2026,Volume 55, Issue 3

>2026 Special Environment Welding

• Microstructure and Properties of 2205 Duplex Stainless Steel Welded by Local Dry Underwater Laser with Adjustable Ring-Mode

  Zhang Qinghua, Liu Yibo, Zhao Yongqing, Sun Qi, Guo Jiawei, Hou Shaojun, Sun Qingjie

  2026,55(3):665-673 DOI: 10.12442/j.issn.1002-185X.20250081

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  Abstract:To address the issues of rapid cooling rate during the solidification in underwater welding and the deterioration of the microstructure and properties, this work conducted local dry underwater welding experiments on 2205 duplex stainless steel using adjustable ring-mode laser. Meanwhile, compared with in-air welds, the effects of the power ratio between center and ring lasers on weld formation, microstructure and mechanical properties were investigated. The results show that the center laser mainly affects the penetration depth. With the increase in proportion of central power, the oxidation degree and surface roughness of the weld become more severe. In terms of microstructure, the underwater weld exhibits an increase in Widmanst?tten austenite content, but a decrease in or even disappearance of intragranular austenite, compared to welds produced with the same parameters in air. With the increase in proportion of ring laser, the austenite content in the weld shows no significant change, the grain size and aspect ratio of the weld decrease, the directionality of columnar crystal growth on both sides of the weld weakens, and the number of low-angle grain boundary increases. In terms of performance, the underwater joints exhibit slightly higher tensile strength but lower elongation than those welds in air. As the proportion of ring laser power increases from 1/3 to 2/3, the elongation of underwater joints increases by about 50%.

• Control Mechanism of Droplet Transfer in Underwater Wet Pulsed Current Welding

  Du Yongpeng, Chen Xiaoqiang, You Jiayu, Guo Ning, Fu Yunlong

  2026,55(3):674-684 DOI: 10.12442/j.issn.1002-185X.20250134

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  Abstract:The formation mechanism of repulsive transition in underwater wet welding was firstly analyzed. Affected by the aqueous environment, molten droplets during underwater welding are subjected to combined effect of multiple forces. The gas pressure, gas drag force, and plasma flow force acting on the droplet fluctuate dynamically with the generation location of arc bubbles and the position of cathode spots. These forces together serve as the main driving forces for the repulsive transition of the droplet. The surface tension impedes lateral detachment of the droplet from the wire tip, while gravity facilitates droplet separation from the wire tip to complete the transition. The influence of pulse frequency, duty cycle, and peak current on weld formation, droplet transfer, and welding stability in underwater wet welding was investigated using the orthogonal experimental method. The weld reinforcement variation coefficient was adopted to evaluate formation quality. The results indicate that optimal welding performance is obtained at a duty cycle from 15% to 20%, a peak current of 350 A, and a pulse frequency of approximately 20 Hz. By applying pulsed current during the peak current phase, the electromagnetic contraction force acting on the droplet is significantly enhanced, promoting droplet transfer and increasing the transition frequency.

• Effect of Thermal Cycling on Microstructure and Properties of TC4 Titanium Alloy Narrow-Gap Welded Joints

  Sun Qi, Sun Qingjie, Huang Wenhua, Hou Shaojun, Liu Yibo

  2026,55(3):685-692 DOI: 10.12442/j.issn.1002-185X.20250124

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  Abstract:Thermal cycling has a significant impact on the microstructure and properties of narrow-gap welded joints in titanium alloy thick plates. In this study, a 60 mm-thick TC4 titanium alloy welded joint was fabricated using oscillating-wire magnetic-controlled arc narrow-gap welding technique. The evolution of the microstructure (α phase, β phase, and grain boundary α_GB), as well as changes in microhardness and its tensile properties under typical thermal cycling conditions were investigated through numerical simulation. The results show that high-temperature thermal cycling induces a complete α→β transformation, promoting the preferential growth of the α phase and forming coarse and uniformly-oriented α colonies. In contrast, subsequent low-temperature thermal cycling causes an incomplete α→β transformation, where lower cooling rate and temperature gradient weaken the preferential orientation, leading to the refinement of lamellar α phase. After the entire thermal cycling process, the thickness of lamellar α phase increases from 0.910.09 μm to 1.020.18 μm, and the proportion of residual β phase increases from 0.02% to 1.89%. The weld root layer exhibits the highest microhardness, attributed to grain refinement strengthening. The root layer also demonstrates the highest tensile strength, while the cap layer shows the highest elongation. The joints exhibit ductile fracture behavior overall.

• Forming, Microstructure and Properties of 10CrNi3MoV High-Strength Steel by Underwater Laser Melting Deposition

  Zhang Zhiqiang, Wang Jiaji, Hu Fengya, Guo Ning, Wu Di, Cheng Qi, Fu Yunlong

  2026,55(3):693-701 DOI: 10.12442/j.issn.1002-185X.20250079

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  Abstract:China has independently developed 10CrNi3MoV high-strength steel, which has become a crucial structural material for manufacturing submarine pressure hulls due to its high strength, excellent toughness, superior explosion resistance, and outstanding corrosion resistance. In this study, the response surface method was used to investigate the effects of laser power, scanning speed, and wire feeding speed on the dilution rate and deposition angle of the underwater single-pass deposition layer. Then the optimized underwater single-pass deposition process parameters were obtained. Based on this, the influence of the water environment on the formation, microstructure, and microhardness of the single-pass deposition layer was investigated. Compared with that in air, the faster cooling rate in the underwater laser melting deposition process leads to a larger deposition angle and a slower dilution rate in the underwater deposition layer. Additionally, the microstructure of the underwater deposition layer is finer, which results in a higher microhardness.

• Influence of Water Environment on Microstructure and Droplet Transfer Behavior of Magnetically Controlled Plasma-FCAW Underwater Hybrid Welding

  Zhang Hongtao, Yang Fan, Yu Jia, Li Lianbo, Sun Yu

  2026,55(3):702-712 DOI: 10.12442/j.issn.1002-185X.20250096

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  Abstract:Magnetically controlled plasma-flux cored arc welding (Plasma-FCAW), as an efficient hybrid arc welding method, is characterized by excellent deep penetration and low spatter. However, the welding process is susceptible to disturbances due to the complex underwater environment. To address this issue, a self-developed electromagnetic excitation device was used in this study to apply a transverse magnetic field to the underwater hybrid Plasma-FCAW process. This magnetic control facilitated flexible coupling between the two arcs, thereby effectively improving the stability of the hybrid welding process and the weld bead formation. On this basis, welding process experiments were carried out in water environment with different salinities and temperatures. The influence of the water condition on droplet transfer behavior, weld formation, as well as microstructure and properties was studied. The results show that increased salinity shortens the droplet transfer cycle, raises the cooling rate, and reduces the weld width. Water temperature significantly affects arc stability and droplet transfer behavior: the droplet transfer cycle shortens at low temperature, while it becomes irregular at high temperature. Both increased salinity and decreased water temperature increase the content of side-plate ferrite and acicular ferrite in the weld zone. In contrast, higher water temperature increases the pearlite content in the heat-affected zone, thereby affecting the hardness of weld.

• Research Progress of Underwater Welding Technology

  Guo Ning, Ye Yifu, Wang Ziyang, Zhang Hongguang, Zhang Xin, Fu Yunlong

  2026,55(3):788-797 DOI: 10.12442/j.issn.1002-185X.20250149

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  Abstract:With the rapid development of marine engineering, the research and application of underwater welding technology has become the key to marine engineering construction. In this review, the classification and characteristics of underwater welding were briefly described. The influence of underwater environment, welding materials, and welding process on the quality of underwater wet welding was analyzed. The application of in-situ observation method and external auxiliary means in the field of underwater wet welding was introduced. The research results of underwater local dry-laser welding with powder feeding/wire feeding were summarized. The research progress of underwater dry method under different water depths was introduced. The research results in the field of underwater friction-stir welding were analyzed.

>Special Issue：High Temperature Alloy

• Evaluation of Low-Damping Properties Induced by Plastic Deformation and Heat Treatment in Co-Ni-Cr-Mo-Based Alloy

  Wang Hao, Tong Haotian, Fujieda Tadashi, Chiba Takemi, Chiba Akihiko

  2026,55(3):573-580 DOI: 10.12442/j.issn.1002-185X.20250058

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  Abstract:The strength and damping properties of Co-Ni-Cr-Mo-based alloys with 0.5wt% Nb addition after various plastic deformation and heat treatment processes were investigated. Through Vickers hardness tests, free resonance Young's modulus measurements, and microstructure analysis, the effects of dislocation density, vacancy formation, and recrystallization on the alloy performance were clarified. Results indicate that increasing the rolling reduction enhances damping property due to higher dislocation density, whereas aging below the recrystallization temperature reduces damping property via dislocation pinning by the Suzuki effect. Recrystallization heat treatment restores the original structure and damping level. This alloy possesses tensile strength of approximately 1500 MPa and logarithmic decrement value δ^-1 in the range of 2×10^-4–3×10^-4, demonstrating superior mechanical properties compared with the Ti-based alloys, which makes it an excellent candidate material for ultrasonic tools and medical applications.

• Phase Transformation on Chemically Corroded Surface of a Single-Crystal Superalloy During In-Situ Tension at Elevated Temperatures

  Wang Rui, Li Jiarong, Yue Xiaodai, Zhao Jinqian, Yang Wanpeng

  2026,55(3):595-601 DOI: 10.12442/j.issn.1002-185X.20250094

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  Abstract:In-situ tensile tests were conducted on a chemically corroded third-generation single-crystal superalloy DD9 at 980 and 1100 ℃. The phase transformation in the surface areas during the tensile process was analyzed using field emission scanning electron microscope, energy dispersive X-ray spectroscope, electron probe X-ray microanalysis, and transmission electron microscope. The phase transformation mechanism on the surface and the influence mechanism were studied through observation and dynamic calculation. During tensile tests at elevated temperatures, chemical corrosion promotes the precipitation of topologically close-packed (tcp) μ phase and σ phase on the alloy surface. Both the precipitation amount and size of these two phases on the surface at 1100 ℃ are greater than those at 980 ℃. The precipitation of tcp phase on the alloy surface results in the formation of an influence layer on the surface area, and the distribution characteristics of alloying elements are significantly different from those of the substrate. The depth of the influence layer at 1100 ℃ is greater than that at 980 ℃. The precipitation of tcp phase prompts the phase transition from γ phase to γ′ phase around the tcp phase.

• Solidification Microstructure and Room-Temperature Mechanical Properties of K4750 Superalloy Prepared by Gravity Casting and Centrifugal Casting

  Yang Yiyan, Yang Guangyu, Zhang Zhaozhong, Wu Hao, Zhang Jun, Jie Wanqi

  2026,55(3):730-739 DOI: 10.12442/j.issn.1002-185X.20240648

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  Abstract:The solidification microstructure and room-temperature mechanical properties of K4750 superalloys prepared by gravity casting and centrifugal casting were investigated. Their second phase distribution, grain size, element segregation, distribution of shrinkage defects, room-temperature mechanical properties and fracture morphology were analyzed comparatively. Results show that the as-cast K4750 superalloys prepared by both casting processes consist of γ matrix phase, intragranular MC-type carbide, fine and dispersed intragranular γ' phase, as well as MC-type and M₂₃C₆-type carbides at grain boundary. However, the precipitate size is found to be more refined in the centrifugal casting process. The average grain size of as-cast K4750 superalloy decreases from 4.52 mm (gravity casting) to 2.22 mm (centrifugal casting). Furthermore, the area fraction of shrinkage defects is reduced from 1.75% (gravity casting) to 0.27% (centrifugal casting). The K4750 superalloy prepared by gravity casting exhibits well-aligned dendritic structures, whereas centrifugal-cast superalloy shows fragmented dendrites and a reduced degree of elemental segregation. The K4750 superalloy samples prepared by centrifugal casting exhibit excellent room-temperature mechanical properties, with yield strength, ultimate tensile strength and elongation of 632 MPa, 938 MPa and 11.2%, respectively. Compared to the gravity-casting counterpart, its ultimate tensile strength is increased by 20.6%, which can be attributed to the combined effects of grain refinement, γ' phase refinement and a reduction in casting defects.

• Quantitative Analysis of Low Cycle Fatigue Fracture Stress in Nickel-Based Single Crystal Superalloys Based on Crack Tip Plastic Zone

  Liu Xinling, Deng Zhiwei, Tian Fuzheng, Wang Xueyun, Li Zhen

  2026,55(3):748-755 DOI: 10.12442/j.issn.1002-185X.20240731

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  Abstract:Low cycle fatigue failure is the main failure mode of tenon part of single crystal turbine blades. Due to the difference between the actual working load and the design load, the stress leading to fatigue failure often needs to be given after fatigue failure, and the fracture is a comprehensive reflection of load and temperature. Quantitative analysis of the fracture and inverse fatigue stress have important engineering application value in blade failure analysis. The unique microstructure and crystal structure of single superalloy make its fatigue fracture characteristics different from those of polycrystalline materials. The main fatigue fracture characteristics of single crystal superalloy are slip plane rather than fatigue band. A model and method for quantitative analysis of crack tip plastic zone were presented in this paper. There is a certain angle between fatigue fracture and load of single superalloy, which is a composite cracking mode rather than a type Ⅰ cracking mode. According to the cracking characteristics of single superalloy, using the test data of DD6 single-crystal high-temperature alloy under the condition of 530 ℃ and strain ratio r=0.05, the hysteresis loop of its different life intervals was analyzed. The results show that the life span is between one thousand and ten thousand times, and its hysteresis loop is very narrow; the life span is greater than ten thousand times, and its hysteresis loop is basically a straight line. in addition, DD6 single-crystal high-temperature alloy under the conditions of 530 ℃ and strain ratio r=0.05 has the small yielding characteristics. Based on this, for the low-cycle fatigue fracture, the characteristics of crack initiation and extension stage and its fracture characteristics were studied, and a quantitative analysis model of fatigue stress fracture was established by considering the composite cracking and based on r_p in the plastic zone at the crack tip. The quantitative analysis of fatigue stress fractures at different locations was carried out using a total of 12 crack locations for 3 specimens. The analysis results show that the error of fatigue initiation stress is within 1.3 times, and that of inverse extrapolation result of the first stage of extension is within 1.5 times of the dispersion band. The results provide models and methods for quantitative fracture analysis of stresses in single-crystal superalloys mainly by slip-surface cracking (non-fatigue strips).

• Optimization Basis and Control of the Vacuum Induction Melting Process for Monel K-500 Alloy

  Sun Panhe, Li Shu, Jiang He, Dong Jianxin

  2026,55(3):756-763 DOI: 10.12442/j.issn.1002-185X.20240733

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  Abstract:During the vacuum induction melting (VIM) casting process of Monel K-500 alloy, a large number of shrinkage defects are likely to occur in the upper part of the ingot, resulting in low yield and poor quality. To address this issue, this study investigates the thermal and physical properties and solidification process of Monel K-500 alloy through thermodynamic calculations using Jmat-Pro. The experimental results show that the solidification range of Monel K-500 alloy is between 1250 and 1350 °C. The solidification path is: L→L+γ→L+γ+MC→γ+MC+M₇C₃→γ′+γ+MC+M₇C₃. During the solidification process, as the mass fraction of the residual liquid phase decreases, Ni exhibits negative segregation, while Cu exhibits positive segregation. Combining the thermodynamic calculation results with a finite element model (FEM), a simulation of the industrial VIM casting process for Monel K-500 alloy of 6 t was conducted. The simulated results were compared with the actual shape and size of the shrinkage defects in the upper part of the induction ingot to verify the reliability of the casting model. In addition, this study explores the effects of different pouring parameters on shrinkage defects in VIM ingot based on the model. The results show that the addition of a riser has the most significant improvement on the shrinkage defects in VIM ingot. As the riser volume ratio increases, the volume of shrinkage defects in the ingot decreases significantly, with no shrinkage defects present in the ingot at a riser volume ratio of 20%. When the pouring speed is in the range of 2.5–17.5 kg/s, the volume of shrinkage defects in the VIM ingot decreases as the pouring speed decreases. However, when the poring speed is below 7.5 kg/s, the shrinkage defects move inward within the ingot.

• Effect of Sandblasting on Recrystallization Defects of Directional Solidification 4777DS Superalloys and Its Mechanism

  Zhang Qiongyuan, Zhang Ziyue, Yang Atao, Yao Zhihao, He Qungong, Wang Haiyang, Dong Jianxin

  2026,55(3):764-771 DOI: 10.12442/j.issn.1002-185X.20240757

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  Abstract:The effects of different sand blasting processes on recrystallization defects and the occurrence of recrystallization in 4777DS alloy were studied using optical microscope and scanning electron microscope. The analysis of the recrystallization structure on the alloy surface after sandblasting shows that the depth of recrystallization on the alloy surface increases with the increase in sandblasting intensity, time, and gravel diameter, and the decrease in sandblasting distance. After sandblasting, the deformed sample shows that the γ′ phase near the sandblasted surface changes from a butterfly shape to a long strip shape, and some of the deformed γ′ phase surrounds the areas with greater deformation. At the same time, a large number of dislocations distributed in the γ matrix channels and γ′ phase are observed by TEM. The different γ′ phases between dendrites affect the growth of recrystallization, resulting in the formation of wavy grain boundaries. No inhibitory effect of eutectic or carbide on recrystallization has been found. Due to the small size of surface recrystallized grains and the presence of residual stress, a new layer of recrystallized grains will form in the subsurface.

>Materials Science

• In-Flight Heating Process of Cerium Oxide Powders in Radio Frequency Thermal Plasma Considering Thermal Resistance Effect

  Su Yi, Liu Ruizhe, Hilal Ahmad, Zhao Peng, Jin Xingyue, Zhu Hailong

  2026,55(3):581-594 DOI: 10.12442/j.issn.1002-185X.20250101

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  Abstract:The in-flight heating process of cerium dioxide (CeO₂) powders was investigated through experiments and numerical simulations. In the experiment, CeO₂ powder (average size of 30 μm) was injected into radio-frequency (RF) argon plasma, and the temperatures were measured using a DPV-2000 monitor. A model combining the electromagnetism, thermal flow, and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed. The melting processes of CeO₂ powders of different diameters, with and without thermal resistance effect, were investigated. Results show that the heating process of CeO₂ powder particles consists of three main stages, one of which is relevant to a dimensionless parameter known as the Biot number. When the Biot value≥0.1, thermal resistance increases significantly, especially for the larger powders. The predicted temperature of the particles at the outlet (1800–2880 K) is in good agreement with the experimental result.

• Effects of Element Y on Grain Refinement and Mechanical Properties of Cast Al-2.2Li-1.5Cu-Based Alloy

  Wang Xu, Dang Qian, Ma Hongyao, Liu Guohuai, Zhang Chi, Wang Zhaodong

  2026,55(3):602-614 DOI: 10.12442/j.issn.1002-185X.20250152

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  Abstract:The effect of trace addition of 0.1wt% Y on the grain refinement and mechanical properties of Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys at as-cast and heat-treated states was investigated. Results show that the addition of 0.1wt% Y into the Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys can elevate the nucleation temperature of the Al₃(Sc, Zr) phase, leading to the preferential precipitation of the Al₃(Sc, Zr) phase and increasing the amount of Al₃(Sc, Zr) phase in the matrix. Al₃(Sc, Zr) phase can also act as a heterogeneous nucleation site in the α-Al matrix to promote nucleation and refine grains. The addition of element Y changes the precipitation phase characteristics at the grain boundaries in the as-cast alloy, which changes the distribution characteristics of secondary phases from initially continuous and coarse strip-like distribution at grain boundaries into the discontinuous dot-like and rod-like distribution. Besides, the size of secondary phases becomes smaller and their amount increases. Under the combined effects of grain refinement strengthening and precipitation strengthening, the Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc-0.1Y alloy after 175 °C/10 h aging treatment achieves an ultimate tensile strength of 412 MPa and an elongation of 6.3%. Compared with those of the alloy without Y addition, the ultimate tensile strength and elongation of the added alloy increase by 16.1% and 53.7%, respectively.

• Thermodynamics of Reduction of Titania by CH₄-H₂ Gas Mixture

  Tian Zhenyun, Chen Jiawen, Zhang Run, Fan Gangqiang, Qiu Guibao

  2026,55(3):615-626 DOI: 10.12442/j.issn.1002-185X.20250147

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  Abstract:Given the considerable global interest in the preparation of Ti and TiC, a novel reduction method for TiO₂ in a CH₄-H₂ atmosphere was proposed, and the reduction thermodynamic behavior, phase equilibrium, and energy consumption of TiO₂ during its reaction with a CH₄-H₂ gas mixture were investigated. The results indicate that the reaction proceeds via a stepwise reduction pathway from TiO₂ to Ti(C, O), with the Magnéli phase (Ti_nO_2n-1) and Ti₃O₅ serving as intermediate phases. Notably, the reduction of TiO₂ by H₂ is more challenging than that by CH₄, which may be attributed to the inhibitory effect of H₂ on the surface carbon precipitation. For the complete carbonization of 1 mol TiO₂, the total energy required at 1000, 1100, and 1200 ℃ is 1159, 925, and 977 kJ/mol, respectively, which may be related to the shift of gas-phase equilibrium and the increase in side reactions at high temperatures.

• Hot Compression Deformation Behavior and Processing Maps of Mg-Zn-Mn(-Sn)-Ca Alloy

  Chen Xia, Zhu Yulong, Liu Quanyi, Zhang Dingfei, Pan Fusheng

  2026,55(3):627-635 DOI: 10.12442/j.issn.1002-185X.20250156

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  Abstract:The hot compression deformation behavior of Mg-6Zn-1Mn-0.5Ca (ZM61-0.5Ca) and Mg-6Zn-1Mn-2Sn-0.5Ca (ZMT612-0.5Ca) alloys was investigated at deformation temperatures ranging from 250 ℃ to 400 ℃ and strain rates varying from 0.001 s^–1 to 1 s^–1. The results show that the addition of Sn promotes dynamic recrystallization (DRX), and CaMgSn phases can act as nucleation sites during the compression deformation. Flow stress increases with increasing the strain rate and decreasing the temperature. Both the ZM61-0.5Ca and ZMT612-0.5Ca alloys exhibit obvious DRX characteristics. CaMgSn phases can effectively inhibit dislocation motion with the addition of Sn, thus increasing the peak ?ow stress of the alloy. The addition of Sn increases the hot deformation activation energy of the ZM61-0.5Ca alloy from 199.654 kJ/mol to 276.649 kJ/mol, thus improving the thermal stability of the alloy. For the ZMT612-0.5Ca alloy, the optimal hot deformation parameters are determined to be a deformation temperature range of 350–400 ℃ and a strain rate range of 0.001–0.01 s^–1.

• Process Optimization and Mechanical Properties of AlMgScZr Alloy Fabricated by Laser Powder Bed Fusion Using Coarse Powder

  Li Ning, Jia Yuting, Xu Dingneng, Fan Haiyang, Yang Shoufeng

  2026,55(3):713-721 DOI: 10.12442/j.issn.1002-185X.20250015

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  Abstract:With the advancement of laser powder bed fusion (LPBF) additive manufacturing, efficient utilization of powders outside the conventional particle size range (15–53 μm) has become critical to improving powder efficiency. This study investigated process optimization, microstructure, and mechanical properties of coarse AlMgScZr alloy powders (53–150 μm) in LPBF. The controlled variable method was employed to analyze parameter effects on density, defects, microstructure, and mechanical properties. Results show that the coarse powder exhibits a narrow process window with high sensitivity of forming stability to parameter fluctuations. The optimized parameters are a layer thickness of 100 μm, a laser power of 450 W, and a scanning speed of 900 mm/s. This parameter set achieves a relative density of 99.3%±0.2%. Microstructural analysis reveals fine equiaxed grains near fusion boundaries transitioning to columnar grains within molten pools, without observable secondary precipitates. The as-printed samples show a microhardness of 99.7±8.9 HV_0.1, tensile strength of 336.5±8.0 MPa, and elongation of 12.7%±0.4%.

• Purification of Ammonium Tungstate via Evaporation Crystallization Based on Single Factor Combined with Box-Behnken Method

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

  2026,55(3):722-729 DOI: 10.12442/j.issn.1002-185X.20240615

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  Abstract:A combination of single factor and Box-Behnken response surface method was employed to optimize the impurity removal process during the evaporation crystallization of ammonium tungstate solution to prepare ammonium paratungstate (APT) with higher purity. Firstly, to reduce the total content of four impurities (Na, K, S and Mo) 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 impurity removal process during the evaporation crystallization of APT was further optimized by Box-Behnken response surface method, and the interactive effects 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 content of four impurities is as follows: initial concentration of ammonium tungstate solution>evaporation temperature>stirring speed. The optimum process conditions are an evaporation temperature of 94 ℃, a stirring speed of 1.25 m/s, and an initial ammonium tungstate concentration of 73 g/L. Under the experimental conditions, the total content of four impurities in the prepared APT is reduced to 39.351 mg/L, which corresponds to a relative error of merely 4.110% compared to the optimal prediction value of the response surface method model. Consequently, the purity of APT reaches 4N level. 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.

• Study on Microstructure and Properties of WC-Co and WC-Ni-Fe Cemented Carbides with Different Binder Phase Contents

  Zhang Fan, Yuan Delin, Ye Yuwei, Chen Hao

  2026,55(3):740-747 DOI: 10.12442/j.issn.1002-185X.20240712

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  Abstract:Two groups of WC-Co and WC-Ni-Fe cemented carbides with varying binder phase contents were prepared using the same process. The research explored the trends in the microstructure changes and the differences in properties between WC-Co and WC-Ni-Fe cemented carbides. The results show that the binder phase of both WC-Co and WC-Ni-Fe cemented carbides exhibits a single-phase structure. As the binder phase content in the alloy increases, there is an increase in average grain size and a decrease in hardness and coercive magnetic force. Additionally, cobalt magnetism, bending strength, and impact toughness all exhibit upward trends. In comparison, the WC-Co cemented carbide exhibits higher coercive cobalt magnetism, magnetic force, and bending strength than WC-Ni-Fe cemented carbide. However, WC-Ni-Fe cemented carbide exhibits better impact toughness with a higher binder phase content, reaching up to 5.9 J/cm². The frictional behavior of WC-Co and WC-Ni-Fe cemented carbides is similar, but the wear degree of the alloys gradually increases as the binder phase content increases. When the contents of binder phase content are the same, the wear resistance of WC-Co cemented carbide is superior to that of WC-Ni-Fe cemented carbide.

• Study on the Plasma Rotating Electrode Atomization Technique for Core-Shell Powder Synthesis

  Ba Yunwei, Yang Xingbo, Sun Nianguang, Xiang Changshu, Wang Hui, Yang Xinwen

  2026,55(3):772-778 DOI: 10.12442/j.issn.1002-185X.20250249

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  Abstract:By modifying the existing plasma rotating electrode atomization (PREP) powder production equipment, the core-shell structure powders with low nitrogen content in the core and high nitrogen content on the surface were successfully prepared by adjusting the nitrogen flow rate during the powder-making process with pure titanium rods. The particle size distribution, microscopic morphology, and microstructure of the powders were systematically characterized using a standard vibrating sieve, laser particle size analyzer, X-ray diffractometer (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscope (XPS). The results show that the particle size of the powders with nitrogen gas were smaller than that without nitrogen gas. As the nitrogen flow rate increases from 3 L/min to 8 L/min, the particle size exhibits a trend of first decreasing and then increasing. Introducing nitrogen gas can significantly suppress the formation of satellite powders in pure titanium metal powders and make the surface of the powders smooth, but it can also result in elongated and insufficiently spheroidized shaped powder particles in the powder. Under different nitrogen gas flow rates, nitrogen is uniformly distributed on the powder surface, forming a Ti-N_x microstructures shell layer, and the nitrogen content on the powder surface layer is significantly higher than that in the core.

• Effect of Charging Temperature on Hydrogen Damage Behavior of TA15 Alloy

  Wu Chaomei, Wang Tiantai, Liu Jiaxing, Zhao Mingjiu

  2026,55(3):779-787 DOI: 10.12442/j.issn.1002-185X.20240748

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  Abstract:In this research, the effect of charging temperature on the hydrogen damage behavior of TA15 alloy was studied. The results show that the strength of the alloy increases first and then decreases with the increase in charging temperature under the condition of 800–900 K, 10 MPa, and hydrogen charging for 1 h, but the elongation decreases continuously. When the charging temperature is 800 K, the tensile strength of the alloy increases by 9% compared with the as-received samples, while the elongation decreases by 12%. When the charging temperature is 900 K, the tensile strength of the alloy decreases by 85%, and the alloy is completely brittle fracture (the embrittlement index reaches 100%). The microanalysis demonstrates that as the hydrogen charging temperature increases from 800 K to 900 K, the hydrides in the alloy undergo a transformation, shifting from precipitating predominantly along the α/β phase boundary to precipitating within the α and β phases. The sizes and quantities of these hydrides increase significantly, resulting in a change in the way of the hydrogen cracking of the alloy. Rather than occurring along the α/β phase boundary, as previously observed, the cracking now propagates along the hydrides within the α and β phases or along the hydride/matrix interfaces.

>Reviews

• Research Progress on High Thermal Conductivity Graphene/Copper-Based Composite Heat Sinks for Electronic Equipment

  Li Hongzhao, Jiang Haojie, Pan Jiabao, Jia Hongsheng, Chen Minghe, Chen Yang

  2026,55(3):636-654 DOI: 10.12442/j.issn.1002-185X.20250140

  Abstract(1) HTML(1) PDF(2.89 M)( 2)

  Abstract:Graphene/copper-based composite heat sinks demonstrate extensive application potential in military equipment thermal management, high-power electronic packaging, new energy vehicles, and 5G communication systems, due to their outstanding properties, including high thermal conductivity, tunable thermal expansion coefficients, excellent mechanical strength, and low density. However, the industrial-scale application of these composites faces critical challenges during the fabrication of components with complex structures, such as inhomogeneous dispersion of graphene within the copper matrix and poor interfacial bonding between the two phases, which substantially undermine the overall performance of graphene/copper-based composites. To address these issues, the preparation methods for graphene/copper-based composite heat sinks were reviewed. For each method, a rigorous analysis was presented to clarify its inherent advantages and unavoidable restrictions. Furthermore, the latest research progress in addressing three core scientific challenges was synthesized, including uniform dispersion of graphene, interfacial optimization mechanisms, and molecular dynamics simulations for elucidating the structure-property relationships. Finally, the future development directions of graphene/copper-based composite heat sinks in engineering applications were prospected.

• Deformation Behavior and Mechanisms of fcc High-Entropy Alloys: Insights from Neutron Diffraction

  Zhao Yanchun, Yao Yatao, Zhang Fan, Huang Yan, Zhang Yibo, Lu Zhichao, Zhang Qi, Fu Xiaoling, Wang Anding, Zhang Fei, Song Wenli, Ma Dong

  2026,55(3):655-664 DOI: 10.12442/j.issn.1002-185X.20250176

  Abstract(0) HTML(0) PDF(2.56 M)( 0)

  Abstract:The multi-principal element characteristic of high-entropy alloys has revolutionized the conventional alloy design concept of single-principal element, endowing them with excellent mechanical properties. However, owing to this multi-principal element nature, high-entropy alloys exhibit complex deformation behavior dominated by alternating and coupled deformation mechanisms. Therefore, elucidating these intricate deformation mechanisms remains a key challenge in current research. Neutron diffraction (ND) techniques offer distinct advantages over traditional microscopic methods for characterizing such complex deformation behavior. The strong penetration capability of neutrons enables in-situ, real-time, and non-destructive detection of structural evolution in most centimeter-level bulk samples under complex environments, and ND allows precise characterization of lattice site occupations for light elements, such as C and O, and neighboring elements. This review discussed the principles of ND, experiment procedures, and data analysis. Combining with recent advances in the research about face-centered cubic high-entropy alloy, typical examples of using ND to investigate the deformation behavior were summarized, ultimately revealing deformation mechanisms dominated by dislocations, stacking faults, twinning, and phase transformations.

• Research Progress on Cracking Causes and Influencing Factors of Wrought Superalloy Ingots

  Fu Baoquan, Zhang Jinyu, Cao Kaili, Liu Jin, Liang Chen, Zhang Jianwei, Cao Guoxin, He Yongsheng

  2026,55(3):798-807 DOI: 10.12442/j.issn.1002-185X.20250289

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  Abstract:To meet the growing demand for enhanced material properties of aero-engines, the alloying element content of wrought superalloys is increasing, which leads to the difficulty of ingot casting. Excessive addition of alloying elements in superalloys tend to induce cracking under the combined action of thermal stress and phase transformation stress. Once cracks occur, it will not only interfere with the stability of process parameters such as current and voltage in the subsequent remelting process, but also raise scrap rate of the ingot, and exert an irreversible impact on the performance and reliability of the final product. Cracks in ingot, as a complex metallurgical defect during superalloy casting, has become a critical technological bottleneck, restricting the size scaling of high-alloyed superalloy ingots. Then, this paper reviews the recent research progress on the causes of cracking in wrought superalloy ingots during triple-melting processes, as well as various influencing factors in crack formation. Corresponding inhibition measures are also proposed for different cracking causes. The research direction of ingot cracking is prospected, aiming to provide a theoretical basis and technical reference for producing defect-free superalloy materials.

• Research Progress of Additively Manufactured Porous Tantalum Orthopedic Implantable Material

  Yang Jingzhou, Ni Xiaojun, Cheng Hao, Wang Jian, Chen Luyuan, Hong Yonglong, Li Qiulin

  2026,55(3):808-829 DOI: 10.12442/j.issn.1002-185X.20250206

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  Abstract:Tantalum, as a high-performance biometallic material with bioaffinity, is widely used in bone structure reconstruction and bone function repair. Porous tantalum exhibits excellent mechanical properties, biological properties, as well as in vivo osseointegration and bone ingrowth performance, showing outstanding clinical treatment effectiveness. This review based on recent research of our team and combined with literature analysis, reviewed the latest research progress in additive manufactured porous tantalum materials, including fabrication processes, structural design and optimization, mechanical properties, biological properties (cell-material interactions), in vivo osseointegration and bone ingrowth capabilities, and clinical applications. In particular, additive manufactured porous tantalum materials and orthopedic implants allow for the precise design and regulation of three-dimensional interconnected biomimetic porous structures, excellent static and dynamic mechanical properties, and bone conduction and bonding abilities. These materials are easy to manufacture anatomically matched personalized products, with promising applications in the repair of bone defects and the treatment of bone diseases.

• Research Progress on Coordinated Deformation of Superconducting Wires Based on Finite Element Method

  Hou Hongli, Hu Le, Zhang Shengnan, Wang Qingyang, Jiang Lang, Liu Jing, Liu Jixing, Li Jianfeng, Zhang Pingxiang

  2026,55(3):830-840 DOI: 10.12442/j.issn.1002-185X.20250077

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  Abstract:The structures of NbTi, Nb₃Sn, MgB₂, and Bi-based superconducting materials are complex. The uniformity of coordinated deformation among metals, between metals and powders, and within core wires determines the processing quality and mechanical properties of wires. The structures of wires and dies, processing parameters, and deformation conditions are important factors affecting their coordinated deformation behavior. The finite element numerical simulation method is an important engineering tool for analyzing and evaluating the coordinated deformation behavior of superconducting wires under multiple factors. This approach can accurately and intuitively simulate the coordinated rheological behavior during the forming process of multi-layer and multifilament composite superconducting wires, as well as the stress/strain distribution among composite phases and their interfaces. This review summarizes recent progress in finite element simulation of superconducting wire forming. It covers the establishment of finite element models, selection of constitutive models, and setting of boundary conditions for superconducting wire forming. At the same time, the review discusses the affecting mechanism of deformation parameters, die structure, and processing technique on coordinated deformation behavior, as well as recent advances in multi-scale analysis.

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• Low-Temperature Impact Toughness and Fracture Mechanisms of a High-Strength, High-Toughness TC4-0.55Fe Titanium Alloy

  Wang Delong, He Miaoxia, Gao Wenshuo, Guo Yumeng, Dong Yuecheng, Igor V. Alexandrov

  Available online:January 12, 2026  DOI: 10.12442/j.issn.1002-185X.20250391

  Abstract(90) PDF(2.32 M)(30)

  Abstract:Because of their exceptional corrosion resistance and superior low-temperature mechanical properties, titanium alloys are ideal structural materials for critical equipment operating under extreme conditions, such as Arctic resource exploitation and polar shipping routes. To further enhance low-temperature toughness and clarify the fracture–failure mechanisms of titanium alloys, a TC4-0.55Fe alloy was produced by micro-alloying with Fe, and its impact performance and fracture behavior were systematically investigated over the temperature range 20?°C toS?196?°C. The alloy exhibits a room-temperature Charpy impact toughness of 66.75?J?cm?2, which remains unchanged down to ?20?°C. When the temperature is lowered to ?70?°C, the toughness decreases to 46.75?J?cm?2, and at ?196?°C it still retains 25.1?J?cm?2—representing a 23.8?% improvement over conventional TC4. Scanning electron fractography confirms that ?196?°C is still above the alloy’s ductile–brittle transition temperature. EBSD characterization reveals abundant deformation twinning in the vicinity of the crack at all test temperatures, with twin density increasing markedly as temperature decreases. The outstanding impact toughness of the TC4-0.55Fe alloy is attributed to the synergistic effects of grain refinement, the dispersion of fine acicular α_s precipitates within the β matrix, and the pronounced rise in twin density at low temperature; together they promote crack-path deflection and significantly enhance resistance to fracture.

• Effect of Mo Element on the Microstructure and Properties of Laser Powder Bed Fusion Co-Cr-Fe Alloy

  He Yazhou, Hou Yaqing, 米志杉, Wang Ziyu, Lu Yongchao, Li Xiaoqun, Zhou Dong, Su Hang

  Available online:December 24, 2025  DOI: 10.12442/j.issn.1002-185X.20250492

  Abstract(50) PDF(1.89 M)(55)

  Abstract:Compositionally graded 15Co-25Cr-(60-x)Fe-xMo (x=0-5, wt.%) specimens were fabricated via laser powder bed fusion (LPBF) using blended elemental powders of Co, Cr, Fe, and Mo, employing an in-situ alloying strategy. The compositional homogeneity, phase constitution, and microstructure of the specimens with varying Mo content were systematically investigated. Furthermore, the influence of Mo content on the magnetic properties was elucidated by integrating experimental findings with first-principles calculations. The results indicate that all specimens achieved full alloying without defects such as porosity or un-melted particles. The magnetic properties exhibit a non-monotonic trend with increasing Mo content, initially enhancing before deteriorating. Optimal magnetic performance is obtained at 3 wt.% Mo, yielding a coercivity (H_c) of 26.54 kA/m, a remanence (B_r) of 0.9 T, and a maximum energy product (〖(BH)〗_max) of 11.56 kJ/m3.Additionally, Mo incorporation was found to enhance the microhardness of the alloys, with the 15Co25Cr57Fe3Mo sample exhibiting a hardness of 424 HV0.5.

• Study on Synergistic Optimization of Microstructure and Mechanical Properties of Zr-based Eutectic Alloy

  Chen Lihe, Wang Rui, Yao Xinwei, Hai Nuo, Gao Yinghong, Zhang Zhouran, Li Shun

  Available online:December 17, 2025  DOI: 10.12442/j.issn.1002-185X.20250283

  Abstract(55) PDF(1.66 M)(55)

  Abstract:This investigation adopts a strategic approach focusing on low-melting point eutectic alloy design supplemented by thermodynamic calculations of phase diagrams to develop and characterize Zrx(NiFe)100-x alloy systems (x=75/83/90 wt.%). Results demonstrate that at Zr concentrations of 83 wt.% and above, the alloys develop a distinctive lamellar eutectic microstructure (tI12-Zr2(Ni/Fe)/FCC-Zr) coexisting with HCP-Zr, featuring nanoscale FeZr3 interphase precipitates at eutectic interfaces. Notably, the liquidus formation temperature exhibits a substantial reduction to approximately 974℃, successfully achieving the desired low-melting point characteristics. The Zr83(NiFe)17 and Zr90(NiFe)10 alloys exhibit compressive strengths of 1352±12 MPa and 1253±10 MPa with corresponding fracture strains of 14.2±0.4% and 17±0.3%, respectively. These values represent a significant enhancement in fracture strain compared to conventional Zr-based amorphous alloys while maintaining comparable strength properties. Fractographic analysis reveals that dislocation pinning mechanisms and shear band bifurcation phenomena induced by eutectic interfaces effectively impede crack propagation, facilitating a transition in fracture mode from brittle cleavage to 45° shear-dominated failure with increasing Zr content. Under dynamic compression, both 83Zr and 90Zr alloys exhibit a strain rate hardening effect, and when the strain rate exceeds a critical value, the alloys undergo a ductile-to-brittle transition. This research establishes a fundamental framework for the design of low-melting point Zr-based eutectic multiphase alloys.

• Effects of Microstructure Characteristics on Impact toughness of GH4151 alloy

  TangChao, Liu Jie, Luo Junpeng, Zhang Maicang, Xie Xingfei, Qu Jinglong, Zhang Ji

  Available online:December 17, 2025  DOI: 10.12442/j.issn.1002-185X.20250461

  Abstract(39) PDF(2.28 M)(55)

  Abstract:Seiries oscilloscope impact tests were conducted for GH4151 alloy under different heat treatment parameters, then microstructure characteristics and grain boundary properties were investigated by using phase diegram calculation, precipitates and EBSD analysis by SEM and detailed phase structure determined by TEM, the relationship between microstructure evolution and impact toughness of GH4151 alloy was systematically studied. The results show that the percentage of primary γ′ phase gets lower with the inceasing of annealing solution temperature, while the average grain size gets greater. The JMat Pro results depict that for GH4151 alloy there exists a certain amount of μ phase, a type of TCP phase, at the grain boundary, besides the secondary carbides of M23C6. Oscilloscope impact tests show that the crack initiation energy including elastic deformation enegy and plastic deformation energy and the propagation enegy for annealing solutioned specimens were all greater than that of annealing aged ones, resulting the good resistance of crack initiation and propagation and good property of inpact toughness. and the impact toughness gets lower when the specimens were annealing aged due to the smaller crack initiation energy and propagation enegy. Further microstructure analysis by TEM shows that the tested impact toughness values were increased with the increase of average grain size and had little relationship with the properties of grain boundary. The main reasons that the sharp decrease of impact toughness for annealing aged specimens were the finer grain size and M23C6 carbides and μ phase precipitate at the grain boundary.

• Study on High-Temperature Oxidation Behavior and Mechanisms of 3rd-Generation TiAl Alloys

  Ji Xiankun, Dang Yuyang, Leng Kun, Wang Ying, Xia Zhizhou, Liu Shaohua, Zhao Chunling, Cui Yuyou, Zhang Chao

  Available online:December 12, 2025  DOI: 10.12442/j.issn.1002-185X.20250465

  Abstract(37) PDF(1.98 M)(50)

  Abstract:The high-temperature environmental adaptability of TiAl alloys is crucial for the service safety of aero-engine low-pressure turbine blades. This study investigates the cyclic oxidation behavior of a cast ZTNM TiAl alloy at 650℃ and 750℃ in accordance with the HB5258 standard. The results indicate that the oxidation weight gain kinetics of the alloy at both temperatures follow a parabolic law. The oxidation rate at 650℃ (k′ = 0.0082 gm^-2h^-1) is lower than that at 750℃ (k′ = 0.0095 gm^-2h^-1), with both rates qualifying as "complete anti-oxidation" grade. The oxidation process comprises three distinct stages: the initial formation of a mixed TiO2 and Al2O3 scale; followed by the development of a continuous TiN/Ti2AlN nitride layer at the scale / metal substrate interface during the intermediate stage; and finally, the formation of an Al-depleted zone within the oxide scale after long-term exposure. The higher temperature (750℃) promotes the growth of TiO2, resulting in a thicker oxide scale. The nitride layer plays a critical role in determining the oxidation rate and the structural stability of the scale.

• Precipitation Behavior During Long-Term Aging of Ni-Cr-W-Mo Alloy and Its Effect on Mechanical Properties

  Gao Shuai, He Xikou, Jia Lei, Tang Zhengxin, Bao Hansheng, Yin Xue, Dong Wenjun, Liu Zhengdong

  Available online:December 09, 2025  DOI: 10.12442/j.issn.1002-185X.20250448

  Abstract(36) PDF(1.58 M)(51)

  Abstract:Using techniques such as SEM, TEM, and phase analysis, the precipitation behavior during long-term aging at 800°C and its effect on the mechanical properties of a Ni-Cr-W-Mo alloy were investigated. The results indicate that during aging, M23C6 carbides precipitated sequentially at grain boundaries, twin boundaries, and within grains in different morphologies. The intergranular lamellar M23C6 was a product of a discontinuous reaction, while the granular M23C6 at twin boundaries grew along the {111} twin planes. The intragranular nanoscale M23C6 contributed to pinning strengthening. M6C carbides underwent degeneration from the exterior to the interior between 1000h and 5000h of aging, decomposing into M23C6, α-(W,Mo), and W- and Mo-poor matrix. Due to the equilibrium segregation of W and Mo, α-(W,Mo) phase precipitated at grain boundary M23C6 after 5000h of aging. Changes in mechanical properties were mainly concentrated in the early aging stage. The increase in strength within the first 200h of aging was caused by a sharp rise in carbides, while the deterioration of ductility and toughness was attributed to the brittleness of intergranular M23C6 and its reduction of grain boundary cohesion. From 200h to 5000h of aging, the properties degraded gradually. The strength reduction in this stage was related to the weakening of solid solution strength by α phase and the coarsening of nanoscale M23C6, while the significant degradation of ductility and toughness was associated with the coarsening of intergranular M23C6 and the decomposition of M6C. The fracture mode transitioned from transgranular ductile fracture to a mixed mode after aging.

• From Withdrawal Rate to Creep Life: Microstructure-Mediated Performance in Directionally Solidified Mar-M247LC

  ganyisheng, wanghaiyang, zhonghong, zhujiaxi, libo, fengzhenyu, lishuangming

  Available online:December 09, 2025  DOI: 10.12442/j.issn.1002-185X.20250488

  Abstract(50) PDF(1.66 M)(70)

  Abstract:Directionally solidified (DS) nickel-based superalloys exhibit excellent creep resistance due to the elimination of transverse grain boundaries perpendicular to the stress axis. Given the strong dependence of creep performance on the initial solidification microstructure, this study reveals how withdrawal rate governs the as-cast microstructure of DS Mar-M247LC and dictates its post-heat-treatment creep life at 980 °C/220 MPa. It was found that an increase in the withdrawal rate of the directionally solidified specimens led to a reduction in the values of primary dendrite arm spacing (from 479 μm to 322 μm) and the average size of γ" precipitates (from 460 nm to 345 nm in interdendritic regions and from 298 nm to 203 nm in dendritic core). In addition, the carbide morphology changes from blocky to script-like. The heat treatment led to the formation of distinct cuboidal γ" precipitates and was accompanied by a significant increase in the γ" volume fraction compared to the directionally solidified microstructure. The alloy solidified at 40 μm/s exhibits elongated γ" rafts with narrowed matrix channels and regular dislocation networks, synergistically extending creep rupture life to 96.6 h. Fractographic analysis confirmed transgranular ductile, with fracture initiation occurring at decomposed MC carbides.

• Preparation and Water Cooling Verification of Pin-fin Diamond/Copper Plates for Electronic Packaging

  Cao Wenxin, Han Kai, Ye Zhijie, Zhao Kunlong, Su Zhenhua, Yao Tai, Wang Jiandong, Zhao Jiwen, Zhu Jiaqi, Han Jiecai

  Available online:July 28, 2025  DOI: 10.12442/j.issn.1002-185X.20250285

  Abstract(113) PDF(1.22 M)(236)

  Abstract:The issue of thermal management in electronic packaging is one of the important technical bottlenecks hindering the development of integrated circuits. Diamond/copper composites have excellent performance in the field of thermal management, but the difficulty in their complex structure formation leads to very limited applications in the field of water cooling in electronic packaging. In this study, we aimed to enhance the sintering performance between the green body and the composite plate by employing a silver doping strategy, thereby addressing the thermal management challenges in electronic packaging. We fabricated composite base plates and pin-fin type composite base plates and evaluated their application benefits in both indirect and direct water cooling scenarios. Our findings demonstrated that the silver-doped copper billet achieved good sintering performance when combined with tungsten-coated diamond/copper composite plates. The composite base plate and the pin-fin type composite base plate effectively reduced the temperature of the heating sheet by 5-6°C and 4-5°C during water-cooling tests respectively. The numerical simulation results were in good agreement with the experimental data, confirming the excellent thermal uniformity of the composite structures. This study successfully overcame the limitations associated with the low thermal conductivity of traditional packaging components and the challenges in fabricating complex structures using diamond/copper composite materials.

• Numerical simulations of dynamical relaxations in metallic glasses: a short review

  Claudio Fusco

  Available online:July 17, 2025  DOI: 10.12442/j.issn.1002-185X.20250367

  Abstract(88) PDF(2.73 M)(240)

  Abstract:Metallic glasses are a unique class of materials with exceptional mechanical properties, including high strength, excellent corrosion resistance, and significant elasticity. These materials display intriguing dy- namical relaxation processes, which influence their mechanical and thermal properties. Understanding the dynamical relaxations in metallic glasses is crucial for optimizing their performance in various applications. Due to the limitations of experimental techniques to access processes at the atomic level, the detailed mechanisms responsible for the dynamical relaxations cannot be easily probed experimentally. Numerical simulations are good candidates to analyze in depth the elementary dynamical processes at the atomic scale and thus to capture the fundamental origin of dynamical relaxations. The development of computing power in the last decades has allowed researchers to reach an enormous advancement in the understanding of the physical mechanisms behind dynamical relaxations in metallic glasses.

• Stability and effect of primary carbides in Inconel 718 superalloy service turbine disk

  Zhang Yan Lin, Chen Shuo, Jiang He, Dong Jian Xin

  Available online:June 19, 2025  DOI: 10.12442/j.issn.1002-185X.20250173

  Abstract(155) PDF(2.76 M)(311)

  Abstract:Taking an Inconel 718 (GH4169) turbine disk with an accumulated service time of approximately 60,000 hours from a specific model of aircraft as the research object, this study systematically investigates the microstructure of various regions of the service turbine disk. Detailed characterization of the microstructure was conducted using research methods such as optical microscopy, scanning electron microscopy, electron probe, extraction phase analysis, inclusion scanner, and nano-indentation. The results show that after long-term service, there is no significant change in the strengthening phases γ" and γ" of the turbine disk. However, the quantity, size, and morphology of primary MC carbides from the center to the edge have undergone noticeable decomposition. The content decreased from 0.166 wt.% to 0.106 wt.%, and the morphology gradually changed from sharp and regular blocky shapes at the interface to irregular near-circular shapes. The nano-hardness decreased, and there was a significant redistribution of elements, with Nb, Ti, and C elements released and diffused into the matrix. The primary MC carbides are prone to dissolution and decomposition during long-term service, leading to a decrease in the concentration and hardness of the carbide elements. The diffusion of carbide-forming elements into the matrix may cause a "disturbance" to the comprehensive mechanical properties of the alloy during the long-term service performance.

• Effect of heat treatment on mechanical properties of TC4-0.55Fe titanium alloy tube

  He Miaoxia, Jiang Qing, Guo Yumeng, Dong Yuecheng, Igor V. Alexandrov

  Available online:June 19, 2025  DOI: 10.12442/j.issn.1002-185X.20250219

  Abstract(185) PDF(2.69 M)(286)

  Abstract:In the face of harsh and complex oil and gas resources exploitation environment, it is urgent to explore titanium alloy oil well pipes with high strength and toughness service performance. In this paper, the cross piercing (RP) TC4-0.55 Fe titanium alloy seamless tube was taken as the research object. The microstructure was controlled by solid solution and aging process. The tensile properties at room temperature and impact properties at -20 °C were tested. The effects of microstructure evolution on mechanical properties were analyzed by SEM, XRD and TEM. The results show that the size of αC and the average grain thickness of αL increase significantly, and the orientation and uniformity of the microstructure are also significantly enhanced after the deformed Widmanstatten structure of the RP sample is aged in the two-phase region (STA910). The tensile strength, yield strength and elongation of RP samples are 904 MPa, 793 MPa and 14.2 %, respectively. The impact energy and impact toughness at -20 °C are 66.2 J and 82.7 J/cm2, respectively. After solution and aging in the two-phase region, the tensile strength, yield strength and elongation of STA910 sample increased to 984 MPa, 904 MPa and 16.2 %. The impact energy and impact toughness at-20 °C decreased slightly, but still maintained at 52.8 J and 66.2 J/cm2. The α/β interface is increased by the precipitation of αS and ω phases in the STA910 sample, which increases the dislocation slip and motion resistance and improves the segregation of alloying elements. The dual effects of grain boundary strengthening and solid solution strengthening are achieved, thus improving the strength and plasticity of the alloy. On the other hand, all TC4-0.55Fe alloys show excellent impact toughness. The fracture modes of the alloys are mainly ductile fracture and transgranular fracture. The coarsening of α phase grain size, the decrease of β phase stability and the precipitation of αS and ω phases in βt lead to the decrease of impact properties of the alloys.

• Study on Dynamic Mechanical Behavior and Low Temperature Mechanical Properties of Porous CoCrNi Medium-Entropy Alloy

  Wei Lai, Wang Xiaohua, Liu Jie, Wang Yifei, Ma Shengguo, Wang Zhihua

  Available online:June 13, 2025  DOI: 10.12442/j.issn.1002-185X.20250166

  Abstract(162) PDF(1.18 M)(313)

  Abstract:Porous CoCrNi MEA with porosity of 60.6% -78.1% and pore size of 1.8 -2.4mm were prepared by powder sintering-dissolution method. The pore distribution is uniform and the metallurgical bonding is good. The dynamic compression test results show that the material has a significant strain rate strengthening effect, and the impact resistance is the best at 500s_-¹ strain rate. The yield strength increases by 52.8% (22.9 MPa to 35.0MPa) with the increase of strain rate from 200s_-¹ to 800s^_-1. The dynamic yield strength increases by 25% compared with the quasi-static yield strength. The energy absorption value reaches 35.4 ~14.5MJ/m^₃ (6.6% ~ 14.0% higher than the quasi-static), and the maximum ideal energy absorption efficiency is close to 0.9. At the same time, under the condition of low temperature (-100°C), the elastic modulus and platform stress are increased by 2.4% ~10.5% and 2.5% ~9.8%, respectively, compared with room temperature. The energy absorption value is 41.3 ~15.2MJ/m^₃, which is twice that of magnesium alloy foam, and the maximum ideal energy absorption efficiency remains 0.8. In summary, the porous CoCrNi MEA has both dynamic strengthening and low-temperature strengthening characteristics, and has good energy absorption capacity and high ideal energy absorption efficiency, showing significant application potential in the field of actual working conditions and extreme environments.

• Effects of Gas Regulation on the Characteristics of Nickel-Based and Titanium Alloy Powders prepared by EIGA

  ZHANG Lichong, CHEN Hao, LIU Yufeng, ZHENG Liang, XU Wenyong, LI Zhou, ZHANG Guoqing

  Available online:June 13, 2025  DOI: 10.12442/j.issn.1002-185X.20250198

  Abstract(152) PDF(1.37 M)(312)

  Abstract:Electrode Induction Melting Gas Atomization (EIGA) is a crucial technique for producing ultra-high-purity metal powders, as it is a crucible-free powder production method. This study focuses on the nickel-based superalloy FGH96 and the titanium alloy TC4, and investigates the effects of atomization pressure and gas temperature on the particle size, morphology, and hollow powder content of the alloys. The study combines atomization experiments with powder characterization. The results show that at a gas temperature of 25°C, increasing the atomization pressure from 2.5 MPa to 4.0 MPa, reduces the median particle size (D??) from 96.3μm to 75.5μm. The sphericity reaches its maximum value 0.9805 at an atomization pressure of 3.5MPa. The powder volume porosity also exhibits a trend of first increasing and then decreasing. At an atomization pressure of 4.0MPa, as increasing the gas temperature to 100°C the powders further refine, with the D?? values for FGH96 and TC4 powders decreasing to 63.8μm and 86.0μm, respectively. The gas heating effect is more pronounced for the superalloy powders. As the gas temperature rises, the powder sphericity of the superalloy remains unchanged, while the powder sphericity of the titanium alloy increases slightly. The powder volume porosity of the superalloy slightly increases. Due to differences in viscosity, surface tension, and density between the two alloy melts, powder characteristics such as particle size and morphology exhibit distinct variation trends. This study provides a theoretical basis for the customization of powder preparation processes for different types of alloys.

• Shape topology optimization method for strain uniformity control of large disk forgings of superalloy

  Menghan Wang, Xin Li, Yuanyuan Zheng, Menglong Du, Songlin Li, Haicheng Zhang

  Available online:April 03, 2025  DOI: 10.12442/j.issn.1002-185X.20240756

  Abstract(97) PDF(1.10 M)(128)

  Abstract:Strain uniformity is an important index to evaluate the performance of large disk forgings in aerospace. Taking turbine disc as the research object, this paper explores the reasons for the formation of low strain zone of turbine disc forgings, and proposes a topological optimization design method suitable for large disc forgings based on the addition and removal rule of "number of subunits - volume - number of subunits". The method adopts the allocation of appropriate volume for each column element, and adapts the relative height of each region by stacking and adjusting modules. Obtain the shape of the preforging with low complexity of the target shape. In order to verify the effectiveness of the optimization method, the paper takes deformation uniformity as the goal to automatically optimize the shape of large turbine disc preforging. After optimization, the deformation uniformity of the forging is increased by 45%, and there is no strain dead zone. The results of numerical simulation and production test show the reliability of the method proposed in this paper.

• Prediction of Five Point Bending Rebound of TC4 Titanium Alloy Plate Based on Variable Elastic Modulus

  Qu Cong, Wang Dongjie

  Available online:November 20, 2024  DOI: 10.12442/j.issn.1002-185X.20240434

  Abstract(106) PDF(1.36 M)(126)

  Abstract:TC4 titanium alloy material will generate significant spring back during the bending process, and its elastic modulus has a significant impact on spring back. However, previous studies have not considered the change in elastic modulus during the plastic strain change process of the material. This study focuses on TC4 titanium alloy and conducts uniaxial tensile and cyclic loading unloading experiments to determine the anisotropy parameters and the variation of material elastic modulus with plastic strain. On this basis, a mathematical model for the variable elastic modulus of TC4 titanium alloy was established. Based on three different constitutive models, namely YLD2000-2D yield criterion and variable elastic modulus, YLD2000-2D anisotropy, and Mises isotropy, numerical simulations were conducted on the five point bending process of TC4 titanium alloy plates at room temperature. In order to verify the numerical simulation results, a five point bending experiment was conducted on TC4 sheets at room temperature. The results showed that the anisotropic constitutive model and the mathematical model of variable elastic modulus significantly improved the prediction accuracy of TC4 titanium alloy bending spring back, the highest prediction accuracy increased by 31.18%.

• Development of ultra-coarse grained WC-8(Co,Ni) cemented carbides with varied Ni:Co ratios leveraging thermodynamic phase diagram calculations

  志伟 商, 志平 孙, 致明 王, 文凯 赵, 雅宁 陈

  Available online:March 22, 2024  DOI: 10.12442/j.issn.1002-185X.E20230047

  Abstract(188) PDF(1.23 M)(355)

  Abstract:This study is grounded in thermodynamic phase diagram calculations and employs powder metallurgy techniques to fabricate ultra-coarse grained WC-8(Co,Ni) cemented carbides with varying Ni:Co ratios. The study delves into the alloy"s microscopic structure, mechanical properties and corrosion resistance. It has been shown that carbon equilibrium can be efficiently maintained by using thermodynamic phase diagram calculations, thus preventing the emergence of harmful phases associated with carbon deficiency or excess in the alloy. As the Ni:Co ratio increases, the density of the alloy first increases and then decreases. The average grain size of WC enlarges, leading to a deterioration in the uniformity of the binder phase distribution. This results in a decrease in hardness, an increase in fracture toughness, and an initial rise followed by a significant decrease in flexural strength. Ni plays a crucial role in mitigating the corrosion rate of the binder phase and thus enhancing the corrosion resistance of ultra-coarse grained cemented carbides. When the Ni:Co ratio is 2:6, the alloy demonstrates optimal integrated mechanical properties and its enhanced corrosion resistance is notably pronounced.

• A new antibacterial and corrosion resistance coating on the AZ31 magnesium alloy prepared via friction stir processing combined with micro arc oxidation

  Zilu Liu, Peng Han, Wen Wang, Qiang Liu, Fengming Qiang, Hairui Xie, Kuaishe Wang

  Available online:November 17, 2023  DOI: 10.12442/j.issn.1002-185X.20230255

  Abstract(444) PDF(1.07 M)(605)

  Abstract:In this paper, the AZ31 magnesium (Mg) alloy coating with antibacterial properties and corrosion resistance was successfully obtained through friction stir processing (FSP) combined with micro arc oxidation (MAO). FSP was firstly utilized to introduce hydroxyapatite (HA) and silver (Ag) particles and prepare the precursor of AZ31 Mg alloy coating. Subsequently, MAO was employed to transfer HA and Ag particles into the surface of Mg alloy, then forming the coating. It is shown that the dispersed HA particles in the precursor promoted the coating growth in the MAO process and increased the thickness of the coatings, improving in the corrosion resistance. The Ag particles with an average size of 2-10 nm refined by FSP were easily to be transferred from the precursors to the Mg alloy coatings during the MAO process, the lower Ag content reduces the corrosion current density of the coating and improves its corrosion resistance. At the same time, the antibacterial performance of the coating has been significantly improved, and the coatings exhibited excellent antibacterial properties with the highest rates of against Staphylococcus aureus and Escherichia coli reaching to 99.4% and 99.6%, respectively.

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