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2022 Vol. 27, No. 2
Published: 2022-04-15
Engineering and Technology
Theoretical Research
Review
Review
121
Research progress on 3D printing of pure copper and copper alloys
WU Yiyou, DING Rou, CHEN Chao, LI Ruidi, ZHOU Kechao
DOI: 10.19976/j.cnki.43-1448/TF.2021084
Pure copper and copper alloys attract more and more attention due to their outstanding properties such as excellent electrical and thermal conductivities, ductility and high corrosion resistance. In this work, the research progress on the process characteristics, mircostructure evolution and mechanical properties of 3D printing pure copper and copper alloys in recent years were mainly summarized. The results show that the major challenge of pure copper and copper alloys fabricated by laser selective melting and laser melting deposition is to reduce the high reflectivity to the laser which can improve the density of the parts, manupulate the microstructure and obtain excellent mechanical properties. Process parameter optimization of selective electron beam melting and binder jetting need to be addressed due to the lower density and greater shrinkage of parts respectively, although it can overcome the problems caused by higher laser reflectivity of pure copper and copper alloys. Besides, this work introduced the application prospects about 3D printing of pure copper and copper alloys. Finaly, the progress on 3D printing of pure copper and copper alloys were also summarized and prospected.
2022 Vol. 27 (2): 121-128 [
Abstract
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2703
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2264
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Theoretical Research
129
Friction temperature field analysis of three brake rings paired with copper-based friction materials
ZHAO Hengyang, LIN Xueyang, LIU Rutie, CHEN Jie, LI Zhengzhou, XIONG Xiang, LIAO Ning
DOI: 10.19976/j.cnki.43-1448/TF.2021110
Based on MM-1000 friction and wear testing machine, the temperature field and heat distribution of different friction pairs were evaluated combining test and simulation. Using Workbench platform, the finite element simulations were implemented on pertaining models built in actual scale. Under various initial rotation speed, by inspecting friction temperature fields of brake rings made of carbon-ceramic, alloyed steel and cast steel, against lab-made copper-based powder metallurgy ring respectively, heat distributions in each brake process were compared and analyzed. The results show that the temperature field of carbon ceramic ring is quite different from that of cast steel ring and alloy steel ring. The temperature rise on the friction surface of the carbon ceramic ring is much higher than that of the alloy steel ring and the cast steel ring, and the axial direction also shows a large temperature rise and temperature gradient. Meanwhile, the copper-based friction ring paired with the carbon-ceramic ring receives more heat distribution and shows a greater temperature rise, which puts forward higher requirements on the high-temperature friction and wear properties of the mating materials paired with carbon-ceramic materials.
2022 Vol. 27 (2): 129-139 [
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739
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Engineering and Technology
140
Microstructure and mechanical properties of powder hot extruded 7075 aluminium alloy
JING Cuiru, ZHANG Jiantao, WEN Liping, XIAO Zhiyu
DOI: 10.19976/j.cnki.43-1448/TF.2021092
7075 aluminum alloy bar was prepared by powder hot extrusion method. The microstructures of the alloy bar were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In addition, the tensile properties of the samples were also tested. The influences of the extrusion ratio on the microstructure and mechanical properties of the bar were investigated, and the strengthening mechanism was calculated in theory. The results show that a large number of second phase MgZn
2
precipitates are desolventized and precipitated during hot extrusion at 500 ℃ with extrusion ratios of 9, 16, 25, and 36. With increasing extrusion ratio, the metallurgical bonding between the powder particles becames more sufficient, and the tensile strength and elongation of the alloy increase continuously. A high tensile strength of 492 MPa with an elongation of 27.6% is obtained at an extrusion ratio of 36. The fracture mode is a ductile-brittle-bonding fracture. The strengthening mechanism is the combined action of fine-grain strengthening, dislocation strengthening, second phase strengthening and solution strengthening.
2022 Vol. 27 (2): 140-150 [
Abstract
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1210
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151
Mechanical and antioxidant properties of C
f
/SiC-ZrC composites prepared by slurry injection
JIANG Yi, LI Guodong, YU Shijie, WANG Yang
DOI: 10.19976/j.cnki.43-1448/TF.2021096
In this paper, SiC and ZrC powders were used as raw materials to prepare a water-based ceramic slurry with a volume fraction of 30% solid content. Slurry injection method and vacuum impregnation method were used to introduce slurry into the carbon fiber preform with a density of 0.2 g/cm
3
. Combined with chemical vapor infiltration and reactive melt infiltration, C
f
/SiC-ZrC composites were prepared. The morphology and microstructure of the blank and C
f
/SiC-ZrC composites were observed and analyzed. The density, porosity, bending strength and oxidation resistance of the composites were measured. The results show that, compared with the vacuum impregnation method, the SiC and ZrC powders can be uniformly introduced into the carbon fiber preform by slurry injection method, and the green body volume is filled by 37.3% at one time. The average density of the injected composites is 2.91 g/cm
3
, and the bending strength of the center and outer layer of the composites is 41.12 MPa and 43.90 MPa, respectively. The fracture modes of the composites are all pseudoplastic fracture. After oxidation in air for 120 min, a relatively continuous and dense oxide layer is formed on the surface of the injected composite. Oxidation tends to be balanced and stable, the samples show good antioxidant properties.
2022 Vol. 27 (2): 151-160 [
Abstract
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729
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847
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161
Densification and mechanical properties of ball milled M2 high speed steel powder reinforced with Mo
2
C
CHEN Nan, LONG Xuehu, TENG Hao, LI Zhiyou
DOI: 10.19976/j.cnki.43-1448/TF.2021100
High-energy ball milled M2 high speed steel powder mixed with 0-10% (mass fraction, the same below) Mo
2
C were cold-pressed and subsequently densified by sintering under vacuum. The densification behavior and mechanical properties of the sintered samples were investigated, and the effect of Mo
2
C on the sintering densification of M2 steel powder was analyzed. The results show that the refinement of raw material powder by high-energy ball milling can improve the sintering activity of powder and promote the densification of the green compact in the middle stage of sintering. Both M2 steel and Mo
2
C reinforced M2 steel with nearly full density (over 98% of theory density) have been obtained at 1 180 ℃ by solid state sintering. The Mo
2
C added to M2 steel powder substantially reacts with Fe matrix and transforms to M
6
C phase at 950 ℃, and the reactive sintering and activated sintering can accelerate the densification of the green compacts at the intermediate stage of sintering. A large number of dispersed M
6
C and M
2
C carbides formed during the mid and later stage sintering inhibit grain growth of matrix and improve the hardness and bending strength of sintered compacts. Attracting mechanical properties of sintered M2 steel reinforced with 10% Mo
2
C particles are achieved, showing satisfactory bending strength of 3 135 MPa and hardness of 59.6 HRC. The sinter ability and mechanical properties of M2 steel are improved effectively by the raw powders refinement, reaction diffusion of Mo
2
C and redox reaction of metal particles, which is expected to provide a technical reference for the preparation of other difficult- to-sinter high speed steels.
2022 Vol. 27 (2): 161-170 [
Abstract
] (
960
)
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171
Effects of confined hydrogen densification treatment on the density and mechanical properties of powder metallurgy Ti-6Al-4V alloy
DUAN Zhongyuan, CHEN Zoujun, ZHU Xianzhi, LIU Bin, LIU Yong, LIANG Xiaopeng, ZHOU Chengshang
DOI: 10.19976/j.cnki.43-1448/TF.2021104
Titanium hydride powder and 6Al-4V pre-alloyed powder were used as raw materials to prepare Ti-6Al-4V alloy by vacuum sintering. Then confined hydrogen densification treatment in a high-purity hydrogen atmosphere was carried out, and finally vacuum annealing was performed to remove the residual hydrogen in the alloy. The microstructure morphology of the alloy was observed by an optical microscope. The density and tensile properties of the alloy were determine, and the fatigue performance testing was tested using the MTS-810 hydraulic servo fatigue testing machine . The results show that the confined hydrogen densification treatment can reduce the residual porosity of the sintered Ti-6Al-4V alloy from 2.5% to 1.3%, and the relative density can reach (98.7±0.3)%. After confined hydrogen densification treatment, the tensile strength of the alloy increases from (936±18) MPa to (959±10) MPa, and the elongation increases from (6.7±1.6)% to (12±1.1)%. At the same time, the fatigue performance is improved, and the cycle times reach 4670 cycles under the condition of 0.5% cyclic strain amplitude.
2022 Vol. 27 (2): 171-179 [
Abstract
] (
615
)
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180
Effects of vacuum hot-pressing time and pressure on the microstructure and mechanical properties of CoCrCuFeNi high-entropy alloy
ZHAO Zhenguo, ZHU Heguo
DOI: 10.19976/j.cnki.43-1448/TF.2021102
The CoCrCuFeNi high-entropy alloy was prepared by vacuum hot-press sintering. The effects of hot-pressing time and pressure on the microstructure and mechanical properties of the CoCrCuFeNi high-entropy alloy were studied. The results show that when the pressure is 10 MPa, all high-entropy alloys contain dual FCC phases and a small amount of Cr-rich phase. With the increase of hot-pressing time, the size of the Cr-rich phase increases and the compressive strength and hardness of the high-entropy alloy first increase and then decrease. When the hot-pressing time is 1.5 h, and the pressure increases from 10 MPa to 30 MPa, the separation phenomenon of Cu-rich FCC phase and Cu-poor phase disappears in the alloy. With the increase of hot-pressing pressure, the compressive strength of the high-entropy alloy first increases and then decreases, but there is no significant change in hardness. When the hot-pressing time is 1.5 h and the pressure is 20 MPa, The alloy has the highest compressive strength of 1 229 MPa and a hardness (HV) of 3 136 MPa.
2022 Vol. 27 (2): 180-186 [
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651
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690
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187
Flexural property of C/C-SiC-Cu composites
BAI Kailun, ZHANG Huan, YIN Jian, XIONG Xiang, ZHANG Hongbo, XIE Fengminyu
DOI: 10.19976/j.cnki.43-1448/TF.2021106
Using carbon non-woven fabric/fibre web as the reinforcements, porous C/C composites were prepared by chemical vapor infiltration (CVI) deposition of pyrolytic carbon, and then SiC was deposited by CVI and Cu was infiltrated under pressure successively. Fianlly, C/C-SiC-Cu composites were obained. The effects of density of porous C/C composites and SiC contents (volume fraction
φ
, the same below) on the flexural property of C/C-SiC-Cu composites were investigated, respectively. The results show that with the increase of porous C/C composites density and SiC content, pyrolytic carbon and SiC form an interface with high binding strength around carbon fibers, and the strengthening effect of them can be fully played. So the flexural strength of C/C-SiC-Cu composites significantly increase. When the bending process is carried out, pyrolytic carbon and SiC matrix can inhibit the pullout of carbon fibers. The flexural load-displacement curve of C/C-SiC-Cu composites is ups and downs step-like, showing obvious characteristics of pseudoplastic fracture.
2022 Vol. 27 (2): 187-195 [
Abstract
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737
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196
Microstructure and wear-corrosion resistance performance of laser cladding martensite/ferrite coating
ZHANG Lei, CHEN Xiaoming, HUO Jiaxiang, ZHANG Kai, CAO Wenjing, CHENG Xinchuang
DOI: 10.19976/j.cnki.43-1448/TF.2021090
To improve the corrosion resistance and wear resistance of piston rod, Fe-based coatings with martensite and ferrite structure were prepared on 45
#
steel by laser cladding. The phase compositions, microstructure and elements distribution of the coatings were characterized by X-ray diffractometer, scanning electron microscope and X-ray energy dispersive spectrometer. The microhardness and wear resistance of the coatings were tested by Vickers hardness tester and dry sliding friction wear tester. Furthermore, the corrosion resistance of laser cladding Fe-based coatings was studied by electrochemical workstation. The results show that the phase of laser cladding Fe-based alloy coating is mainly composed of α-Fe, Ni-Cr-Fe, γ-(Fe,C), Fe
9.7
Mo
0.3
. The main microstructure is martensite, ferrite and a small amount of residual austenite. The dendritic structure of coating is uniform, compact, without cracks or pores. The coating and the substrate are bonded metallurgically. The hardness and wear resistance of the coatings increase with increasing laser power. The average microhardness (HV) of the coatings at 2.4 kW is as high as 647.64 and the wear resistance is 9.37 times that of 45 steel. The wear mechanisms of the coatings are abrasive wear. The corrosion resistance of laser cladding Fe-based alloy coating firstly increases and then decreases with the increase of laser power. When the laser power is 2.0 kW, the coating has the best corrosion resistance, which is significantly higher than the commonly used carbon steel, stainless steel and electroplating hard for piston rods. It can replace electroplated chromium in related fields.
2022 Vol. 27 (2): 196-204 [
Abstract
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891
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205
Microstructure and mechanical properties of Al-Mg-Sc-Zr alloy prepared by selective laser melting
ZHU Xi, YUNA Tiechui, WANG Minbu, HUANG Lan, LI Ruidi, LÜ liang, YI Chushan, LUO Qiang
DOI: 10.19976/j.cnki.43-1448/TF.2021103
Al-Mg-Sc-Zr alloy were prepared by selective laser melting (SLM) technology with gas atomization powders as raw materials. The effects of processing parameters on metallurgical defects, microstructure, and tensile properties of SLM-fabricated samples were investigated through optical microscope analysis, scanning electron microscopy analysis, and unidirectional tensile test at room temperature, etc. The results show that SLM-fabricated Al-Mg-Sc-Zr alloy is characterized with mixed grains structure in which fine equiaxed grains and coarse columnar grains alternate. It can be obviously found that element segregation in fine equiaxed grain region and precipitated Al
3
(Sc,Zr) particles pin at the grain boundary. When the laser power increases from 260 W to 380 W, the porosity of the sample decreases first and then increases, while the changing trend of mechanical property is opposite. When the laser power is 300 W, the optimum parameter is obtained with the relative density reaching 99.4%. There are only a few small shrinkage pores in the sample due to the insufficient supply of liquid metal. The ultimate tensile strength, yield strength, and fracture elongation are 429.7 MPa, 363.5 MPa and 17.7%, respectively. After aging treatment at 325 ℃ for 10 h, the ultimate tensile strength, yield strength, and fracture elongation are 530.1 MPa, 506.4 MPa and 9.0%, respectively.
2022 Vol. 27 (2): 205-214 [
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1289
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215
Structure and properties of wet forming carbon fiber paper with gradient porous structure
WANG Yuyan, ZHAN Zhenxiang, XIE Zhiyong, LEI Ting
DOI: 10.19976/j.cnki.43-1448/TF.2021108
Carbon fiber felts with different areal densities were firstly fabricated by wet process using short-cut carbon fibers as raw materials. Afterwards, carbon fiber paper (CP) with gradient porous structure was prepared through double-layer or multi-layer molding, resin impregnation and heat treatment. The pore structure, pore size distribution along with porosity and air permeability of as-prepared CP were measured by scanning electron microscope (SEM), mercury intrusion method and porous analyzer. The results show that the CP has gradient structure with graphitization degree of 93.14%. The average porosity of the multi-layer paper is 75.5%, and the average porosity of the double-layer paper is 81.4%. The air permeability, in-plane resistivity, tensile strength and flexural strength of multi-layer paper are 5 272 m/(kPa∙h), 11.78 mΩ∙cm, 20.62 MPa and 60.88 MPa, respectively, exceeding those of commercial CP. In addition, CP with gradient porous structure shows superior corrosion resistance over commercial CP in acid solution.
2022 Vol. 27 (2): 215-223 [
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826
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224
Effect of AC magnetic field on the OER properties of nitrogen-doped porous carbon derived from MOFs in-situ loaded carbon paper
LI Yuling, WANG Yuanli, LI Dongyun, QIN Hang, GUO Wenming, LIU Xiaopan, GAO Pengzhao, XIAO Hanning
DOI: 10.19976/j.cnki.43-1448/TF.2021094
In-situ loaded two kinds of precursors MOF(denoted as Zn-MOF-74 and ZIF-8) on the surface of carbon paper (CP) were successfully prepared by solvothermal method. After high temperature heat treatment, the precursors were derived into nitrogen-doped porous carbon, and the nitrogen-doped porous carbon @CP electrocatalyst material samples were obtained, named CP-Zn-MOF-74-900-N
2
and CP-ZIF-8-900-N
2
, respectively. The effects of CP composition, pore structure and magnetic field intensity on OER(oxygen evolution reaction) were investigated. The results show that the in-situ loaded ZIF-8 forms a dense layer of rectangular dodecahedral particles on the fiber surface of CP, and forms a uniform nanoscale nitrogen-doped carbon material on the fiber surface after heat treatment. ZIF-8-900-N
2
has a specific surface area of 1559 m
2
/g, pore size of 0.57 nm and pore volume of 1.59 cm
3
/g, which has the best magnetic properties and magneto-heating properties. CP-ZIF-8-900-N
2
achieves a lowest OER overpotential of 334 mV(current density of 10 mA/cm
2
, iR-corrected) and Tafel slope of 187 mV/dec among carbon paper and nitrogen-doped porous carbon @CP materials. When the external magnetic field exists, the OER overpotential of the catalyst first decreases and then remains unchanged with the increase of magnetic field intensity. And CP-ZIF-8-900-N
2
obtains the lowest overpotential of 316 mV (current density is 10 mA/cm
2
, non-iR-corrected) under a magnetic field intensity of 5.54×10
-3
T, which is 20.4% lower than that without AC magnetic field. This is mainly due to the reduction of bubble size and the enhancement of bubble coalescence caused by the magneto hydrodynamic effect, which improves the desorption of bubbles from the electrode surface.
2022 Vol. 27 (2): 224-236 [
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590
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