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Quick Search     Adv Search   2022 Vol. 32, No. 01 Published: 2022-02-10   1 Recent development of fourth generation powder metallurgy superalloys in America and Europe Hot! ZHANG Yiwen，LIU Jiantao，JIA Jian，LIU Mingdong，LI Xiaokun， BAI Jiaming，ZHANG Haopeng，LI Xinyu，XING Pengyu DOI: 10.13228/j.boyuan.issn1006-6543.20210105 In order to meet the service requirements of advanced aero- engines, especially hot- end components such as high-pressure turbine disks, it is extremely necessary to develop higher-performance fourth generation powder metallurgy superalloys. The characteristic of these materials is the achievement of a maximum service temperature of 815℃. In this review, the fourth generation PM superalloys developed by the United States and the United Kingdom in the past decade has been introduced. The main content is focused on ME501 and TSNA-1 alloys developed in the US, and novel alloys developed in the UK (including high-Co and Ta content alloys, low-cost alloys with high-Ta content and a series of RRHT alloys with high-Nb content). The design characteristics of the chemical composition, microstructure stability, mechanical properties and oxidation resistance of these alloys are concerned in this paper. 2022 Vol. 32 (01): 1-14 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 15 Preparation and properties of spherical tungsten powders by plasma rotating electrode process for additive manufacturing Hot! LI Xiaohui，CHEN Binke，FENG Zhihua，YANG Xingbo DOI: 10.13228/j.boyuan.issn1006-6543.20210017 The melting point of tungsten and its alloys is as high as 3 410 ℃, and it has the characteristics of high temperature strength, good heat and corrosion resistance, etc., and is widely used in aerospace, military, nuclear power and other fields. These characteristics also make tungsten products difficult to process during forming and post-processing, especially in the deep processing process; and the price of tungsten is also high, so the utilization rate of raw materials is also particularly important. Metal 3D printing technology is known as one of the key technologies leading the "third industrial revolution". Compared with traditional processing technology, it has extremely high material utilization rate. It is especially suitable for free design of complex structures and integrated forming of complex parts, it is an important supplement to traditional tungsten processing technology. Metal 3D printing is the main research direction of advanced manufacturing technology. Metal powder, as its most important raw material, directly affects the performance of printed products. The spherical tungsten powder was prepared by plasma rotary electrode atomization technology, and the particle size distribution, oxygen content, micromorphism and surface tissue of tungsten powder were characterized by laser particle size analyzer, O-N analyzer, scanning electron microscope (SEM). The results show that the spherical tungsten powder particle size is concentrated in a single- peak distribution of 45~150 μm, the measured average particle size of 80 μm is close to the theoretical average particle size of 85.5 μm. The oxygen increment of tungsten powder is less than 0.001 5%, and the average oxygen content of the 45~150 μm powder is 0.000 93%, the oxygen increment is 0.000 38%, and the average oxygen content of the 15~53 μm powder is 0.002%. The oxygen increase is 0.001 45%. The surface of the 15~53 μm tungsten powder is smooth and clean, and the surface morphology of the 45~150 μm tungsten powder is relatively small petal- like cellular dendrites with almost no hollow powder. Tungsten powder has excellent physical properties, fluidityis 6.0~6.2 s/50g, loose density is 11.26~11.35 g/cm3, tap density is 12.4~12.5 g/cm3, and the performance of tungsten powder with a particle size of 45~150 μm is better than that of 15~53 μm. This research conducted a comprehensive evaluation of the chemical composition, surface morphology, cross- sectional morphology and physical properties of spherical tungsten powder prepared by PRPE technology, revealing the advantages of PRPE technology for preparing high-quality refractory metal powders, and at the same time it helps promote the application of high-quality refractory metal powders in areas such as additive manufacturing and powder metallurgy. 2022 Vol. 32 (01): 15-19 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 20 Investigation on the PM technology and induction heat treatment processes of the dirve sprocket for oil pump Hot! ZHAO Hongli，WU Mei，LUO Zan，LUO Cheng，WANG Tianguo，BAI Haolong DOI: 10.13228/j.boyuan.issn1006-6543.20210018 Powder metallurgy is a kind of green manufacturing technology with high efficiency, low consumption and material saving. However, the powder metallurgy parts have pores, uneven density, low strength and hardness, which limit its applications. This paper mainly studies the powder metallurgy forming and sintering process flow of the sprocket of the oil pump transmission mechanism, as well as the inductor design and the key parameters of the induction quenching process of the sprocket. The results show that the density of the sprocket compaction is higher than 6.7 g/cm3, and the hardness of the sprocket compaction reaches 76HRB after copper penetration and sintering at 1 100-1 120 ℃. The hardness of the sprocket compaction reaches 71HRA after induction quenching with 60kW power, which meets the performance requirements of the product. The service life of sprocket is extended effectively. 2022 Vol. 32 (01): 20-24 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 25 Comparison between extrusion surface densification and rolling surface densification Hot! DING Xia，PENG Jingguang，CHEN Di DOI: 10.13228/j.boyuan.issn1006-6543.20210030 Selective surface densification process mainly includes extrusion densification and rolling densification. Based on the production of surface densified parts, this paper compared and analyzed the differences between extrusion densification and rolling densification from the aspect of parts performance testing. The experimental results show that a uniform surface dense layer can be formed at the tooth profile of the parts prepared by the two processes, and the surface strength and hardness of the parts are greatly improved. Extrusion densification process will lead to flanging on the end face of sintered parts, which is easy to cause appearance quality problems of subsequent sintered parts, while rolling densification process will not produce similar appearance quality problems. In the extrusion densification process, the extrusion feed depends on the die size, which can not be adjusted at will, and it will change with the wear of the radial size of the die. In the rolling densification process, the rolling feed can be quickly adjusted by adjusting the distance between the central axis of the two roller dies, and the required surface densification layer can be prepared. Therefore, rolling densification is better than extrusion densification. 2022 Vol. 32 (01): 25-30 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 31 The relationship between deformation mechanism and porosity performance of metal fiber felt Hot! HOU Liqiang，LUWenjing，LU Xiaofeng，ZHANG Xiaoqing DOI: 10.13228/j.boyuan.issn1006-6543.20210022 In order to explore the effects of different strain variables on the pore characteristics of metal fiber felt, the relationship between deformation mechanism and pore performance of metal fiber felt were analyzed. Using stainless steel fiber with diameter of 6 μm and 22 μm as raw material, metal fiber felt of certain thickness was sintered at high temperature through stacking, the changes of strain, porosity, air permeability, first bubble point pressure and compression ratio of fiber layer were tested under the compressive strength of 5,10, 15, 20, 30 and 40 MPa.The results show that the ability of fiber felt to resist compression deformation increases with the increase of strain, and the compression curve can be divided into two stages: weak deformation strengthening and strong deformation strengthening. The resistance of 22 μm fiber layers to initial deformation are less than 6 μm fiber layers. In the initial compression strain stage, the porosity and the pore diameter of compound ((6+22) μm) fiber felt decrease slowly, the resistance to gas and bubble point pressure have little scope to rise, suggesting that the compression strain has little impact on the filtration performance. However, when the compression strain exceeds 40%, the porosity of fiber felt decreases obviously and the trend of gas permeability and bubble point pressure intensifies, which has a serious impact on the filtration effect. Comparing the thickness changes of 6 μm and 22 μm fiber layers during compression, it can be seen that in the original metal fiber felt structure, 22 μm fiber layers have much larger pores than 6 μm fiber layers, performing the weak deformation resistance and low compression stress and becoming the main part of the initial deformation. With the increase of compression stress, 22 μm fiber layers are densified rapidly and the part bearing the overall deformation change to 6 μm fiber layers, then the pore change becomes a greater impact on the filtration performance. Until the deformation reaches the limit, it turns to 22 μm fiber to bear the deformation again. The whole deformation shows the alternate deformation mechanism of the coarse is fiber layers - the fine fiber layers - the coarse fiber layers. 2022 Vol. 32 (01): 31-35 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 36 Study on friction and wear properties of Cu-C-SnO2 porous materials sintered by powders Hot! ZHU Mingtao，MENG Yunna，FAN Yali，LU Chen，HOU Yushan，NI Feng DOI: 10.13228/j.boyuan.issn1006-6543.20200276 Copper- graphite composite material is an excellent electrical conductive wear- resisting material. But the wettability of copper and graphite is very poor, resulting in deficient wear resistance of the material. In this paper, Cu- C-SnO2 porous materials were prepared by powder metallurgy adding SnO2 which had good affinity to graphite. The effects of sintering temperature and composition proportion on porosity, physical properties, friction and wear properties of the Cu-C-SnO2 porous materials were investigated. The experimental results show that the porosity of the sintered body decreases with the increase of sintering temperature or non-metal/Cu mass ratio, and increases with the increase of graphite/SnO2 mass ratio. The density, hardness, and oil penetration rate of sintered body are closely related to the porosity. As the porosity increases, the density and hardness show a decreasing trend, and the oil penetration rate shows an upward trend. However, the hardness of the sample changes complicatedly due to the influence of Cu2O production and the recrystallization of Cu particles, and a sudden change occurs near the sintering temperature of 830 ℃. Under dry friction conditions, the friction and wear characteristics of the sample are affected by multiple factors such as material hardness and graphite phase self-lubrication, and the wearrate decreases with the increase of sample hardness or graphite content. After oil impregnated treatment, the friction and wear characteristics of the sample are mainly controlled by oil film lubrication. Compared with dry friction, the relative friction factor and wear rate are significantly reduced. The wear rate of the sample decreases with the increase of the oil penetration rate, but there is a sudden saltation near the graphite/SnO2 mass ratio of 0.155. 2022 Vol. 32 (01): 36-44 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 45 Study on optical properties of graphene oxide Hot! XING Ruzhen，JIANG Xu DOI: 10.13228/j.boyuan.issn1006-6543.20210019 The optical properties of single layer graphene oxide (GO) aqueous dispersion were studied in this paper. The relations of concentration and excitation wavelength to optical spectra were discussed. The results show that there is a wide absorption peak in the range of 360-500 nm and a sharp absorption peak centered at 360 nm for the higher concentration samples, and there have absorption peaks at 230 nm and 300 nm for the lower concentration samples. Under 365 nm excitation, the emission peak position changes from 560-600 nm to blue emission with the concentration decrease. For 0.4 mg/ml sample, the emission peak position is not affected by the excitation wavelength obviously, but the emission intensity changes obviously and the emission peak is very broad. For 0.02 mg/ml sample, emission peak is fairly sensitive to excitation wavelength, for this, graphene oxide will be of great potential applications in tunable photoelectric areas. 2022 Vol. 32 (01): 45-49 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 50 Microstructure and Mechanical Properties of TA1 Titanium Alloy Prepared by Selective Laser Melting Hot! ZHENG Yun DOI: 10.13228/j.boyuan.issn1006-6543.20210095 The microstructure and properties of TA1 alloy prepared by selective laser melting (SLM) were investigated. The results show that the TA1 alloy prepared by SLM has excellent mechanical properties and its tensile strength, elongation and reduction of aera all meet the requirements of GJB 2744A-2007. Especially the tensile strength reaches more than 600 MPa. The performance of the 3D printed parts is slightly different in different printing directions XYZ. The Y direction is the best, the X direction is better, and the Z direction is good(580 MPa). After annealing, the samples have more uniform microstructure, and the tensile strength, shrinkage and hardness of the samples reduced slightly, and the elongation increased slightly. The TA1 alloy prepared by SLM can replace forgings in the application of complex precision parts, and save raw materials, which may be providing reference for the printing application of 3D printing TA1 alloy. 2022 Vol. 32 (01): 50-54 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 55 Sintering properties and conductivity of BaZrO3-xNa2CO3 powder alloys for semiconductors Hot! GUO Meili，LIU Yi DOI: 10.13228/j.boyuan.issn1006-6543.20190257 In order to improve the comprehensive properties of BaZrO3 powder alloy for semiconductor, the mixed powders were added with different proportions of sodium salt (Na2CO3), heated to 1 360 ℃ and sintered for 3 h, and the sintering properties and electrical conductivity were characterized by experiments.The results show that pores are formed in the cross-section area of the sample, and most of the grain sizes are between 0.5 and 0.7 μm. When the addition amount of BaZrO3 increases to 10%, dispersed pores are formed in the microstructure of powder alloy, and higher density is obtained. With the increase of sintering temperature, the density and shrinkage of the sample increase obviously.The addition of Na2CO3 is beneficial to complete the sintering process of BaZrO3 powder alloy, and the microstructure of powder alloy becomes more dense through liquid phase sintering. Adding appropriate content of Na2CO3 can lower the sintering temperature of BaZrO3 powder alloy, and obtain better sintering effect. The electrical conductivity of BaZrO3-Na2CO3 powders increases with the temperature increasing. The addition of Na2CO3 can improve the ionic conductivity of BaZrO3 powder alloy 2022 Vol. 32 (01): 55-58 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 59 Characterization of HAl77-xTi aluminum brass alloy for heat exchange tube preparation by powder metallurgy Hot! WANG Yanqin，HUANG Jin DOI: 10.13228/j.boyuan.issn1006-6543.20200025 Ti and HAl77 powder were fully mixed and then subjected to discharge plasma sintering treatment and hot extrusion. The changes of phase structure and microstructure distribution caused by Ti addition in aluminum brass under different solid-phase sintering processes were analyzed, and the interface microstructure and mechanical strength of samples were tested.The results show that there are two kinds of microstructure phases in HAl77 matrix without adding titanium. After the addition of Ti element, a number of dispersed second- phase grains are formed in the HAl77 matrix. When the Ti content gradually increases, the second-phase particles obtained also continue to increase, showing an irregular shape structure, the mechanical properties of the alloy samples change linearly, the mechanical properties of aluminum brass were improved. In addition, the number of microcracks decreases, forming more dimples and presenting uniform distribution at the fracture site. Under the action of external force, the dislocation will make Ti and Cu2Ti4O particles interact, hinder the deformation of the matrix, and significantly improve the alloy strength. 2022 Vol. 32 (01): 59-63 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 64 Study on surface microstructure and properties of titanium alloy based on TiC/TiB2 laser cladding Hot! SONG Xiaolei DOI: 10.13228/j.boyuan.issn1006-6543.20200053 The TiC/TiB2 composite coating was prepared by laser cladding on titanium alloy surface. The microstructure, microhardness and wear resistance of TiB2+15%TiC composite coating were analysed by SEM, microhardness tester and friction and wear equipment respectively. The results show that the upper part of the coating is mainly composed of coarse TiB2 dendrites and a small amount of white granular TiC/TiB eutectic microstructure, while the middle part of the coating is mainly composed of rod- like, fine needlelike TiB2 phase and small block TiC phase. The lower part of the coating is composed of dendritic phase, massive TiB2 phase, large flake TiC phase and a small amount of minor flake TiAl intermetallic compound. The hardness of the coating (960HV0.2) is about 2.7 times of that of the substrate (350HV0.2). The wear resistance of the coating is improved significantly, and the coating appears less peeling, slight wear marks and particle debris, and the surface of the substrate is mainly furrow wear. The wear of the coating is 1.132 mg, 20% of that of the substrate (5.342 mg). 2022 Vol. 32 (01): 64-68 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 69 Study on the technology of gas atomization for production of 3D printing metal powders Hot! YANG Jun，WANG Xiaofeng，GE Zhenghao DOI: 10.13228/j.boyuan.issn1006-6543.20200213 In the metal 3D printing industry, powder is used as a direct raw material, and its preparation methods are diverse. At present, the application of gas atomization pulverizing technology is the most widely used. This article mainly summarizes the main performance parameters of metal powder and the basic principle of preparing metal powder by gas atomization. According to the different atomization nozzles and heating elements, a variety of gas atomization technologies are derived. For these technologies, a simple explanation, analysis and comparison are carried out. Among them, the close-coupled gas atomization technology is widely used, and the non-crucible electrode induction melting gas atomization is suitable for the preparation of active metal powder. Finally, the technology of preparing 3D printing metal powder by gas atomization method is summarized. 2022 Vol. 32 (01): 69-77 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 78 Research progress on catalytic doping modification of Li-Mg-B-H hydrogen storage system Hot! ZHOU Zhangwei，LIU Chunrong，HU Chuan，ZHAOWang，LONG Kewen，LI Ping DOI: 10.13228/j.boyuan.issn1006-6543.20200233 This article summarizes the latest research progress of Li-Mg-B-H hydrogen storage system in recent years. In view of the high hydrogen absorption and desorption temperature and slow kinetic performance of the composite system, especially the long incubation period between the two hydrogen release steps, the research methods of catalysts doping modification in recent years are summarized, and the future research and development of this system are prospected. 2022 Vol. 32 (01): 78-85 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 86 Research progress on powder-layering and melting behavior in powder additive manufacturing Hot! SI Liang，ZHOU Mengyuan，LI Maoyuan，ZHANG Yun，ZHOU Huamin DOI: 10.13228/j.boyuan.issn1006-6543.20200258 In recent years, the powder-based additive manufacturing has become one of the fastest developing and most widely used additive manufacturing technologies with significant advantages in forming complex shapes and parts with excellent performance. The process involves complex behaviors at multiple scales, such as microstructure evolution, mesoscopic powder flow/melting, and macroscopic stress deformation. A deep understanding of these behaviors is the key to the stable forming of parts with excellent properties. In this paper, the research status of powder properties and processing conditions on powder flow stratification, and powder layer quality and processing parameters on powder melting behavior in fabrication are reviewed. 2022 Vol. 32 (01): 86-92 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 93 Research progress of pressureless sintered SiC ceramics Hot! WANG Kun，FENG Rong，YANG Shangquan，CHENG Longsheng，MENG Fanran，ZHANG Aili DOI: 10.13228/j.boyuan.issn1006-6543.20200130 Properties such as high hardness, high intensity, corrosion resistance, abrasion resistance and high elastic modulus have made SiC ceramics become the indispensable material for aerospace, power electronics and mechanical industry. However, disadvantages such as high synthesis temperature and low sinterability, have limited the fabrication of these ceramics. In recent years, with the deep research of SiC ceramics’sintering mechanism and the diversification of additives, the preparation of high- performance SiC ceramics by pressureless sintering has gradually become the most commonly used method. This paper introduced the research progress of additives in pressureless sintering SiC technology in recent years, and summarized the effects of additives and dosage, sintering temperature and time on the performance of sintering SiC ceramics. 2022 Vol. 32 (01): 93-99 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 100 Design of on-line powder classification system based on laser dry detection technology Hot! ZHANG Jinchen，LIU Zihong，XIANG Kefeng，ZENG Yangji DOI: 10.13228/j.boyuan.issn1006-6543.20210044 To improve the current situation of low efficiency and long cycle of off-line sample detection of powder classifier, an online powder classification system based on laser dry detection technology was designed and built.In the control of powder classifier, a control platform of "spiral conveying - powder sorting - dust collecting" process was built based on PLC industrial control technology. For the characteristics of small particle size and large particle speed in the process of powder selection, the closed-loop control of process regulation with particle size distribution as process feedback variable was realized by using laser dry sampling on line. According to the platform experiment, the cycle of closed loop detection system can be reduced to 1 sec and the result of on-line powder classification is consistent with that of traditional Marvin offline detection which is as high as 98.8%. On the basis of the accuracy of online detection can meet the requirements, real-time data can be obtained for feedback adjustment. The results show that the system can keep the parameters of each batch of finished product consistent on the basis of high precision online detection and feedback adjustment which can ensure that the quality of products is more stable and reliable. 2022 Vol. 32 (01): 100-105 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 106 EBSD of the factors affecting the calibration rate of pulverized beryllium materials and its solution Hot! HUANG Xugang，ZHANG Jiankang，LI Meisui DOI: 10.13228/j.boyuan.issn1006-6543.20200227 Beryllium has special physical properties and is used in nuclear and aerospace applications. As a new analysis technique, EBSD (Electron backscatter diffraction) has been used more and more widely in beryllium production. The low calibration rate of beryllium was found by the State Key Laboratory of Rare Metal Materials in the practical application of EBSD analysis of beryllium. In this paper, the residual stress on the surface of beryllium sample can be effectively reduced by optimizing the sample preparation parameters, the influence of background and noise signal can be reduced by adjusting the gain parameters of EBSD, and the identification of the disturbed information can be improved by adjusting the parameters of the parser, the calibration rate of beryllium was increased by an average of 27% by EBSD. 2022 Vol. 32 (01): 106-110 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 111 U-FAST technology in research and development of advanced materials Hot! Marcin Rosinski，DING Haining DOI: 10.13228/j.boyuan.issn1006-6543.20210040 This paper intruduces an upgraded field assisted sintering technology—U- FAST (SPS) equipment, which uses new generation pulses power technology and has very high heating speed，can be widely used in R&D of advanced materials., such as sintered carbides (WC-Co), thermoelectric materials (PbTe), Zr-Cu-Al-Nb (bulk metallic glass), composite materials, ceramic materials, biological materials and diamond enhanced composite materials( EDC), etc., and introduces the characteristics of U-FAST. The starting of the sintering process at a lower temperature and a shorter time makes the U-FAST technology an ideal tool for producing nanocrystalline and submicron materials without adverse grain growth.This electric field-assisted sintering technology will be promoted to new level by the FAST technology 2022 Vol. 32 (01): 111-116 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 117 Isothermal compression test and dynamic recrystallization of the powder metallurgy superalloy FGH4102 Hot! HOU Qiong，TAO Yu，DONG Zhiguo，LIU Qiaomu，ZHANG Guodong，QU Jinglong DOI: 10.13228/j.boyuan.issn1006-6543.20200147 Nickel-based powder metallurgy (PM) superalloys were widely used to manufacture the components in gas turbine engines owing to their outstanding mechanical properties at extremely high temperatures. In order to design a new generation aircraft engine with a higher thrust-weight ratio and satisfy the performance requirements, a fourth generation PM superalloy has been studying worldwide. The alloy FGH4102 in this study was a newly designed fourth generation PM superalloy, which exhibited excellent high- temperature stress rupture and creep properties compared with the previous three generations' PM superalloys, FGH4095, FGH4096, and FGH4098. This work aims to study the thermal deformation behavior of hot isostatic pressured (HIPed) alloy under different deformation conditions and provided a reference for subsequent extrusion and isothermal forging process parameter design. The hot deformation behavior of HIPed alloy FGH4102 was studied by using isothermal simulation compression experiments. The effects of different deformation conditions (strain rate, strain temperature, and strain variables) on the volume fraction and grain size of dynamic recrystallization were analyzed, and the role of γ 'phase in dynamic recrystallization was discussed. The results show that the dynamic recrystallization of HIPed alloy FGH4102 occurs in different degrees within the range of deformation parameters. When the strain exceeds the critical strain, dynamic recrystallization takes place first near the original grain boundary. With the increase of strain, dynamic recrystallization grains gradually replace original coarse grains, and the volume fraction of dynamic recrystallization keeps increasing. After low temperature and high strain rate deformation, the dynamic recrystallization of the alloy is sufficient, and the grain size becomes smaller than the previous. The increase of deformation temperature and strain rate decreases the nucleation rate of dynamic recrystallization and increases the grain size of recrystallization. After the deformation at 1 140 ℃, the grain grows significantly, which leads to the deterioration of the hot working property of the alloy, and the sample is prone to cracking. When deformed in the γ+γ′ two-phase region, the fine secondary γ′ phases dispersed in the matrix have an inhibitory effect on dynamic recrystallization. As the size of the initial γ′ phase increases, the inhibition of recrystallization is gradually weakened. As for the HIPed alloy FGH4102, the micron-sized γ′ phases can promote dynamic recrystallization during hot deformation. When deformed at low temperature and high strain rate, γ′ phases promote dynamic recrystallization nucleation, and recrystallized grains are relatively small. When deformed at high temperature and low strain rate, grain growth gradually dominates. Moreover, the recrystallized grain sizes are comparatively large. 2022 Vol. 32 (01): 117-124 [Abstract] ( 4 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 125 Micro-scale powder of Al-Ni-Co alloy and its SLM 3D-printed magnets Hot! ZHU XiaoYu，LIU Tao，WANG Lie，WANG shuai，FANG Yikun DOI: 10.13228/j.boyuan.issn1006-6543.20200112 Al-Ni-Co powder was prepared by inert gas atomization (IGA), and the maximum particle size of the powder was less than 150 μm after the initial screening. The morphology, phase composition and magnetic properties of Al-Ni-Co powder with different particle size range were studied by hall flowmeter, XRD, SEM and VSM. The results showed that the spheroidization rate of the powder was about 95%. The fluidity of micro-powders in the range of 50~80 μm is relatively the best. Due to small particle size, the composition segregation of micro-powders under 20 μm is serious; 80~150 μm micro-powders's surface adsorps satellite small particles, the roughness is poor; the magnetism of Al-Ni-Co powder is soft one, and the phases are AlNi and FeCo. Six groups of Al-Ni-Co cylindrical magnets were prepared by SLM method with 20~80 μm Al-Ni-Co micro powder. The density and magnetic properties of the magnets after heat treatment reached the performance of the cast Al-Ni-Co magnets, which indicated that SLM could be used to prepare 3D-printed Al-Ni-Co magnets. 2022 Vol. 32 (01): 125-132 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 4 )

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