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    2024,Volume 53, Issue 7

      >ARTICLE
    • Zhao Yanchun, Song Haizhuan, Ma Huwen, Hu Ruonan, Feng Li, Duan Wangchun, K Liaw Peter

      2024,53(7):1817-1825 DOI: 10.12442/j.issn.1002-185X.20230636

      Abstract:(Fe63.3Mn14Si9.1Cr9.8C3.8)99.5?xCuxAg0.5 (x=1, 2, 3, 4, 5, at%) alloys were prepared by water-cooled copper crucible magnetic levitation vacuum melting furnace. The effects of Cu contents on microstructure, corrosion resistance, and antibacterial performance of the alloys were investigated. The results show that the medium entropy alloys possess fcc phase after solid solution and aging treatment. With the increase in Cu content, the Cu-enriched and Ag-enriched fcc2 phase is precipitated on the fcc1 Fe-rich matrix. The corrosion resistance of the alloys in 3.5wt% NaCl solution is superior to that of AISI304. The corrosion current density first decreases and then increases, and the impedance arc radius first increases and then decreases, indicating an initial enhancement and subsequent weakening of the corrosion resistance as the Cu content increases. Moreover, the corrosion rate of the alloys in Escherichia coli suspension shows a trend of increasing first and then decreasing. When x=2 the alloy exhibits the best corrosion resistance, and there is a trade-off effect between the corrosion resistance and antibacterial performance. The fcc2 phase effectively enhances the antibacterial performance of the alloy, and the alloy of x=5 shows the optimal antibacterial rate of 99.94%.

    • Li Yan, Shi Aizun, Zhang Wenbin, Liu Cuirong

      2024,53(7):1826-1835 DOI: 10.12442/j.issn.1002-185X.20230644

      Abstract:The corrugated cold rolling bonding (CCRB) process, as a new rolling technique, has gained widespread attention in the preparation of metal composite plates. However, the mechanical properties of corrugated composite plates and the microstructure of the interface at different reduction levels are not yet clear. Numerical simulation and experimental methods were employed to investigate the preparation of Cu/Al corrugated composite plates under reduction levels of 55%, 60%, 65%, and 70%. A three-dimensional model was established by finite element simulation software ABAQUS to simulate the normal stress and strain curves during the rolling process. The interface morphology of the composite plate was characterized by scanning electron microscopy, electron backscatter diffraction, and X-ray energy dispersive spectroscopy. Results show that the ultimate tensile strength and shear strength reach the maximum values at a reduction level of 65%, measuring 221.08 and 79 MPa, respectively; while they reach the minimum values at a reduction level of 55%, measuring 169.34 and 45 MPa, respectively. Particularly, at reduction levels of 65% and 70%, the composite plate exhibits elongated grains and fine equiaxed grains due to severe plastic deformation. At a reduction level of 70%, excessive rolling force causes microcracks in the matrix metal, leading to a decrease in tensile performance, which is consistent with the mechanical test results.

    • Ren Lina, Zhang Qunbing, Lei Xiaowei, Qi Liang, Yang Jiadian, Zhang Jianxun

      2024,53(7):1836-1844 DOI: 10.12442/j.issn.1002-185X.20240084

      Abstract:TC17 titanium alloy was weld under different laser heat input conditions. Optical microscope, scanning electron microscope, transmission electron microscope, tensile and fatigue tests were used to compare the macroscopic morphologies, microstructures, and mechanical properties of the welded joints. The results show that with the increase in heat input, the morphology of weld changes from Y- to X-shaped. The number of pore defects in the weld increases first and then decreases. The pore defects are mainly distributed in the middle and lower part of the weld zone. The weld is composed of coarse columnar grains with strip dendrites inside, and the spacing of dendrite increases gradually with the increase in heat input. The heat affected zone comprises finer equiaxed grains, and the increase in heat input leads to the refinement of α phase and coarsening of β phase. Moreover, the TC17 laser welded joints all fracture at the weld zone in the tensile and fatigue tests. Under the influence of dendrite size, the tensile strength decreases with the increase in heat input. The welding pore is the main reason for the fatigue fracture, and the fatigue life peaks when the number of pore defect is the lowest.

    • Teng Haihao, Xia Yufeng, Yu Yingyan, Yin Hui

      2024,53(7):1845-1854 DOI: 10.12442/j.issn.1002-185X.20230520

      Abstract:The microstructure of TC18 titanium alloy die forging shows delamination. The brighter microstructure has lower performance and is often called cold die microstructure (CDM). Decreasing the cooling rate can hinder the generation of CDM, but it may also aggravate the die wear. The balance relation between microstructure delamination of TC18 frame forging and the die wear in different parameters was studied by simulation and experiment. The programs to predict the CDM and wear depth were built and realized by secondary development. Continuous forging production process was simulated by DEFORM software and the characteristics of CDM and wear were researched. The balance relationship between the die wear and the CDM content in different parameters was discussed by the response surface method and the optimal parameters. Results show that the preheating temperature of die plays a dominant role in the variation of the wear depth. The most influential factor of CDM content is the contact condition. Applying glass fiber can reduce the CDM content without increasing the wear depth.

    • Xu Yang, Liu Gaoshang, Liu Chengbao, Zheng Leizhi, Chen Feng, Qian Junchao, Qiu Yongbin, Meng Xianrong, Chen Zhigang

      2024,53(7):1855-1862 DOI: 10.12442/j.issn.1002-185X.E20230043

      Abstract:With the rapid depletion of fossil fuels and a series of environmental problems, it is urgent to develop and to utilize new electrochemical energy storage devices, and the design, preparation and optimization of electrode materials are key factors to determine the performance of supercapacitors. Hydrothermal method was used to convert hollyhock stalks into porous carbon matrix with MnO and Co nanocrystals anchored on it. Results show that the prepared biocarbon has porous structure and good electron transport properties, and the nanosrystal MnO-Co on it has high capacitance. Due to the unique nanostructure of carbon skeleton and large specific surface area (345.9 m2·g-1), MnO-Co nanocrystal/porous carbon shows excellent electrochemical capacitance (146 F·g-1 at 1 A·g-1) and cycle stability. After 1000 cycles, the specific capacity still remains 99.4%.

    • Liu Shixi, Chen Furong, Fan Yufeng, Zhao Bobo, Gao Yunxi

      2024,53(7):1863-1873 DOI: 10.12442/j.issn.1002-185X.20230639

      Abstract:It is difficult to achieve Al/Cu dissimilar welds with good mechanical properties for T-lap joints, due to the low heat input and poor plastic flow of the inner corner of the T-joint in friction stir welding (FSW), which leads to easy occurrence of wormholes, tunnel, bonding line defects, etc, and thus further causes stress concentration. Therefore, pre-set welding wires at the fillet were innovatively applied to 6061-T6 aluminum alloy (4 mm in thickness) and pure copper dissimilar plate FSW T-lap joints, in order to improve the internal plastic flow of T-joints, reduce defects, and obtain joints with good microstructure and properties. The effect of three types of pre-set wires on the microstructure and mechanical properties of Al/Cu dissimilar FSW T-lap joints was analyzed. Results reveal that three types of pre-set wire joints exhibit onion ring-like pattern in the large pin stirring zone at a constant travel speed of 35 mm/min and a rotation speed of 700?800 r/min. The progressive tool at all rotation speeds effectively inhibits migration of large amounts of stringer material to the skin and avoids base materials mixing. Small amounts of Cu particles are mechanically stirred and have a long flow path in the large pin stirring regions, which inhibits the formation of brittle Al/Cu intermetallic compound (IMC) phases during welding. Al/Cu forms effective metallurgical bonding, and the IMC thickness of the Al/Cu interface is less than 1 μm. The Al/Cu T-joints with pre-set Cu are similar to butt joints of the same material in the skin direction, showing a typical ductile fracture. In Al/Cu T-joints with pre-set Al, the direction of the bonding line defects is changed, a certain height of Al/Cu mixing zone is obtained in the direction of the stringer, achieving optimal mechanical interlocking bonding, and break mostly occurs at the intersection, with a tensile strength of 157 MPa, showing hybrid fracture. The pre-set welding wire is proved to be a good method for Al/Cu dissimilar FSW T-lap joints.

    • Li Leyu, Tian Fuzheng, Li Zhen, Zhang Jingang, Deng Zhiwei, Chen Xing, Liu Xinling

      2024,53(7):1874-1881 DOI: 10.12442/j.issn.1002-185X.20230618

      Abstract:The fatigue crack propagation behavior of DD6 nickel-based single-crystal superalloy was investigated at temperatures ranging from 530 °C to 850 °C. The fatigue properties were assessed along the [001] direction, parallel to the loading axis in tension. After the fatigue crack propagation test, the fracture morphology was examined by scanning electron microscope and classified into four zones, including source zone, prefabricated crack zone, stable extension zone, and rapid extension zone. Electron backscatter diffraction was utilized to observe the profiles of plastic deformation perpendicular to the fracture. Additionally, the dislocation motion mechanism near the fracture was studied by transmission electron microscope. Results show that oxidation occurs at 650 °C under combined influences of the temperature field, stress field, and exposure time. Furthermore, due to weakened γ′ phase, a significant number of consecutive dislocations form in the γ and γ′ phases between 650 and 760 °C, resulting in increased oxidation of alloy. Besides, a notable decrease in fatigue propagation life can be observed at 760 °C.

    • Chen Leli, Gao Pei, Luo Rui, Cheng Xiaonong, Meng Xiankai

      2024,53(7):1882-1886 DOI: 10.12442/j.issn.1002-185X.E20230040

      Abstract:Regional microstructure characteristic always appears in shear-compression deformed GH4169 superalloy, which is detrimental to subsequent cold-rolling process in engineering. Recrystallization annealing treatments within temperature range of 1000?1080 °C and holding time range of 1?3 h were carried out to investigate the microstructure evolution behavior, and the cold-forming property of GH4169 superalloy was optimized by regulating the grain size. Results show that static recrystallization (SRX) grains are fully nucleated at 1000 °C and the original coarse grains are completely replaced by fine recrystallized grains. Bulges of high angle grain boundaries are the preferred nucleation points of SRX. At 1020?1060 °C, grain annexation takes place among adjacent SRX grains, causing partial grains to increase, while the original dynamic recrystallization (DRX) grains keeps tiny in the strain con-centration region. Recrystallized grains (both SRX and DRX) uniformly grow up, with an average grain size of 87.89 μm at 1080 °C, at which the regional characteristic completely disappears, and the microstructure is significantly homogenized. Step twins appear at 1080 °C due to the SRX growth accidents, and the length fraction of twin boundaries (Σ3) reaches 35.8%, which can effectively improve the high temperature resistance of GH4169 superalloy. Ultimately, the optimal recrystallization annealing of shear-compression deformed GH4169 superalloy is determined as 1080 °C-1 h, followed by water cooling.

    • Zheng Deyu, Xia Yufeng, Teng Haihao, Yang Wenbin, Yu Yingyan

      2024,53(7):1887-1896 DOI: 10.12442/j.issn.1002-185X.20230637

      Abstract:The forging load of super large turbine disc with a diameter over 2 m may approach or even surpass the limit of 800 MN of the largest press machine in China, which is the extreme manufacturing. Thus, maintaining good mechanical properties and controlling forging load are two key factors during the forging process of super large turbine disc. 25 groups of forging parameters was designed based on Taguchi method. The multi-objective optimization of finite element method simulation results was conducted by SNR and ANOVA methods. Results show that the most uniform and refined recrystallization microstructures are obtained under optimal forging load. The optimal combination of process parameters is determined under extreme manufacturing condition: temperature=1120 °C, strain rate=0.06 s-1, pre-forging size=985/610/475 mm, and die temperature=280 °C. The order of importance of each parameter to the simulation results is as follows: temperature>strain rate>billet shape>>die temperature. The experimental results obtained under the optimal parameters combination show good agreement with the simulated results, which demonstrates that this approach may be used to manage the load and microstructure of super large forgings while avoiding a significant number of experiments and numerical simulations.

    • >REVIEW
    • Chen Yang, Hu Jichong, Huang Hailiang

      2024,53(7):1897-1908 DOI: 10.12442/j.issn.1002-185X.20230649

      Abstract:Ni-based superalloys exhibit exceptional mechanical properties and high-temperature resistance, making them suitable for use in aggressive environments. The oxidation behavior of Ni-based superalloys is primarily influenced by the intrinsic material properties and oxide scale properties, which are largely dependent on the complex composition and content of alloying elements. Various environmental parameters, including atmosphere composition, temperature, stress and molten salts, directly impact the oxidation behavior of materials. The effects of alloying elements and the service environment on the oxidation behavior of Ni-based superalloys were comprehensively reviewed. Aluminium, chromium and cobalt are considered as favorable elements to form compact and adherent scales that protect the matrix. The addition of titanium, molybdenum, niobium, tungsten and tantalum is traditionally believed to be detrimental. However, recent researches have presented different opinions, which were discussed. The oxidation mechanism was also explored and an insight into the future developments of Ni-based superalloys was provided.

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    • Zhencen Zhu, Xiaoqiang Li, Cunliang Pan, Shengguan Qu

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240089

      Abstract:This article refers to the composition of MA754 alloy and prepared Ni-based alloy powders with high melting point containing Ti and Nb as framework, as well as low melting point Ni-based alloy powders with B and Zr as wetting agents by high-energy ball milling, respectively. A Ni-based ODS alloy with excellent performance was prepared by the way of spark plasma sintering after mixing two kinds of powder in the optimal ratio. The influence of sintering temperature and the content of low melting point powder in composite powder on the microstructure and mechanical properties of the alloy was studied. The results showed that dispersed oxides could be observed in the alloy structure prepared by this method, and the mechanical properties were improved compared to MA754 alloy. As the content of low melting point alloy in the composite powder increases, the alloy structure first becomes small and uniform, then acicular aggregate phases and coarse block phases appear. The tensile strength of the alloy shows a trend of first increasing and then decreasing. When the sintering temperature is 1025 ℃ and the content of low melting point alloy powder in the composite powder is 3 wt.%, the alloy has the highest tensile strength of 951.87 MPa, which is significantly improved compared to commercial MA754 alloy.

    • Sun Yetao, Feng Jietao, Yin Jiaxin, Wang Rong, Wang Deqing, Li Chengjun, Wang Yingmin, Fang Canfeng

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240098

      Abstract:In order to investigate the effect of Be on the transformation of Fe-containing phases during solution treatment, a series of experiments combining Be with different solution treatment processes were designed, and the intrinsic relationship between its effect on the morphology of eutectic silicon and Fe-containing phases and the mechanical properties was deeply studied, aiming to comprehensively improve the overall performance of the hypoeutectic Al-Si-Mg alloy. The results showed that Be delayed the decomposition of Mg2Si phase and promoted the transformation of π-AlSiMgFe phase to β-AlFeSi phase. The accelerated transformation of the morphology of the π-AlSiMgFe phase structure not only enhanced the strengthening effect, but also weakened the cleavage effect of the π-AlSiMgFe phase on the matrix, thus synchronously improving the strength and plasticity of the alloy.

    • Yu Lei, Cao Rui, Ma Jin Yuan, Yan Ying Jie, Dong Hao, Wang Cai Qin

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240100

      Abstract:The interface microstructure, micro-hardness, and tensile properties of hot isostatic pressing (HIP) densified Inconel 690 cladding on low alloy steel were investigated during the 600℃-aging process. The interface region can be divided into four zones - carbon-depleted zone (CDZ), partial melting zone (PMZ), planar growth zone (PGZ), and brownish feature zone (BFZ) - from base metal to deposited metal. 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. Micro-hardness of the interface shows that the highest hardness appears in the PGZ and BFZ region, which is related to carbon accumulation and precipitates in this region. Tensile failure occurs on the base metal side due to the high strength mismatch between these two materials and is located at the boundary of CDZ and base metal due to the lower strength of only ferrite. The ultimate tensile strength decreases by only 50 MPa after aging for 1500 h, and the interface region maintains high strength with no significant deformation.

    • SUN Yuling, LIANG Hanliang, ZHU Jiansheng, MA Honghao, WANG Luqing, ZHANG Bingyuan, LUO Ning, SHEN Zhaowu

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240103

      Abstract:In this paper, explosion welding is carried out on the basis of vacuum hot melt W/CuCrZr composite plate. Metallurgical microscopy, scanning electron microscopy (SEM) analysis and energy dispersive X-ray spectroscopy (EDS) analysis were used to observe the microscopic morphology of the bonding interface. At the same time, combined with finite element calculations, the evolution mechanism of the interface of the hot melt explosion W/CuCrZr composite plate was explored. The results show that the interface bonding of the hot-melt explosion welded W/CuCrZr composite plate is good,with 3~8μm cross-melting zone, but cracks developed on the W side; The numerical simulation reproduces the changes of combined interface pressure, stress, strain and internal energy in the process of hot melt explosion welding. The location of the crack generated by the experiment coincides with the high stress position calculated by numerical simulation.The high pressure and high temperature near the hot-melt explosion welding interface further promote the bonding of the interface.

    • Huang Wei, Li Jun, Liu Ying

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240104

      Abstract:Using high-purity tungsten powder and amorphous boron powder as raw materials, high-purity W2B alloy powder was efficiently synthesized at low temperatures by mechanical activation and combination reactions. The effects of mechanical activation time on the morphology, particle size distribution, and specific surface area of the powders were investigated, and the relationship between phase composition, synthesis temperature, and reaction mechanism was elucidated. The results indicated that mechanical activation could effectively refine the particles, and the surface area and dislocation density of the powder increased as the mechanical activation time lengthened. The content of the W2B phase in the reaction-synthesized powder increased as the mechanical activation time increased. After 20 hours of mechanical activation, the true density of the reaction-synthesized powder reached 17.01 g/cm3, with the W2B phase content of 96 wt%. The powder synthesized by thatcontained 23 wt% more W2B phase compared to the powder without the mechanical activation reaction. During the synthesis reaction, the B atoms diffused into the W matrix, resulting in the formation of the low-density WB phase. Mechanical activation introduced a significant number of dislocation defects, which created a channel for atoms diffusion and accelerated the transformation of the WB phase to the W2B phase.

    • Luo Jiajun, Quan Ciwang, Zhang Jianjun, Chen Shuixiang, Zhang Xitong, Hang Mengyao, Liang Bingliang, Chen Weihua

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240105

      Abstract:In this paper, core-shell MoSi2@Nb powder was successfully prepared by electrostatic layer self-assembly method. Zeta potential of the suspension were tested by Zeta potentiometer. SEM, TEM and EDS were used to characterize the phase, morphology, structure and element distribution of synthetic materials. The results showed that when the SDS concentration was 2mmol/L, the CTAB concentration was 3mmol/L and the pH value of Nb suspension was 5, the coating effect was better after secondary cladding. NbSi2 phase was found at the interface between Nb and MoSi2 after calcination at 200℃ for 2h in Ar atmosphere under HRTEM and XRD analysis, indicating that Nb is highly active and reacts with Si. Then, the fact that core-shell structure was still retained in MoSi2@Nb material after SPS at 1450℃ for 2h with uniaxial pressure 40Mpa under the SEM and EDS analysis. However, XRD results shown that Nb reacted strongly with MoSi2, and most of the Nb phase was reacted. This issue needs to be addressed in subsequent studies. But, compared MoSi2 material (KIC=3.32 MPa?m0.5), the fracture toughness of MoSi2@Nb material has been significantly improved to 5.75 MPa?m0.5.

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

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240107

      Abstract:High-strength Cu/Al2O3 composites usually exhibit obviously deteriorated electrical conductivity when compared with their low-strength counterparts. In this work, a chemical and mechanical alloying-based strategy was adopted to fabricate an ultrafine composite powder with low-content reinforcement and construct 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 interior. As a result, the composite showed an excellent combination of high tensile strength (654±1 MPa) and high electrical conductivity (84.5±0.1% IACS), which was ascribed to the synergistic strengthening effect of ultrafine grains, dislocations and in-situ Al2O3 nanoparticles. This approach using ultrafine composite powder with low-content reinforcement as a precursor followed by low-temperature and high-pressure sintering may have the potential to be applied to large-scale industrial production of high-performance oxide dispersion strengthened alloys.

    • lijuan, liuchang, wanglu, lidongting, zhouliyu, liuying

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240108

      Abstract:In order to improve the hardness and wear resistance of titanium (Ti), in this paper, it is proposed to introduce TiB2 hard phase into pure titanium (Ti), accurately control the reaction process of the two based on the discharge plasma sintering (SPS) technology, and construct a TiB2-TiB-Ti "hard-core-strong-interface" structure in Ti matrix that inherits the diffusion path of B elements. Finally, at 40% TiB2 addition, a high hardness of 863.5 HV5 at room temperature and 720.9 HV5 at 400℃ in the middle and high temperatures is obtained, which makes its friction performance better than that of commercial TC4 high-temperature titanium alloys under the same friction conditions in the temperature range from room temperature to 400℃. At the same time, thanks to its excellent bonding interface, the alloy also exhibits unique high-temperature and high-toughness properties, maintaining a high compressive strength of 1120 MPa and compression of more than 10% at 400℃. The design concept of this study is inspirational and useful. The design idea of this study is inspiring and universal, which is expected to provide a new method for the research and development of new medium-high-temperature and high-toughness wear-resistant titanium alloys, and to promote the application of related materials in aerospace field.

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

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240109

      Abstract:Laser beam welding was used to join a near-β titanium alloy (Ti-3Al-6Mo-2Fe-2Zr), and afterwards, aging treatment at different temperatures were conducted on the laser welded joints. The relations among aging temperature, microstructure, and tensile properties of joints were revealed in detail. For as-welded joints, the fusion zone features primarily single β phase. The reason is attributed to the high Mo equivalency of this alloy and the fast cooling rate in laser beam welding. After aging treatments, a large amount of α precipitates forms in the fusion zone and HAZ. The rising aging temperature coarsens α precipitates and reduces the volume fraction. Compared with the as-welded joints, the joints’ tensile strength and elongation are improved after undergoing aging treatments. The increasing aging temperature weakens the strengthening effect because of the decreasing volume fraction of α precipitates. After the 500°C/8h aging treatment, 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.

    • 宋博, Honglei Xi, Yu Fu, Junshuai Wang, Wenlong Xiao, Yanbiao Ren, Chaoli Ma, Lian Zhou

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240111

      Abstract:The influence of pre-strain on phase transformations, microstructures and hardening response in near β Ti alloy Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe (wt.%) during aging treatment is studied in this work. The results showed that obvious α phase refinement and stronger age hardening effect can be achieved when slightly deformed before aging treatment. Because the intermediate phases (O′, ω and O′′) formation suppressed long-range stress induced martensitic transformation and mechanical twinning, the samples were mainly deformed via dislocations slipping during loading. Numbers of crystal defects were generated during pre-deformation. With the pre-strain increasing, the number density of dislocations increased gradually. These crystal defects generated by pre-deformation would partly annihilate upon early aging, but the precipitation of α was also be promoted and resulted in refined α precipitates. In the sample pre-strained to 5 %, the average thickness of α precipitates was decreased by 57 % during aging at 600 oC than the unstrained sample, and the number density was increased from 7.0±1 laths/μm2 to 22.0±3 laths/μm2. Some platelet-shaped α were formed when the samples experienced comparably large pre-strains, i.e. 12 % and 20 %. It proved clearly that the refined α precipitates and higher hardening effect could be obtained by pre-deformation plus aging treatment in titanium alloy.

    • Wang Chunhui, Yang Guangyu, Qin He, Kan Zhiyong

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240112

      Abstract:The I phase (Mg3GdZn6, icosahedral quasicrystal phase) is widely considered as the strengthening phase in Mg-Zn-Gd system alloys, offering more significant improvements in the mechanical properties compared to the W phase (Mg3Gd2Zn3, cubic phase). However, both the W phase and the I phase typically coexist in the as-cast Mg-Zn-Gd alloy, thereby weakening its mechanical properties. There has been limited systematic research dedicated to investigating the crystallization mechanism of these phases during solidification. In this study, the equilibrium solidification and Scheil solidification paths of Mg-xZn-2Gd (x = 0~12, wt.%) alloys were calculated using Thermo-Calc software. The effects of cooling rate and alloy composition on the fraction of the I phase were studied. The results show that the equilibrium solidification structure of the alloy with a Zn/Gd atomic ratio of 6.0 only contains the I phase. In contrast, limited solute diffusion in the solid phase hampers the transformation of the W phase into the I phase during non-equilibrium solidification, forming a mixed structure composed of both the W phase and the I phase. The variation of cooling rate and alloy composition affects the solute enrichment rate in the Liquid during the solidification process of the primary α-Mg phase, alters the solute content and temperature of the residual Liquid when the secondary phase begins to crystallize, and influences the type and fraction of the secondary phase as determined by the solidification driving force. Higher solidification cooling rates and an increased Zn/Gd atomic ratio inhibit the W phase and promote the formation of the I phase during Mg-Zn-Gd alloy preparation, resulting in the alloy with a higher proportion of the I phase.

    • Luan Lijun, Xu Changyan, Zhang Ziqiu, Xie Haichen

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240113

      Abstract:The garnet type CexY3-xFe5O12 doped with Ce3+ was prepared by an optimized sol-gel method (x = 0, 0.1, 0.2, 0.3; Ce:YIG) crystal, the optimal solution is to obtain crystals with no derived impurities and high magneto-optical properties by pre-sintering and sintering in a wide temperature range of 900-1400 ℃. Thermogravimetric analysis was used to determine the synthesis temperature of the crystal at 890 ℃. XRD results show that the crystal lattice constant varies from 12.37241 ? to 12.4121 ?, and the impurity phase CeO2 appears when Ce > 0.2. SEM analysis shows that the grain size of Ce:YIG increases with the increase of sintering temperature and Ce3+ content, and its size distribution ranges from 0.257 to 6.52 mm, which is the maximum size of YIG crystal obtained at present. All Ce: YIG samples were ferromagnetic at room temperature, with saturation magnetization varying from 23.47 to 28.10 emu/g. The permeability of Ce0.1Y2.9Fe5O12 crystal sintered at 1200 ~1300 ℃ is as high as 3.68 ~ 3.90. According to the relationship between Faraday rotation Angle and permeability, the crystal sintered in this temperature range is likely to obtain the best Faraday rotation performance.

    • CHEN Jianbo, YANG Xiaojiao, YANG Ningjia, NIU Yibo, OUYANG Linfeng, Ying Liu

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240114

      Abstract:Kilogram-scale micro-nano SrVO3 powder was produced with the sol-gel method combined with hydrogen reduction and heat treatment. Then SrVO3 bulks were prepared by cold pressing and sintering the sifted powders using different mesh sizes (unsifted powder, 100 mesh, 200 mesh, and 300 mesh). The thermal stability of SrVO3 powder and bulks under air was investigated, and the effects of powder granularity sifting on granularity and distribution of their raw material, bulk grain size, and electrical conductivity were also evaluated. The results show that: SrVO3 bulk has better thermal stability in air than SrVO3 powder; the temperature at which oxidative weight increase occurs is enhanced from 335 °C for the powder to 430 °C for the bulk. The mean particle size of the raw material powders decreases, the electrical conductivity of the related cold-pressing sintering bulks is significantly raised, and the conductivity of the powders rises with increasing granularity sifting mesh. Granularity sifting can be used to acquire smaller and more uniform powder raw materials, which will increase the density of the bulks produced by cold-pressing sintering. Furthermore, the material’s more effective routes for the conduction of electric charge are established and the conductivity of the prepared SrVO3 bulk reaches 20,000 S/cm, which is 37% higher than that of the bulk produced by unsifted powder. Granularity sifting is essentially the optimization of the raw material’s particle size. More sifting of the SrVO3 powder’s particle size is expected to yield improved bulk material performance, providing the foundation for its use in transparent conductive films, semiconductor devices, sensors, and other areas.

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

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240115

      Abstract:In this paper, the microstructure and corrosion behavior of a 1.0 wt.% Gd duplex stainless steel annealed at different temperatures were studied. Electron microscopy revealed that the content of secondary Gd-containing phase was increased along with the increasing annealing temperatures and then decreased at 1080℃ as an inflection point. A dual-phases M-Gd intermetallic with M3Gd as the core phase and M12Gd as the shell was the main type of secondary phase in the sample annealed at 1080℃. In the sample annealed at 1140℃, M3Gd phase was dominant. The corrosion behaviors of the two annealed steel samples were analyzed in NaCl, HCl and H3BO3 solutions. It showed that the sample annealed at 1140℃ had lower corrosion rate. M3Gd was more electrochemically active than M12Gd when the sample was immersed in NaCl and HCl solutions but more noble in H3BO3 solution.

    • Hao Huirong, Wang Jiawei, Zhao Wenchao, Ren Jiangpeng

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240116

      Abstract:The present study uses a predictive model to design a heavy-duty metal rubber (MR) shock absorber used to mount the powertrains of heavy-load mining vehicles. The microstructural characteristics of the wire mesh are elucidated using fractal graphs. A numerical model based on virtual fabrication technology is established to inform a design scheme for the proposed wire mesh component. Four sets of wire mesh shock absorbers with various relative densities are manufactured. A predictive model based on these relative densities is established through mechanical testing. To further enhance the predictive accuracy, a variable transposition fitting method is introduced to refine the model. Residual analysis is employed to quantitatively validate the results against those obtained from an experimental control group. The findings demonstrate that the improved model exhibits higher predictive accuracy than the original model, with the coefficient of determination (R2) reaching 0.9624. This study provides theoretical support for designing wire mesh shock absorbers with reduced testing requirements and enhanced design efficiency.

    • Xu Qinsi, Zhang Mingchuan, Liu Yi, Cai Yusheng, Mu Yiqiang, 任德春, Ji Haibin, Lei Jiafeng

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240118

      Abstract:The "bond line" of the diffusion bonding interface is a common characteristic of the diffusion-bonded region in nickel-based superalloys. It significantly impacts the performance of the diffusion joint. Thermal deformation machining is an effective method to improve the microstructure and properties of a diffusion bonding interface. In this study, the thermal deformation behavior of the GH4169 alloy diffusion-bonded region was investigated at a deformation temperature of 1213~1333 K with a strain rate of 0.01~10 s-1 using a Gleeble 3800 thermal-mechanical simulation test machine. The results show that the "bond line" in the diffusion bonding region of GH4169 alloy can be effectively eliminated through thermal deformation. The evolution of the δ phase in the diffusion bonding interface region is affected by deformation conditions. When the deformation temperature is lower than the solution temperature of the δ phase, the residual spheroidized δ phase prevents the growth of recrystallization nucleation grains and affects the subsequent recrystallization process. The spheroidization degree of the δ phase can be enhanced by reducing the strain rate. When the deformation temperature exceeds the dissolution temperature of the δ phase, the dissolution of the δ phase creates an extra driving force for recrystallization, thereby significantly enhancing the extent of recrystallization. A hyperbolic sinusoidal Arrhenius constitutive equation, incorporating strain compensation, is used to describe the correlation between flow stress and deformation conditions in the diffusion-bonded region of the GH4169 alloy. The calculated values of the constitutive equation agree with the experimental values. According to the dynamic model of the GH4169 alloy diffusion bonded region, the optimal processing parameters have been determined. The deformation temperature is 1310~1333 K, and the strain rate is 0.01~0.05 s-1.

    • Yu Zhiqi, liu Tianzeng, Zhao Yanchun, Feng Li, Li Jucang, Pan Jixiang

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240122

      Abstract:In this paper, the static corrosion experiment of 347H stainless steel alloyed with Cu and Mo elements was carried out in nitrate (60 % NaNO3+40 % KNO3) at 565 °C for 720 h. The effects of Cu and Mo elements on the corrosion resistance of 347H stainless steel in molten salt were studied by analyzing the phase composition, microstructure and chemical composition of the corrosion products. The results show that the grain refinement of Mo element makes the stainless steel have the best corrosion resistance of medium grain size. Furthermore, the formation of MoC contributes significantly to enhancing the intergranular corrosion resistance of the stainless steel. The stainless steel exhibited uniform corrosion in the nitrate solution. The corrosion layer displayed a dual-layer structure, with corrosion products of the protective matrix present in both the inner and outer layers. The outer layer comprised a mix of Fe oxide (Fe2O3, Fe3O4), NaFeO2, and a minor portion of MgFe2O4. Conversely, the inner layer primarily consisted of a spinel layer (FeCr2O4, MgCr2O4) and a thin Cu2O layer. The oxidation of Cu in the inner layer led to the development of a dense Cu2O layer, effectively impeding O2- plasma infiltration into the matrix.

    • lujianqiang, wanglinlin, oumeiqiong, houkunlei, wangmin, wangping, mayingche

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240125

      Abstract:As the thrust-to-weight ratio of the aero-engine increases, the turbine inlet temperature increases significantly, leading to a significant increase in the service temperature of other key hot-end components. In the process of service, nickel-based superalloys need to withstand the combined effect of high temperature, stress and environment, and the alloy surface will inevitably occur high temperature oxidation. High temperature oxidation often preferentially penetrates along grain boundaries, resulting in micro-voids and micro-cracks at grain boundaries, which seriously affects the properties of the alloy. Therefore, it is necessary to explore ways to improve the oxidation resistance of alloys at high temperatures. In this work, the effect of Hf on oxidation behavior of K4800 nickel-based superalloy was studied. The results show that the oxidation weight gain of K4800 and K4800+0.25Hf alloys increases with the extension of exposure time during static oxidation at 800℃ and 850℃, and the oxidation kinetics curves follow the parabola rule. However, the initial static oxidation rate of K4800+0.25Hf alloy (0.0265 g/m2·h at 800°C for 20 h and 0.0617 g/m2·h at 850°C for 20h) is lower than that of K4800 alloy (0.041 g/m2·h at 800°C and 0.0669 g/m2·h at 850°C). The oxide layer of the two experimental alloys comprises an outer oxide layer and an inner oxide layer.The outer oxide layer primarily consists of dense Cr2O3, while the inner oxide layer mainly contains dendritic Al2O3. However, with the Hf content increasing from 0 wt.% to 0.25 wt.%, the thickness of the Cr2O3 outer oxide layer decreases from 2.71 μm to 2.17 μm after oxidation at 800°C for 1000 h and from 5.83 μm to 4.09 μm after oxidation at 850°C for 1000 h.The results of EPMA analysis indicate the formation of HfO2 at the grain boundary of the oxide layer in the K4800+0.25Hf alloy, promoting the formation of Al2O3 around HfO2 and accelerating the growth of Al2O3. The presence of Al2O3 and HfO2 at the grain boundary contributes to reducing the outward diffusion rate of Cr3+ and delaying the thickening of the Cr2O3 oxide layer. Consequently, the addition of Hf enhances the oxidation resistance of the K4800 alloy.

    • Guo Peimin, Shen Yaozong, Wang Lei, Kong Ling-bing, WANG Dond-xin, GUO Qing

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240130

      Abstract:Modern methods of beryllium metallurgy are based on the theory of sulfuric acid dissociation and chemical purification. Since the high solubility of sulfate produced by sulfuric acid dissociation and the overlap of the condition interval of the chemical method of separation resulted in low purity of the beryllium product and the presence of Be2+ in the separated phase, which would form a hazardous waste and reduce the yielding rate of beryllium. A transformative beryllium metallurgy theory and methodology based on the low-temperature dissociation of hydrofluoric acid and purification by exploiting the large difference of fluoride solubility is proposed. Hydrofluoric acid can quickly dissociate beryllium ore powder directly at low temperature or room temperature with a dissociation rate of more than 99%. The solubility of AlF3, FeF3, CrF3 and MgF2 is low. Coupled with the presence of common ion effect, 99.9% beryllium products can be prepared without chemical purification. For high-purity beryllium products of grade 4N or higher, high-purity beryllium can be prepared by utilizing the superior property that the pH intervals of iron, chromium, and other hydroxide precipitates are distinctly different from the pH intervals corresponding to Be(OH)2 precipitates. The new method covers a wide range of beryllium products that can be prepared by modern beryllium metallurgy.

    • GuoShuGuo, LiuQuan, JiaZheng, KouRongHui, LiuxuDong

      Available online:June 26, 2024  DOI: 10.12442/j.issn.1002-185X.20240131

      Abstract:In this paper, The effect of Y on the homogenization of Mg-6Zn-0.25Ca in terms of corrosion resistance was studied. The microstructure and corrosion resistance of the homogenized Mg-6Zn-0.25Ca and Mg-6Zn-1Y-0.25Ca alloys were investigated by XRD, OM, SEM, weight loss, hydrogen evolution and polarization curve experiments. The results show that the second phase of the homogeneous Mg-6Zn-0.25Ca alloy is Mg2Ca, and the average grain size increases slightly after the addition of Y element, the Mg2Ca phase decreases, and new second phases Mg12ZnY and Mg3Y2Zn3 are generated, and the volume fraction of the second phase increases and the distribution is more uniform. This results in the formation of a denser and more compact corrosion film on the magnesium matrix in the corrosion test, which can act as a barrier, and the newly formed Mg12ZnY and Mg3Y2Zn3 are distributed near the grain boundary or between the branches, and the electrochemical performance is low. These results reduce the hydrogen precipitation of Mg-6Zn-0.25Ca alloy in 3.5% NaCl solution, increase the self-corrosion potential of Mg-6Zn-0.25Ca alloy by increasing the Y element, and reduces self-corrosive current density. These improve the corrosion resistance of homogeneous Mg-6Zn-0.25Ca alloys. Therefore, the corrosion resistance of Mg-6Zn-1Y-0.25Ca alloy is much higher than that of Mg-6Zn-0.25Ca alloy.

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    Latest number
    Rare Metal Materials and Engineering
    2024,Volume 53, Issue 7
    Editor in chiefPingxiang Zhang
    Associate editorYingjiang Shi
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