[an error occurred while processing this directive]
[an error occurred while processing this directive]
Quick Search
Adv Search
2025 Vol. 30, No. 1
Published: 2025-02-15
Engineering and Technology
Engineering and Technology
1
β-Si
3
N
4
whiskers preparation from Si
3
N
4
@MgSiN
2
core-shell structure powders
WANG Weide, LIU Yiming, PAN Yong, MO Yong, WANG Weiming, MA Qingsong
DOI: 10.19976/j.cnki.43-1448/TF.2024078
One dimensional single crystal β-Si
3
N
4
whiskers possess excellent thermal, mechanical, high- temperature and corrosion resistance properties, and are widely used as resin based, metal based, and ceramic based reinforcement materials. β-Si
3
N
4
whiskers prepared with oxides as sintering aids have shortcomings such as high residual impurities and low aspect ratio, which limit their reinforcement effect. This study utilized the molten salt synthesis to prepare Si
3
N
4
@MgSiN
2
core-shell structured powders with controllable shell thickness at lower temperature, and further prepared β-Si
3
N
4
whiskers from this powder through sintering. The phase composition and microstructure of powders and whiskers were studied using X-ray diffractometer, energy dispersive spectrometer, and scanning electron microscope. The results show that at high temperatures, α-Si
3
N
4
undergoes a phase transformation and Ostwald ripening in the liquid phase formed by the shell MgSiN
2
through a “dissolution-precipitation” mechanism, resulting in the formation of β-Si
3
N
4
whiskers with high aspect ratio. Raising the sintering temperature and increasing the Mg/Si
3
N
4
mass ratio in the raw material can enhance the diffusion mass transfer in the liquid phase, which is beneficial for the growth of whiskers along the [001] direction, manifest as an increase in whisker length and aspect ratio. At the same time, the unstable nature of MgSiN
2
at high temperature promotes its decomposition into Mg, N
2
, and Si
3
N
4
, ensuring the high purity of the whiskers. Therefore, high-purity, high aspect ratio, and easily dispersible β-Si
3
N
4
whiskers are prepared by sintering at 1 750 ℃ for 1 h. The new preparation strategy of whiskers proposed in this study is economically feasible and provides a new approach for the preparation of high-performance β-Si
3
N
4
whiskers.
2025 Vol. 30 (1): 1-10 [
Abstract
] (
48
)
HTML
(0 KB)
PDF
(1068 KB) (
61
)
11
Effects of TiC content on microstructures and properties of laser cladding Inconel 718 composite coatings
LU Shengru, TONG Yonggang, HU Yongle, WU Pengfei, JI Xixi, WANG Kaiming
DOI: 10.19976/j.cnki.43-1448/TF.2024082
In order to improve the high-temperature wear resistance of nickel-base alloy cladding, this paper employs laser cladding technology to prepare TiC reinforced Inconel 718 composite cladding layers, and investigats the effects of TiC content on the microstructures and high-temperature friction behaviour of Inconel 718 composite cladding layer by scanning electron microscope, energy spectrometer, super depth of field microscope, and ball-disc high temperature friction and wear test machine. The results show that the addition of TiC results in the formation of (Nb,Ti)C, NbC, and different scale TiC particles, the grains of the composite cladding layers are refined. The composite cladding layer with
w
(TiC)=30% has the highest hardness (HV
0.2
) of 660.0, which is 150.0% higher than that of the Inconel 718 cladding layer (264.0); at room temperature, the volume loss of the composite cladding layer is 93.4% lower than that of the Inconel 718 cladding layer; and at high temperature, the composite cladding layer still has excellent wear resistance with a volume loss of 0.83×10
8
μm
3
. The wear mechanism of cladding layers change from abrasive wear to adhesive wear with the increace of TiC content. The improvement in hardness and room and high temperature wear resistance of the cladding layers is attributed to the formation of different scale carbide-reinforced phases and grain refinement.
2025 Vol. 30 (1): 11-21 [
Abstract
] (
54
)
HTML
(0 KB)
PDF
(1299 KB) (
54
)
22
Influences of cold deformation and annealing on the microstructures and mechanical properties of in-situ carbon nanosheet/copper composites
FAN Leilei, LIU Ying, YAO Yupeng, TU Ruibo, WU Yanxia, WANG Jian, JING Lin, ZHANG Caili
DOI: 10.19976/j.cnki.43-1448/TF.2024084
The microstructure regulation of the copper matrix constitutes an effective way to overcome the inverse relationship between the strength and plasticity of carbon nanosheet/Cu composites. In this paper, the composites were in-situ synthesized by powder metallurgy technology and subjected to cold-rolling deformation and annealing treatment. The influences of cold-rolling deformation and annealing temperature on the microstructures and mechanical properties of the in-situ synthesized carbon nanosheet/Cu composites and the corresponding mechanism were investigated. The results show that during the rolling process, the grain size of Cu matrix is gradually reduced with the increase of cold-rolling amount, forming a {110}〈113〉 texture, as well as the density of dislocations increase greatly. With the effects of grain refinement, deformation texture and dislocation strengthening, the strength of the carbon nanosheet/Cu composites is significantly enhanced, especially, the composite with the deformation amount of 40% exhibits the most obvious enhancement, the yield strength and tensile strength reaches 332 MPa and 375 MPa, respectively, which are enhanced by 73.8% and 22.1% in comparison with the undeformed composites, however, due to the formation of deformation texture, the plasticity decreases, and the elongation is only maintained at 6.7%. After annealing, there is a slight reduction in the strength of the cold deformed carbon nanosheet/Cu composites but the plasticity restores because of the dislocation recovery or recrystallization of the copper matrix and the more uniform grain orientation. The composite annealed at 200 ℃ exhibits the best matching of strength and plasticity, and the best mechanical properties with the yield strength, tensile strength, and elongation of 284 MPa, 373 MPa, and 10.6%, respectively, the tensile strength is increased by 21.5% compared with the initial state, and its elongation is decreased by only 2.1%.
2025 Vol. 30 (1): 22-34 [
Abstract
] (
48
)
HTML
(0 KB)
PDF
(1453 KB) (
66
)
35
Evolution rule of powders during preparation of tantalum powders by magnesiothermic reduction-acid leaching
CHENG Yuewei, CHEN Yi, WANG Ruifang, XING Yichen, HAN Zhenghao, CHE Yusi, HE Jilin
DOI: 10.19976/j.cnki.43-1448/TF.2024085
Currently, the tantalum powders prepared by sodium reduction of potassium fluorotantalate cannot meet the requirements of high-end capacitors for the morphology uniformity and oxygen content of tantalum powders. This paper prepared tantalum powders by magnesium reduction of tantalum oxide-acid leaching process. The phase composition, micro-morphology, element content, and particle size distribution of tantalum powders before and after the acid leaching were studied using X-ray diffractometer, scanning electron microscope, energy spectrometer, laser particle size analyzer, oxygen/nitrogen/hydrogen analyzer, and inductively coupled plasma emission spectrometer. The results indicate that the tantalum powder particles inherit the morphology of the raw material. When
n
(Mg)∶
n
(Ta
2
O
5
)=5∶1, a few of the tantalum powders absorb hydrogen forming Ta
2
H during acid leaching owing to the fine grain and high activity of the tantalum, the insufficient magnesium led to the formation of Mg
4
Ta
2
O
9
resulting from the reaction of unreacted Ta
2
O
5
and MgO at this moment, which is difficult to separate from tantalum powders; when
n
(Mg)∶
n
(Ta
2
O
5
)=7.5∶1, the tantalum oxides are completely reduced to tantalum; when
n
(Mg)∶
n
(Ta
2
O
5
)=10∶1, the oxygen content of tantalum powders decreases to 0.58%, and the morphology uniformity is obviously improved.
2025 Vol. 30 (1): 35-41 [
Abstract
] (
48
)
HTML
(0 KB)
PDF
(739 KB) (
53
)
42
Preparation and properties of ZrC-AlN reinforced Mo-based composites
YAN Chunlei, SONG Dongji, REN Junye
DOI: 10.19976/j.cnki.43-1448/TF.2024087
In order to meet the application needs of a new generation thermal structure materials of high temperature resistance, anti-radiation, oxidation resistance, and high strength and toughness, Mo-based composites with different ZrC-AlN contents were prepared by three-dimensional dry ball milling, cold isostatic pressing, and high-temperature argon atmosphere sintering. The influences of ceramic content on the dispersion of composite powders, as well as the microstructures, oxidation behavior, and properties of composites, were studied using scanning electron microscope, X-ray diffractometer, and simultaneous thermal analyzer. The results indicate that uniformly dispersed metal ceramic composite powders can be obtained through three-dimensional dry ball milling. After oxidation from room temperature to 1 200 ℃, the mass loss rate of the composites decreases greatly with the increase of ceramic phase content, indicating the improved oxidation resistance of composites by introducing antioxidant ceramic phases. When introducing ceramic phase, the compressive strength of the composites increase greatly with the maximum of 1 315.8 MPa, increasing by about one time compared to pure Mo, it’s because the ceramic phases with high hardness, high modulus, and low compressibility which enhance the compressive property of the composites. However, the bending strength of composites decrease, which is a comprehensive result of closed pores, interface reactions, and the mechanical properties of each phase itself.
2025 Vol. 30 (1): 42-50 [
Abstract
] (
53
)
HTML
(0 KB)
PDF
(1589 KB) (
61
)
51
Friction properties of silver-based alloy slip rings under vacuum current-carrying
ZHANG Shumin, LIU Lanying, YU Yide, WANG Yupeng, LIU Shuai, LIU Qingkai
DOI: 10.19976/j.cnki.43-1448/TF.2024092
To optimize the material selection for the friction pair of silver-based slip rings, this study selected AgCu alloy, AgCuNi alloy, and Ag-based composite as the ring body materials. These materials were paired with Ag-based and Au-based brush wires to form friction pairs for vacuum current-carrying life experiments. Oscilloscope recorder, digital microscope system, and scanning electron microscope were used to study the electrical contact performance, wear surface morphology, debris morphology and composition of different friction pairs. The results show that AgCu alloy and AgCuNi alloy, when grinding against Ag-based and Au-based brush wires, produce elongated filamentous debris with a layered extrusion morphology. Introducing WS
2
and MoS
2
two-dimensional materials into the Ag alloy ring can change the debris morphology, forming gray-black fine flake-like debris, thus avoiding the generation of filamentous debris at the source of the materials and effectively reducing the risk of slip ring short circuits caused by debris.
2025 Vol. 30 (1): 51-59 [
Abstract
] (
44
)
HTML
(0 KB)
PDF
(1074 KB) (
49
)
60
Photothermal conversion performance of Fe-Mn-Al-Ni-C lightweight steel
LI Shiyao, ZHANG Fei, CHEN Meijie, LI Kaiyang, XIONG Zhiping, SONG Min, WANG Zhangwei
DOI: 10.19976/j.cnki.43-1448/TF.2024094
In this paper, combined with surface etching and in-situ oxidation process, X-ray diffractometer, scanning electron microscope, energy spectrometer, X-ray photoelectron spectrometer, fiber optic spectrometer, and Fourier transform infrared spectrometer were used, the variations in the oxidation products on the surface of Fe-Mn-Al-Ni-C lightweight steel and their effects on photothermal conversion performance were studied by adjusting the oxidation temperature. The results show that applying etching pretreatment promotes the generation of nano-lamellar oxides, thereby effectively improving the photothermal conversion performance of the alloys compared to using the in situ oxidation process alone. After etching, the oxide size increases as the oxidation temperature rises from 300 ℃ to 400 ℃, leading to an improvement in the photothermal conversion performance of the alloy; the solar energy absorptance and photothermal conversion efficiency of the alloy reach peaks of 96.1% and 90.2%, respectively, after oxidation at 400 ℃ for 2 h; when the oxidation temperature increases to 500 ℃, increased thermal stress due to the mismatch of thermal expansion coefficients causes slight detachment of the oxide layer from the alloy surface, resulting in a decline in photothermal performance; oxidation at 600 ℃ leads to severe oxide layer detachment and the formation of Al2O3, further reducing the photothermal performance.
2025 Vol. 30 (1): 60-70 [
Abstract
] (
49
)
HTML
(0 KB)
PDF
(971 KB) (
79
)
71
Preparation and properties study of nacre-inspired lamellar Al/Al
2
O
3
composites by freeze casting and pressure infiltration
YANG Likai, LÜ Boliang, CEN Junchi, LIN Qiaoli, SHI Yu
DOI: 10.19976/j.cnki.43-1448/TF.2024096
Drawing inspiration from the high performance of natural materials such as nacres, which derive their advantages from a unique lamellar structure, and combined with the concept of bionics. This study prepared Al/Al
2
O
3
composites with a nacre-inspired lamellar structure using freeze casting and pressure infiltration. The effects of basalt sintering aids and sintering temperature on the microstructure and compressive strength of the porous Al
2
O
3
framework were studied by scanning electron microscope and material testing machine, and the microstructure and phase volume fraction of the composites were observed and analyzed by micro-CT. The results show that the porous Al
2
O
3
framework has a lamellar structure with alternating arrangement of pores and ceramics. The formation mechanism of this structure is attributed to the directional growth of ice crystals, during the growth process, the ice crystals push the ceramic particles to the sides to form the directional lamellar structure. The addition of basalt sintering aids or an increase in sintering temperature can significantly enhance volume shrinkage and compressive strength of ceramic framework. Chemical bonding is established at the Al/Al
2
O
3
interface, which enables the melt and skeleton to be effectively composited. Al/Al
2
O
3
composites feature high densification and show a delicate lamellar structure, largely achieving the design goal of the nacre-inspired structure.
2025 Vol. 30 (1): 71-78 [
Abstract
] (
40
)
HTML
(0 KB)
PDF
(1950 KB) (
61
)
[an error occurred while processing this directive]
[an error occurred while processing this directive]
