Abstract:The transient liquid-phase (TLP) diffusion bonding of GH5188 with a BNi-5 interlayer was focused on. Parameters were chosen and optimized for GH5188 alloy according to the TLP joining mechanism. The microstructure evolution and mechanical properties of the joints were studied. Results show that the relatively complete isothermal solidification zone (ISZ) ensures a reliable connection of the base metal (BM). Within the temperature range of 1110–1190 °C, higher bonding temperatures can widen ISZ and promote joint composition homogenization, thus improving mechanical properties. However, the increase in precipitated phase has an adverse effect on the mechanical properties of the joint. The maximum shear strength, reaching 482 MPa, is achieved at 1130 °C, representing 84.6% of BM strength. Within the pressure range of 5–15 MPa, both precipitated phases in adiabatic solidification zone (ASZ) and voids generated by partial melting increase. On the contrary, their sizes decrease significantly under higher bonding pressure, resulting in an upward trend in alloy mechanical properties. The maximum shear strength of 490 MPa is attained at a bonding pressure of 15 MPa. The joint exhibits a typical mixed fracture pattern, with the small brittle M₂₃C₆ phase and voids significantly impacting mechanical properties. Nano-indentation tests indicate that ASZ is a potential source of cracks.

Abstract:To investigate the complex interaction mechanism between elements Re and Ru, a dataset containing composition, microstructural parameters, kinetic parameters, physical parameters and macroscopic properties with the aid of high-throughput calculations were established, which effectively reduces the experimental cost and time. Results show that the addition of Re and Ru improves the creep life of the alloys by lowering the effective diffusion coefficient and stacking dislocation energy. The addition of the element Ru reduces the stacking dislocation energy and the antiphase domain energy, which in combination with the solid solution strengthening of Ru together affect the yield strength of the alloys, resulting in no significant change in the yield strength. At the same time, the four alloy systems were studied, element Re significantly promotes the tcp phase precipitation, while element Ru does not inhibit or promote the tcp phase precipitation. The element distribution behavior and the phase stability structure diagram of nickel-based superalloy was analyzed whether Ru inhibited or promoted the tcp phase precipitation.

Abstract:FGH4097 alloy was treated by the hot isostatic pressure (HIP) process. The dissolution and precipitation behavior of γ' phase in the alloy during solid solution and cooling were studied by SEM and TEM. The results show that during the solid solution process, dislocations assist the diffusion of Al and Ti atoms and promote the splitting and dissolution of γ' phase. The secondary γ' phase is preferentially dissolved by splitting into fine γ' phase, and the primary γ' phase is dissolved by splitting into smaller γ' phase through the γ/γ' phase interface. Based on the JMAK equation, a kinetic equation describing the dissolution of γ' phase was established. The linear fitting correlation coefficient R=0.9933 and the average relative error value is 10.01%, which can predict the area fraction of γ' phase in the range of 850?1200 ℃. During the cooling process, under the action of dislocations, the primary γ' phase preferentially precipitates at the grain boundary and grows irregularly along the direction perpendicular to the grain boundary, resulting in the formation of curved grain boundaries. The secondary γ' phase is precipitated in the crystal. With the decrease in intermediate temperature (MT) from 1200 ℃ to 850 ℃, the size of γ' phase precipitated in the crystal increases from 76 nm to 521 nm, and the microhardness of the alloy decreases from 471.45 HV to 394.18 HV, indicating that the microhardness of the alloy decreases with the increase in γ' phase size.

Abstract:The effects of B content on the durability of GH4738 nickel-based superalloy were studied by SEM, TEM and EPMA. The results show that B content can significantly improve the content and distribution of M₂₃C₆ carbides at grain boundaries, and improve the precipitation and dispersion uniformity of M₂₃C₆ at grain boundaries. B element is mainly concentrated in the carbide in the alloy, and may participate in the carbide precipitation as a carbide forming element. The content of B has no effect on the precipitation of γ' strengthening phase. With the increase in B content, the durability of the alloy is improved, the durability life increases by 8?12 times, and the durability plasticity increases by 2?4 times. The permanent fracture mode changes from brittle intergranular fracture to mixed fracture. The effect of B content on the tensile properties of the alloy is small, and the slight increase in grain size results in a slight decrease in the strength of the alloy.

Abstract:The hot deformation behavior of as-extruded Ti-6554 alloy was investigated through isothermal compression at 700– 950 °C and 0.001–1 s^-1. The temperature rise under different deformation conditions was calculated, and the curve was corrected. The strain compensation constitutive model of as-extruded Ti-6554 alloy based on temperature rise correction was established. The microstructure evolution under different conditions was analyzed, and the dynamic recrystallization (DRX) mechanism was revealed. The results show that the flow stress decreases with the increase in strain rate and the decrease in deformation temperature. The deformation temperature rise gradually increases with the increase in strain rate and the decrease in deformation temperature. At 700 °C/1 s^-1, the temperature rise reaches 100 °C. The corrected curve value is higher than the measured value, and the strain compensation constitutive model has high prediction accuracy. The precipitation of the α phase occurs during deformation in the two-phase region, which promotes DRX process of the β phase. At low strain rate, the volume fraction of dynamic recrystallization increases with the increase in deformation temperature. DRX mechanism includes continuous DRX and discontinuous DRX.

Abstract:A near β-type Ti-5.5V-4Mo-2.2Cr-Fe-3.6Al alloy was designed based on the multi-alloying principle of critical compo-sition, combined with parameters, such as electron concentration, molybdenum equivalent and B_o-M_d, that can influence the stability of β phase. The homogenized alloy was subjected to solid solution, intermediate annealing during the rolling process, and aging treatment. The microstructure and mechanical properties of the alloy were analyzed by optical microscope, scanning electron microscope, X-ray diffractometer, electron backscattered diffraction and transmission electron microscope, as well as room-temperature tensile properties. The results show that martensitic transformation occurs in the alloy during rolling. The grain size of the alloy after intermediate annealing is only 38 μm, because the martensite is a hindrance to grain boundary migration. Grain refinement endows the annealed alloy with a good match of strength and plasticity, a yield strength of 1050 MPa and an elongation of 15%. A large number of α phases are precipitated in the microstructure of the rolled alloy after aging treatment, which further improves the properties of the alloy: the strength of the alloy exceeds 1500 MPa and the elongation is 5%.

Abstract:The anisotropy of the room temperature (RT) tensile properties, especially plasticity, of Ti-55531 alloy bars was investigated. RT tensile and fracture toughness tests were conducted, as well as OM, SEM, and EBSD characterization. The raw structure, fracture morphology, and crack propagation path were analyzed to reveal the reasons for the anisotropy of the tensile properties of Ti-55531 alloy bars. The results show that due to the <110> texture of the β phase, the Schmid factors for {101}<111> slip systems with different loading directions are different, leading to anisotropy in yield strength; the tensile plasticity is correlated with fracture toughness of Ti-55531 alloy, indicating that the anisotropy of RT plasticity mainly depends on the crack propagation stage and is influenced by the relevant structural characteristics; the anisotropy of RT plasticity Ti-55531 alloy mainly depends on the morphological texture of β grains, and is affected by the orientation texture of β phase and distribution of equiaxed α_P.

Abstract:The isothermal transformation process of TC17 alloy was investigated by microstructure analysis and numerical simulation. The experimental results show that TC17 alloy firstly precipitates α phase at or near grain boundaries. And with the increase in aging time, a large number of needle-like α phases precipitated inside the grains, and the precipitated α phase gradually becomes fine with the decrease in aging temperature. With the decrease in the aging temperature, the rate of precipitated α phase shows a tendency of increasing and then decreasing, and both the phase transition driving force and solute atom diffusion rate reach the maximum matching degree at aging temperatures of 600?650 °C. The maximum rate of precipitated α phase is reached currently. At the aging temperature of 600?650 °C, the phase transition driving force and the diffusion speed of solute atoms reach the maximum matching degree, and the rate of precipitating α phase reaches the maximum currently. Numerical simulation results show that the precipitation rate of α phase is the fastest at an isothermal temperature of 650 °C, and the results are in good agreement with the experimental results.

Abstract:The evolution of microstructure and tensile properties of Ti-5Al-6.5Mo-1.5Fe low-cost titanium alloy under different forging parameters was studied, and it is found that there is a significant correlation between the microstructure and properties of the alloy under different forging parameters. The results show that when the alloy is forged in α+β phase region, the content and size of the equiaxed primary α phase (α_p) in the microstructure decrease gradually with increase in temperature, and the tensile strength and plasticity fluctuate slightly. As the forging deformation increases, the morphology of α_p phase in the microstructure changes obviously, and the strength and plasticity of the alloy remain stable. There is a continuous accumulation of misorientation inside the α_p phase to promote spheroidization and recrystallization. The orientation of β phase gradually transforms into the Cube texture {001}<100> under deformation force. When forged in the single β phase region, the alloy obtains coarse original β grains, the α_p phase completely disappears, the intragranular secondary α phase (α_s) increases, the long strip grain boundary α phase (α_GB) precipitates, and the plasticity of the alloy drops sharply. The coexistence of equiaxed α_p phase, which can coordinate deformation, and nanoscale α_s phase, which significantly improves the strength of the alloy in the microstructure, can achieve high strength and high toughness at the same time, allowing the alloy to obtain better mechanical properties in α+β phase region. The β coarse grain is the main reason for the decrease in plasticity after forging in the single β phase region of the alloy, and the tensile fracture mechanism of the specimen changes from single dimple fracture after forging in α+β phase region to cleavage-dimple mixed fracture after forging in single β phase region.

Abstract:AZ31 magnesium alloy was used as the object of study to fabricate an alloy with the bimodal grain structure using single-pass hot rolling, and to explore how this structure enhances the strength and plasticity of the alloy. The results show that the formation of the bimodal grain structure is more pronounced at rolling temperatures ranging from 350 °C to 450 °C, especially under conditions of large reduction (≥40%). The optimized proportion and distribution of the bimodal grain structure play a pivotal role in simultaneously enhancing the strength and ductility of the alloy, significantly impacting the mechanical properties. The rolled sheet with the bimodal grain structure achieves an ultimate tensile strength of 258.3 MPa and an elongation of 17.1% under a rolling reduction of 40% with the rolling rate of 75 m/min and rolling temperature of 400 °C. Adjusting rolling parameters, including temperature, reduction ratio and rolling rate, is crucial for optimizing the bimodal grain structure, thereby achieving a balance between plasticity improvement and high strength maintenance.

Abstract:The bending springback of magnesium alloys is difficult to predict accurately by numerical simulations because of their anisotropic characteristics. The springback of magnesium alloy V-shaped roll-bending was analyzed using the error optimization function in Matlab to optimize the anisotropic potential values required for the Hill'48 yield criterion in ABAQUS. The optimized Hill'48 yield criterion model was used to numerically simulate the springback of magnesium alloy V-shaped roll-bending. The simulation results were compared with the experimental results. Results show that the error between the springback change ratio obtained using the optimized Hill'48 yield criterion and experimentally formed parts is within 2%. Overall, the optimized Hill'48 yield criterion improves the prediction accuracy of springback in magnesium alloy V-shaped roll-bending.

Abstract:The effect of adding 1wt% Sn on the corrosion resistance of homogeneous Mg-6Zn-0.25Ca alloy was studied. The corrosion resistance of Mg-6Zn-Sn-0.25Ca and Mg-6Zn-0.25Ca alloys was analyzed by OM, XRD, SEM, hydrogen evolution, mass loss and polarization curve experiments. The results show that the main secondary phase in Mg-6Zn-0.25Ca alloy is Mg₂Ca phase, and after Sn addition, the main existence form of the secondary phase in Mg-6Zn-Sn-0.25Ca alloy is Mg₂Sn phase, Mg₂Ca phase and a small amount of CaMgSn phase. After adding Sn, the secondary phase of the alloy is more evenly distributed and the average grain size of the alloy decreases from 145.6 μm to 114.2 μm, because the Mg₂Sn phase with high melting point can act as a heterogeneous nucleation core for non-spontaneous crystallization of the α-Mg matrix, thereby refining the grain size. Under their combined effect, the oxide film produced during alloy corrosion becomes denser, thereby preventing the hydrogen evolution reaction. In addition, the polarization curves show that the self-corrosion potential and self-corrosion current density of Mg-6Zn-0.25Ca alloy are –1.729 V and 2.106×10^-5 A/cm², respectively. After adding 1wt% Sn, the self-corrosion potential increases to –1.525 V, while the self-corrosion current density decreases to 8.561×10^-6 A/cm², which enhances the corrosion resistance of Mg-6Zn-Sn-0.25Ca alloy.

Abstract:In-situ alloying employs compositional design to mix commercially available powders in specific ratios as feedstock for fabricating alloy components by selective laser melting (SLM), potentially addressing challenges in preparation of pre-alloyed powder. Melt-track and bulk samples of multi-component rare-earth Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr magnesium alloy were fabricated by SLM in-situ alloying method using Mg, Y, Sm, Zn, and Zr commercial powders as raw materials. The formability, relative density, surface morphology, microstructure and microhardness of the samples under different process parameters were investigated and compared with those of the pre-alloyed powder formed samples. The results show that single melt-track can obtain a stable and smooth melt-track at a laser power of 80 W, and the melt pool is in conduction mode. The bulk sample has the maximum relative density of 98.71% at a laser power of 80 W, and a scanning speed of 300 mm/s, with the fewest pores and unmelted particles and a microhardness of 98.97 HV. The phase composition of the in-situ alloyed samples is composed of Mg matrix, Y-Zr-O rare-earth oxides, and eutectic phase (Mg,Zn)₃(Y,Sm), and the microstructures are mostly fine equiaxed grains.

Abstract:The equal channel angular bending (ECAB) of AZ31 magnesium alloy rolled sheet (2 mm) under different paths was conducted at 150 ℃. The evolutions of microstructure and mechanical properties of the sheet were investigated after 5-pass ECAB along the same path, normal direction rotation path and rolling direction (RD) rotation path. The results show that after 5-pass ECAB, a large amount of extension twinning (ETW) and a certain amount of contraction twinning (CTW) and double twinning (DTW) are introduced into the sheet, which can effectively improve the basal texture of the base plane. After annealing treatment, the elongation of the sheets undergone ECAB is obviously improved. In particular, the area fraction of ETW in the deformed sheet rotated 5 passes around the rolling direction (RD) can reach 28.74%, and after annealing, the elongation can reach 28.8% with a tensile strength of 235.7 MPa. Compared with the original sheet, the relative increase ratio of the elongation is 57.4%, while the tensile strength is only 3.8% lower.

Abstract:The effect of different intermediate annealing heat treatments on the surface microstructures and anodic oxide film structures of rolled Al-5.6Mg sheets was studied. The results show that when the continuous annealing is used to control microstructures of the sheets instead of the static state annealing in the intermediate annealing process, the surface grain size of the sheets can be reduced by about 65.7%, and the size of the Mg precipitation phase (Mg₂Al₃) can be reduced by about 67%. Under the combined influence of grain size, precipitation phase, and texture, the highest glossiness can be obtained, which is attributed to continuous intermediate annealing and stabilization annealing at low temperature. The uniform grain and precipitation structures is beneficial to reducing the inhomogeneous dissolution of the oxide film and to obtain the anodic oxide film with uniform thickness and high glossiness.

Abstract:AlScN piezoelectric films prepared by AlSc alloy sputter targets are essential materials for 5G radio frequency filters. The thermophysical properties of AlSc alloy targets are closely related to their welding processes and applications. Al-xSc alloys (x=5, 10, 15, 20, 25, at%) were prepared by vacuum induction melting, whose purity is mainly determined by the raw materials and the production process. The results reveal that as the Sc content increases from 5at% to 20at%, the volume fraction of the Al₃Sc phase in the alloy increases from 26.9% to 80.2%, and the average grain size of the Al₃Sc phase increases from 12.9 μm to 67.7 μm during this period. Additionally, both the coefficient of thermal expansion (CTE) and thermal conductivity (TC) of AlSc alloys exhibit a downward trend. Based on experimental data and first-principles calculations, the effective medium theory and the Turner model effectively predict the TC and CTE of Al-xSc alloys. The optimal characteristic parameter (k₀) of the Turner model is determined to be 50. The model predictions align well with the experimental results.

Abstract:A straightforward, highly effective, and environmentally friendly technique was investigated for protecting carbon steel surfaces from corrosion, i. e., depositing Cu-Ni alloy coatings on the workpiece's surface to impede corrosive medium. The effects of current density and copper ion concentration (Cu²⁺) on the composition, morphology, and properties of the coating were analyzed using scanning electron microscope, X-ray energy dispersive spectrometer, Vickers hardness tester, friction and wear tester, and electrochemical testing. Results show that a cauliflower-like Ni-rich protrusion structure appears on the coating surface. The lower current density and Cu²⁺ concentration affect the Vickers hardness and wear resistance of the coating by altering the microstructure and Cu/Ni content, both leading to a decrease in hardness and wear resistance. When the current density is 10 mA·cm^-2 and the Cu²⁺ concentration is 0.1 mol·L^-1, the corrosion current density of the deposited sample reaches 1.389×10^-5 A·cm^-2, and its surface corrosion damage is reduced compared to the uncoated sample after 24 h of salt spray test. Research on the deposition mechanism indicates that Cu²⁺ undergoes instantaneous nucleation under diffusion control, tending to grow vertically and form cauliflower-like protrusions, while Ni²⁺ is discharged uniformly across the surface under electrochemical control.

Abstract:Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr, followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties. The results show that after the modification treatment, the room-temperature tensile strength of the alloy remains nearly unchanged, the elongation at break slightly increases from 1.82% to 3.34%, and the electrical conductivity significantly increases from 40.1% international annealed copper standard (IACS) to 42.0% IACS. After the modification, the alloy was subjected to solid solution treatment at 515 ℃ for 8 h, followed by aging treatment at 180, 200, 220 and 240 ℃ for 6 h. With increasing aging temperature, the electrical conductivity increases monotonously from 41.4% IACS to 45.5% IACS, while the room-temperature tensile strength initially increases and then decreases. At 200 ℃, the alloy achieves an optimal balance between electrical conductivity and room-temperature tensile strength: the electrical conductivity is 42.5% IACS, and the room-temperature tensile strength is 282.9 MPa. When the aging temperature continues to rise, the alloy undergoes overaging. Although the conductivity continues to increase, the room-temperature tensile strength drops sharply, and it is only 177.1 MPa at 240 ℃.

Abstract:The failure of mechanical components is mainly caused by three key mechanisms: wear, corrosion, and fatigue. Among these failure modes, wear of mechanical components notably increases energy consumption and leads to substantial economic losses. Fe-Cr-C-B-Ti-Y wear-resistant cladding metals were prepared by the plasma cladding method. The wear performance of the cladding metals was analyzed using an MLS-23 rubber wheel wet sand wear tester. X-ray diffraction, scanning electron microscope, electron backscatter diffraction, and transmission electron microscope were employed to investigate the phase composition and microstructure of the cladding metals, followed by a discussion of their strengthening and wear mechanisms. The results indicate that the microstructure of Fe-Cr-C-B-Ti-Y cladding metals is composed of austenite γ-Fe, M₂₃(C,B)₆ eutectic carbide, and TiC hard phase. As the Y₂O₃ content increases, the hardness and wear resistance of the cladding metal show a trend of first increasing and then decreasing. When the Y₂O₃ content is 0.4wt%, the precipitation of TiC hard phase and M₂₃(C,B)₆-type eutectic carbides reaches maximum, and the grain size is the finest. The cladding metal exhibits optimal formability, featuring the smallest wetting angle of 52.2°. Under this condition, the Rockwell hardness value of the cladding metal is 89.7 HRC, and the wear mass loss is 0.27 g. The dominant wear mechanism of cladding metals is abrasive wear, and the material removal process involves micro-cutting and plowing.

Abstract:The effect of material elastic modulus on stress and strain distribution in implants and bone tissue was investigated. Utilizing dental manufacturer and clinical statistical data, implant and mandible bone models were established. Material parameters for prepared Zr30Ti and Zr22Nb alloys were obtained through tensile testing, with Ti6Al4V (elastic modulus: 110 GPa) and Zr24Nb (elastic modulus: 30 GPa) selected as contrasting materials. Bone tissue was modeled using orthotropic material properties closer to real characteristics. Vertical and oblique loads were applied according to ISO 14801 standards, with a tilt angle of 30°. All studies were referenced against Ti6Al4V. Results show that the decrease in implant elastic modulus detrimentally affects its load-bearing capacity under oblique loads, with stress increments for Zr30Ti (76 GPa), Zr22Nb (59 GPa), and Zr24Nb (30 GPa) of 2.98%, 5.47%, and 14.55%, respectively. However, maximum stresses still remain below their strengths (952, 611, and 800 MPa). The stress transmission from implants is primarily borne by cortical bone, with maximum stress increments in cortical bone under oblique loads for Zr30Ti, Zr22Nb, and Zr24Nb of 17.59%, 31.92%, and 79.14%, respectively. The risk of cortical bone overloading increases with decrease in implant elastic modulus, but the stresses generated by Zr30Ti and Zr22Nb within cortical bone remain below cortical bone strength, ensuring favorable application safety. The stress transmitted from implants to cortical bone increases and becomes more uniform with decrease in elastic modulus, with average Mises stress increments at the implant-bone interface for Zr30Ti, Zr22Nb, and Zr24Nb under oblique loads of 12.75%, 122.94%, and 155.11%, respectively; while the stress difference at the interface for implant-bone decreases by 16.82%, 29.45% and 65.41%, respectively. This is attributed to larger deformation zones within implants with lower elastic modulus, where under oblique loads, the internal maximum strains in the neck region of Zr30Ti, Zr22Nb, and Zr24Nb implants are 2 times, 2.6 times, and 4.9 times greater than that of Ti6Al4V, respectively, with minimal differences in modulus between implants and bone tissue, promoting more coordinated deformation at the interface. Thereby, this can promote stress transfer to cortical bone and reduce interfacial stress difference. With decrease in elastic modulus, the stress at the bottom of cancellous bone implant sites gradually decreases, and the overall stress is concentrated in the upper part. The stress distribution of the cancellous bone in Zr30Ti and Zr22Nb zirconium alloy implants is more uniform.

Abstract:The hydrogen storage properties of Ti_0.8Zr_0.2Mn_1.2Cr_0.6(V-Fe)_0.2 alloy and its rare earth modification effect were studied. The results show that Ti_0.8Zr_0.2Mn_1.2Cr_0.6(V-Fe)_0.2 alloy has excellent comprehensive hydrogen storage performance, with a hydrogen storage capacity more than 2 wt% at room temperature. After adding rare earth La or Ce for modification, the activation performance is further improved. The alloy added with 5wt% Ce can be activated by only one hydrogen absorption and desorption cycle, and has good hydrogen absorption and desorption cycling stability. After 100 hydrogen absorption and desorption cycles, the hydrogen absorption rate does not change significantly, and the capacity retention rate is 99%. A tubular hydrogen storage equipment with capacity greater than 180 N·m³ was designed and manufactured using this alloy as the medium, and it was combined with a fuel cell to form a hydrogen-electric conversion system, which could provide stable power generation and generate power more than 200 kW·h at one time when filled with hydrogen.

Abstract:The creep properties of W-4Re-0.27HfC (wt%) alloy at temperatures of 1800, 1900, and 2000 ℃ was investigated by SEM, EBSD, and density functional theory (DFT). The grain size, grain type, dislocation density, fracture morphology, and the mechanism of creep failure of W-4Re-0.27HfC alloy ware analyzed after creep at different temperatures. The results indicate that the steady-state creep rates at creep temperatures of 1800, 1900 and 2000 °C are 9.8×10^-6, 1.0×10^-5, and 2.1×10^-5 s^-1, respectively. With the increase in creep temperature, the proportion of low-angle grain boundaries decreases while the proportion of high-angle grain boundaries increases, resulting in the increase in average grain size. During the creep process, grain undergoes plastic deformation, forming numerous ductile dimples. The poor deformation compatibility of high-angle grain boundaries leads to the formation of voids, accelerating creep failure. EDS results illustrate that the HfC particles in W-4Re-0.27HfC alloy are oxidized severely. DFT calculations show that the interface binding energy between HfC and matrix decreases from –11.221 J/m² to –3.935 J/m² after HfC oxidation, reducing the strengthening effect of the second phase.

Abstract:Mechanical alloying combined with spark plasma sintering (MA-SPS) was adopted to prepare W_23.5Ta_23.5Cr_23.5V_23.5Ti₆ high-entropy alloys. The effects of ball milling durations on the elemental distribution and microstructure of the alloys were explored. Results show that the powder after 40 h ball milling has a homogeneous particle size with 3.65±1.91 μm, and presents an equiaxed particle morphology. The dense and uniform alloy can be obtained after SPS at 1500 ℃. The WTaCrVTi_x solid solution with bcc structure is continuously distributed, in which the atomic ratios of W, Ta, Cr and V are close to the equiatomic ratios. A small amount of Laves phase is distributed in the matrix. The TiO particles with fcc structure have an average size of 1.08±0.38 μm and are uniformly distributed in the matrix. The room-temperature compressive yield strength, high-temperature compressive yield strength and microhardness of the alloy are 2870, 1954 MPa and 873.4 ±7.6 HV, respectively.

Abstract:The electrical conductivity and corrosion resistance of the amorphous carbon-based coating were improved by doping an appropriate amount of Ti nanocrystals. The magnetron sputtering system and the self-developed high-frequency oscillating pulsed electric field were used to prepare several groups of carbon-based coatings with different Ti doping amounts. The effect of Ti nanocrystal addition on the electrical conductivity and corrosion resistance of amorphous carbon-based coatings was studied. The results show that with increasing the Ti target current from 0.35 A to 0.7 A, the Ti doping amount in the coating is increased with the Ti content reaching 8.20at%, and the carbon-based coating changes from amorphous structure to Ti nanocrystalline/amorphous carbon composite structure. In addition, appropriate doping of Ti is beneficial to improve the density, electrical conductivity, hydrophobicity and corrosion resistance of the coating. When the Ti target current is set as 0.7 A, the sheet resistance of the coating reaches its minimum value of 4.5 Ω/□. When the Ti target current is increased to 0.9 A, the water contact angle of the coating achieves its maximum value of 97.75°, while the corrosion current density decreases to its minimum value of 1.408×10^-5 A·cm^-2.

Abstract:TiZrN/TiN nano-multilayer films were deposited by hybrid method of arc ion plating and high-power impulse magnetron sputtering techniques on M2 high-speed steel and single crystal silicon substrates. The microstructure, element composition, phase structure, adhesion strength between the film and substrate, nanohardness, friction and wear properties and corrosion resistance of TiZrN/TiN nano-multilayer films were investigated. Results show that with the increase in pulsed bias voltage, the surface roughness of TiZrN/TiN nano-multilayer films is decreased to 0.345 μm when the pulsed bias voltage is –500 V, and the thickness of the films exhibits a fluctuant trend. The preferred orientation of TiZrN/TiN nano-multilayer films shifts from (111) crystal plane to (220) crystal plane. At a pulsed bias voltage of –200 V, the adhesion strength level between TiZrN/TiN nano-multilayer films and substrate reaches to HF2. The nanohardness and elastic modulus of the TiZrN/TiN nano-multilayer film are increased to 47.02 GPa and 382.28 GPa, respectively. The hardness is 5.2 times higher than that of M2 high-speed steel substrate (about 9 GPa). At the pulsed bias voltage of –200 V, the wear rate reaches 4.38×10^-8 mm³·N^-1·mm^-1, which indicates that the TiZrN/TiN nano-multilayer films have good wear resistance. The electrochemical corrosion test shows that the self-corrosion current density of TiZrN/TiN nano-multilayer films reaches the minimum value of 0.566 μA/cm², which is approximately 1/17 of that of the high-speed substrate (9.654 μA/cm²), and the film exhibits the slowest corrosion rate. Using the hybrid method of arc ion plating and high-power impulse magnetron sputtering can reduce the surface roughness of TiZrN/TiN nano-multilayer films. With the increase in pulsed bias voltage, the ion energy can be changed, which significantly enhances the hardness, wear resistance, and corrosion resistance of TiZrN/TiN nano-multilayer films compared with those of the M2 high-speed steel substrate.

Abstract:Because of the special dimension effect and interface effect, film materials have unique advantages compared with bulk materials. Fe(Se,Te), an iron-sulfur superconductor, is more conducive to the study on superconducting mechanism because of its simple crystal structure. It has been found that single-layer FeSe superconducting films grown on SrTiO₃ (STO) substrate significantly increase the superconducting transition temperature (T_c), which makes the study on FeSe superconducting films a new direction to understand the mechanism of unconventional superconductors. In addition, it is also found that the critical transition temperature of FeSe multilayer films is higher than that of bulk materials. The recent research achievements on the preparation of Fe(Se,Te) superconducting films and the enhancement of T_c by stress effect and interface effect were reviewed.

Abstract:Thermal barrier coatings (TBCs) can effectively reduce the actual operating temperature of hot-end components of advanced turbines and engines and improve their service reliability and durability. Yttria-stabilized zirconia (YSZ) TBCs are currently the most mainstream thermal barrier coating system, but as the thrust-to-weight ratio continues to increase, higher requirements have been placed on the performance of YSZ TBCs. As an important surface strengthening technique, laser remelting has been proven by many researchers to be used to strengthen YSZ TBCs and improve their overall performance. In this paper, the effects of laser remelting on the microstructure and properties of thermal sprayed YSZ TBCs and the strengthening mechanism are reviewed, including their microstructure, phase composition, thermal shock resistance, high- temperature oxidation resistance, calcium-magnesium-aluminum-silicon (CMAS) corrosion resistance and foreign-particle erosion resistance. Finally, the future development of this technique is discussed, which provides valuable reference for the research and application of thermal sprayed YSZ TBCs by laser remelting.

Abstract:Improving the hot working performance of difficult-to-deform alloys, such as powder metallurgy superalloys, is an important way to improve their formability, yield rate and the development of high performance alloys. Hot extrusion can effectively improve the microstructure of the alloy and enhance its hot working properties during the preparation process. This paper reviews the research progress on hot extrusion process parameters of powder metallurgy superalloys in recent years, systematically discusses the influence of hot extrusion parameters on the extrusion process and microstructure, and summarizes the research work on the selection and optimization of hot extrusion parameters. At present, the influence of extrusion speed and extrusion ratio on alloy microstructure, numerical simulation of hot extrusion process and optimization of extrusion device need to be further studied. This paper is used to provide reference for understanding the hot extrusion process and subsequent engineering practice, and to provide certain theoretical guidance and technical support for regulating the alloy microstructure, optimizing the hot working process and improving the hot working performance.