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2021 Vol. 26, No. 6
Published: 2021-12-15
Engineering and Technology
Theoretical Research
Review
Review
483
Research progress on the fabrication technology of porous alumina ceramics
HE Xiang, HUANG Qianli, CHEN Yuhui, LIU Bowei, LIU Yong
DOI: 10.19976/j.cnki.43-1448/TF.2021064
Porous alumina ceramics are widely used as refractory materials, electrical insulators, wear-resistant mechanical parts, filtering materials and catalytic support due to their excellent mechanical properties, corrosion resistance, large specific surface area and stable chemical properties. The pores in porous alumina ceramics are commonly created by partial sintering, replica, sacrificial template or direct foaming method. Specific porous structure and porosity can be obtained by employing appropriate pore-creating method. Conventional sintering of alumina ceramics is usually characterized by high temperature, long duration, easy formation of coarse grains and residual pores. The application of advanced sintering technologies such as oscillatory pressure sintering, spark plasma sintering and microwave sintering can effectively overcome these shortcomings and comprehensively improve material properties. In order to provide references for the investigation, development and application of novel porous alumina ceramics, we reviewed the research progress on two aspects including pore-creating method and sintering technology involved in the fabrication process of porous alumina ceramics.
2021 Vol. 26 (6): 483-491 [
Abstract
] (
2057
)
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(268 KB) (
3487
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492
Research progress of oxide dispersion strengthening copper alloys
WANG Weiyang, XIAO Zhu, LEI Qian, ZHANG Xiukuang, LI Zhou
DOI: 10.19976/j.cnki.43-1448/TF.2021067
As one of advanced Cu-based alloys, oxide particle-enhanced dispersion-strengthened copper alloys are widely used in rail transit, national defense industry and nuclear reactors. In this paper, copper alloy composites reinforced with Al
2
O
3
, Y
2
O
3
and ZrO
2
oxide particles are reviewed, and their fabriaction, microstructure and physical properties are summarized. The relative problems existing in development and application are given, and the development trend is analyzed and forecasted.
2021 Vol. 26 (6): 492-499 [
Abstract
] (
1371
)
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(0 KB)
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(670 KB) (
3062
)
Theoretical Research
500
Precipitated activation energy and TTT curves of primary α phases in TB17 titanium alloy
LÜ Yaping, ZOU Jindian, ZHANG Hongling, FAN Kai, LI Chao, ZHU Zhishou
DOI: 10.19976/j.cnki.43-1448/TF.2021069
The precipitation behavior and temperature range of grain boundary α phase and Widmanstatten α phase during the process of uniform cooling (5 K/min) from single-phase region (5 K/min) to two-phase regionin TB17 titanium alloy were investigated by microstructure observation and differential thermal analysis. The temperature ranges of the two phases are determined to be 1 120-992 K and 920-895 K, respectively. Then the Avrami-Johnson-Mehl criterion was adopted to calculate the activation energy of the two type α phases and the results are
Q
αb
=253.236 kJ/mol, and
Q
αI
= 503.188 kJ/mol, and the precipitation kinetics equation of the two kinds of α phase are acquired, subsequently. The TTT curves of two type α phases are constructed based on the equation. According to the TTT curves results, the tip temperature of grain boundary α and Widmanstatten α phase is about 1 023 K and 905 K respectively.
2021 Vol. 26 (6): 500-506 [
Abstract
] (
1211
)
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(0 KB)
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(642 KB) (
2018
)
Engineering and Technology
507
Platinum paste sintering process of thick film heating element on nickel alloy substrate
LI Zhiqiang, LEI Ping, YOU Junheng, LI Tinghua, HAN Jingmei, LÜ Xi, WANG Hao, SHANG Shanzhai, ZHU Donglai
DOI: 10.19976/j.cnki.43-1448/TF.2021071
The glass-ceramics insulating layer was prepared on the surface of GH783 alloy by print-sintering process, and then the platinum paste layer was sintered on the surface of the insulating layer to obtain the thick film heating circuit. The surface and section morphology of the resistance layer after the sintering of platinum paste were observed by SEM. The resistance of thick film heating circuit was measured by DC resistance meter. The resistance temperature coefficient of the heating circuit was measured by the resistance value and temperature characteristic test system of ceramic heating plate. The effects of sintering temperature and holding time on the microstructure and resistance value of resistance layer were studied. The optimal sintering process parameters of platinum paste were determined as follows: sintering temperature of 850 ℃, holding time of 5 min. The accuracy of resistance temperature coefficient of GH783 thick film heating element is 0.24%, and it is 4.86 s when it is heated from room temperature to 350 ℃. It shows excellent heating performance, which provides design ideas and experimental cases for the preparation of metal-based heating element.
2021 Vol. 26 (6): 507-514 [
Abstract
] (
1026
)
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(0 KB)
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(1673 KB) (
1103
)
515
Structure and properties of Ti/HAp composites prepared by indirect 3D printing
LIU Yanjun, LIU Ye, TAN Yanni
DOI: 10.19976/j.cnki.43-1448/TF.2021072
Rb-Hydroxyapatite (Rb-HAp) powders with different Rb content were prepared by ion-doped modification method, and then Ti/Rb-HAp composites were prepared by indirect 3D printing method. The morphology and phase composition of the composites were analyzed, the mechanical properties of the composites were determined, and the biological properties of the composites were studied by cell culture and cell proliferation and differentiation experiments in vitro. The results show that Ti/Rb-HAp composites have higher porosity, and the porous structure is favorable for the inward growth of new bone tissue and the transport of body fluid. The addition of Rb can improve the bending strength and compressive strength of Ti/HAp composites, and the compressive strength increases slightly with the increase of Rb content. Compared with the pure Ti group, Ti/Rb-HAp composites promote the proliferation and ALP activity of MG-63 cells, so the composite has good cytocompatibility. After immersion in simulated body fluid, a dense apatite layer formed on the surface of the composite, indicating that the Ti/HAp composites have excellent biological activity.
2021 Vol. 26 (6): 515-524 [
Abstract
] (
719
)
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(0 KB)
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(972 KB) (
801
)
525
Effects of sintering aids on microstructure and properties of non-isothermal sintering alumina ceramics
FANG Haojie, HE Yiwen, ZHANG Xiaoyun, NIU Wenbin, WU Lixiang, GUO Weiming, HUANG Rongxia, QIAO Guanjun, LIN Huatai, ZENG Xiong
DOI: 10.19976/j.cnki.43-1448/TF.2021074
On the basis of pressure less sintering, the effects of MgO-Y
2
O
3
, MgO-Y
2
O
3
-La
2
O
3
additives and sintering process containing one-step and two-step non-isothermal sintering on the microstructure and properties of Al
2
O
3
ceramics were studied. The results show that using non-isothermal sintering method can significantly refine the Al
2
O
3
grains. When MgO-Y
2
O
3
are used as sintering aids, the closed porosity of Al
2
O
3
ceramics prepared by one-step sintering and two-step non-isothermal sintering method are 1.88% and 3.93%, respectively, and its corresponding Al
2
O
3
grains are 0.42 μm and 0.38 μm, respectively. At the same time, when MgO-Y
2
O
3
-La
2
O
3
are used as sintering additives, the closed porosity of ceramics prepared by one-step sintering method and two-step non-isothermal sintering method are 3.59% and 2.82%, respectively, and its corresponding Al
2
O
3
grains are 0.40 μm and 0.42 μm, respectively. When MgO-Y
2
O
3
and MgO-Y
2
O
3
-La
2
O
3
are used as sintering aids, the Al
2
O
3
ceramics prepared in a one-step sintering process have higher hardness, and they are (18.3±0.5) GPa and (18.2±0.6) GPa, respectively. In order to obtain the higher fracture toughness, it is necessary to use MgO-Y
2
O
3
as a sintering aid to prepare Al
2
O
3
ceramic by one-step sintering method, and the fracture toughness value can reach (4.6±0.3) MPa·m
1/2
.
2021 Vol. 26 (6): 525-530 [
Abstract
] (
895
)
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(0 KB)
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(406 KB) (
962
)
531
Preparation and friction properties of bronze-graphite-MoS
2
self-lubricating materials
WANG Huiling, JIANG Feng, TONG Mengmeng, WU Mingjin, YE Pengcheng
DOI: 10.19976/j.cnki.43-1448/TF.2021060
Powder metallurgy bronze-graphite-MoS
2
self-lubricating material was prepared by Cu-25%Sn alloy, copper-coated graphite and MoS
2
powders at sintering temperature of 740-820 ℃. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) were used to observe and analyze the microstructure of the sintered materials and wear surface morphology after friction under 4 N and 10 N loads, respectively. The results show that with the increase of sintering temperature, the hardness and density of the bronze-graphite-MoS
2
self-lubricating materials show a trend of first increasing and then decreasing. The size and number of pores of the material sintered at 780 ℃ are smaller, so the density and hardness of materials are relatively large. The average friction coefficient under 10 N and 4N loads are 0.28 and 0.36, respectively. In the process of friction and wear, a layer of lubricating film composed of graphite and MoS
2
is formed on the surface of the materials, which provides lubrication for the self-lubricating material and a better lubrication effect is under a load of 10 N.
2021 Vol. 26 (6): 531-536 [
Abstract
] (
708
)
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(0 KB)
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(564 KB) (
981
)
537
Effects of sintering temperature on microstructure and properties of carbon polymer dot/copper composites
YANG Yajie, LI Zhaojie, ZHAO Wenmin, BAO Rui, YI Jianhong
DOI: 10.19976/j.cnki.43-1448/TF.2021066
Carbon polymer dot/copper composites were prepared by powder metallurgyusing carbon polymer dot (CPD) as copper reinforcement. The density, hardness, tensile properties and wear resistance of CPD/Cu composites at different sintering temperatures (350-750 ℃) were analyzed and measured. The results show that CPD is uniformly dispersed in the copper matrix, and the amorphous carbon in the CPD shell network is conducive to the formation of a good interface bond between the CPD and the copper matrix. The relative density of the CPD/Cu matrix composites is more than 95%, indicating that the compactness of the composites is high and the porosity is small. The mechanical properties and friction and wear properties of CPD/Cu composites are significantly higher than those of pure Cu materials. With the increase of sintering temperature, the density, hardness and tensile strength of the CPD/Cu composites show the rules of increase and then decrease. The hardness is higher than Cu matrix by 49.4 HV, the composite sintered at 550 ℃ obtains the best comprehensive properties, the tensile strength (334.0 MPa) is about 25.6% higher than that of pure Cu, and the volume wear rate is 17.67×10
-12
m
3
/m.
2021 Vol. 26 (6): 537-546 [
Abstract
] (
823
)
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(0 KB)
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(858 KB) (
1086
)
547
Microstructure and properties of new nickel-based superalloy powder prepared by argon atomization
NONG Bizhong, ZHANG Yazhou, LIU Zuming, WEI Bing, CAO Bin
DOI: 10.19976/j.cnki.43-1448/TF.2021044
New nickel-based superalloy powder for selective laser melting with a total mass fraction of Al and Ti less than 4% was prepared by argon atomization. The composition, phase, morphology, microstructure and properties of the new nickel-based superalloy powder were characterized. The results show that the total mass fraction of Al and Ti in the new nickel-based superalloy powder was 3.82%. Small particle size powder (particle size<20 μm) has a compact interior structure, mainly cellular structure, and uniformly composition, and its micro-hardness (HV) reaches 265. As the particle size of the powder increases, the number of dendrites in the powder increases, and solidification shrinkage pore and particle-coating defect appear in some large-diameter (particle size>40 μm) powder. After sieving, the powder with a particle size of 15-44 μm has a concentrated particle size distribution, a median diameter
D
V50
of 19.7 μm, the flow- ability and apparent density are 15.14 s/50 g and 4.15 g/cm
3
, respectively.
2021 Vol. 26 (6): 547-553 [
Abstract
] (
704
)
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(0 KB)
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(904 KB) (
1308
)
554
Preparation of anisotropic Sm
2
Fe
17
N
3
magnetic powders with enhanced coercivity by high-energy ball milling
LI Wei, GUO Jiarui, ZUO Siyuan, WANG Yana, HUANG Guangwei, ZHENG Liyun
DOI: 10.19976/j.cnki.43-1448/TF.2021063
Sm
2
Fe
17
N
3
magnetic powders were prepared by high-energy ball milling. The effects of ball milling times on the magnetic properties and microstructure of Sm
2
Fe
17
N
3
magnetic powders were studied. The results show that the coercivity of Sm
2
Fe
17
N
3
powders increases first and then decreases with the milling time increases from 0 min to 60 min. When the milling time is 12 min, the grain size of Sm
2
Fe
17
N
3
phase decreases from 40.8 nm of the original powder to 31.8 nm. The powder has the highest coercivity of 875.6 kA/m, and the magnetic powder still maintains anisotropy. However, when the ball milling time is 30 mins, although the grain size is further reduced, the Sm
2
Fe
17
N
3
decomposes to form soft magnetic phases such as SmN and α-Fe, resulting in a decrease in the coercivity of the magnet. When the milling time is 60 min, the coercivity of magnetic powders decreases to 477.6 kA/m. This work provides an effective way for the preparation of high-quality Sm
2
Fe
17
N
3
powder precursors for the preparation of high-performance Sm
2
Fe
17
N
3
bonded magnets.
2021 Vol. 26 (6): 554-559 [
Abstract
] (
808
)
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(0 KB)
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(493 KB) (
1137
)
560
Preparation of Ni-Fe alloy by carbothermal reduction of high iron red mud
SUN Kai, WANG Wei, ZHANG Ziyang, ZHU Guang
DOI: 10.19976/j.cnki.43-1448/TF.2021042
Ferro-nickel alloy was prepared by direct reduction at high temperature with Bayer process using high iron red mud and laterite nickel ore as raw materials and coke powder as reducing agent. The effects of different reduction conditions on the reduction process of red mud and laterite nickel ore were studied by analyzing and testing the alloys and residues prepared at different temperatures, reducing agent ratio and additive ratio. The results show that the reduction yield of the alloy increases with the increase of the coke powder contents of reducing agent. When the addition ratio of coke powder is 30% and the reduction temperature is 1 550 ℃, the total recovery of the iron alloy reaches 89.6%. With the addition of additives CaO and Na
2
CO
3
, the separation effect of metal and slag is significantly improved. When the addition ratio of Na
2
CO
3
is 6%, the nickel in laterite nickel ore will be reduced completely to the alloy. The retained austenite decreases and then transforms into martensite and improves the Rockwell hardness to 52.5.
2021 Vol. 26 (6): 560-566 [
Abstract
] (
715
)
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(0 KB)
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(1249 KB) (
694
)
567
Effect of hot rolled deformation on microstructure and mechanical properties of Fe-14Cr-3W-0.4Ti alloy
LU Sizhe, LIU Zuming, LI Quan, REN Yake, WEI Bing, PENG Weicai
DOI: 10.19976/j.cnki.43-1448/TF.2021055
The atomized Fe-14Cr-3W-0.4Ti (mass fraction, %) alloy powder was subjected to mechanical ball milling for 60 h, hot extrusion forming at 950 ℃, hot rolling at 950 ℃ and annealing at 1 050 ℃/1 h to obtain Fe-14Cr-3W-0.4Ti alloy. The effects of hot rolling deformation on the microstructure and mechanical properties of Fe-14Cr-3W-0.4Ti alloy were studied by Scanning Electron Microscopy (SEM) and Electron Backscattering Diffraction (EBSD) analysis. The results show that hot rolling deformation can effectively control the grain size of Fe-14Cr-3W-0.4Ti alloy and improve the mechanical properties of the alloy. After hot rolling, the grain size of the extruded alloy is obviously refined, the grain size decreases first and then increases, and the tensile strength of the alloy also increases first and then decreases with the increase of hot rolling deformation, and the optimum hot rolling parameters of the alloy are 950 ℃/40%. After hot rolling at 950 ℃/40% deformation, the average grain size of the alloy is the smallest and for 1.39 μm, and the tensile strength and elongation of the alloy reach 1 161 MPa and 9.5%, respectively. The tensile strength is increased by 31.2% compared with that of the extruded alloy.
2021 Vol. 26 (6): 567-574 [
Abstract
] (
701
)
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(0 KB)
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(756 KB) (
603
)
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