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2021 Vol. 26, No. 4
Published: 2021-08-15
Engineering and Technology
Theoretical Research
Theoretical Research
285
Liquidus surface projection for the Al-Co-Er ternary system
ZHENG Linghong, ZHANG Ligang, ZHAO Fenyan, LIU Libin, WANG Dong, WU Chenjian
Recently, global warming and energy issues have attracted more and more attention, with the rapid economic development. In order to promote the sustainable development of resources light weight and high performance of materials can save resources and protect the environment. Aluminum alloys have important applications in the field of aerospace and transportation. The study of phase diagrams of related systems can provide important basic data for the design of high-strength aluminum alloys. The liquidus surface projections of the Al-Co-Er system were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe micro-analysis (EPMA) techniques. A total of 10 ternary compound phases were measured and a number of alloy solidification channels were established. On this basis, the projection of liquidus in Al-Co-Er ternary system was constructed by combining with the phase diagram of binary system reported in literature. In conclusion, 25 four-phase equilibrium reactions were deduced, of which 8 reactions were ternary eutectic and 17 reactions were ectoectic.
2021 Vol. 26 (4): 285-297 [
Abstract
] (
467
)
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1711
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Engineering and Technology
298
Effects of WC content on the microstructure and mechanical properties of TiB
2
-based cermets
WANG Shuai, WANG Jianying, LOU Jia, WANG Jiong, ZHANG Xiang, YANG Hailin
The TiB
2
-WC-0.8Cr
3
C
2
-20(Co/Ni) (mass fraction, %) cermets (
w
(WC) are 0-20%) with high-density were prepared by powder metallurgy (P/M) method. The effects of WC content on the microstructure and mechanical properties of TiB
2
-based cermets were investigated. The results indicate that with the increase of WC content, the solubility of TiB
2
in the bonded phase decreases, and the TiB
2
/ bonded phase interface decreases, which makes the grains of TiB
2
based cermets finer and more uniform. In addition, the addition of WC can significantly improve the mechanical properties of TiB
2
based cermets. When
w
(WC) is 15%, the properties of cermets are the best, and the hardness (HRA), bending strength and relative density reach 92.6±0.2, (1 256±65) MPa and (99.65±0.20)%, respectively. However, the addition of excessive WC (20%) will lead to the partial agglomeration of WC phase and the formation of decarburized phase W
2
C, which will reduce the mechanical properties of TiB
2
based cermets.
2021 Vol. 26 (4): 298-305 [
Abstract
] (
342
)
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717
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306
Effect of three-position doping on thermoelectric properties of BiCuSeO based functional ceramics
FENG Bo
BiCuSeO functional ceramics were doped by Bi/Cu/Se, and Bi
1-
x
Ba
x
/2
Pb
x
/2
Cu
1-
x
Ni
x
Se
1-
x
Te
x
O (
x
=0, 0.02, 0.04, 0.06, 0.08, 0.10) ceramics were prepared by mechanical alloying (MA) and spark pressing sintering (SPS) process. The phase, microstructure, electrical transport parameters and thermal transport parameters were analyzed before and after doping to study the influence on the thermoelectric properties of BiCuSeO functional ceramics. The results indicate that three position doping can hybridize the beneficial effects of several elements, which can significantly improve the conductivity and power factor of BiCuSeO functional ceramics while maintaining a high Seebeck coefficient. The best doping amount
x
is 0.10. The highest power factor of 0.71 mW/(m∙K
2
) and the maximum thermal power value of 1.06 are obtained at 873 K, which are about 2.5 times and 2 times of undoped ceramics.
2021 Vol. 26 (4): 306-312 [
Abstract
] (
371
)
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949
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313
Dimensional stability and mechanical properties of HK30 stainless steel by metal injection molding
TANG Zhihao, PAN Chaomei, HE Pengjiang, LUO Hao, SONG Xinqiang, ZENG Keli
The automotive turbine wheels of HK30 stainless steel were prepared by the metal injection molding (MIM). The effects of MIM process parameters on the dimensional stability and mechanical properties of the turbine wheels were investigated. The results show that when the multi-component plastic-based binder formulation is 90%POM +4%PP+2.5%PW+1%SA+2%EVA+0.5%EBS, the molding has the best shape retention. The optimum powder loading (volume fraction) of feedstock is 60%. The melt flow index (MPF) of feedstock is 1 220.7 g/10 min and the sintering shrinkage uniformity of the samples is the optimal. The best injection conditions are the injection temperature of 190 ℃ and the injection pressure of 237.6 MPa. The shape of the injection blank is intact and the quality consistency is the best. The optimum sintering temperature is 1 310 ℃. The turbine blades has the best dimensional stability at 1 310 ℃, and the relative density of the sample is 99.72%, and the tensile strength, yield strength and hardness (HV) are 600 MPa , 289 MPa and 170, respectively.
2021 Vol. 26 (4): 313-319 [
Abstract
] (
470
)
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1072
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320
Phase field simulation of grain growth in alumina fiber sintering under the influences of temperature, grain size and distribution
ZHANG Lu, LIU Luqun, TANG Sai, MA Yunzhu, LIU Wensheng
The phase field method was used to simulate the growth of pure α-Al
2
O
3
grain generated in situ during high temperature sintering process of alumina fiber prepared by the sol-gel method. Combined with experiments, study the growth behavior and dynamics of α-Al
2
O
3
grains at different sintering temperatures and different initial Al
2
O
3
grain size in the high temperature sintering stage was studied. Both phase field simulation and experimental results show that in the sintering temperature range of 1200-1 500 ℃, the grain growth rate increases significantly with the increase of the sintering temperature, and the grain growth rate is the fastest in the temperature range of 1 400-1 500 ℃. The smaller the initial grain size, the greater the grain growth rate. The simulation result shows that the increasing unevenness of grain size can also promote grain growth.
2021 Vol. 26 (4): 320-328 [
Abstract
] (
648
)
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(834 KB) (
1946
)
329
Electromagnetic wave absorption properties of FeSi@SiO
2
@CoFe
2
O
4
composite powders prepared by chemical co-precipitation method
LAN Haixin, CHEN Qiuli, ZHU Shengzhi, GAO Zhi, LI Liya
FeSi powders were surface modified and coated with TEOS, CoCl
2
∙6H
2
O and FeCl
3
∙6H
2
O, which were used as raw materials to fabricate FeSi@SiO
2
@CoFe
2
O
4
composite powders by chemical co-precipitation method. The effects of calcination temperature on the coating layer structure, magnetic properties and electromagnetic wave absorption properties of composite powders were systematically investigated. The results show that with the increase of calcination temperature from 500 ℃ to 800 ℃, CoFe
2
O
4
@SiO
2
particles evenly were covered on the surface of FeSi powders gradually gather and grow up, which lead to the destruction of the local structure of the coating. The composite powders calcined at 600 ℃ have a uniform and dense SiO
2
@CoFe
2
O
4
coating layer structure, high saturation magnetization (173.2 (A∙m
2
)/kg, high coercivity (3 047.8 A/m) and excellent electromagnetic wave absorption properties. All of the composite powders exhibit maximum reflection loss (RL
max
) of (-53.5)-(-56.5) dB and effective bandwidths (RL≤-10 dB) of 4.64-5.68 GHz. Specially, the composite powders calcined at 600 ℃ achieve effective and strong absorption properties in a wide frequency band under thin thickness. They have three strong absorption peaks with the RL
max
values of -56.5 dB (8.76 GHz, 2.78 mm), -49.2 dB (14.00 GHz, 2.11 mm) and -40.5 dB (15.28 GHz, 1.60 mm), and wide effective bandwidths with the effective bandwidths (RL≤-10 dB) of 4.80 GHz, 6.24 GHz and 3.44 GHz, respectively. The electromagnetic wave loss mechanism of the powder is excellent impedance matching characteristics, high electromagnetic wave attenuation constant, multiple dielectric relaxation process, multiple interface polarization, high magnetic loss and dielectric loss ability.
2021 Vol. 26 (4): 329-337 [
Abstract
] (
427
)
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1403
)
338
Preparation and hydrogen evolution performance of polyaniline coated NiSe electrode
BAI Yuting, BAI Linghong, LEI Ting
A two-step method of hydrothermal and electrochemical deposition was used to prepare a polyaniline-coated nickel selenide hydrogen evolution electrode (PANI/NiSe/NF) supported on nickel foam. The morphology, constitution and electrochemical properties of the as-prepared specimen were characterized by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical tests. The results show that using nickel chloride as the nickel source, the needle-like NiSe supported on nickel foam was successfully prepared by hydrothermal method, and the coating of conductive polymer polyaniline has not change its morphology. The electric double layer capacitance of PANI/NiSe/NF electrode is 12 560 μF/cm
2
, which is larger than that of the NiSe/NF electrode 9 200 μF/cm
2
. PANI/NiSe/NF electrode has a larger electrochemically active area, 58 mV lower initial over potential for hydrogen evolution than uncoated NiSe/NF electrode and 133 mV/dec Tafel slope. PANI/NiSe/NF electrode exhibites a hydrogen evolution over potential of 203 mV at current density of 10 mA/cm
2
, showing excellent hydrogen evolution catalytic activity. The coating of the conductive polymer PANI can not only improve the hydrogen evolution activity of NiSe/NF electrode, but also reduce the charge transfer resistance, and accelerate the charge transfer rate, and significantly improved the electrode stability.
2021 Vol. 26 (4): 338-345 [
Abstract
] (
349
)
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1099
)
346
Rolling behavior and mechanical properties of Ti-Cu-Mo laminated composites
CUI Yuhao, CAO Yuankui, LI Na, LI Mou, LIU Yong
Ti-Cu-Mo laminated composites were fabricated through hot pressing and subsequent hot rolling by using Ti, Cu and Mo foils as raw materials. The effect of rolling behavior of Ti-Cu-Mo laminated composites and the rolling amount on the microstructure evolution of each layer were studied, and the influence mechanism of component layer and interface structure on the overall strength and plasticity of the composites was further revealed. The results show that hot rolling mainly results in refining and continuous hardening of Cu layers, but has limited influence on Ti and Mo layers in Ti-Cu-Mo laminated composites. The yield strength of the composites conforms to the rule of mixing, but it is also affected by the hardening and necking of the layer components. The Ti-Cu-Mo laminated composite achieves satisfied combination of yield strength (561 MPa) and plasticity (elongation is 7%) at a rolling deformation of 80%, mainly due to the sufficient hardening of Cu layers and the continuity maintaining of Mo layers.
2021 Vol. 26 (4): 346-354 [
Abstract
] (
376
)
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(795 KB) (
925
)
355
Catalytic debinding and sintering process of metal injection molding used by Ti/TiH
2
YAO Yincheng, QIU Yaohong, XIAO Zhiyu
In order to solve the problem of titanium processing and reduce the processing cost, cheap TiH
2
powders were mixed with spherical titanium powders with different mass proportions to form Ti/TiH
2
composite titanium powders, which were mixed with polyoxymethylene-based binder for catalytic debiuding and sintering process of metal injection molding. In the research of catalytic debinding process, by comparing the debinding rate of the four groups of injection blanks at different debinding temperatures and time, it was determined that the optimal catalytic debinding temperature was 120 ℃ and the best debinding time was 5 hours. Under these conditions, the debinding rate of the four groups of injection blanks all exceeded 85%, reaching the expected catalytic debinding target. In the sintering process research, the shrinkage, density and tensile strength of the four groups of debinding blanks at different sintering temperatures were studied, and the optimal sintering temperature was 1 250 ℃. Under the sintering condition of 1 250 ℃ for 2 h, with the increase of the proportion of TiH
2
, the comprehensive mechanical properties of the sintered samples decrease. The sintered sample with Ti and TiH
2
mass proportions of 4:1 has good comprehensive mechanical properties, with a tensile strength of 649 MPa, a hardness of 241 HV, and an elongation of 6.9%. The TiH
2
powder can effectively reduce costs, and has a good industrial application prospect. It is of great significance to the wide application of titanium and titanium alloys.
2021 Vol. 26 (4): 355-362 [
Abstract
] (
526
)
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(869 KB) (
1171
)
363
Effects of sintering temperature and aging process on microstructure and properties of Cu-Fe alloy prepared by Cu@Fe composite powder
MAO Mincong, GAN Xueping, ZHOU Kechao, ZHAO Qi, ZHU Fan
50Cu@50Fe composite powder was prepared by electroless copper plating, and then the coated composite powder was compression molded and sintered in a hydrogen atmosphere at 850-1 050 ℃ to prepare 50Cu-50Fe alloy, and then the alloy was subjected to cold rolling deformation, solid solution and aging heat treatment. The effects of sintering temperature, aging temperature and aging time on the structures, tensile strength and electrical conductivity of 50Cu-50Fe alloy were studied. The results show that after sintering at 1 050 ℃ for 1 h, the relative density of the 50Cu-50Fe alloy reaches 95.5% and the tensile strength is 392 MPa. The sintered 50Cu-50Fe alloy after deformation and solid solving, the relative density increases to 99.4%, the tensile strength is 422 MPa, and the electrical conductivity is 18.11 IACS%. After aging at 450 ℃ for 4 h, a large number of dispersed spherical Fe-rich phase particles precipitate in the Cu matrix, the tensile strength reaches 492 MPa, and the electrical conductivity is 39.11 IACS%. When the ageing temperature is higher than 450 ℃, the Fe-rich phase particles aggregate and grow at the grain boundaries of the Cu matrix, resulting in a decrease in the mechanical properties of the 50Cu-50Fe alloy. After aging at 550 ℃ for 4 h, the tensile strength of the 50Cu-50Fe alloy is 422 MPa, and the electrical conductivity is 45.22 IACS%.
2021 Vol. 26 (4): 363-371 [
Abstract
] (
397
)
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478
)
372
Hot deformation behavior and processing map of Al-Cu-Mg-Mn-Sc-Zr aluminium alloy
ZHOU Xu, LIU Zuming, HUANG Lanping, AI Yongkang, CAO Bin, YE Shupeng
The hot deformation behavior of Al-Cu-Mg-Mn-Sc-Zr aluminium alloy is a basis for formulating deformation processing technology. The isothermal compression simulation experiment was carried out on the homogenized Al-Cu-Mg-Mn-Sc-Zr aluminium alloy by Gleeble-3500 system under temperature of 633-753 K and strain rate of 0.01-10 s
-1
, the true strain-true stress curves were obtained, and deformation activation energy was calculated, and processing map was built-up. The results show that flow stress decreases and the softening mechanism changes from dynamic recovery to dynamic recrystallization with the increase of deformation temperature or the decrease of strain rate. The precipitates in the deformed alloy pin dislocation slip and grain boundary migration, and hinder recrystallization. The activation energy is 153.5 kJ/mol. 633-663 K, 0.01-0.07 s
-1
and 693-723 K, 0.01-0.1 s
-1
are the best deformation regions.
2021 Vol. 26 (4): 372-380 [
Abstract
] (
392
)
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(801 KB) (
645
)
381
Synergistic improvement of optical properties of Cs
4
PbBr
6
nanocrystals by water and dimethyl sulfoxide
SHI Zikuan, YANG Yu, LIN Liangwu
We developed a new ligand assisted reprecipitation method (LARP) for synthesis of highly luminescent and stable Cs
4
PbBr
6
nanocrystals, in which acetone, oleamine (OM) and oleic acid (OA) were used as precursor, water and dimethyl sulfoxide (DMSO) as adjuvant. The synergistic influence mechanism of water and DMSO on the optical properties of Cs
4
PbBr
6
was analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD), diffuse reflection absorption spectrum, fluorescence spectroscopy and fourier transform infrared spectroscopy (FTIR). The results showed that the addition of water and dimethyl sulfoxide can completely occupy the vacancy of lead ion and promote the crystallization, which makes bromine ion easier to embed into the site, and so that the crystallization is better. The synergistic effect of water and dimethyl sulfoxide can effectively promote the binding of the ligand to the surface of Cs
4
PbBr
6
, thus optimizing the passivation effect. At the same time, this synergistic effect can promote the formation of Cs
4
PbBr
6
/CsPbBr
3
mosaic structure in Cs
4
PbBr
6
nanocrystalline matrix, which greatly improves the optical properties of Cs
4
PbBr
6
nanocrystals.
2021 Vol. 26 (4): 381-386 [
Abstract
] (
390
)
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