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2023 Vol. 28, No. 3
Published: 2023-06-15
Engineering and Technology
Theoretical Research
Theoretical Research
203
First-principles study of mechanical properties and electronic structure of transition metal doped TaN hard coating
DAI Weike, WANG Jiong
DOI: 10.19976/j.cnki.43-1448/TF.2023018
The stability, mechanical properties, and electronic structure of transition metal (TM, TM=Ti, V, Cr, Y, Zr, and Hf) elements doped tantalum nitride (Ta
7
TMN
8
) were investigated by first-principles calculations. According to the calculation results of structure and stability, all the doped compounds are stable, and Ta
7
TiN
8
is energetically more favorable than others. The doping of Y, Zr, and Hf can cause lattice and volume expansion of TaN, while Ti, V, and Cr play an opposite role. The calculated mechanical properties reveal that the addition of Ti and V can significantly improve the shear modulus, elastic modulus, and theoretical hardness of TaN, while doping Cr can only increase the volume modulus but significantly decrease the theoretical hardness. Based on the calculation results of the total and partial density of states of Ta
7
TMN
8
, the density of states at the Fermi level indicates that all compounds exhibit metallic nature. The contribution of Ti-3d, V-3d, and Cr-3d orbitals at the Fermi level is quite more than other TM atoms, leading to a more metallic character of Ta
7
TiN
8
, Ta
7
VN
8
, and Ta
7
CrN
8
.
2023 Vol. 28 (3): 203-211 [
Abstract
] (
1328
)
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212
Flow stress analysis and Arrhenius constitutive equation of near β titanium alloy Ti-55511 during thermoplastic deformation
LUO Deng, HU Bin, WANG Zhen, ZHOU Wenhao, KONG Bin, ZHANG Xiaoyong
DOI: 10.19976/j.cnki.43-1448/TF.2023027
Hot deformation behavior of Ti-55511 titanium alloy was studied at deformation temperatures of 700-850 ℃, strain rates of 0.01-10 s
-1
and true strain of 0.6. The results indicate that the flow behavior of Ti-55511 titanium alloy is significantly affected by deformation temperature and strain rate. With the decrease of temperature and the increase of strain rate, the peak stress increases. In order to eliminate the deformation temperature rise effect in the process of hot compression and improve the accuracy of the model, a new temperature correction method was adopted in this paper. The temperature correction of the experimental flow stress curve was carried out through the Arrhenius constitutive equation derivation and combined with the mathematical extrapolation method. The results show that with the decrease of deformation temperature and the increase of strain rate, temperature rise and flow stress increment increase. The Arrhenius constitutive equation of strain-compensated is established, and the value of correlation coefficient (
R
2
) and average absolute relative error (AARE) between experimental and predicted stress are 0.991 and 6.65%, respectively. This indicates that the established constitutive equation can accurately predict the flow stress under different thermal deformation conditions.
2023 Vol. 28 (3): 212-222 [
Abstract
] (
299
)
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1093
)
Engineering and Technology
223
Preparation of ZrB
2
-SiC-LaB
6
ultrafine multiphase powders by sol-gel and carbothermal/borothermal reduction
ZHOU Zhe, XIA Dawang, LI Zhi, LIAO Huanyi, JIN Xin
DOI: 10.19976/j.cnki.43-1448/TF.2023005
ZrB
2
-SiC-LaB
6
ultrafine multiphase powders were prepared by the way of sol-gel method and carbothermal/borothermal reduction process, using zirconium oxychloride (ZrOCl
2
·8H
2
O), boric acid (H
3
BO
3
), hydrated lanthanum chloride (LaCl
3
·7H
2
O), ethyl orthoate (TESO), and glucose (C
6
H
12
O
6
) as the main raw materials, polyethylene glycol (PEG) as the dispersant. The effects of different temperatures and raw material ratios on the synthesis process of composite powders were studied and characterized by X-ray diffraction, SEM, infrared spectroscopy, and differential thermal scanning. The results show that when
n
(Zr)∶
n
(B)∶
n
(Si)∶
n
(La)∶
n
(C) =1∶3∶0.7∶0.16∶8 in the raw material, ZrB
2
-SiC-LaB
6
superfine multiphase powders can be synthesized by holding at 1 500 ℃ for 2 h under argon atmosphere. The average particle size of multiphase powder is 300 nm, in which ZrB
2
phase is hexagonal crystal system, SiC and LaB
6
phase are cubic system, and the average size of ternary crystallite is 33.2 nm.
2023 Vol. 28 (3): 223-232 [
Abstract
] (
276
)
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739
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233
Pore structure and properties of capillary wicks prepared by printing process
SHEN Peng, CAI Yanbo, WANG Dezhi, LIU Xinli, DUAN Bohua
DOI: 10.19976/j.cnki.43-1448/TF.2023011
Using electrolytic dendritic copper powder with an average particle size of 55-112 μm as raw material and urea as pore forming agent, adding organic component binder, solvent and other organic matter to prepare slurry, using printing process to prepare capillary wick green, and then degreasing and sintering to prepare capillary wick with thickness of (0.2±0.02) mm. The effects of copper powder particle size, urea addition and slurry organic components on the pore structure and capillary performance of the capillary wick were studied. The results show that the addition of poreforming agent urea can increase the porosity, average pore size and permeability of the capillary wick structure, and reduce the capillary force and fractal dimension. As the particle size of copper powder decreases from 112 μm to 55 μm, the porosity, average pore size, average area, average perimeter, fractal dimension, permeability and capillary performanca parameters of the capillary wick all decrease, while the capillary force increases, its fractal dimension decreases from 1.39 to 1.20. The fractal dimension is related to the permeability, and as the permeability decreases, the fractal dimension decreases gradually. Its capillary performanca parameters are directly proportional to permeability and inversely proportional to capillary force. The capillary wick prepared by 112 μm copper powder has the best performance, the permeability is 2.02×10
-10
m
2
, the capillary force (Δ
P
c
) is 1.29 kPa, and the capillary performanca parameter (Δ
P
c
·
K
) reaches 2.61×10
-7
N.
2023 Vol. 28 (3): 233-243 [
Abstract
] (
380
)
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917
)
244
Microstructure and thermal shock resistance of Nb/Y
2
O
3
coating prepared by slurry sintering
LIN Shiqi, YUAN Tiechui, WANG Fei
DOI: 10.19976/j.cnki.43-1448/TF.2023015
For the reuse of crucibles used to smelt nuclear metals and the recovery of spent fuel, a series of double-layer gradient composite Yttria-coatings were prepared on the surface of Niobium 521 alloy by slurry sintering process. Trace amounts of Si and Mo were added as reinforcing agents in the coating, the surface of the coating was pure Y
2
O
3
. With the help of finite element simulation, X-ray diffractometer, scanning electron microscopy, energy spectrometer and other means, the microstructure and thermal shock resistance of the coating were studied. The results show that the Nb/Y
2
O
3
coating has a typical layered structure, which is composed of irregular powder particles stacked on top of each other, and the matrix area, diffusion area, transition layer and Y
2
O
3
layer have distinct structures. The finite element simulation calculation and experimental results both prove that the double-layer gradient coating can change the stress distribution and effectively reduce the stress generated inside the material during thermal shock. Among them, the maximum principal stress of the 70%Y
2
O
3
+22% Nb+6%Si+2%Mo (7022) coating is 163.2 MPa, which decreases by 47.93% compared to the single-layer Y
2
O
3
coating (313.4 MPa). After 60 thermal cycles, the microstructure of the 7022-Y
2
O
3
coating is dense without obvious defects, and the morphology is the least damaged.
2023 Vol. 28 (3): 244-253 [
Abstract
] (
277
)
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890
)
253
Effects of MgF
2
doping on structure and microwave property of 0.95MgTiO
3
-0.05CaTiO
3
ceramics
RAN Wen, LIU Fan, LI Hao, LIU Shaojun
DOI: 10.19976/j.cnki.43-1448/TF.2023022
MgF
2
doped 0.95MgTiO
3
-0.05CaTiO
3
(95MCT) microwave ceramics were synthesized by solid-phase reaction. The effects of MgF
2
doping on the sintering temperature, crystal structure, microstructure and microwave properties of 95MCT ceramics were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and vector network analyzer. The results show that a small amount of MgF
2
doping can promote the uniform growth of ceramic grains. The addition of MgF
2
inhibits the transition of Ti
4+
ions to Ti
3+
ions and enhances the Ti—O bonding strength of [TiO
6
] octahedra, thus significantly improving the quality factor of ceramics from 30 335 GHz to 89 470 GHz. MgF
2
doped with 1% (mass fraction) of 95MCT ceramic sintered at 1 225 ℃ has excellent microwave properties: the relative permittivity
ε
r
is about 19.74, the
Q×f
value is about 89 470 GHz, and the resonant frequency temperature coefficient
τ
f
is about -10.2×10
-6
℃
-1
.
2023 Vol. 28 (3): 253-261 [
Abstract
] (
223
)
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573
)
262
Tribological performance and mechanism of B
4
C modified Cu-based brake pads mated with C/C-SiC
LUO Yong, LI Zhuan, WU Jiaqi
DOI: 10.19976/j.cnki.43-1448/TF.2023026
Copper based brake pads have the problems of matrix softening and friction film breaking during high-speed cycle braking. Cu-based brake pads with boron carbide (B
4
C) mass fraction of 0-6% were prepared using powder metallurgy (PM) method, and C/C-SiC brake discs were selected as dual components to study the effect of B
2
O
3
friction film formed during the braking process on friction and wear performance, and to analyze the wear mechanism. The results show that the density of copper based friction materials can be reduced by modifying with B
4
C. When the mass fraction of B
4
C is 4% and 6%, the material density significantly decrease and the strength increase, and the most excellent thermal degradation resistance and the lowest wear rate are obtained, respectively. During the braking process, B
2
O
3
formed by B
4
C oxidation has a layered crystal structure similar to MoS
2
and graphite, which is easy to shear at the sliding interface, thereby improving the mean friction stability coefficient and reducing wear rate. B
2
O
3
formed on the surface of B
4
C combines well with the Cu matrix. When the mass fraction of B
4
C exceeds 4%, the wear mechanism of Cu-based brake pads shifts from delamination wear to oxidation wear.
2023 Vol. 28 (3): 262-275 [
Abstract
] (
286
)
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569
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276
Microstructure and electrocatalytic hydrogen evolution performance of self-supported Ni-Sn-B electrode prepared by electrodeposition method
YANG Gang, HE Hanwei
DOI: 10.19976/j.cnki.43-1448/TF.2023031
To develop efficient and stable hydrogen evolution electrocatalysts, Ni-Sn-B hydrogen evolution electrode were prepared on Ni mesh substrate by galvanostatic electrodeposition method. The morphology, structure, elemental composition, and electrocatalytic hydrogen evolution properties of the electrode were characterized and tested by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical workstation. The results show that the surface of Ni-Sn-B electrode is composed of rough cellular particles, which are closely packed and have amorphous characteristic structure. Ni-Sn-B electrode has excellent catalytic performance and stability for hydrogen evolution in alkaline solution. The overpotential is only 63 mV at current density of 10 mA/cm
2
, which is 38.2% and 59.1% lower than that of Ni-Sn and Ni-B electrodes. The charge transfer resistance of electrode is 1.56 Ω, and the excellent hydrogen evolution activity is still maintained after 5 000 cycles of voltammetry and 72 h electrolysis. The abundant surface morphology and amorphous characteristic structure can significantly increase the electrochemical active surface area and catalytic active site. The regulation of B and Sn on the electronic structure of Ni effectively decreases the charge transfer resistance and improves the properties of electrocatalytic hydrogen evolution reaction.
2023 Vol. 28 (3): 276-287 [
Abstract
] (
410
)
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1279
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288
Effects of sintering temperature on mechanical and grinding properties of Ti-Al intermetallic-bonded diamond grinding block
TANG Zhou, HE Yuehui, CHEN Shuaipeng
DOI: 10.19976/j.cnki.43-1448/TF.2023032
Diamond grinding wheels with intermetallic compound as binder are widely used in grinding sapphire, silicon carbide and other fields. The binding state between binder and diamond directly affects the mechanical and grinding properties of the diamond grinding wheels. In order to study the interface binding of binder and diamond, Ti-Al intermetallic-bonded diamond grinding blocks were prepared by hot pressing, and the binding state and the grinding property of grinding blocks were studied by various material characterization methods and friction wear tests. The results show that Ti-Al intermetallic compound is generated in the binder after hot pressing, and Al will be enriched on the diamond surface to improve the holding force of the binder on the diamond particles. When the sintering temperature is 900 ℃, the binder has the highest holding force on diamond particles, and the mechanical and grinding properties of the grinding block are the best, the maximum strength and hardness (HRB) are 160.48 MPa and 114.4, respectively, and the abrasion radio of grinding sapphire is 22.3 and the surface roughness of sapphire is 1.37 µm. However, the excessive oxidation of the binder will reduce the grinding property of the grinding block with the further increase of the temperature.
2023 Vol. 28 (3): 288-295 [
Abstract
] (
295
)
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691
)
296
Effects of alloy additives on oxidation behavior and correlative characteristics of WC-based cemented carbides
WANG Chunguang, ZHANG Li, HUANG Xiang, NIE Renxin, ZHONG Zhiqiang, LONG Jiawei
DOI: 10.19976/j.cnki.43-1448/TF.2023042
To explore the methods to improve the oxidation resistance at high temperature and the physical and mechanical properties simultaneously. Thus, this research designed WC-6Co-6Ni, WC-6Co-6Ni-1Cr
3
C
2
, WC-6Co- 6Ni-1CeO
2
and WC-12Co-1CeO
2
WC-based cemented carbides, corresponding to alloys 1
#
-4
#
, respectively. The microstructure, physical and mechanical properties and oxidation behavior of the alloys at 700 ℃ for 16 h were investigated by comparison. The results show that the presence of rare earth-containing oxide dispersion phase in the alloy does not lead to the decrease of alloy strength, and the alloy hardness follows the coupling law of hardness, grain size and volume fraction of the phase components. The hardness of alloy 4
#
is the highest, followed by alloy 2
#
. The influence of Co and Ni binder metals on the hardness of cemented carbides is significant. Both Cr
3
C
2
and CeO
2
can significantly improve the oxidation resistance of the alloys at 700 ℃, but the improvement effect of Cr
3
C
2
is better than that of CeO
2
. The high temperature oxidation resistance and physical and mechanical properties of WC-based cemented carbide can be improved synchronously by adding appropriate amount of Cr
3
C
2
and CeO
2
, and using Ni to partially replace Co.
2023 Vol. 28 (3): 296-304 [
Abstract
] (
285
)
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