibit reduced average grain size (D-alpha(-Fe)) and coercivity (H-c) of alpha-Fe, while alloy counterparts with M=Ti/Zr show increased D-alpha(-Fe) and H-c. All doped alloys demonstrate slightly decreased saturation magnetic induction (B-s). Notably, the Mo-doped alloy achieves optimal nanocrystalline structure and soft magnetic properties, showing D-alpha(-Fe)=14.9 nm, H-c=8.3 A/m and B-s =1.84 T, which significantly outperforms the results as 17.9 nm, 22.1 A/m and 1.90 T of reference alloy, respectively. Mo doping attains optimized matching between N-d and d(alpha)(-Fe) of pre-existing alpha-Fe grains in melt-spun alloys, which enhances the coordinated intergranular competitive growth effects during thermal crystallization. This mechanism effectively refines the nanocrystalline structure, reduces magnetocrystalline anisotropy, and consequently improves soft magnetic properties.
The effect of speed ratio factor of friction stir processing on microstructure, microhardness and superplasticity of Al-3Mg-0.1Sc-0.1Zr alloy was investigated. The results show that with the increase in speed ratio factor and heat input, the area of stir zone and the grain size are increased, the dynamic recrystallization is more complete, while the peak hardness in stir zone is decreased. All alloys processed at different speed ratio factors show high-strain-rate superplasticity when they are tensile-tested at 475 degrees C with strain rate of 10(-2) s(-1). Three types of true stress-true strain curves are observed during tensile tests. The optimal elongation of 2500% is achieved in the alloy processed with a speed ratio factor of 4, and significant strain hardening occurs before tensile fracture, which improves the common softening loss of stress at the later stage of superplastic forming, implying high engineering application value. The outstanding superplasticity is mainly attributed to equiaxed fine grains with excellent thermal stability and a high proportion of high angle grain boundaries. Based on the analysis of grain aspect ratio, cavity evolution, and morphology of fracture profile, the dominant mechanism of superplastic deformation under all speed ratio factors is grain boundary sliding.
The effect of heat treatment on the microstructure and mechanical properties of a high-boron Ni3Al-based superalloy was investigated by scanning electron microscope, tensile test and stress rupture test. The results show that when the solid solution temperature increases from 1080 degrees C to 1150 degrees C, the volume fraction of gamma ' phase in dendrite trunk decreases gradually, the morphology changes from blocky to spherical, and fine tertiary gamma ' phases are precipitated inside the gamma channel. When the temperature rises from 1080 degrees C to 1120 degrees C, the skeleton-like primary borides are partially dissolved, and the granular secondary borides are precipitated. The precipitation tendency of secondary borides is increased with the increase in temperature, and the borides are completely dissolved when the temperature rises to 1150 degrees C. After aging at 900 degrees C for 10 h, the alloy solid-solution-treated at 1080 degrees C achieves the ultimate tensile strength of 900 MPa during the tensile test at 800 degrees C and the stress rupture life of 144.5 h under the condition of 580 MPa/800 degrees C, exhibiting the best comprehensive mechanical properties. Therefore, the optimal heat treatment process of the test alloy is 1080 degrees C & times;4 h -> air cooling+900 degrees C & times;10 h -> air cooling.
The connections of dissimilar materials LA103Z magnesium-lithium alloy and 1060Al alloy were achieved by electromagnetic pulse welding (EMPW). The effects of discharge energy on interface morphology, wave formation mechanisms, and element diffusion were systematically investigated through numerical simulations and experiments. The results indicate that the induced magnetic field and current are determined by the welding current's magnitude and rate of change, respectively. The increase in discharge energy enhances the Lorentz force experienced by 1060Al, thereby increasing the impact velocity, while the impact angle almost remains unaffected. The rebound phenomenon, which alters the contact state between the flyer plate and the target plate, is identified as the key factor in forming the annular weld seam. Both the simulated and actual interface morphologies are sinusoidal, with the amplitude increasing from 3.02 mu m at 32 kJ to 6.48 mu m at 38 kJ. The wave formation is attributed to shear-induced instability and metal-plastic flow triggered by high-speed collision. No melting is observed at the interface. The maximum shear strength of the joint reaches 90.38% of that of the aluminum base material. Numerical simulations confirm that the interface temperature remains below the melting points of both base materials, which is critical for improving the mechanical performance of the joint.
Inconel617 alloy has significant application potential in Generation IV nuclear energy systems. The effects of Mo content on carbide precipitation at grain boundaries (GBs) and high-temperature tensile properties of Inconel617 alloy were studied by mechanical testing and advanced techniques such as scanning electron microscope, transmission electron microscope, and electron backscatter diffractometer. The results show that there are only fine granular M23C6 carbide at GBs when the Mo content ranges from 8wt% to 9wt%. However, as Mo content increases from 9.3wt% to 9.6wt%, massive M23C6 and M6C carbides could be predominantly observed at GBs. As Mo content increases from 8.0wt% to 9.6wt%, the elongation increases initially and then decreases, and the alloys with the Mo content of 8.5wt%-9.3wt% achieve optimal strength-ductility balance. The fractographic analysis reveals that the precipitation of granular M23C6 at GBs effectively strengthens grain boundaries, resulting in the transgranular fracture features on the high-temperature tensile fracture surface. When massive M23C6 and M6C carbides precipitate at GBs, the initiation of intergranular crack is promoted and the intergranular fracture features are observed on the high-temperature tensile fracture surface. The Mo content of Inconel617 alloy for high-temperature components in Generation IV nuclear systems cannot exceed 9.3wt% and it should be controlled with in the range of 8.5wt%-9wt%
Diverse heat treatment schedules were designed and their effects on microstructural evolution and tensile properties at 750 degrees C were investigated by SEM, EDS, TEM, and mechanical testing. The results demonstrate that multi-stage heat treatment schedules lead to a multi-modal size distribution of gamma ' precipitates within the alloy, where fine gamma ' precipitates contribute to strength, while coarse gamma ' phases enhance ductility. At 750 degrees C, the alloy subjected to the heat treatment of 1030 degrees C/4 h, AC+1000 degrees C/4 h, AC+875 degrees C/16 h, AC+725 degrees C/16 h, AC develops a trimodal gamma ' phase distribution. This microstructure balances the strength between intragranular and grain boundary regions, facilitating the transfer of dislocation slip and enhancing the ductility of the alloy. The alloy exhibits the best overall mechanical properties, with a tensile strength of 706 MPa and an elongation after fracture of 9.3%.
The surface composition and microstructure evolution of a second-generation Ni-based single crystal superalloy were investigated during vacuum solution heat treatment. The effects of adding argon partial pressure and not adding argon partial pressure on the surface layer of casting were studied. Results show that during the high-temperature vacuum heat treatment of the test bars, when argon partial pressure is applied during solution heat treatment, a Cr-depleted layer forms on the surface, exhibiting three-layer structure: transition layer (adjacent to the substrate) composed of gamma ' phase and topologically close-packed (TCP) phase; sub-surface layer composed of gamma ' phase, TCP phase, and beta phase; surface layer composed of gamma ' phase and beta phases. In this case, Al and Ni are deposited on the surface. Conversely, when heat treatment is conducted without argon partial pressure, a Cr-depleted layer still forms, but with a two-layer structure: transition layer composed of gamma ' phase and TCP phase and surface layer composed of gamma ' phase, TCP phase, and beta phase. During vacuum heat treatment, reactions such as volatilization, deposition, oxidation, and diffusion of surface elements occur simultaneously. Depending on the temperature, vacuum level, and argon partial pressure, condensation layer, depletion layer, and interdiffusion layer may be formed on the surface. This study analyzed these phenomena in detail based on the thermodynamics and kinetics of relevant reactions.
N36 zirconium alloy specimens were prepared by the severe plastic deformation process of equal channel dual angle pressing (ECDAP), followed by annealing and aging treatment. The initial microstructure was observed by OM. The types and morphological characteristics of the precipitated phases were analyzed by SEM and TEM. The bonding mechanism at the interface between the alpha-Zr matrix and the (Zr, Nb)(2)Fe precipitated phase after aging treatment was analyzed by combining the difference of valence electron density and the tensile strength. The influence of the precipitation behavior of the (Zr,Nb)(2)Fe on the microstructure and properties of N36 zirconium alloy prepared by the ECDAP process was investigated. The results indicate that the ECDAP process can significantly refine the grain and promote the uniform distribution of the precipitated phase in N36 zirconium alloy, which mainly consists of Zr(Nb,Fe)(2) and (Zr,Nb)(2)Fe with a large number of internal striated dislocations. The difference of valence electron density at the interface between the alpha-Zr matrix and the (Zr,Nb)(2)Fe precipitated phase is 91.02%, and the lattice mismatch leads to increased resistance and instability of interfacial dislocation motion, which can generate susceptibility to relative motion and laminar dislocation initiation. Interfacial dislocations can induce matrix dislocation shifts to meet deformation demands. The increment in tensile strength after aging for 4 and 8 h reaches 2.14% and 10.36%, respectively, which is due to the increase in the reinforcement of the precipitated phase resulting from the strong electronic discontinuity between the precipitated phase and the matrix.
Ti-47.5Al-6.8Nb-0.2W-xY (x=0,0.1,0.2, at%) alloys were prepared by high-energy ball milling and spark plasma sintering processes, and the effects of Y microalloying on the high-temperature compression creep properties of Ti-47.5Al-6.8 Nb-0.2W alloys were investigated by SEM, EBSD and TEM. Creep experiments were carried out at 800-850 degrees C, with a stress of 250 MPa and a time of 50 h. The results show that the Ti-47.5Al-6.8Nb-0.2W-xY alloys are all composed of equiaxial gamma grains, the bulk alpha(2) and B2 phases at gamma grain boundaries, and alpha(2)/gamma lamellar colonies. The added Y mainly exists in the form of Al2Y particles at the grain boundaries to form a chain structure and Y can refine the grains and increase the alpha(2)/gamma lamellar colonies. When the Y content is increased from 0 to 0.2at%, the grain size is reduced from 12.1 mu m to 7.8 mu m, exhibiting the most significant refining effect. After creep, gamma grains in the alloy are slightly flattened, accompanied by lamellar bending and degradation phenomena, and a large number of fine recrystallized grains and spherical B2 phase appear within the lamellar clusters. Creep temperature increase can promote the formation of dynamic recrystallisation. The addition of Y significantly improves the compressive creep properties of the alloy. At 800 degrees C, the maximum creep strain of the 0.2Y alloy is 8.96%, and the steady creep rate is 4.01 & times;10(-7) s(-1), reduced by 32.83% and 38.31% compared with those of the alloy without Y, respectively. The improvement in the mechanical properties of the alloys is attributed to the precipitation strengthening of the second phase Al2Y particles, lamellar refinement, and reduction of the B2 phase.
Tensile mechanical tests at room temperature with varying strain rates (0.001, 0.01, and 0.07 s-1) were conducted on Cu tubes (as-processed state), Nb tubes (soft state), and Mg rods (extruded state) used for internal magnesium diffusion (IMD)-MgB2 single-core wires. Uniaxial unidirectional mechanical tests and cyclic compression mechanical tests at room temperature were performed on B powder to obtain the stress-strain curves. Based on the abovementioned analysis results, Johnson-Cook constitutive models for three metals at room temperature were established, as well as the function between the elastic modulus of B powder and its relative density. Furthermore, the bulk deformation of IMD-MgB2 single-core wires during room-temperature rolling was simulated using the DEFORM finite element software, and the deformation behavior and stress distribution of materials were analyzed. Results demonstrate that the Johnson-Cook models established for three metals and the elastic modulus-relative density function of B powder accurately describe the flow behavior of Cu, Nb, and Mg in IMD-MgB2 wires, as well as the elastic deformation of B powder. DEFORM finite element simulation results can also effectively reflect the deformation behavior of IMD-MgB2 single-core wires. The overall deformation during the rolling process is uniform with a homogeneous stress distribution; however, the surface still has defects. This study provides a theoretical basis for optimizing the plastic forming process of IMD-MgB2 superconducting wires.
Commercially applied 1060 current collector battery aluminum foil was selected as the base material for the addition of rare-earth element Ce. Melting, degassing, filtration, hot rolling, and cold rolling processes were conducted on the Ce-added aluminum foil. The influence of Ce addition on the 1060 current collector battery aluminum foil was analyzed. Results indicate that AlCeSi intermetallic phases are generated in the 1060 current collector battery aluminum foil and act as heterogeneous nucleation sites, therefore refining the grains. In the cold rolling deformation process, the Ce-containing secondary phase particles at the grain boundary produces a strong Zener pinning effect, increases the dislocation density, and inhibits the recrystallization. Consequently, the mechanical properties of the aluminum foil are enhanced through the synergistic actions of grain refinement strengthening and dislocation strengthening. Ce addition also reduces the impurity element solubility in the matrix, modifies lattice distortion scattering, and therefore enhances electrical conductivity. Adding the rare-earth element Ce can refine grains and promotes the positive shift of corrosion potential, thereby improving the corrosion resistance.
The hot deformation behavior of platinum was investigated through hot compression experiments. A constitutive equation for the prediction of the flow behavior of platinum was derived from analysis of stress-strain curves. Using the constitutive equation, the peak stress of platinum during hot working was calculated across varying temperatures and strain rates. Results show that the predicted values have strong agreement with experimental results. Electron backscatter diffraction analysis further reveals the thermal deformation mechanisms under distinct conditions within the safe processing region. The optimal processing parameters are identified as deformation temperatures of 860-910 K and strain rates of 0.01-0.1 s-1. Discontinuous yielding observed at elevated strain rates is attributed to the multiplication and movement of the mobile dislocations at grain boundaries.
Al-Ga-Mg-Sn soluble aluminum alloy was selected for a one-step hydrometallurgical technique. Acid leaching agents, including organic acid solutions (e.g., oxalic, malic, and acetic solutions) and inorganic acid solutions (e.g., nitric acid) were used. The type of leaching agent, pH value, temperature, and solution concentration are key factors influencing the recovery of Ga during hydrogen production. Recovery results show that under the temperature of 70 degrees C and the agent concentration of 0.2 mol & centerdot;L-1, the organic acid solution successfully recovers gallium, with oxalic acid exhibiting the highest recovery efficiency (86.88%), followed by malic acid (73.40%) and acetic acid (13.17%). In contrast, the inorganic acid (nitric acid) solution fails to recover gallium. Oxalic acid, with an initial pH value of approximately 3.8, achieves a recovery efficiency of 94.38% under 70 degrees C/0.3 mol & centerdot;L-1 and 93.78% under 90 degrees C/0.2 mol & centerdot;L-1. The leaching behavior of gallium was then tested and analyzed based on changes in pH value, shape of the recovered gallium, solid particle size and Zeta potential of the product during the hydrolysis process. The results show that the recovery of gallium from oxalic acid leachate increases with the decrease in particle size of the product and increase in absolute value of Zeta potential. The highest recovery efficiency (94.38%) is achieved with a product particle size of 155 nm and a Zeta potential value of-31.29 mV.
To design a porous titanium alloy structure suitable for cervical spine implants, according to different stress conditions of cervical spine, such as compression, compression-shear, compression-torsion, and compression-bending, four types of unit cell structures, TO-C, TO-CS, TO-CT, and TO-CB, were constructed by combining topology optimization and computer-aided design. The mechanical properties were analyzed by compression simulation. Finally, the quasi-static compression test of porous samples with porosity of 60% prepared by laser powder bed fusion technique was conducted. The results of finite element simulation and compression test show that the compressive properties and elastic moduli of the four porous structures meet the requirements of human bone implants. Among them, the TO-CB structure has the best compressive performance and is suitable for porous titanium alloy cervical spine implants.
The effects of solid solution and aging treatments on the microstructural evolution and hardness of the GWZ932 alloy in the rolled state were investigated by means of optical microscope, X-ray diffractometer, Vickers hardness tester, scanning electron microscope, transmission electron microscope, and high-angle annular dark-field scanning transmission electron microscope. The results show that the alloy microstructure in the rolled state mainly consists of alpha-Mg, massive 18R-LPSO phase, lamellar 14H-LPSO phase, rare-earth-rich phase and Zn-Zr phase. The lamellar 14H-LPSO is almost completely dissolved into the matrix by solid solution treatment at 500 degrees C for 2 h; the elongated acicular 14H-LPSO is precipitated from the alpha-Mg matrix after 4 h of solid solution, and its volume fraction gradually increases with the extension of time; the volume fraction of acicular 14H-LPSO reaches 16% after 6 h of solid solution; the acicular 14H-LPSO phase dissolves and re-precipitates the lamellar 14H-LPSO (about 14.9 & micro;m in length and 8.2 & micro;m in width), and a small amount of undissolved acicular 14H-LPSO phase grows to form rod-like 14H-LPSO (23.4 & micro;m in length and 1.98 & micro;m in width). Increasing the solid solution temperature to 520 degrees C, the solute atom diffusion rate is accelerated, thus the complete dissolution and re-precipitation time of lamellar 14H-LPSO is advanced to 1 and 2 h, respectively, and the size of the re-precipitated lamellar 14H-LPSO phase (12.6 & micro;m in length, 5.1 & micro;m in width) is smaller than that of the re-precipitated one after solid solution at 500 degrees C for 8 h. Precipitation and transformation do not occur during solid solution treatment at 520 degrees C, indicating that the precipitation and dissolution of the acicular 14H-LPSO phase and its content are affected by the solid solution temperature and time. The age-hardening curves reach peak hardness under conditions of 520 degrees C, 4 h+225 degrees C, 64 h. On this basis, the age-hardening behaviour of the alloy after solution treatment at 520 degrees C for 4 h was investigated and the results show that the alloy reaches peak hardness after age treatment at 225 degrees C for 64 h. The room-temperature tensile strength (UTS), yield strength (YS) and elongation (EL) of the alloy under peak aging conditions are 396.3 MPa, 274 MPa, and 12.7% increase by 23.8%, 7.4%, and 69.3%, compared to those of the rolled state, respectively. The excellent strength and plasticity of the alloys arise from the precipitation of a columnar beta' phase (about 28.9 nm in length and 8.9 nm in width with an average area fraction of about and a basal in the matrix.
Taking beta-Ti as the research object, the first-principles calculations based on density functional theory were performed to construct a model of Ti-V system with different V contents by substituting Ti atoms with V atoms and to calculate the mechanical properties and electronic structures. The calculation results indicate that the addition of V atoms decreases the elastic constant and elastic modulus of beta-Ti and improves the plasticity and toughness of the system. This is because during the formation of the Ti-V system, both atoms lose electrons. Therefore, the electronic mobility of the system increases, the bonding strength of the metallic bond is enhanced, and the plasticity and toughness of the system are improved. In addition, the 3d-orbitals of Ti and V atoms are mainly involved in bonding, which is the key reason for the improvement of plasticity and toughness. Meanwhile, there are also some electrons with directivity gathered around the two atoms, which indicates that there is also a covalent bond within the system. The existence of covalent bond is the key to enhancing the mechanical stability of the system.
Mo14Re powders were prepared by high-energy ball milling (HEBM) and spray drying-hydrogen reduction (SPHR), separately. Then, the Mo14Re alloys were obtained by spark plasma sintering (SPS). The phase structure, microstructure, element distribution, and grain size were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The deformation mechanisms of Mo14Re alloy under room temperature tension and compression were discussed. The XRD results indicate that the (101)-spacing of the Mo14Re-SPHR is smaller than that of the Mo14Re-HEBM. The EDS results show that the segregation of Re is observed at the grain boundary of the Mo14Re-HEBM, while uniform elements distribution in the Mo14Re-SPHR alloy. The room temperature compression results show that the compressive yield strength of the Mo14Re-SPHR is 679.11 MPa, higher than that of the Mo14Re-HEBM (602.71 MPa). EBSD results show that when the compression deformation is larger than 5.0%, the proportion of grains with {123} <111> as the main slip system in Mo14Re-SPHR increases, while the proportion of grains with {110}<111>and {112}<111> as the main slip systems decreases. The change trend of the three slip systems in Mo14Re-HEBM is opposite to that in Mo14Re-SPHR, resulting in a strain hardening rate of Mo14Re-HEBM higher than that of Mo14Re-SPHR. Room temperature tensile results show that Mo14Re-SPHR exhibits better plasticity and toughness.
The influence of titanium carbide (TiC) content on the microstructure and mechanical properties of molybdenum (Mo)-based composites was investigated, aiming to provide a scientific basis for the development of high-performance and heat-resistant molybdenum materials for aerospace engines. TiC/Mo composites containing 10wt%, 20wt%, and 30wt% TiC were prepared using spark plasma sintering (SPS) technique. The results indicate that the strengthening mechanisms of TiC/Mo composites are primarily attributed to intragranular particle strengthening and grain boundary strengthening. At elevated temperatures, TiC diffuses into the Mo matrix, forming a transition zone of measurable width at the interface of the two phases. XRD analysis confirms that this transition zone comprises (Ti, Mo)C. The crystal lattices of the TiC and Mo phases exhibit strong bonding, which is further corroborated by atomic-scale observations. Tensile and hardness tests reveal that TiC/Mo composites with 10wt% and 20wt% TiC demonstrate superior mechanical properties. The fracture behavior of these composites is primarily governed by the propagation of intergranular microcracks, which is influenced by the competition between intergranular and intragranular crack development. This study provides critical insights into the coupling effects of intergranular and intragranular TiC particles on the mechanical performance of TiC/Mo composites.
Ni-based composite coatings with directly added Cu and Cu-coated diamond were prepared by induction heating technology. The effects of Cu addition on the microstructure, phase evolution, microhardness and wear properties of Ni-based composite coatings were investigated. The results show that the direct addition of Cu and the introduction of Cu in the form of Cu-coated diamond in the diamond-nickel-based composite coatings inhibit the generation of carbides in the nickel alloy matrix, and in the form of Cu-coated diamond, almost no carbides are observed in the nickel alloy matrix. The average microhardness of the coating with Cu-coated diamond is decreased by 76.7 HV compared to that of the direct addition of Cu; moreover, the coating shows more excellent wear resistance in the 15-45 min wear stage of the abrasive wear test.
The isothermal oxidation behavior of DD6 single-crystal superalloy with different hole geometric structure at 1050 degrees C was studied using field emission scanning electron microscope, energy dispersive spectroscope, X-ray diffractometer, and ABAQUS finite element method. The results show that at two angles of 45 degrees and 90 degrees, the average oxidation rate varies with the film-hole spacing, both being 0.75 mm>0.95 mm> 0.55 mm>0.39 mm. The effect of film-hole spacing on the oxidation mass gain of single-crystal superalloys is more significant than that of hole angle. At the same film-hole spacing, the degree of oxidation at 45 degrees is relatively more severe than that at 90 degrees. Finite element analysis shows that the growth of the oxide layer on the inner wall of the hole is mainly affected by the temperature field, while the growth of the oxide layer on the surface of the hole is mainly affected by the detachment stress. As the film-hole spacing increases, the stress cancellation area gradually decreases, and the detachment stress continues to increase, reaching its peak at 0.75 mm. At this time, the oxide film detachment is most severe, and after the peak point, it shows a downward trend.
