粉末冶金技术

Preparation and research progress of AlON transparent ceramics

ZHANG Yiming, WU Haoyang, JIA Baorui, QU Xuanhui, QIN Mingli

2024, 42(2): 97-106, 134. doi: 10.19591/j.cnki.cn11-1974/tf.2021110014

Abstract(612) HTML (78) PDF(27)

Abstract:
AlON transparent ceramics have been widely used in many fields due to the excellent optical and mechanical properties. The development of AlON transparent ceramics was introduced in the paper, and the reasons affecting the light transmittance of ceramics were illustrated in terms of reflection, absorption, and scattering. The research status of the powder preparation, sintering aid system, molding technology, and sintering technology for the AlON ceramics were described in detail, the existing technical problems were analyzed, and the optimization directions were proposed.

Reaction behavior, microstructure, and mechanical properties of FeAl-316 stainless steel joints

CAI Xiaoping, YIN Jinnan, ZHANG Zhipeng, FENG Peizhong

2024, 42(2): 107-114. doi: 10.19591/j.cnki.cn11-1974/tf.2021110009

Abstract(112) HTML (19) PDF(5)

Abstract:
The effective joining between the FeAl intermetallic compounds and the 316 stainless steels was realized by the combination of thermal explosion reaction and powder metallurgy. The effect of joining temperature (700, 800, 900 ℃) on the interface composition and mechanical properties were studied. The results show that, the temperature of FeAl reaction layer rises to 1050 ℃ instantaneously when it is heated to 637 ℃, and the obvious thermal explosion reaction occurs, accompanied by the intense heat release lasting about 15 s. With the increase of joining temperature from 700 ℃ to 900 ℃, the interface is composed of Fe-316SS and 316SS(Al) alternately, which is transformed into FeAl-316SS(Al)-316SS. Sound metallurgical bonding is formed at all these three temperatures. When the joining temperature is 800 ℃, the shear strength reaches 75 MPa.

Effect of sintering temperature on microstructure and mechanical properties of Ti(C,N)-HfN/Ti(C,N)-WC laminated ceramics

GAO Jiaojiao, PING Ping, HU Shiheng, SONG Jinpeng

2024, 42(2): 115-121. doi: 10.19591/j.cnki.cn11-1974/tf.2023040006

Abstract(62) HTML (21) PDF(13)

Abstract:
Ti(C,N)-HfN/Ti(C,N)-WC laminated ceramics were prepared by alternately making layer method and vacuum hot pressing sintering technology, using Ti(C,N) as the matrix phase, HfN and WC as the reinforced phases for the different layers, and metal Ni and Mo as the binder phases. The effects of sintering temperature on the microstructure and mechanical properties of the laminated ceramics were investigated. The results show that with the increase of sintering temperature, the grains grow up gradually. When the sintering temperature is 1350 ℃ and 1400 ℃, the grains are small but unevenly distributed with many micro-defects. At the sintering temperature of 1450 ℃ and 1500 ℃, the grains are uniform (~1 μm) and there are fewer micro-defects. However, when the sintering temperature reaches 1550 ℃, a large number of coarse grains (~2 μm) appear. Moreover, with the increase of the sintering temperature, the flexural strength, Vickers hardness, and fracture toughness of the laminated ceramics increase first and then decrease. The laminated ceramic sintered at 1450 ℃ shows the better comprehensive mechanical properties, the flexural strength, Vickers hardness, and fracture toughness are (1263.6±17.1) MPa, (18.5±0.3) GPa, and (8.2±0.1) MPa·m^1/2, respectively. In addition, the Ti(C,N)-HfN/Ti(C,N)-WC laminated ceramics exhibit the co-existence model of intergranular fracture and transgranular fracture.

Diamond reinforced aluminum matrix composites by laser powder bed fusion

GAO Wenzhe, HAN Xiao, WEI Haibin, LU Zhengzhen, ZHANG Li, LI Xiaofeng

2024, 42(2): 122-127. doi: 10.19591/j.cnki.cn11-1974/tf.2024030002

Abstract(43) HTML (22) PDF(9)

Abstract:
6061 aluminum matrix composites added by 3% diamond particles (mass fraction) were prepared by laser powder bed fusion (LPBF). The microstructure, relative density, and tensile properties of the 3%diamond/6061 aluminum matrix composites were characterized and analyzed by optical microscope, scanning electron microscope, X-ray diffractometer, electronic densitometer, and electronic universal testing machine. Results show that the diamond reacts with the Al matrix, generating the needle-like Al₄C₃ phase, which deposits in the α-Al matrix. Those formed Al₄C₃ increases dislocations at the grain boundaries, enhances the materials’ strength, and delays the failure to fracture. The addition of diamond facilitates the elimination of thermal cracks, but the porous defects remain in 6061 aluminum alloys. The lower scanning speed extends the contact duration between the laser spot and the processed material, leading to the graphitization of the added diamond and the partial evaporation of the Al matrix. Thus, the internal defects exist, exhibiting the low densification of the composite (relative density 97%). The addition of diamond significantly increases the tensile strength of the LPBF formed diamond/6061 aluminum matrix composites, and the ultimate tensile strength reaches the maximum value of 244.2 MPa, the yield strength is 211.6 MPa, and the elongation is 2.1%, respectively, when the laser power is 350 W and the scanning speed is 800 mm·s⁻¹.

Effect of ZrP on properties of CuBi-steel-backed double-layer metal composites

DING Xiaolong, YANG Zhaofang, ZHENG Hejing

2024, 42(2): 128-134. doi: 10.19591/j.cnki.cn11-1974/tf.2021100013

Abstract(231) HTML (46) PDF(10)

Abstract:
The copper-bismuth (CuBi)-steel-backed double-layer metal composite plates were prepared by the sintering and press-rolling composite technology, the effect of zirconium phosphate (ZrP) on the bonding strength, hardness, and tribological properties of the CuBi-steel-backed composite plates was studied. In the results, the addition of ZrP can effectively improve the anti-friction and wear resistance of the CuBi-steel-backed composite plates and enhance the load-bearing capacity. As the ZrP mass fraction increases, the bonding strength of the CuBi-steel-backed composite plates gradually decreases, and the hardness first increases and then decreases. In the constant speed and load test, compared with the CuBi-steel-backed composite plates without ZrP, the addition of 2% and 4% ZrP by mass can effectively improve the friction and wear resistance of the CuBi-steel-backed composite plates, reduce the friction coefficient of the friction pair, and rise the surface temperature. In the constant-speed variable-load test, the addition of ZrP can significantly improve the frictional bearing capacity of the CuBi-steel-backed double-layer materials. Under the condition of end face oil circulation, the limit PV value (friction pair contact surface pressure × friction linear velocity) of the CuBi-steel-backed composite plates by adding ZrP with the mass fraction 4% reaches 14 MPa∙m∙s^‒1, which is about 75% higher than that without ZrP (8 MPa∙m∙s^‒1).

Microstructure and properties of Ti/(TiB+TiC) composites prepared by low-cost TiH₂ powders

LIN Dongjian, LIU Zhongqiang, TANG Hao, ZHANG Jiantao, XIAO Zhiyu

2024, 42(2): 135-143. doi: 10.19591/j.cnki.cn11-1974/tf.2022010002

Abstract(240) HTML (46) PDF(7)

Abstract:
Ti/(TiB+TiC) titanium matrix composites with the excellent mechanical properties were prepared by vacuum pressureless sintering and hot extrusion by using low-cost TiH₂ powders instead of pure titanium powders and adding B₄C to in-situ produce TiB and TiC reinforcements. The effects of preparation technology and reinforcements on the microstructure and properties of the Ti/(TiB+TiC) composites were analyzed. The results show that the TiH₂ powders have the good sintering activity, and the relative density of the sample after dehydrogenation and sintering can reach 97.7%, which is further increased to 99.9% after the hot extrusion as closed to full density. The TiB reinforcements are short fibrous, and the TiC reinforcements are granular, which are uniformly distributed in the equiaxed α-Ti matrix, restraining the growth of equiaxed grains and refining the grains. The hot extrusion process can further refine the grains and make the microstructure more uniform and compact, the as-extruded titanium matrix composites show the high hardness and good matching of strength and ductility. The TiH₂+4%B₄C (volume fraction) extruded composites have the Vickers hardness of Hv_0.3 310, yield strength of 683 MPa, tensile strength of 851 MPa, and elongation of 15.1% after fracture.

Preparation of M62 bearing steel powders by EIGA and PREP

QI Jinkun, YUE Yongwen, HU Jian, WANG Shuli, ZHAO Gang, KOU Xiaolei, QI Guoqiang, ZHAO Jinghui, REN Shubin

2024, 42(2): 144-152. doi: 10.19591/j.cnki.cn11-1974/tf.2023070006

Abstract(39) HTML (14) PDF(11)

Abstract:
High-purity bearing steel powders were prepared by electrode induction melting gas atomization (EIGA) and plasma rotating electrode atomization (PREP), respectively. The particle size distribution, nitrogen and oxygen content, and microstructure of the two high-purity bearing steel powders were analyzed and compared by laser particle size analyzer, oxygen nitrogen analyzer, and scanning electron microscope. The results show that both of the powders are mainly spherical with the PREP powders (M62-PREP) having the higher sphericity, while the EIGA powders (M62-EIGA) has the higher proportion of satellite powders and irregular powders. The median particle size (D₅₀) of the M62-PREP powders is 108.11 μm, significantly higher than that of M62-EIGA powders (D₅₀=38.68 μm). The composition of the two powders is evenly distributed, there is no obvious element segregation, and the M62-EIGA powders are finer. Both of the powders have the good flowability. The N content (mass fraction) of the pre-alloy electrode rods, M62-PREP powders, and M62-EIGA powders are 0.0070%, 0.0072%, and 0.0068%, respectively. The content of N element does not change much. The O content (mass fraction) of M62-PREP powders increases from 0.0008% of the pre-alloy electrode rods to 0.0035%, while the O content of M62-EIGA powders increases to 0.0089%, indicating the significant increase in the O content. The M62-EIGA powder bearing steels after hot isostatic pressing and sintering have the more oxygen containing inclusions, and the M62-PREP powder bearing steels should have the better performance.

Dynamic compressive behavior of PTFE/Cu composite materials

TANG Xuezhi, WANG Zhijun, ZHANG Xuepeng, XU Yongjie

2024, 42(2): 153-158, 164. doi: 10.19591/j.cnki.cn11-1974/tf.2021080008

Abstract(255) HTML (42) PDF(6)

Abstract:
Six kinds of polytetrafluoroethylene (PTFE)/Cu materials with the different Cu contents were prepared by cold isostatic pressing and cold press sintering, respectively. The effects of density and preparation method on the dynamic mechanical properties of PTFE/Cu materials were studied by split Hopkinson bar testing (SHPB). The results show that the density of the cold press sintered specimen decreases due to the longitudinal expansion during the cold press sintering process, and a metal film is formed on the specimen surface. The dynamic mechanical properties of the cold press sintered specimen are better than that of the cold isostatic pressed specimen. The PTFE crystals in the cold press sintered PTFE/Cu materials are better developed, and the PTFE encapsulation force on the Cu particles is greater, resulting in the greater interfacial bonding force and improving the mechanical properties of the cold press sintered PTFE/Cu materials.

Preparation of Ni–MgO core-shell nano powders

GUO Shun, ZHENG Jinfeng, LI Junyi, CHENG Yuewei, LIANG Hongyuan

2024, 42(2): 159-164. doi: 10.19591/j.cnki.cn11-1974/tf.2021020005

Abstract(217) HTML (30) PDF(3)

Abstract:
Nickel nanopowders coated by magnesium oxide used for inner electrode of multilayer ceramic capacitor (MLCC) were prepared by coating thermal decomposition sintering method. The effects of reactant concentration and dispersant content on the particle size and homogeneity of the nano-coated nickel salt precursors were investigated, and the influences of reduction sintering temperature on the sphericity and dispersion of the coated nano-nickel powders were discussed. The nickel nanopowders coated by MgO were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermomechanical analyzer (TMA). The results show that the nano-nickel salt particles can be obtained when the reactant concentration reaches enough to cause the reaction explosion nucleation. The well-dispersed nano-nickel salt precursor particles can be obtained by adding the proper dosage of dispersant. The nickel nanopowders coated by MgO with good sphericity and dispersion can be obtained at the reduced sintering temperature of 700 ℃. The core-shell structure of the nickel nanopowders coated by MgO is formed, which show the good shrinkage delay effect.

Densification and physical properties of SiC-diamond polycrystalline materials produced by pressureless sintering

ZHANG Xiuling, CHEN Yuhong, QI Wubin, ZHANG Qiang, HAI Wanxiu

2024, 42(2): 165-169, 176. doi: 10.19591/j.cnki.cn11-1974/tf.2021090009

Abstract(257) HTML (49) PDF(15)

Abstract:
SiC-diamond polycrystalline materials doping by diamond with different mass fraction were prepared by pressureless sintering with AlN−Y₂O₃−Sc₂O₃ as liquid phase. The microstructure and thermal properties were analyzed by scanning electron microscopy and laser flash method, respectively. The effects of mass fraction (1.0%, 2.5%, 5.0%) and particle size (0.25 μm, 1.00 μm) of diamond on the densification and mechanical properties of the SiC-diamond polycrystalline materials were studied. The results show that, the relative density of the sintered samples is over 94% when the diamond mass fraction is below to 5.0%, while the relative density of the sample with 5.0% diamond is lower than that of other samples. The relative density of SiC polycrystalline materials decreases with the increase of diamond content, and the excessive diamond in raw materials may reduce the densification of samples. Under the experimental conditions, the grain size does not grow abnormally. The hardness, fracture toughness, and bending strength of the samples are in ranges of 16~18 GPa, 3.8~4.4 MPa·m^1/2, and 239~540 MPa, respectively. The thermal conductivity and thermal diffusion coefficient of samples decrease with the increase of temperature, and the porosity is the main factor affecting the thermal conductivity of the sintered samples.

Preparation of high thermal conductivity spherical aluminum nitride fillers by water-based spray granulation

ZHAO Dongliang, QIN Mingli, LU Huifeng

2024, 42(2): 170-176. doi: 10.19591/j.cnki.cn11-1974/tf.2023030011

Abstract(66) HTML (27) PDF(4)

Abstract:
Aluminum nitride (AlN) is an ideal material for the thermally conductive fillers in thermal interface materials due to its excellent thermal conductivity and electrical insulation. The surface modification of the AlN powders was firstly carried out to improve the hydrolysis resistance of AlN powders in this paper, then the spray granulation was carried out using the water-based solvents. The process parameters, such as ball milling time and binder dosage, were optimized during the slurry configuration. The AlN spherical fillers with high sphericity were prepared. Finally, the AlN fillers with low oxygen content, high sphericity, and high thermal conductivity were fabricated by debinding and sintering. In the results, the phosphoric acid-modified AlN powders can maintain the good hydrolysis resistance after the ball milling for 16 h. The binder content (mass fraction) has the significant effect on the green shape after the spray granulation. The powders prepared with 2% PVB+2% PEG binders show the good sphericity and surface smoothness. After debinding and sintering, the thermal conductivity and flexural strength of the AlN ceramic microspheres reach 171.2 W·m⁻¹·K⁻¹ and 340 MPa, respectively, showing the good fluidity. In conclusion, the water-based spray granulation is suitable for the preparation of high thermal conductivity spherical aluminum nitride fillers.

Influence of heat treatment on performance of Fe−6.5%Si magnetic powder core

QIU Yue, HE Yihai, WANG Yifu, LIN Shaochuan, KONG Hui, WANG Rui

2024, 42(2): 177-183. doi: 10.19591/j.cnki.cn11-1974/tf.2021120001

Abstract(489) HTML (57) PDF(28)

Abstract:
Fe−6.5%Si (mass fraction) powders were subjected to the heat treatment experiments at the different temperatures combined with the heat treatment of the magnetic powder cores. The effect of heat treatment on the magnetic properties of Fe−6.5%Si magnetic powder cores, such as permeability and loss, was investigated. In the results, the powder heat treatment can greatly eliminate the defects caused by the impact of high pressure gas on the alloy powders during the gas atomization powder production and reduce the carbon and oxygen content in the powders. With the increase of heat treatment temperature, the coercive force of the powders first increases and then decreases, and the saturation magnetization gradually decreases. The magnetic properties of the prepared Fe−6.5%Si magnetic powder cores can also be improved by heat treatment. After the heat treatment at different temperatures, the loss is maintained between 600 and 700 mW∙cm⁻³, and the lowest value is 625 mW∙cm⁻³. Compared with other comparison samples, the magnetic powder cores made of the Fe−6.5%Si powders heat-treated at 900 ℃ have the better magnetic conductivity and loss after the subsequent heat treatment at 800 ℃.

Effect of trace Y₂O₃ on microstructure and properties of WC−6Co cemented carbides with inhomogeneous structure

TANG Yanyuan, YANG Qiumin, XU Guozuan, WANG Hongyun, ZHONG Zhiqiang

2024, 42(2): 184-191. doi: 10.19591/j.cnki.cn11-1974/tf.2021120008

Abstract(172) HTML (26) PDF(6)

Abstract:
Inhomogeneous structure WC−6Co cemented carbides with the different Y₂O₃ additions (mass fraction) were prepared by low pressure sintering. The microstructure and properties of the cemented carbides were investigated by scanning electron microscope (SEM), X-ray diffraction analyzer (XRD), energy dispersive spectrometer (EDS), metallographic microscope, electronic universal mechanical test machine, hardness meter, and coercivity magnetometer. The results show that, the relative density and phase composition of the cemented carbides are not affected by Y₂O₃ addition. Y₂O₃ forms a stable solid solution with the impurity elements such as sulfur and oxygen, which disperses in the WC grain boundary, hinders the fusion and growth of WC grains, reduces the size of WC grains, and inhibits the homogenization of WC grains in inhomogeneous structure. With the increase of Y₂O₃ mass fraction, the hardness of the cemented carbides increases gradually, and the bending strength shows a trend of rapid rise and then decline. The optimum properties of the cemented carbides are obtained when the Y₂O₃ mass fraction is 0.048%, the hardness and bending strength are 1530 kgf·mm⁻² and 2902 MPa, respectively.

Effect of ball milling process on mechanical properties of medical Ti–Mg composites

XIA Pengzhao, XU Ying, CAI Yanqing, ZHAO Sitan, SONG Pan

2024, 42(2): 192-199. doi: 10.19591/j.cnki.cn11-1974/tf.2021090013

Abstract(325) HTML (75) PDF(22)

Abstract:
Ti–15Mg composites were prepared by ball milling, cold pressing, and microwave heating sintering. The effects of ball milling parameters on the properties of the Ti–15Mg mixed powders and the mechanical properties of the sintered composites were studied. The results show that, the average particle size of the mixed powders decreases significantly with the extension of the milling time at the ball milling speed of 200 r·min⁻¹ for 8～10 h, the particle size distribution gradually concentrates in the range of 10～45 μm, and the sphericity of the powders increases. In the process of long-time ball milling, the soft Mg particles are subjected to the strong impact and ground, eventually leading to the soft Mg particles wrapped in the brittle Ti particles. After ball milling for 8 h, there are no obvious oxidations in the mixed powders. The distribution of Ti and Mg powders in the mixed powders are relatively uniform, and the mechanical properties of the composites are relatively excellent, which meets the requirements of medical materials. At low milling speed, the increase of milling speed can not lead to the significant change in the powder’s properties and the sintered composite properties. The optimal ball milling parameters are obtained as the ball milling time of 8 h and the milling speed of 200 r·min⁻¹ with n-hexane as the process control agent.

Effect of phosphorus content on the mechanical and friction properties of oil-impregnated bronze bearings

FAN Xinyi, HU Lingui, DENG Zehaochen, YANG Jiaqi, SHEN Xiaoping

2024, 42(2): 200-206. doi: 10.19591/j.cnki.cn11-1974/tf.2021090006

Abstract(200) HTML (27) PDF(6)

Abstract:
Oil-impregnated bronze bearings with the different phosphorus contents (0~1%, mass fraction) were produced at the different sintering temperatures. To study the effect of P content on the friction and mechanical properties of the bearings, the friction coefficient and wear loss at the certain speed and load were measured, and the open-loop strength of bearings was examined. In addition, the optimized bearing content and sintering process parameters under the certain working conditions were obtained. The results show that, with the increase of P content, the wear loss of the bearings reduces, while the mechanical performances are improved. However, when the P content is excessed, the oil content reduces which is lower than the minimum standard. As the sintering temperature increases, the mechanical properties of the bearings are improved, but the friction coefficient is unstable. The open-loop strength and oil content of the oil-impregnated bronze bearing samples with 0.7% P content by mass after sintering at 650 ℃ are 22 MPa and 13.52%, respectively, showing the good comprehensive performance as the stable friction factor and the best sintering state.

Accurate modeling of equal-distance spiral bevel gear and the trial production by metal powder injection molding process

LIU Ganhua, TANG Naifu, WANG Qi

2024, 42(2): 207-214. doi: 10.19591/j.cnki.cn11-1974/tf.2021100012

Abstract(186) HTML (33) PDF(3)

Abstract:
As a new type of bevel gear, the equal-distance spiral bevel gear is suitable for the mass production by metal powder injection molding (MIM) due to the characteristic as the normal equal-distance of spiral tooth surface. According to the coordinate transformation theory, the parametric equations of spherical involute and equal-distance conical spiral curves were derived. The mathematical model of tooth surface was established by the formation principle of tooth surface. The mathematical model of tooth surface was programmed by MATLAB to calculate the coordinates of discrete points on tooth surface, and the accurate modeling of equal-distance spiral bevel gear was completed by reverse engineering of UG. The meshing contact of equal-distance spiral bevel gear was simulated to obtain the transmission performance in ANSYS. Finally, the trial production of equal-distance spiral bevel gear was completed base on the MIM process. In the results, the mathematical model of tooth surface combined with the inverse modeling of discrete points can ensure the accuracy of 3D model, and MIM process can be used to produce the equal-distance spiral bevel gears for mass production.

Current Articles 2024, Volume 42, Issue 2

Current Articles
2024, Volume 42, Issue 2