2025,Volume 54, Issue 4

>ARTICLE

• Design Guidelines for Composition of Brazing Filler Metals and Evolution Mechanisms of Typical Microstructures

  Long Weimin

  2025,54(4):837-853 DOI:

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  Abstract:Brazing filler metals are widely applied, which serve as an industrial adhesive in the joining of dissimilar structures. With the continuous emergence of new structures and materials, the demand for novel brazing filler metals is ever-increasing. It is of great significance to investigate the optimized composition design methods and to establish systematic design guidelines for brazing filler metals. This study elucidated the fundamental rules for the composition design of brazing filler metals from a three-dimensional perspective encompassing the basic properties of applied brazing filler metals, formability and processability, and overall cost. The basic properties of brazing filler metals refer to their mechanical properties, physicochemical properties, electromagnetic properties, corrosion resistance, and the wettability and fluidity during brazing. The formability and processability of brazing filler metals include the processes of smelting and casting, extrusion, rolling, drawing and ring-making, as well as the processes of granulation, powder production, and the molding of amorphous and microcrystalline structures. The cost of brazing filler metals corresponds to the sum of materials value and manufacturing cost. Improving the comprehensive properties of brazing filler metals requires a comprehensive and systematic consideration of design indicators. Highlighting the unique characteristics of brazing filler metals should focus on relevant technical indicators. Binary or ternary eutectic structures can effectively enhance the flow spreading ability of brazing filler metals, and solid solution structures contribute to the formability. By employing the proposed design guidelines, typical Ag based, Cu based, Zn based brazing filler metals, and Sn based solders were designed and successfully applied in major scientific and engineering projects.

• Preparation and Brazing Performance of Low-Silver SnAgCu Composite Solder Reinforced by Nickel Coated Al₂O₃

  Wang Bingying, Zhang Keke, Fan Yuchun, Wu Jinna, Guo Limeng, Wang Huigai, Wang Nannan

  2025,54(4):854-861 DOI:

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  Abstract:Dopamine polymerization reaction and hydrothermal method were used to prepare nickel coated Al₂O₃ reinforcement phase (Ni/Al₂O₃). Ni/Al₂O₃ reinforced Sn1.0Ag0.5Cu (SAC105) composite solder was prepared using traditional casting method. The result shows that the nickel coating layer is continuous with uneven thickness. The interface between nickel and aluminum oxide exhibits a metallurgical bonding with coherent interface relationship. The strength, toughness and wettability of the SAC105 solder on the substrate are improved, while the conductivity is not decreased significantly. The fracture mode of composites transitions from a mixed toughness-brittleness mode to a purely toughness-dominated mode, characterized by many dimples. The prepared composite brazing material was made into solder paste for copper plate lap joint experiments. The maximum shear strength is achieved when the doping amount was 0.3wt%. The growth index of intermetallic compound at the brazing interface of Ni/Al₂O₃ reinforced SAC105 composite solder is linearly fitted to n=0.39, demonstrating that the growth of intermetallic compound at the interface is a combined effect of grain boundary diffusion and bulk diffusion.

• Effect of Cu and Mo Alloying on Microstructure and Molten Salt Corrosion Resistance of 347H Stainless Steel

  Yu Zhiqi, Zhao Yanchun, Liu Tianzeng, Feng Li, Ma Huwen, Li Jucang, Pan Jixiang

  2025,54(4):862-870 DOI:

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  Abstract:A static corrosion experiment of 347H stainless steel alloyed with elements Cu and Mo was carried out in a nitrate molten salt (60% NaNO₃+40% KNO₃) at 565 °C for 720 h. The effects of elements Cu and Mo on the corrosion resistance of 347H stainless steel in molten salt were investigated by analyzing the phase composition, microstructure and chemical composition of the corrosion products. The results show that the grain refinement induced by element Mo imparts the stainless steel with optimal corrosion resistance at a medium grain size. Furthermore, the formation of MoC significantly enhances the intergranular corrosion resistance of the stainless steel. The stainless steel exhibits uniform corrosion in the nitrate solution. The corrosion layer displays a dual-layer structure, and the corrosion products protecting matrix are present in both the inner and outer layers. The outer layer consists of a mixture of Fe oxides (Fe₂O₃, Fe₃O₄), NaFeO₂, and a minor amount of MgFe₂O₄. Conversely, the inner layer is primarily composed of a spinel layer (FeCr₂O₄, MgCr₂O₄) and a thin Cu₂O layer. The oxidation of Cu in the inner layer leads to the formation of a dense Cu₂O layer, effectively impeding O^2- plasma infiltration into the matrix.

• Annealing Treatment and Corrosion Behavior of Gd-containing Stainless Steel

  Xie Manman, Jia Dongxiao, Jia Xilin, Zhao Fei, Liang Tian, Zhou Yangtao

  2025,54(4):871-878 DOI:

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  Abstract:The microstructures and corrosion behavior of 1.0wt% Gd-containing neutron-absorbing duplex stainless steel annealed at different temperatures were studied. Results reveal that the content of Gd-containing secondary phase increases with increasing the annealing temperatures to 1080 ℃, and then decreases. In the sample annealed at 1080 ℃, M-Gd (M=Fe, Cr, Ni) intermetallic with M₃Gd as the core phase and M₁₂Gd as the shell is the primary secondary phase. In the sample annealed at 1140 ℃, M₃Gd phase is dominant. The corrosion behavior of the two annealed steel samples were analyzed in NaCl, HCl and H₃BO₃ solutions. It is found that the sample annealed at 1140 ℃ has lower corrosion rate. M₃Gd is more electrochemically active than M₁₂Gd when the sample is immersed in NaCl and HCl solutions, but more noble in H₃BO₃ solution.

• Effects of Thermal Aging on Microstructure and Mechani-cal Properties of Interface of Hot Isostatic Pressing Densified Low Alloy Steel with Inconel 690 Cladding

  Yu Lei, Cao Rui, Ma Jinyuan, Yan Yingjie, Dong Hao, Wang Caiqin

  2025,54(4):879-885 DOI:

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  Abstract:The microstructure, micro-hardness, and tensile properties of interface between hot isostatic pressing densified low alloy steel and Inconel 690 cladding were investigated during the aging process at 600 ℃. The results show that the interface region can be divided into four zones from base metal to deposited metal: carbon-depleted zone (CDZ), partial melting zone (PMZ), planar growth zone (PGZ), and brownish feature zone (BFZ). Dimensions of these zones do not significantly change during aging. However, type I carbides noticeably increase in size in the PMZ, and precipitates clearly occur in the PGZ. The main reason for their growth and occurrence is continuous carbon migration. The highest micro-hardness appears in the PGZ and BFZ regions, which is related to carbon accumulation and precipitates in these regions. Tensile failure occurs on the base metal side due to the high strength mismatch between these two materials. The CDZ, composed of only ferrite, has lower strength and fractures at the boundary between CDZ and base metal. The ultimate tensile strength decreases by only 50 MPa after aging for 1500 h, and the interface region maintains high strength without significant deformation.

• Erosion-Corrosion of Ti(C, N)-Mo₂C-Ni Cermet and WC-Co Cemented Carbide in Alkaline Conditions

  Deng Chengjun, Lin Fukai, Yang Tianen, Hong Huaping, Liang Lei, Peng Huabei, Xiong Ji

  2025,54(4):886-897 DOI:

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  Abstract:Ti(C, N)-Mo₂C-Ni cermet as alternative materials was explored for use in alkaline conditions, replacing the WC-Co cemented carbides, since Co is classified as a potentially carcinogenic substance and there is potential hazard of “hard metal disease” under the exposure to cobalt dust. The changes in microstructure, corrosion rate and volumetric loss rate of the two materials were compared under electrochemical corrosion and erosion-corrosion in alkaline environment. The results demonstrates that Ti(C, N)-Mo₂C-Ni cermet undergoes passivation when exposed to electrochemical corrosion of NaOH solution, resulting in a significant increase in oxygen content on the corroded surface. The corrosion rate of cermet is approximately one order of magnitude lower than that of the cemented carbide. Under the erosion-corrosion of an alkaline sand-water mixture, both the cermet and cemented carbide experience a gradual increase in volumetric loss rate with prolonging the erosion time. During erosion, the rim phase in cermet is fragile, so cracks easily penetrate it while the core phase remains intact. The medium-grained cemented carbide commonly demonstrates transgranular fracture mode, while in the fine-grained cemented carbide, cracks tend to propagate along phase boundaries. The erosive wear and damage caused by sand particles play a predominant role in the erosion-corrosion process of alkaline sand-water mixtures. This process represents an accelerated destructive phenomenon influenced and intensified by the combined effects of corrosion and erosion. It is confirmed that using cermet as an alternative anti-wear material to cemented carbides is feasible under alkaline conditions, and even better.

• Influence of Microstructures on Hot Deformation Behavior and Microstructure Evolution of FGH4113A Superalloy

  Yang Jinlong, Xiong Jiangying, Yin Chao, Cheng Junyi, Guo Jianzheng, Feng Ganjiang

  2025,54(4):898-907 DOI:

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  Abstract:The hot compression curves and deformed microstructures were investigated under various hot deformation conditions in three states: hot isostatic pressing (HIP, A1), HIP+hot extrusion at 1100 ℃ (A2), and HIP+hot extrusion at 1150 ℃ (A3). The results show that A2 sample, extruded at 1100 ℃ with uniform γ+γ′ duplex microstructures, demonstrates excellent hot deformation behavior at both 1050 and 1100 ℃. The true stress-true strain curves of A2 sample maintain a hardening-softening equilibrium over a larger strain range, with post-deformation average grain size of 5 μm. The as-HIPed A1 sample and 1150 ℃ extruded A3 sample exhibit a softening region in deformation curves at 1050 ℃, and the grain microstructures reflect an incomplete recrystallized state, i.e. combination of fine recrystallized grains and initial larger grains, characterized by a necklace-like microstructure. The predominant recrystallization mechanism for these samples is strain-induced boundary migration. At 1150 ℃ with a strain rate of 0.001 s^-1, the influence of the initial microstructure on hot deformation behavior and resultant microstructure is relatively less pronounced, and post-deformation microstructures are fully recrystallized grains. Fine-grained microstructures are conducive to maximizing the hot deformation potential of alloy. By judiciously adjusting deformation regimes, a fine and uniform deformed microstructure can be obtained.

• Introducing High-Volume-Fraction Ultrafine Grains to Obtain Superior Balance of Strength and Electrical Conductivity for Cu/Al₂O₃ Composite

  Zhang Jun, Liu Xi, Li Yi, Chang Guo, Peng Haoran, Zhang Shuang, Huang Qi, Zhao Xueni, Li Liang, Huo Wangtu

  2025,54(4):908-919 DOI:

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  Abstract:Compared with Cu/Al₂O₃ composites, high-strength Cu/Al₂O₃ composites usually exhibit obviously deteriorated electrical conductivity. A chemical and mechanical alloying-based strategy was adopted to fabricate ultrafine composite powders with low-content reinforcement and constructed a combined structure of Cu ultrafine powders covered with in-situ Al₂O₃ nanoparticles. After consolidation at a relatively lower sintering temperature of 550 ℃, high-volume-fraction ultrafine grains were introduced into the Cu/Al₂O₃ composite, and many in-situ Al₂O₃ nanoparticles with an average size of 11.7±7.5 nm were dispersed homogeneously in the Cu grain. Results show that the composite demonstrates an excellent balance of high tensile strength (654±1 MPa) and high electrical conductivity (84.5±0.1% IACS), which is ascribed to the synergistic strengthening effect of ultrafine grains, dislocations, and in-situ Al₂O₃ nanoparticles. This approach, which utilizes ultrafine composite powder with low-content reinforcement as a precursor and employs low-temperature and high-pressure sintering subsequently, may hold promising potential for large-scale industrial production of high-performance oxide dispersion strengthened alloys.

• Hot Deformation Behavior and Microstructure Evolution of Electrolytic Copper

  Zhang Han, Sang Chen, Zhang Yan, Xu Yangtao, Qiao Jisen, Xia Tiandong

  2025,54(4):920-929 DOI:

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  Abstract:The hot deformation behavior of electrolytic copper was investigated using a Gleeble-3500 thermal simulation testing machine at temperatures ranging from 500 °C to 800 °C and strain rates ranging from 0.01 s^-1 to 10 s^-1, under 70% deformation conditions. The true stress-true strain curves were analyzed and a constitutive equation was established at a strain of 0.5. Based on the dynamic material model proposed by Prasad, processing maps were developed under different strain conditions. Microstructure of compressed sample was observed by electron backscatter diffraction. The results reveal that the electrolytic copper demonstrates high sensitivity to deformation temperature and strain rate during high-temperature plastic deformation. The flow stress decreases gradually with raising the temperature and reducing the strain rate. According to the established processing map, the optimal processing conditions are determined as follows: deformation temperatures of 600–650 °C and strain rates of 5–10 s^-1. Discontinuous dynamic recrystallization of electrolytic copper occurs during high-temperature plastic deformation, and the grains are significantly refined at low temperature and high strain rate conditions.

• Influence of Aging Treatment on Microstructure and Pro-perties of Ti-3Al-6Mo-2Fe-2Zr Laser-Welded Joint

  Wan Xuan, He Chaowei, Zhang Kezhao, Liu Dong, Yan Chunyan, Bao Yefeng

  2025,54(4):930-936 DOI:

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  Abstract:Laser beam welding was used to join a near-β titanium alloy (Ti-3Al-6Mo-2Fe-2Zr), followed by aging treatments. The relations among aging temperature, microstructure, and tensile properties of joints were revealed. For as-welded joints, the fusion zone features primarily single β phase. It is attributed to the high Mo equivalency of this alloy and the fast cooling rate in laser beam welding. After aging treatments, many α precipitates form in the fusion zone and heat affected zone. The rising aging temperature coarsens α precipitates and reduces the volume fraction of α precipitates. Compared with the as-welded joints, the aging treated joints'' tensile strength and elongation are improved. The increasing aging temperature weakens the strengthening effect because of the decreasing volume fraction of α precipitates. After the aging treatment at 500 °C for 8 h, the joints obtain the optimal match between strength and plasticity. The fracture mode of joints changes from quasi-cleavage fracture in as-welded condition to microvoid coalescence fracture after heat treatments.

>Materials Science

• As-cast Microstructure of Centrifugal-Cast 27Cr44Ni5W3Al+MA Ethylene Cracking Furnace Tube

  Wu Zhigang, Chen Tao, Liu Chunjiao

  2025,54(4):937-944 DOI: 10.12442/j.issn.1002-185X.20240136

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  Abstract:To investigate the original as-cast microstructure of 27Cr44Ni5W3Al+MA ethylene cracking furnace tube manufactured by centrifugal casting, the phase composition and microstructure of the as-cast furnace tube were analyzed using XRD, OM, SEM and TEM. The results show that the original as-cast microstructure of the furnace tube is mainly composed of austenite matrix (γ phase) and fishbone-like multi-phase carbides at grain boundaries; the inside of the multi-phase carbides is lamellar M₇C₃, while the edge is blocky M₂₃C₆. In addition, two shapes of Ni₃Al (γ′ phase) are observed, namely the granular phase distributed near the junction between M₂₃C₆ and matrix, and the blocky phase adjacent to M₂₃C₆. Both of M₂₃C₆ and granular γ′ have the cube-on-cube orientation relationship with the γ matrix ( , , ; , , . , , ; , , ). In addition, a large number of dislocations are observed in the as-cast microstructure, with sparse distribution away from M₂₃C₆ and dense distribution near M₂₃C₆. The precipitation mechanism of γ′ and M₂₃C₆ during centrifugal casting was also discussed. The W element reduces the lattice misfit between M₂₃C₆ and γ phase, thereby promoting the precipitation of M₂₃C₆. The chemical composition of M₂₃C₆ and γ′ phase exhibit complementarity, and the precipitation of M₂₃C₆ further facilitates the formation of γ′ phase.

• Fracture Behavior of Laminated Ti/TiNb Composites with Diffusion Layers

  Kou Wenjuan, Yin Yanfei, Zhou Feng, Shi Zhaohui, Zhao Yongqing

  2025,54(4):945-951 DOI: 10.12442/j.issn.1002-185X.20230783

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  Abstract:The laminated Ti/TiNb composites with diffusion layers were fabricated by spark plasma sintering combined with hot rolling. In-situ tensile test monitored by SEM was applied to analyze the crack initiation and propagation behaviour of the composites in different states, so as to understand the effects of Ti component thickness and diffusion layer microstructure on the fracture behavior of the composites. The results show that the length of microcracks can be effectively controlled by reducing the thickness of Ti component, thus delaying the extension of shear bands in adjacent TiNb layers. The microstructure of diffusion layer has a significant effect on the fracture behavior of the composite. Compared with the composite with “hard” diffusion layer, the composite with “soft” diffusion layer has more cracks and shear bands before tensile fracture, and shows a more tortuous crack propagation path after the overall fracture.

• Preparation and Wear-Resistant Mechanism of Highly Wear-Resistant GNPs/AlSi10Mg Composites

  Yang Yan, Han Xinyang, Qiu Yuxiao, Lin Bin, Chen Junfeng, Chen Yulong, Chen Shujian, Zou Linchi, Chi Haitao, Zhang Wei

  2025,54(4):952-963 DOI: 10.12442/j.issn.1002-185X.20230757

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  Abstract:Through the surface modification of graphene nanoparticles (GNPs) by ethyl cellulose (EC), combined with solution ultrasonic dispersion and wet ball milling, GNPs and aluminum matrix were uniformly mixed and GNPs damage was suppressed. Then, highly wear-resistant GNPs/AlSi10Mg composites were prepared by the suppression of interfacial reaction through rapid sintering with discharge plasma. The microstructure and wear-resistant properties of GNPs/AlSi10Mg composites were characterized and analyzed by scanning electron microscope, transmission electron microscope and friction testing machine. The results show that moderate addition of GNPs can effectively improve the mechanical properties of the composites. When the addition amount of GNPs is 0.5wt%, the wear rate and coefficient of friction of the composites are the lowest, which are 7.8×10^-4 mm³/(N·m) and 0.417, respectively. The wear rate is reduced by 28.4% compared with that of the matrix material (10.9×10^-4 mm³·N^-1·m^-1). The wear mechanism of GNPs/AlSi10Mg composites is mainly abrasive wear, accompanied by slight oxidative wear and adhesive wear. During the friction process, when the composite specimen is in contact with the dyad, GNPs emerge on the surface to form a thin film under the action of shear force, which can be used as a lubricant to reduce the contact point between the dyad and the matrix, preventing excessive spalling and delamination and thereby protecting the matrix.

• Mechanism of Grain Boundary Widening of Typical Nickel-Based Superalloys Under Near Service Conditions

  Ma Danrui, Guo Jing, Zhang Maicang

  2025,54(4):964-974 DOI: 10.12442/j.issn.1002-185X.20230799

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  Abstract:This research focused on two candidate materials (alloy A and alloy B) for superheater and reheater in high-parameter advanced ultra-supercritical power plants. It systematically analyzed the phenomenon of local grain boundary widening, the kinetics, and the mechanism of grain boundary widening of two kinds of Ni-based superalloys during long-term aging. The results show that the main precipitates of two alloys in the widening grain boundary region are M₂₃C₆ carbide and grain boundary γ′ phase during high-temperature and long-term aging. The evolution of grain boundary widening of two alloys with aging time follows the JMAK equation. The formation process of grain boundary widening consists of three stages. In the first stage, the M₂₃C₆ carbides near the grain boundaries are treated by meltback, inducing the coarsening of M₂₃C₆ carbides at grain boundary and the grain boundary migration. In the second stage, new M₂₃C₆ carbides are precipitated after grain boundary migrating, which makes M₂₃C₆ carbides in the grain boundary area arrange in multiple layers, and the width of grain boundary increase. In the third stage, the γ′ phase will precipitate at the M₂₃C₆/γ interface with the decreased coarsening rate of carbides, and the short-circuit diffusion of grain boundary makes the γ′ phase grow and the width of grain boundary further increase.

• Preparation of La₂O₃/LaB₆-Modified ZrC-SiC Ceramics by Spark Plasma Sintering and Their Ablation Resistance

  Xie Jing, Teng Chengcheng, Sun Guodong, Li Hui, Jia Yan, Zhao Peng

  2025,54(4):975-982 DOI: 10.12442/j.issn.1002-185X.20230768

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  Abstract:To improve the ablative properties of ZrC-SiC ceramics, a series of ZrC-SiC multiphase ceramics modified with different contents of La₂O₃ and LaB₆ were prepared by discharge plasma sintering method at 1600 ℃ and 50 MPa. The ablative properties of the materials were tested under oxygen-acetylene flame with a heat flux of 2380 kW/m². The results show that the addition of La₂O₃ and LaB₆ not only improves the sintering performance and density of ZrC-SiC, but also improves the thermal shock resistance. With the increase in addition amount, the surface oxide layer of the samples gradually becomes intact from fracture after ablation. In contrast, the ZrO₂-La₂Zr₂O₇ solid solution layer formed on the ablative surface after La₂O₃ modification still has more holes and cracks, and the combination with internal ceramics is poor, resulting in the poor protection effect. With the addition of LaB₆, the volatilization of low melting-point borides during ablative process can reduce the ablative temperature of the material by nearly 300 ℃. La₂Zr₂O₇-LaBO₃-ZrO₂ outer oxide layer with good thermal stability and lanthanum-rich Zr-O-La-B inner oxide layer with good adhesion are formed on the surface of the ablation center of the sample. The double-layer protective film becomes a dense barrier to prevent the oxidation air from entering the inside of the material, which effectively improves the ablation resistance of the material. The ZrC-SiC ceramic with 20vol% LaB₆ has the best comprehensive ablative performance. After oxygen-acetylene ablation for 60 s, its mass and linear ablative rate are 7.5×10^-4 g/s and 2.1×10^-3 mm/s, respectively.

• Tribological and Electrochemical Properties of CoCrNi-Based Medium and High Entropy Alloys Prepared by Laser Cladding

  Meng Yichen, Chu Yinrun, Shi Yuelin, Liu Xiaomei, Wang Liang, Zhang Qunli, Yao Jianhua

  2025,54(4):983-992 DOI: 10.12442/j.issn.1002-185X.20230774

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  Abstract:In this work, medium and high entropy alloy coating was prepared on the surface of 38CrMoAl by laser cladding technique. The effects of adding elements such as Al, Si, Fe, and Nb to CoCrNi series alloys on the phase, microstructure, and element distribution of the alloy coating were studied. The hardness, wear resistance, and electrochemical properties of the coating were analyzed and characterized. The results indicate that CoCrNi alloy has a face-centered cubic (fcc) crystal structure, and the addition of Al and Fe promotes the formation of body-centered cubic (bcc) phase. After the addition of Nb and Si elements, a Laves/bcc eutectic+Nb-riched composite phase is formed in the septenary-element-alloy coating, and the microstructure is significantly refined. The comprehensive performance of CoCrNi-based medium and high entropy alloy coatings is superior to that of 38CrMoAl substrate. Compared with CoCrNi and AlCoCrFeNi alloy coatings, the hardness, wear resistance, and corrosion resistance of AlSiCoCrFeNiNb coatings have been significantly improved: the surface hardness is 713.3 HV_0.1, which is 3.24 times higher than that of the substrate. The wear mechanism is mainly slight abrasive wear and adhesive wear, with an average coefficient of friction of 0.52 and a wear rate of 115.73×10^–12 mm³/(N·m), reduced by 64.4% compared with that of the substrate. The self corrosion potential (E_corr) is –0.3392 V, and self corrosion current density (I_corr) is 0.472 μA·cm^-2.

• Microstructure and Wear Properties of Titanium-Doped Diamond-Like Films on Titanium Alloy Fasteners

  Xu Zhaoying, Su Yongyao, Zhang Tengfei, Wang Jinbiao, Chen Qiaowang

  2025,54(4):993-1001 DOI: 10.12442/j.issn.1002-185X.20230805

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  Abstract:In this research, based on the concept of surface engineering and composite multi-component structure design, the titanium-doped diamond-like carbon (DLC) films were prepared on the surface of titanium alloy threaded fasteners by microwave plasma enhanced magnetron sputtering technique. Titanium-doped DLC composite films with different structures and properties were prepared by regulating acetylene flow. The microscopic morphology of titanium-doped DLC films were analyzed by transmission electron microscope. The microstructure, residual stress, nano-hardness, adhesive strength and wear properties were studied by XRD, Raman spectrometer, profilometry technique, nanoindenter and friction test machine. The results show that TiC crystalline phase is formed in titanium-doped DLC films, and the residual stress of titanium-doped DLC film can be effectively reduced with appropriate acetylene gas flow. The sp³ hybrid bond content is decreased gradually with the increase in acetylene flow. The titanium-doped DLC film with acetylene gas flow of 0.025 L/min has higher hardness, elastic modulus, toughness and the largest H/E and H³/E² ratios, which can resist the scratch of the indenter. Therefore, the film maintains good adhesion in the scratch, and has the best wear resistance, which can effectively improve the service life of titanium alloy fasteners.

• Effect of Annealing Temperature on Microstructure and Mechanical Properties of Large-Diameter Ti6321 Titanium Alloy Seamless Tube

  Li Chong, Shi Hongjie, Sun Erju, Xu Yali, Xu Lingyu, Chen Chunyang, Sun Xiaoyi, Song Dejun

  2025,54(4):1002-1007 DOI: 10.12442/j.issn.1002-185X.20230792

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  Abstract:Large-diameter Ti6321 alloy seamless tube with Φ450 mm×20 mm was prepared using forging billet by cross piercing and hot rolling process, and the effect of annealing temperature on microstructure and mechanical properties of seamless tube were investigated. The results show that the microstructure of as-rolled tube is mainly composed of α phase and transformed β phase. Equiaxial structure is obtained after annealing at 940 ℃, duplex structure is obtained after annealing at 970 ℃, and Widmanstatten structure is obtained after annealing at 1020 ℃. With the increase in annealing temperature, the yield strength and tensile strength at room temperature of the tube are gradually decreased. The plasticity of the tube does not change much below the transformation point, but decreases sharply above the transformation point. The impact toughness first increases and then decreases. According to comprehensive analysis, the suitable annealing temperature for the prepared large-diameter Ti6321 alloy seamless tube is about 970 ℃, when the tube has the best impact performance and impact energy is 62 J. The average yield strength, tensile strength, and elongation of the tube after annealing at 970 ℃ are 786 MPa, 878 MPa, and 16.25%, respectively.

• Effect of Detonation Characteristics on TiO₂ Particle Size During Gaseous Detonation Synthesis

  Wu Linsong, Wang Xingzhi, Lu Shiwei, Chen Xiang, Yan Honghao

  2025,54(4):1008-1014 DOI: 10.12442/j.issn.1002-185X.20240058

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  Abstract:This research investigated the growth characteristics of TiO₂ nanoparticles in the instantaneous high-temperature and high-pressure gaseous detonation reaction. Computational fluid dynamics was used to simulate the flame propagation process and the temperature-time relationship of the gas explosion in the detonation tube, and it was introduced into the particle growth model. The model was modified through experiments. The results show that the reaction temperature and time are the main factors affecting the particle growth in the gaseous detonation reaction. A particle size correction coefficient k is proposed to improve the classical particle growth model. The improved numerical model can accurately predict the growth characteristics of TiO₂ nanoparticles, which provides effective theoretical support for the controllable synthesis of TiO₂ nanoparticles.

• Phase Precipitation Behavior of New High-Boron Cast Ni-based Superalloy

  Wang Liang, Hu Yiwen, Zhou Peishan, Wang Bin, Zheng Hualin

  2025,54(4):1015-1025 DOI: 10.12442/j.issn.1002-185X.20230782

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  Abstract:The effects of alloying elements on the phase precipitation behavior of a new high-boron Ni-based superalloy were studied using JMatPro thermodynamic software and compared with the actual cast microstructure. The results indicate that the as-cast microstructure of the new high-boron Ni-based superalloy exhibits a typical dendritic morphology, mainly composed of γ, γ′, carbides, borides, and (γ+γ′) eutectic (about 15.5vol%). The segregation of Hf and Ta elements is obvious during the solidification process. Thermodynamic calculations indicate that Ti, Ta, Hf, Al, and B elements have great influence on the melting temperature of alloys. The initial precipitation temperature of γ′ phase and its precipitation amount at 900 ℃ are increased with the increase in Al content, while the influence of Ti element is relatively small. In addition, the Ta and Hf elements will promote the precipitation of MC-type carbide, and the influence of Cr element on the precipitation amount of M₂₃C₆ carbide is greater than that of M₆C carbide. The precipitation of borides is mainly influenced by Cr and W elements, while Mo element has a significant impact on the precipitation temperature of M₃B₂ borides. As the content of Co, Cr, W, and Mo elements increases, the precipitation amount and precipitation temperature of μ phase both show an increasing trend.

• Microscopic Damage Simulation of Porous W/Zr-Based Metallic Glass Composite

  Wei Zhuang, Gao Min, Duan Jingbo, Shi Dongmei, Li Chen, Zhang Yuling, Li Wenzhao

  2025,54(4):1026-1033 DOI: 10.12442/j.issn.1002-185X.20230772

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  Abstract:To investigate microscopic microstructural damage of porous W/Zr-based metallic glass composite, the microscopic-scale finite element model of the composite was established based on their scanning electron microscope images, and the quasi-static compression process of the composite was numerically simulated in conjunction with the cohesive zone model. The effects of interface stiffness, interface strength and fracture energy on the mechanical properties of the composite were investigated, and the values of cohesive zone model parameters were determined by comparing them with quasi-static compression experimental data. Results show that there are three damage modes of porous W/Zr-based metallic glass composite during compression process, which are cleavage fracture of the W particle, shear band fracture within the Zr-based metallic glass and interfacial crack between the two phases. The cohesive zone model parameters have a great influence on the simulation curve: the greater the interface stiffness, the higher the slope of the simulation curve; the greater the interface strength, the higher the yield point of the simulation curve; the larger the fracture energy, the shorter the plastic stage of the simulation curve. As the interface stiffness, interface strength and fracture energy are taken as 10 000 GPa/μm³, 500 MPa and 0.055 J/m², respectively, the simulation results are well consistent with the experimental results, and the simulation model is able to accurately describe the mechanical behavior of porous W/Zr-based metallic glass composite.

• Carburizing Behavior of Four Kinds of Fe-Cr-Ni Alloy Cracking Furnace Tubes at 1075 ℃

  Chen Tao, Liu Chunjiao, Wu Zhigang

  2025,54(4):1034-1043 DOI: 10.12442/j.issn.1002-185X.20230779

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  Abstract:To analyze the carburizing resistance of Fe-Cr-Ni alloy cracking furnace tube, solid carburizing agent with particle size of 1.5–3 mm was used to conduct carburizing test on two kinds of traditional furnace tubes (25Cr35NiNb+MA and 35Cr45NiNb+MA) as well as two kinds of aluminum-added alloy furnace tubes with prolonged coke cleaning period (27Cr44Ni5W3Al+MA and 29Cr44Ni4Al+MA). The test was carried out at 1075 ℃ for 50–200 h. The composition, microstructure and properties of the furnace tubes after carburizing test were analyzed by optical emission spectrometer, scanning electron microscope, X-ray diffractometer and Vickers hardness tester, and the carburizing kinetics and microstructure transformation rules were studied. The results show that the thickness of the carburized layer of four kinds of materials is increased with the prolongation of carburizing time. After carburizing at 1075 ℃ for 200 h, the thicknesses of the carburized layers of the furnace tubes are about 2.0, 1.8, 1.0 and 0.7 mm, and the average carburizing rates are about 0.01, 0.009, 0.005 and 0.0035 mm/h. The carburizing resistance of the two aluminum-added alloy tubes is better than that of the traditional tubes. The microstructure in the aged zone of 27Cr44Ni5W3Al+MA furnace tube is composed of austenite, blocky M₂₃C₆ and fishbone-like M₇C₃. The "M" in carbides contains elements such as Cr and W. In the carburized zone, blocky M₂₃C₆ is transformed into blocky M₇C₃ and WC, and fishbone-like M₇C₃ coarsens. The microstructure in the aged zone of 29Cr44Ni4Al+MA furnace tube is composed of austenite, blocky M₂₃C₆ and NbTiC. The "M" in carbides is mainly Cr element. In carburized zone, blocky M₂₃C₆ is transformed into blocky M₇C₃, and NbTiC changes from blocky to granular. The inner walls of two aluminum-added alloy furnace tubes form a dense and stable Al₂O₃ film. Compared with the Cr₂O₃ film on the inner walls of traditional furnace tubes, the Al₂O₃ film can more effectively block the penetration of carbon atoms into the substrate, thereby enhancing the anti-carburization performance.

• Impact Toughness and Sliding Wear Behavior of Stellite 6B Alloy

  Zhang Yawei, Xu Guohua, Shen Yu, Ju Quan, Zhang Ji

  2025,54(4):1044-1052 DOI: 10.12442/j.issn.1002-185X.20240071

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  Abstract:The impact toughness and sliding wear behavior with GH5605 alloy at room temperature of solution-and solution+aging-treated Stellite 6B alloy were evaluated. The relevant microstructure, impact fracture surface, worn surface and dissected section were observed and analyzed by Thermal-Calc software, OM, SEM and TEM. The results show that the wear rate of Stellite 6B alloy is significantly reduced by aging treatment after solution, and consequently the wear amount is reduced by approximately 70%. However, the impact toughness of the aging-treated alloy is only 30% of that of the solution-treated alloy. Further analyses indicate that the wear mechanism of solution-treated Stellite 6B alloy is mainly adhesive wear, and adhesive bonding layer is cut off in the matrix. Aging treatment promotes the martensitic transformation and significantly improves the resistance to adhesive wear. The wear mechanism is a small amount of adhesive wear as well as long-term fatigue wear. Since carbide at grain boundary is the main factor affecting the impact toughness of aging alloy, increasing martensitic transformation tendency of the matrix, reducing the total amount of carbides and inhibiting the precipitation of secondary carbide along grain boundary are the process and component optimization direction to comprehensively improve the adhesion wear resistance and impact toughness of Stellite 6B alloy.

• Research Progress of Directionally Solidified Superalloy for Gas Turbine Blade

  Fan Yunpeng, Zhao Xinbao, Zhou Yu, Xia Wanshun, Yue Quanzhao, Gu Yuefeng

  2025,54(4):1053-1071 DOI: 10.12442/j.issn.1002-185X.20230787

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  Abstract:Directionally solidified superalloys are widely used in turbine blades of advanced power propulsion systems such as industrial gas turbines due to their excellent high-temperature strength, creep resistance, corrosion and oxidation resistance, as well as good structural stability and casting properties. Directionally solidified superalloys for gas turbines have been developed from the first generation to the fourth generation by adjusting the proportions of different solid solution strengthening, precipitation strengthening and grain boundary strengthening elements. The intragranular structures are mainly composed of γ phase and γ? phase. There are carbides, borides and other precipitates at the grain boundaries that can pin the grain boundaries. Under the joint influence of these strengthening phases, nickel-based directionally solidified superalloys have better tensile and creep properties that can change with temperature. Starting with the composition characteristics and microstructure characteristics, this article combines the current application status of directionally solidified superalloys in gas turbines, and further analyzes its performance characteristics. Finally, it looks forward to future research on directionally solidified superalloys.

• Prospect and Outlook of Ceramic Cores in Hot Isostatic Pressing Process

  Lu Jiahao, Cai Jili, Cai Chao, Shi Yusheng

  2025,54(4):1072-1086 DOI: 10.12442/j.issn.1002-185X.20230767

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  Abstract:Hot isostatic pressing combined with mold control technique can achieve near-net shaping of complex high-performance components. The mold core is crucial for controlling the internal structural accuracy of the formed parts. Presently, mold cores predominantly employ metallic materials. However, these metallic cores are susceptible to substantial deformation under elevated temperatures and pressures. The removal of acid-induced corrosion is not only inefficient but also environmentally unsound. The diffusion of foreign elements from the metal mold cores results in contamination of parts. Additionally, issues such as embedding of forming powder into the surface lead to poor surface quality of the parts. These problems hinder the development of hot isostatic pressing to the forming of complex internal cavity parts. Ceramic mold cores exhibit low chemical reactivity and minimal interdiffusion with metal elements. Its high temperature hardness and stiffness confer resistance to deformation, and its core removal rate is high under alkaline conditions. The above advantages offer a potential solution to issues caused by metal cores. Based on representative literature and research advancements in the field of ceramic mold cores for casting, this paper focuses on analyzing the synergistic relationship between the mechanical and dissolution properties of ceramic mold cores used in hot isostatic pressing. This paper provides a detailed introduction and comparison of the optimization strategies for mechanical properties, dissolution performance, and moisture resistance of silicon oxide, aluminum oxide, calcium oxide, and magnesium oxide-based ceramics used in hot isostatic pressing cores. This paper also explores complex high-precision structural formation, sintering, and post-processing methods. Additionally, it anticipates challenges and future directions for the application of ceramic cores in the near-net shaping hot isostatic pressing process.

• Design Idea and Research Status of Cr-based Accident-Tolerant Coating on Zirconium Alloy

  Zhang Jin, Zhang Conghui, Wang Yanfeng, Zhu Wenguang, Liu Lintao

  2025,54(4):1087-1095 DOI: 10.12442/j.issn.1002-185X.20230764

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  Abstract:Zirconium alloy coating can improve the accident resistance of zirconium alloy cladding without changing the present fuel system, which is one of the hot research directions to improve the accident-tolerant ability of nuclear fuel assemblies. Cr-based coating is the most widely concerned coating material at the current stage. The development progress and design ideas from Cr coatings to various Cr-based coatings after Fukushima nuclear accident were systematically reviewed in this paper. The selection basis and high-temperature oxidation failure mechanism of Cr-based coating were introduced. The solution ideas and research progress were discussed from two aspects of composition design and structure design. Finally, the development prospect of Cr-based coating on zirconium alloy in the future was proposed. The review has important reference significance for the development and application of the new generation of accident tolerant fuel coating technique in the future.

• Research Status and Prospect of Brazing of Ti and Ti Alloys with ZrO₂ Ceramics

  Ji Fei, Li Yuanxing, Dong Wenxin, Chen Hui

  2025,54(4):1096-1111 DOI: 10.12442/j.issn.1002-185X.20240048

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  Abstract:Ti and Ti alloys and ZrO₂ ceramics are extensively used in high-precision fields due to their excellent characteristics, playing an increasingly important role in modern industry. The reliable connection of Ti and Ti alloys with ZrO₂ ceramics is crucial to complete the complementary properties of dissimilar materials and expand their range of applications. However, there are some problems to be solved in the welding process of dissimilar materials, which are mainly to improve the wettability of filler metal on the surface of base metal and to alleviate the interface stress. This paper focuses on the analysis of the connection difficulties of the two materials, reviews the research progress of brazing of related ceramics and metals, expounds the influence of different pretreatment methods on the joint performance, and finally puts forward the prospect of dissimilar material connection.

• Progress on Preparation and Hydrogen Storage Properties of Nanostructural ZrCo Alloys

  Yuan Yingbo, Yu Jianshi, Li Zhenyang, Huang Gang, Liu Xiaofang

  2025,54(4):1112-1120 DOI: 10.12442/j.issn.1002-185X.20230780

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  Abstract:ZrCo alloy has been initially applied in nuclear fusion experimental reactor due to its high hydrogen isotope storage capacity, low equilibrium pressure at room temperature and no radioactivity. However, ZrCo alloy has some issues, such as long activation time, poor kinetic properties and easy disproportionation, which restrict its engineering process. Therefore, it is of great significance to improve the hydrogen storage performance of ZrCo alloy and realize the synchronous improvement of dynamic characteristics, cycle stability and anti-disproportionation performance, which is crucial for revealing hydrogen storage mechanism of ZrCo alloy and promoting its engineering application. This review summarizes recent progress on nanostructural ZrCo alloys, especially the fact that nanostructural ZrCo alloy particles can shorten the activation time to less than 10 s, effectively improve the hydrogen absorption kinetics, and enhance the anti-disproportionation ability by more than 50% at 500 ℃, significantly improving the comprehensive hydrogen storage performance of ZrCo alloys. In this paper, the latest research trends of nanostructural ZrCo alloys are systematically summarized, and the mechanism of nanostructure on improving hydrogen storage performance is emphatically elaborated. The future research and application prospects of nanostructural ZrCo-based hydrogen storage isotope alloys are prospected.

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• Effect of Annealing Temperature on Microstructure and Properties of Nickel-based Powder Superalloy Formed by L-PBF

  Wang Yao, Ren Xiaona, Chen Zhipei, Ge Changchun

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240541

  Abstract(28) PDF(2.50 M)(32)

  Abstract:Different temperature annealing treatments were conducted on a laser powder bed melted FGH4096M nickel-based superalloy. The microstructure of the alloy was analyzed using SEM and EBSD, while tensile tests were performed to investigate the impact of the annealing process on the microstructural evolution and mechanical properties of the laser powder bed melted FGH4096M superalloy. The results revealed that as the annealing temperature increased, dendritic and columnar crystals gradually disappeared in the formed alloy, with a significant precipitation of γ" phase observed at an annealing temperature of 900℃. Additionally, there was a gradual increase in hardness value, along with an upward trend in both tensile strength and yield strength; however, fracture elongation rate remained low at only 5%. Analysis of grain orientation difference distribution indicated that annealing could partially eliminate residual stress. These research findings provide valuable data support for enhancing the performance of laser powder bed melted nickel-based superalloys.

• Static recrystallization kinetics of the metal beryllium

  Xu Demei, Li Meisui, Li Zhinian, Ye Shupeng, He Lijun, Li Feng

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240551

  Abstract(32) PDF(9.72 M)(33)

  Abstract:The microstructure evolution and the kinetics of static recrystallization have been investigated in beryllium during annealing at 680 ℃-880 ℃ through the implementation of the isothermal compression test and the measurement of the recrystallized fraction by hardness. The beryllium was subjected to compression on an Instron 5582 testing machine under varying strain temperatures (250 ℃-450 ℃), strain rates (10-1 s-1 to 10-4 s-1), and true strains (16%-92%). The results show that decreasing the strain temperature and increasing the strain rate promotes the progress of beryllium recrystallization. As the strain is increased, the beryllium recrystallized grains exhibit refinement, and the recrystallization rate is accelerated. However, the effect of increasing the strain on improving the recrystallization rate of beryllium diminished when the strain was increased to more than 60%. Increasing the annealing temperature, the recrystallization rate of beryllium was significantly accelerated. In particular, when the annealing temperature is elevated from 750 ℃ to 780 ℃, the recrystallization rate of beryllium enhances dramatically. At 880 ℃, the time for beryllium to complete recrystallization is reduced to approximately five minutes. The static recrystallization activation energy of beryllium is 396.56 kJ/mol at 680 ℃-750 ℃, while it is only 72.93 kJ/mol at 780 ℃-880 ℃. A static recrystallization kinetic model of beryllium with a modified Avirami component n is constructed. The calculated values of the model are in good agreement with the experimental values, indicating that the model is capable of predicting the static recrystallized fraction of beryllium deformed at low temperatures (250 ℃-450 ℃) and meets the requirements of engineering applications.

• Dynamic Recrystallization Behavior and Microstructure Evolution of GH4710 Alloy Prepared by Ingot Extrusion

  Chen Youhong, Lan Bo, Lin Yingying

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240555

  Abstract(21) PDF(4.82 M)(25)

  Abstract:The dynamic recrystallization (DRX) behavior and microstructure evolution of the as-extruded GH4710 alloy were investigated through isothermal compression experiments and quantitative metallographic analysis. The study was conducted at temperatures ranging from 1050 to 1120 °C and strain rates ranging from 0.01 to 5 s_^-1. True stress-strain curves, average grain size, and DRX volume fraction data were obtained under various deformation conditions. Model for the DRX volume fraction and grain size of the as-extruded GH4710 alloy have been established using a statistical regression method. The developed model was implemented in the Derform-3D software, and isothermal compression simulations were conducted using the finite element method (FEM). The simulation results of the isothermal compression experiments have verified the accuracy of the model. Subsequently, a simulation of a turbine disk forging was conducted using the model to determine the optimal process parameters by analyzing the results of the simulation. The comparison revealed a strong correlation between the simulated results and the actual microstructure of the turbine disk forged with the optimal process parameters. Therefore, the established DRX model serves as a fundamental reference for understanding the microstructure evolution during the as-extruded GH4710 alloy hot-deformation process.

• Study of ultra-precision polishing of outer surface of tube using a magnetic compound fluid wheel

  Wang Youliang, Jiang Zhe, Zhang Wenjuan, Yin Xincheng, Liang Bo

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240558

  Abstract(31) PDF(3.46 M)(25)

  Abstract:The stainless steel tube are widely used in aviation, medical treatment due to the corrosion resistance properties. In this study, a novel method employing a magnetic compound fluid (MCF) wheel was proposed for polishing the outer surface of stainless steel tube. Firstly, a polishing apparatus was constructed, in addition, the distribution of magnetic field of MCF wheel on the workpiece surface was explored by Maxwell software and Tesla meters, and the relationship between magnetic field distribution and material removal on the workpiece surface was investigated. Then, a material removal (MR) model was established and proved by the experimental results under the given conditions. Finally, The influence laws of carbonyl iron powder particle size d_CIP, abrasive particle size d_AP, magnet speed n_m, workpiece speed n_c and supply of MCF V on surface roughness Ra and reduction rate Ra% were investigated through experiments, and the mechanism of different parameters on surface quality was explored. The results show that the magnetic induction intensity during polishing is positively correlated with the polished profile of the workpiece. The trend of MR simulation is consistent with the experimental value, which prove the MR model is accurate. The smoothest surface of stainless steel tube can be achieved wherein the revolution speed of the magnet and workpiece (n_m = 200 rpm, n_c = 5000 rpm), amount of MCF slurry(V = 2 mL) were given using MCF containing carbonyl iron powder (15 μm) 50 wt. %, abrasive particle (7 μm) 12 wt. %, α-fiber 3 wt. %, magnetic fluid 35 wt. %. The final surface roughness decreased from 0.411μm to 0.007μm after 100 min polishing, the reduction rate is 98.297%, which demonstrated that this novel method is appropriate for polishing outer surface of tube.

• Study on erosion resistance and damage evolution of Ti-doped Ta₂O₅ high transmittance coatings

  Ye Borui, Chao Rui

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240563

  Abstract(33) PDF(1.86 M)(28)

  Abstract:In order to verify the wear resistance and erosion resistance of Ti-doped Ta₂O₅ coating (TTO), a series of TTO coatings were prepared by magnetron sputtering technology by controlling the power of Ti target. The growth structure, microstructure and tribological properties of TTO coatings with Ti target power were studied. After the erosion test, the variation of erosion damage behavior of TTO coatings with mechanical properties under different erosion conditions was further studied. The results show that the TTO coatings eliminates the roughness, voids and defects in the material due to the mobility of the adsorbed atoms during the growth process, and a flat and dense smooth surface is obtained. Tribological tests show that the TTO coatings is mainly characterized by plastic deformation and micro-crack wear mechanism. Higher Ti target power can improve the wear resistance of TTO coatings. The results of the erosion test show that the impact crater, furrow, micro-cutting, brittle spalling and crack formation are the main wear mechanisms of the TTO coatings samples under erosion.

• Investigation on the heterogeneous deformation behavior and strain rate sensitivity of the metastable β-Ti-1023 alloy

  wangxueli, lifuguo, jiapenglai, zhangzhimin, wangqiang

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240576

  Abstract(33) PDF(13.09 M)(44)

  Abstract:The digital image correlation (DIC) technology has been used to track promptly the strain distribution and local strain evolution under different strain rates in this paper, and the propagation behavior of strain distribution and its strain rate sensitivity have been investigated. And the electron backscatter diffraction (EBSD) has been selected to analyze the microstructure evolution, the distribution of stress induced α" martensite transformation (SIMT) and martensite twinning after deformation. Besides, the scanning electron microscope (SEM) has been adopted to observe the fracture morphology of the material. The following conclusions can be drawn: (1) The strain distribution evolved from an approximate uniform distribution to a non-uniform distribution, then showing a phenomenon of strain concentration, and ultimately occurring fracture in the strain concentration area, and the significanted necking phenomenon has been displayed at the low strain rates. (2) A clear double yield phenomenon has been exhibited in the stress-strain curves with producing higher strain hardening rates at the low strain rates, it means that the materials show a negative strain rate sensitivity effect. (3) The content of α" martensite increased significantly, the grain size refined obviously, and the average values of KAM (Kernel average misorientation) and GNDs (Geometrically necessary dislocations) increased dramatically with the strain rate decreasing, it indicates that the SIMT increase can contribute to the accumulation of dislocation density in the deformed sample and be more conducive to the coupling effect of multiple plastic deformation mechanisms. (4) The fracture morphology mainly occur tensile fracture by the aggregation of ductile dimples and voids. The stress on the dimples rapidly develops from unidirectional tension to triaxial tension resulting in sufficient growth of the dimples during the deformation process. Therefore, the ductile fracture characteristics dominated in the low strain rates deformation with promoting the occurrence of this phenomenon.

• Application Research of Nanofibrous LSCF@GDC Composite Cathode in Reversible Solid Oxide Fuel Cells

  Sun Xu, Zhang Bingqi, Zhao Jingqi, Sun Yue, Liu Xin, Zhou Hongyang

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240581

  Abstract(29) PDF(1.74 M)(28)

  Abstract:Reversible solid oxide cells (RSOCs) can theoretically achieve a relatively high energy conversion efficiency. The key to its widespread application is to further enhance the current density so as to increase hydrogen production and output current. However, insufficient catalytic activity of the oxygen electrodes has become an obstacle to the application of reversible solid oxide cells. The paper successfully fabricates composite LSCF@GDC nanofibers with reversible oxygen evolution and reduction electrocatalytic activity by employing electrospinning technology. Compared with the oxygen electrodes materials synthesized by the traditional sol-gel method, the three-dimensional nanofiber structure oxygen electrodes described greatly reduces the battery polarization impedance, increases the discharge power density and electrolytic current density, and shows better reversibility and stability in long-term tests. The research confirms the advantage of electrode morphology engineering control in expanding the catalytic interface and reaction sites.

• Corrosion resistance enhancement of GH3625 alloy tube in high-temperature KCl-MgCl₂ molten salt environment via Microstructure tailoring

  Gao Yubi, Wang Xin, Zhen Bing, Xu Jiayu, Ding Yutian

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240588

  Abstract(23) PDF(9.52 M)(28)

  Abstract:The influence of microstructure with different ratios of twin boundaries on the corrosion behavior of GH3625 alloy pipes in high-temperature (600 ℃~800 ℃) KCl-MgCl₂ molten salt was studied using EBSD, XRD, SEM, and EDS methods. The results showed that with the increase of annealing temperature, the proportion of annealing twin boundaries in the equiaxed grains of GH3625 alloy tube increased, and the higher the proportion of twin boundaries in the alloy at the same corrosion temperature, the better its high-temperature resistance to KCl-MgCl₂ molten salt corrosion. Meanwhile, as the corrosion temperature increases, the high-temperature resistance of the same group of samples to KCl-MgCl₂ molten salt corrosion decreases. In addition, under the same grain size conditions, the higher the proportion of annealing twin boundaries in GH3625 alloy tubes, the better their high-temperature resistance to KCl-MgCl₂ molten salt corrosion. This is mainly attributed to the high-density stable annealing twin boundaries themselves have excellent corrosion resistance, and the triple junction containing twin boundaries breaks the connectivity of the original high angle grain boundary network, suppressing the corrosion of the grain boundaries.

• Anisotropy Control of Titanium Alloy Porous Materials Based on the Modified Gibson-Ashby Model

  Ding Chao, Xie Tenglong, Xu Shenghang, Huang Minghao, Zhang Zhaoyang, Yang Xin, Tang Huiping, Zhao Yang

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240596

  Abstract(28) PDF(1.91 M)(26)

  Abstract:According to the varying load in different directions, the anisotropy control of porous materials can significantly enhance the load-bearing efficiency of materials, thus better addressing the need for lightweight designs. In this paper, a modified G-A model for srtut-based porous materials accounting for the geometric parameters was established by taking G7 and BCCZ types of TC4 porous materials as examples. This model could serve as a guide for the precise control of anisotropy for strut-based porous materials. By adjusting the geometric parameters of common unit cells, a range of anisotropic porous materials with similar configurations but distinct properties were created. The influence of cellular geometric parameters on the anisotropic mechanical properties and failure modes of these materials was investigated through both vertical and lateral compressive tests, which also validated the efficacy of our modified model. The research results indicated that the mechanical properties of strut-based porous materials were primarily determined by the aspect ratio and the inclination angle of their struts. By fine-tuning the inclination angle of these struts, the anisotropic mechanical properties of the porous materials can be effectively modulated. At identical density levels, it could result in a substantial increase in the vertical compressive strength of G7 and BCCZ types of TC4 porous materials by 105% and 45%, respectively, with only a minor reduction in lateral compressive strength of 16% and 13%, by increasing the inclination angle of the diagonal struts from 35° to 55°.

• Study on hot cracking sensitivity of Wrought superalloy GH4975 with high alloying

  ZHU Xing, JIANG He, DONG Jianxin, WAN Zhipeng

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240603

  Abstract(26) PDF(7.66 M)(29)

  Abstract:In order to study the hot cracking sensitivity of high alloying refractory superalloy GH4975, the crack morphology and microstructure characteristics of the ingot of GH4975 were observed, and the causes of hot cracking were analyzed by means of solidification behavior and thermodynamic calculation. The results show that the crack spreads along grain boundaries and dendrites, and the equiaxed crystal region has a greater tendency to crack than the columnar crystal region. Shrinkage holes are easy to appear in the center of the ingot. The formation of continuous shrinkage holes leads to insufficient overlap between dendrites, which is easy to be pulled apart under the action of stress to form a crack source. At the same time, the segregation of Al, Ti and Nb elements between dendrites is serious, and complex precipitates, especially a large number of (γ+γ ") eutectic phases, promote the nucleation and propagation of cracks. JMatPro"s calculation shows that GH4975 alloy has a large shrinkage rate in the solid-liquid two-phase zone and a wide range of non-complementary temperature, which is easy to form a shrinkage hole and become a crack source. Meanwhile, the linear expansion coefficient of the alloy changes greatly in the non-complementary temperature range, and the crack is easy to expand.

• Effect of Temperature on the Interface Microstructure andMechanical Properties of AZ31/Al/Ta Composites Prepared by Vacuum Hot Compression Bonding

  Yu Zhilei, Li Jingli, Han Xiuzhu, Li Bairui, Xue Zhiyong

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240604

  Abstract(23) PDF(1.80 M)(21)

  Abstract:The Mg/Ta composite material exhibits both exceptional resistance to high-energy particle irradiation and lightweight characteristics, enabling it to more effectively address the requirements of future deep-space exploration. However, joining these two dissimilar metals is challenging due to their significant differences in properties. In this work, AZ31/Al/Ta composites were successfully prepared using the vacuum hot compression bonding (VHCB) method. The effect of hot compressing temperature on the interface microstructure evolution, phase constitution, and shear strength at the interface was investigated. Moreover, the interface bonding mechanisms of the AZ31/Al/Ta composites under the VHCB process conditions were explored. The results demonstrated that as the VHCB temperature increased, the phase composition of the interface between Mg and Al changed from the Mg-Al brittle IMCs (Al12Mg17, Al3Mg2) to the Al-Mg solid solution. Meanwhile, the width of the Al/Ta interface diffusion layer increased to 450℃ compared to that at 400℃. The shear strengths were 24 MPa and 46 MPa at 400℃ and 450℃, respectively. The interfacial bonding mechanism of AZ31/Al/Ta composites involves the coexistence of diffusion and mechanical meshing. Avoiding the formation of brittle phases at the interface can significantly improve interfacial bonding strength.

• Study of Electric Parameters to regulate Corrosion Resistance of MAO Coating on TC4

  Wang Sheng, Zhang Yali, Liu Haoming, Liu Yuchang, Wang Haoxu, Ma Ying, Li Yuandong

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240609

  Abstract(28) PDF(1.33 M)(22)

  Abstract:This paper investigates the effects of voltage, pulse frequency, duty cycle and processing time on the corrosion resistance of micro-arc oxidised TC4 titanium alloy coatings using polar analysis of variance (ANOVA), with a subsequent objective of exploring the significance relationship and the optimum combination of the factor levels of the electrical parameters. Concurrently, an investigation was conducted into the mechanisms through which electrical parameters influence the corrosion resistance of the film layer, with a particular focus on its morphology and physical composition. A regression equation is established to facilitate regulation of the corrosion resistance properties of micro-arc oxidized films through manipulation of electrical parameters. The findings indicate that the duty cycle exerts the most significant influence on the electrochemical corrosion resistance of the membrane layer, the next most influential factors are pulse frequency and voltage, processing time was observed to have a comparatively lesser effect. The duty cycle and pulse frequency influence both structure and performance characteristics of the film layer by altering arc ignition discharge duration as well as arc quenching cooling times. An increase in voltage, duty cycle, processing time, or a decrease in pulse frequency can result in an enhanced power output from the power supply, this leads to an increase in film thickness along with larger pore sizes within microporous structures while reducing densification. Additionally, it promotes more efficient generation of Al2TiO5 within the film layer, however, this ultimately results in diminished electrochemical corrosion resistance. The results of the correlation coefficient testing demonstrate a strong relationship between the dependent and independent variables within the established regression equation. This finding provides theoretical support for predicting methods aimed at regulating performance characteristics in titanium alloy micro-arc oxidation films.

• Ammonium tungstate evaporation crystallization purification based on single factor combined with Box-Behnken method

  Xiao Lairong, Li Shaohao, Zhao Xiaojun, Wang Xinyue, Wang Zihao, Cai Zhenyang, Lu ekang, Liu Sainan, Li Qingkui

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240615

  Abstract(23) PDF(1.31 M)(21)

  Abstract:The single factor + Box-Behnken response surface method was used to optimize the impurity removal process of ammonium tungstate solution evaporation crystallization method to prepare higher purity ammonium paratungstate (APT). Firstly, in order to reduce the total content of four impurities (Na, K, S, Mo elements) in APT, the preferred range of crystallization temperature, stirring speed and initial concentration of ammonium tungstate solution was preliminarily determined by single factor method. Secondly, the evaporation crystallization impurity removal process of APT was further optimized by Box-Behnken response surface method, and the mutual influence of three factors on the total amount of four impurities in APT was studied. The results show that the order of influence of three factors on the total amount of four impurities is : initial concentration of ammonium tungstate solution > evaporation temperature > stirring speed ; the optimum process conditions were as follows : evaporation temperature 94 °C, stirring speed 1.25 m/s, initial concentration of ammonium tungstate solution 73 g/L. Under the experimental conditions, the total content of the four impurities in the prepared APT was reduced to 39.351 ppm, and the relative error with the optimal prediction value of the response surface method model was only 4.110 %, and the purity of APT reached 4N. The generated APT crystal is a columnar cuboid morphology with a small amount of broken crystals. The layered structure is obvious, the particle size distribution is uniform, and the grain refinement is obvious.

• New opportunities in refractory niobium alloys via additive manufacturing：A review

  Lan Hang, Lu Kaiju, Tong Yonggang, Wang Jie, Qiao jinjin, Chen Yongxiong, Hu Zhenfeng, Liang Xiubing

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240617

  Abstract(21) PDF(2.96 M)(25)

  Abstract:Due to their low density, good room-temperature plasticity, and excellent high-temperature toughness, refractory niobium alloys have been used in hot-end components in the aerospace field. However, niobium alloys prepared by traditional casting methods are difficult to process parts with complex geometries, and met problems like long processing period, expensive price and high buy-to-fly ratio. The rapid development of additive manufacturing technology in recent years not only reduces the production period and cost, but also obtains superior mechanical properties, which brings new opportunities for the further application of niobium alloys. To this end, this paper reviews the current state-of-art research on additively manufactured niobium alloys, focusing on the laser and electron-beam additive manufacturing of two generations of typical niobium alloys, namely C-103 and Nb521, in particular with regard to the modulation of their mechanical properties and microstructure. In addition, common types of niobium alloys and additive manufacturing methods are briefly introduced. Finally, the future direction of additively manufactured niobium alloys and the problems that still need to be solved are proposed. By reviewing the field of additively manufactured niobium alloys, this paper provides a reference for the further application of niobium alloys in the aerospace field for hot-end components of complex structures.

• Fracture Behavior of High Cycle Fatigue of Nickel-based Single Crystal Superalloys at 850 ℃

  zhangjingang, liuxinling, chenxing, lizhen, liujiabin, tengpeng, liuchangkui

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240631

  Abstract(17) PDF(3.32 M)(20)

  Abstract:Study on the high cycle fatigue fracture characteristics and damage mechanism of nickel based single crystal superalloys at 850 °C. The results indicate that high cycle fatigue cracks in single crystal superalloys generally originate from defect locations on the subsurface or interior of the specimen at 850 °C. Under the condition of stress ratio R=0.05, as the fatigue load decreases, the high cycle fatigue life gradually increases. The high cycle fatigue fracture is mainly characterized by octahedral slip mechanism. At high stress and low life, the fracture exhibits single or multiple slip surface features. Some fractures originate along a vertical small plane and then propagate along the {111} slip surface; At low stress and high lifespan, the fracture surface is prone to alternate and expand along multiple slip planes after originating from subsurface or internal sources, exhibiting characteristics of multiple slip planes. Through electron backscatter diffraction analysis and transmission electron microscopy analysis, it is known that there is oxidation behavior on the surface of the high cycle fatigue fracture, and the fracture section is composed of polycrystalline layer, distortion layer, and matrix layer from the outside to the inside. Among them, the main components of the polycrystalline layer are Ni and Co oxides; The distortion layer is mainly distributed in the form of elongated or short rod-shaped Al, Ta, and W oxides; The substrate layer is a single crystal layer.

• Study on the creep fracture mechanism of a new nickel-based single crystal superalloy

  Xiangfeng Liang, Jili Wu, Xizhou Kai, Yong Dai, Shi Cangkun, Yutao Zhao

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240632

  Abstract(28) PDF(3.06 M)(29)

  Abstract:In this paper, through the creep performance test, microstructure morphology observation and composition analysis of a new type of nickel-based single-crystal superalloy under the condition of 1100°C/140 MPa, the variation characteristics of the creep rate and the evolution characteristics of the microstructure before and after creep during the creep fracture process of the alloy were investigated, and the creep fracture mechanism of the new nickel-based single-crystal superalloy was revealed. The results indicate that the creep life of the alloy is 104.5 h, the strain can reach 33.58%, the creep rate decreases first and then increases, and finally tends to be stable until fracture. At the initial stage of creep, the creep rate shows a phenomenon of decreasing first, then rising and then decreasing again with time. Furthermore, the creep fracture microstructure is composed of dimples and tearing edges, without obvious slip planes. Oxides and recrystallized structures exist inside the fracture surface, and the voids inside the fracture are elongated and perpendicular to the stress axis, showing a fracture mechanism of microcrack accumulation.

• Microstructure and properties of ZrC nanoparticles strengthened WNiFe alloys

  Yang Run, Wang Hui, Liu Rui, Wu Xuebang, Wang Xianping, Fang Qianfeng, Liu Changsong

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240635

  Abstract(19) PDF(4.74 M)(23)

  Abstract:Tungsten (W) is one of the most promising plasma-facing materials in nuclear fusion devices and candidate target materials for spallation neutron source, however its applications are greatly hindered by its room-temperature brittleness and irradiation-induced embrittlement. W heavy alloys with room temperature ductility and low cost were considered as alternative materials. In this work, 93W-4.9Ni-2.1Fe alloys strengthened by nanoscale ZrC particles were fabricated by spark-plasma-sintering (SPS) and hot rotary swaging, respectively. The addition of a small amount of ZrC nanoparticles can refine grain size and increase the hardness of the WNiFe alloys, but hinder the formation of the γ-(Ni, Fe) phase during SPS. The SPS WNiFe and WNiFe-ZrC alloys are brittle at room temperature, while the swaged WNiFe and WNiFe-0.5 wt% ZrC alloys are ductile at room temperature. At 400 °C, the swaged WNiFe-0.5 wt% ZrC alloy exhibits both higher tensile strength and better ductility than the swaged WNiFe. The nanoscale particles distributed in the W grains and γ-(Ni,Fe) phase provided a good pinning effect and enhanced the strength. The thermal conductivity of swaged WNiFe-0.5 wt%ZrC is 71 Wm-1K-1 at room temperature, but it increases to about 100 Wm-1K-1 at 800 °C, which is close to that of pure W (121 Wm-1K-1). These results show the potential of WNiFe alloys as candidate materials for fusion applications.

• Research on BJ3DP and sintering densification of AlTiCrNiCu low-density high entropy alloy prepared by mechanical alloying

  Zhu Dezhi, Chen Haipeng, Cai Liangfu

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240636

  Abstract(22) PDF(2.11 M)(23)

  Abstract:The binder jetting 3D printing (BJ3DP) process is currently a research hotspot. Generally, the powder bed printing process requires spherical powders, which limits the preparation and printing of some HEA powders with large melting point differences. This study mainly focuses on the BJ3DP printing-sintering behavior of non-spherical particles. The results showed that the near-spherical AlTiCrNiCu low-density HEA powder with BCC structure was prepared by mechanical alloying, with a particle size ranged from 6.72 to 67.52 μm and an average particle size of 21.17 μm, which met the requirements of the BJ3DP printing process. The results of the orthogonal experiment indicate that when the binder saturation is 60%, the layer thickness is 120 μm, and the powder feeding speed is 15 pps, the green density of BJ3DP printing is the highest (about 44.7%). After sintering at 1190℃ for 4 hours, the density of the green body reaches 91.6%. The AlTiCrNiCu low-density HEA has a multiphase structure, with the B2 phase as the matrix, including BCC, FCC, and a small amount of L2₁ phase. The AlTiCrNiCu low-density HEA has high compressive properties, with a yield strength and compressive strength of approximately 840 MPa and 960 MPa, respectively. The research results provide ideas and reference for the BJ3DP printing and sintering of non-spherical metal powders, further expanding the application scope of metal powder BJ3DP printing and forming.

• Non-uniform Microstructure and High Temperature Coordinated Deformation Behavior of 2A97 / 5A06 Dissimilar Aluminum Alloy Friction Stir Butt Welded Plate

  Qin Zhonghuan, Wu Aiping, Yin Hongliang, Li Baoyong, Liu Qi, Wu Yong

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240637

  Abstract(21) PDF(2.83 M)(22)

  Abstract:In this paper, the non-uniform microstructure and high temperature coordinated deformation behavior of 2A97 / 5A06 dissimilar aluminum alloy friction stir welded plate were studied. The microstructure of each area of the welded joint was observed, and the high temperature mechanical properties of each area and the whole joint was studied. It was found that the grains in the weld nugget zone of 2A97 and 5A06 were fine. The grain size of each region on the 2A97 side was small and basically close, and the grain size of each region on the 5A06 side was slightly larger and the difference was obvious. Under the process parameter of 430 °C and 10_-3 s_-1^{, the} high temperature properties of 2A97 and 5A06 base metals are better, and the elongations are 278.8 % and 118.6 %, respectively. The strength and elongation of the nugget zone of the joint are 18.4 MPa and 176.1 %, respectively, which are between 2A97 and 5A06. The strength is about 2 times that of the 2A97 base metal, and the elongation is about 1.5 times that of the 5A06 base metal. The overall performance shows an obvious superposition principle. The deformation resistance of each region is different. The vertical weld specimen fractured after concentrated deformation in the 2A97 thermo-mechanically affected zone. After correction, the flow stress was slightly higher than that of the base metal and the elongation was close to that of the base metal. The grain size and flow stress of each region after welding meet the creep equation. The smaller the grain size, the lower the flow stress.

• An effective mechanical constitutive model for the fission gas bubbles in irradiated U-10Mo fuels

  Li yong, Yan feng, Zhang jing, Zang li ye, Ding shu rong

  Available online:April 10, 2025  DOI: 10.12442/j.issn.1002-185X.20240640

  Abstract(22) PDF(1.28 M)(29)

  Abstract:The bubble pressure of the fission gas bubbles (FGBs) in irradiated nuclear fuels causes mechanical interaction between the FGBs and the surrounding fuel skeleton. To calculate the micromechanical stress fields of the irradiated nuclear fuels with pressured FGBs, an effective mechanical constitutive model for the FGBs is deduced and verified based on the modified Van der Waals equation and the effect of the surface tension. Based on the established model, the micromechanical fields of irradiated U-10Mo fuels with randomly distributed FGBs during the uniaxial tensile test are calculated by finite element (FE) method. The macroscopic elastic constants of the irradiated U-10Mo fuels are obtained according to the homogenization theory, and the effects of bubble pressure, bubble size, and porosity on the macroscopic elastic constants are investigated. The conclusions can be drawn that: (1) The bubble pressure of the FGBs is balanced by the constraint stress of the surface tension and the surrounding fuel skeleton. The constraint stress of the surrounding fuel skeleton is determined by its deformation states, not equal to the hydrostatic pressure of the surrounding fuel skeleton or that of the macroscopic material points of fuel elements; (2) Adjacent FGBs exist stress interference and are prone to result in stress concentration in the surrounding fuel skeleton; (3) The macroscopic elastic constants of irradiated U-10Mo fuels decrease with macroscopic porosity according with the Mori-Tanaka model, while bubble pressure and size have insignificant effects on the macroscopic elastic constants of irradiated U-10Mo fuels.

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