[an error occurred while processing this directive]
[an error occurred while processing this directive]
Quick Search
Adv Search
2021 Vol. 26, No. 1
Published: 2021-02-15
Engineering and Technology
Theoretical Research
Theoretical Research
1
Research on die forging process of powder metallurgy TiAl alloy blade based on numerical simulation
ZHANG Qiang, LI Huizhong, LIANG Xiaopeng, TAO Hui
The die forging process of powder metallurgy Ti-47Al-2Cr-2Nb-0.2W (mole fraction, %) alloy blade was studied by the way of numerical simulation using Deform-3D finite element software. The effects of preheating temperature and upper die speed on the distribution of effective strain field and effective stress field, as well as the load of upper die were analyzed. The results show that with the increase of the preheating temperature and the decrease of the upper die speed, the distribution of the effective strain field and the effective stress field of the blade forgings becomes more uniform, which is beneficial to improve the uniformity of the blade microstructure. During the die forging process, due to the increase of TiAl alloy work hardening and the friction between the forging blank and the die, the load continues to increase, and the increase in the preheating temperature and the decrease of the upper die speed can significantly reduce the load of upper die. The optimal deformation process parameters of die forging for powder metallurgy TiAl alloy blade are preheating temperature of 1 200 ℃ and upper die speed of 0.5 mm/s.
2021 Vol. 26 (1): 1-8 [
Abstract
] (
419
)
HTML
(0 KB)
PDF
(719 KB) (
618
)
Engineering and Technology
9
Effects of Al
2
O
3
content on microstructure and properties of Al
2
O
3
/Cu composite materials prepared by spark plasma sintering
ZHANG Yanglin, LUO Zigui, HU Xiaoming, FENG Bo, LI Rusong, FAN Xi’an
Al
2
O
3
/Cu composite materials, with micron Cu powders as matrix phase and nano Al
2
O
3
particles as insulating phase were prepared by mechanical ball milling combined with spark plasma sintering. The effects of Al
2
O
3
content on the microstructure, resistivity and thermal conductivity of the Al
2
O
3
/Cu composite materials were investigated. The results show that the Al
2
O
3
/Cu composite materials are core-shell structure. With the increase of Al
2
O
3
content, the covering effect of the Al
2
O
3
coating on the copper substrate is gradually enhanced. When
w
(Al
2
O
3
) is 5%, the thermal conductivity of the Al
2
O
3
/Cu composites is relatively high, which is 85.92 W/(m·K), but the resistivity is relatively low (12.6 mΩ·cm). When
w
(Al
2
O
3
) increases to 15%, the density of the Al
2
O
3
/Cu composites decreases to 6.69 g/cm
3
and the porosity is higher. But the resistivity significantly increases to 2.09×10
8
mΩ·cm, which is about 10
11
times of Cu and the thermal conductivity is 7.6 W/(m·K), which is obviously higher than that of the traditional metal substrate.
2021 Vol. 26 (1): 9-14 [
Abstract
] (
347
)
HTML
(0 KB)
PDF
(855 KB) (
599
)
15
Mechanical properties and friction-wear properties of copper modified carbon nanotubes reinforced Ag-based composites
QU Yun, ZHANG Lei, SUN Yang, KANG Xiao, WU Chuanzong
Using multi-walled carbon nanotubes (CNTs) and Cu-plated carbon nanotubes (Cu@CNTs) as the reinforcing phase, the Ag-based composites were prepared by hot pressing method. The effects of CNTs surface modification on mechanical properties, friction properties and wear properties were studied. The results show that the CNTs clusters in the Ag-2Cu@CNTs (volume fraction) composite decrease, and a structure of from Ag to Cu and then to CNTs is formed from the inside to the outside. The mechanical properties of that composite are excellent, the hardness (HV) reaches 105.6, and the tensile strength reaches 248.5 MPa, which is 30.05% and 127.98% higher than pure silver respectively. Compared with pure silver, the friction and wear performance of the Ag-2Cu@CNTs composite is significantly improved, the average friction factor is reduced from 0.86 to 0.28 compared with pure silver, and the volume wear rate is reduced from 88.54×10
-4
mm
3
/(N·m) to 3.96×10
-4
mm
3
/(N·m).
2021 Vol. 26 (1): 15-23 [
Abstract
] (
418
)
HTML
(0 KB)
PDF
(1268 KB) (
1118
)
24
Effect of annealing treatment on microwave absorbing properties of FeCo nanoparticles
LIU Yanzi, SU Yuchang, DONG Qiaoqiao, SHI Congcong
FeCo nanoparticles were prepared using KBH
4
as a reducing agent through chemical reduction method and then annealed at 400-600 ℃. FeCo nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The electromagnetic parameters of FeCo nanoparticles were measured by network vector analyzer (NVA). The microwave absorbing properties of FeCo nanoparticles were analyzed. The effect of annealing temperature on the microwave absorbing properties of FeCo nanoparticles was studied. The results show that the sample prepared under chemical reduction has the maximum reflection loss of -14.9 dB at 2.24 GHz and at the thickness of 5.0 mm, and the main loss mechanism is dielectric loss. With annealing temperature increasing from 400 ℃ to 600 ℃, the dielectric loss decreases and the magnetic loss increases. The sample has the optimal matching performance and the strongest reflection loss after annealed at 400 ℃. The reflection loss of -49.14 dB at 4.48 GHz can be obtained at a thickness of 3.55 mm.
2021 Vol. 26 (1): 24-31 [
Abstract
] (
354
)
HTML
(0 KB)
PDF
(798 KB) (
807
)
32
Effect of calcining process of APT on growth mechanisms of WO
2.72
crystals
LONG Benfu, LIN Gaoan, ZHANG Taiquan, SHEN Siqi
WO
2.72
powder was prepared by calcining APT powder at various temperatures and holding time in an industrial rotary furnace. The results indicate that the single-phase WO
2.72
powder can be obtained above 800 ℃. The morphology and size of WO
2.72
grains are strongly affected by calcining temperature, and the morphology changes from long-needle-like to short coarse rod-like at about 770-800 ℃ with increasing temperature. For long needle-like grains, with increasing temperature, their diameters increase slightly, but their lengths increase sharply. The growth mechanism is that monocrystalline grains nucleate grow into APT particles, accompanying by a small amount of WO
x
·n
H
2
O vapor deposition-re-reduction on the surface of APT particles. For short coarse rod-like grains, with increasing temperature, an opposite result is obtained. The growth mechanism is that the multiple grains clustery nucleate and grow into APT particles to form rod-like grains. With increasing holding time, there is no obvious change in the morphology of WO
2.72
grains, and their diameter and length increase slightly.
2021 Vol. 26 (1): 32-39 [
Abstract
] (
419
)
HTML
(0 KB)
PDF
(798 KB) (
898
)
40
Effects of Ni on the magnetic and mechanical properties of hot-deformed Nd-Fe-B magnets
ZHANG Yanghu, HE Hongjiang, ZUO Zhijun, SHI Rongying, LI Jianjun, ZHAO Lixin, HUANG Guangwei, ZHENG Liyun
To improve the mechanical properties of hot-pressed/hot-deformed anisotropic Nd-Fe-B magnets, high-melting-point metal element Ni with weak magnetism has been doped into the magnets. The influence of Ni on the magnetic, mechanical properties and microstuctures of the Nd-Fe-B magnets were investigated. The results show that average bending strength of the Ni-doped Nd-Fe-B magnets increases fistly and then decreases with increasing Ni mass fraction from 0 to 5%. The Nd-Fe-B magnet with 2%Ni exhibites the highest average bending strength (212 MPa), and the maximum energy product still retains at more than 40 MGOe. The morphology of the fracture surface of the magnets reveales that the enriched Ni near the pore can strengthen and toughen the grain boundary phase, therefore enhence the crack propagation resistance of grain boundary phase, and improve the bending strength of the magnets.
2021 Vol. 26 (1): 40-46 [
Abstract
] (
394
)
HTML
(0 KB)
PDF
(1068 KB) (
1033
)
47
Effects of Ti(C,N) content and sintering temperature on the thickness of β-free layer of graded cemented carbides
CHENG Dengfeng, SUN Dongping, LIU Nana
WC-TiC-Ti(C,N)-TaC-NbC-Co cemented carbide was prepared in denitrification atmosphere with Ti(C,N) as N source. The effects of Ti(C,N) content and sintering temperature on the thickness of β-free layer, properties and microstructure of the cemented carbides were investigated. The results show that the thickness of β-free layer increases with increasing mass fraction of Ti(C,N) from 0.5% to 1.5%. With the increase of sintering temperature, the thickness of β-free layer increases, and the increment increases with increasing Ti(C,N) content. The density, hardness and coercivity of the alloy are not affected by Ti(C,N) content. However, with the increase of sintering temperature, the hardness decreases, the coercivity decreases, and the average grain size of WC increases and becomes straight. There is no obvious abnormal growth of WC grains in the β-free layer, and the thickness of β-free layer is determined by the diffusion of Ti and the content of N.
2021 Vol. 26 (1): 47-54 [
Abstract
] (
433
)
HTML
(1 KB)
PDF
(615 KB) (
1379
)
55
Biocompatibility of single-phase carbon materials
ZHOU Yu, YU Shu, LI Yunping
Four single-phase carbon materials of resin carbon, carbon fiber, pyrolysis carbon and graphite were studied on the particle shedding and biocompatibility of the materials in simulated body fluids. The amount of particles falling off the surface of materials were studied by using simulated body fluid shock immersion method. The biocompatibility of materials were studied by MTT assay and direct contact experiment. The growth morphology of cells were observed by an inverted biological microscope. The results show that the amount of particles shedding on the surface of the four materials reaches the peak value after soaking in simulated body fluid for 72 h. With the continuous increasing soaking time, the shedding amount of particles decreases and tends to be stable. The most of accumulated shedding amount is graphite for 3.01 mg in the 168 h and the least one is resin carbon for 2.23 mg. The relative growth rates of cells in contact with the four kinds of single-phase carbon material extracts are all greater than 75% within 168 hours, and the cytotoxicity are all for grade 1. The four single-phase carbon materials can inhibit the growth and proliferation of cells, and the degree of inhibition is graphite, pyrolytic carbon, carbon fiber and resin carbon in descending order. The toxicity mechanism of single-phase carbon materials to cells is that the entry of carbon particles into the cell causes the degradation of mitochondria, which can destroy the energy station of the cell, and damage the cell’s DNA. It causes the cell to grow abnormally and even died.
2021 Vol. 26 (1): 55-62 [
Abstract
] (
319
)
HTML
(0 KB)
PDF
(839 KB) (
486
)
63
High performance iron-based alloy fabricated by activated powder sintering
CAO Guangyu, LIU Rutie, DANG Shengyun, XIONG Xiang, CHEN Jie, LIAO Ning
Mixing the mechanical milled pre-alloy with atomized iron and carbonyl iron, respectively, Fe-3Mo- 3Cr-1.2V-0.5Mn-2C alloy was prepared by vacuum sintering. The microstructure and mechanical properties of the as-prepared samples by mechanically activated pre-alloy and carbonyl iron were studied. The results show that mechanically activated milling can effectively improve the diffusion of pre-alloy in atomized iron and densification of iron based powder metallurgy materials. With the highly surface-activated carbonyl iron powder as raw material, higher density and mechanical properties can be obtained in low sintering temperature. The iron-based powder metallurgy sample sintered at 1 120 ℃ has low porosity and medium grain size. The density, brinell hardness and bending strength are 7.68 g/cm³, 538 and 1 222 MPa, respectively.
2021 Vol. 26 (1): 63-69 [
Abstract
] (
347
)
HTML
(0 KB)
PDF
(1662 KB) (
1120
)
70
Wear resistance and corrosion resistance of La
2
O
3
modified WC-20Cr
3
C
2
-11NiMo coatings sprayed by HVAF
ZHANG Kai, LIU Wei, ZHANG Lei, ZHAO Jian, FU Li, CHEN Xiaoming
In order to improve the wear resistance, seawater corrosion resistance and seawater cavitation resistance of high-quality WC coating, WC-20Cr
3
C
2
-11NiMo coating modified by La
2
O
3
were prepared on 0Cr13Ni5Mo substrate by HVAF. The micro-hardness, porosity, friction coefficient, friction and wear performance, seawater corrosion resistance and seawater cavitation resistance of the coatings were investigated by micro-hardness test, plane pore test, friction and wear test, electrochemical experiment and simulated seawater ultrasonic cavitation experiment. The effects of La
2
O
3
on the wear resistance and corrosion resistance of WC-20Cr
3
C
2
-11NiMo coating were studied. The results show that the micro-hardness of the modified coatings increases to about 1 400 HV
0.2
, and the average porosity of the modified coatings decreases by about 48.6%. The wear amount of the modified coatings decreases by about 33%. The friction coefficient of the modified coating decreases by 30%, and the micro-pits and micro-cracks on friction and wear surfaces of the modified coating decrease significantly. The electrochemical self-corrosion potential shifts to the right, and the electrochemical self-corrosion current density decreases significantly. The loss of cavitation mass decreases by about 20%, and the cavitation pits decreases significantly. Compared with the unmodified WC-20Cr
3
C
2
-11NiMo coating, La
2
O
3
modified WC-20Cr
3
C
2
-11NiMo coating can slightly improve the hardness of the coating, the compactness, wear resistance, seawater corrosion resistance and seawater cavitation resistance are significantly improved. Besides the surface fatigue wear, the mechanism of surface friction and wear changes from severe abrasive wear to slight abrasive wear. The cavitation mechanism is mainly fluid shock wave erosion.
2021 Vol. 26 (1): 70-76 [
Abstract
] (
276
)
HTML
(0 KB)
PDF
(918 KB) (
700
)
77
Effects of B
4
C content on the microstructure and mechanical properties of ZrB
2
ceramics
DU Yuhui, TANG Zhenxiao, PENG Ke, ZHOU Yuanming, YI Maozhong
Aiming at the problem that ZrB
2
ceramics powder were easily mixed with ZrO
2
during ball milling, which affected the sintering denstification of ZrB
2
ceramics, B
4
C was introduced as sintering additive, and ZrB
2
ceramics were prepared by pressureless sintering. The effects of B
4
C content on the microstructure and mechanical properties of the materials were investigated. The results show that B
4
C can inhibit grain coarsening and reduce grain size by reacting with ZrO
2
on the grain surface. With the increase of B
4
C content, the grain size and relative density of the ZrB
2
ceramics increase gradually, while the flexural strength and hardness first increase and then decrease. When the mass fraction of B
4
C is 7%, the grain size of ZrB
2
are fine, and the flexural strength and hardness of the material reach the maximum value, which are 242 MPa and 12.65 GPa respectively. As increasing the content of B
4
C to 9%, the grains grow abnormally and the mechanical properties decrease.
2021 Vol. 26 (1): 77-83 [
Abstract
] (
354
)
HTML
(0 KB)
PDF
(637 KB) (
1238
)
84
Microstructure and properties of carbon-free Fe-Co-Mo high speed steel coating prepared by laser cladding
XIONG Guo, XIE Fengwei, YUAN Ziren, KANG Xiyue, HE Yuehui
Carbon-free high-speed steel coatings were prepared on 40Cr substrates by synchronous powder-feeding laser cladding technology with water atomized alloy powder as raw material. The microhardness, red hardness and tempering resistance of the coating were tested and analyzed. The effects of process parameters on the morphology and hardness of the coating were studied. The results show that, under suitable parameters, a carbon-free high-speed steel coating without macro cracks and pores was obtained on the surface of the substrate. The coating has high density and low dilution rate, and exhibits a good metallurgical bond with the substrate. The microhardness (HV
0.2
) of the coating in the cladding state is 700, and the coating hardness (HV
0.2
) is significantly increased to 900 after aging at 600 ℃ for 1 h. After aging at 600 ℃for 1 h for 4 times, the coating hardness (HV
0.2
) remains at 800. In addition, after a long time tempering at 600 ℃ for 30 h, the coating can still maintain a hardness (HV
0.2
) of 750, which has better tempering resistance than conventional high-speed steel ASP2030 and hot work die steel H13.
2021 Vol. 26 (1): 84-90 [
Abstract
] (
408
)
HTML
(0 KB)
PDF
(606 KB) (
1191
)
[an error occurred while processing this directive]
[an error occurred while processing this directive]
