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2018 Vol. 23, No. 1
Published: 2018-02-20
Theoretical Research
1
Experimental investigation of the phase equilibria of the Al-Ce-Ge system at 500 ℃
LIU Minbo, LIU Shuhong, DU Yong
Combined with optical microscope (OM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA), phase equilibria of the Al-Ce-Ge system at 500 ℃ was investigated by equilibrated alloys method. The results show that, five ternary compounds, i.e. α(CeAl
1.62
Ge
0.38
), β(CeAl
2
Ge
2
), γ(CeAlGe), δ(CeAlGe
2
) and ε(Ce
2
AlGe
6
) as well as the liquid phase are verified at 500
o
C and the homogeneity range of the δ phase is Ce
24.7~24.8
Al
33~33.9
Ge
41.3~42.3
. Two new ternary compounds, i.e. η(Ce
61.3
Al
21.9
Ge
16.8
) and μ(Ce
55.9
Al
11.1
Ge
33
), are observed. In addition, seven three-phase regions α+CeAl
3
+γ, Ce
3
Al
11
+CeAl
3
+γ, αCeGe
2-x
+CeGe+γ, CeAl+CeAl
2
+Ce
5
Ge
3
, Ce
3
Ge+Ce
5
Ge
3
+Ce
3
Al, CeAl+Ce
3
Al+η and CeAl
2
+Ce
5
Ge
3
+μ are observed.
2018 Vol. 23 (1): 1-8 [
Abstract
] (
249
)
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347
)
Engineering and Technology
9
Heat treatment process of rigid particle reinforced iron-based powder metallurgy valve seat for new energy vehicle
XIAO Zisheng, LUO Cheng, HUA Jianjie, ZHANG Minghui, ZHANG Zhi
The valve seat frame body was pressed using W6Mo5Cr4V2 as based powder and adding Fe-Mo, Co-Cr-Mo and other hard particles. The particle reinforced iron-based powder metallurgy valve seat was prepared by vacuum high temperature infiltration method using special copper powder (Cu-Fe-Mn) as infiltration agent, with quenching and tempering heat treatment. The effects of quenching temperature and tempering temperature on the micro hardness of valve seat matrix and particles and the friction and wear properties of the valve seat materials were studied. The orthogonal treatment was used to optimize the heat treatment process. The results show that the quenching temperature has a great influence on the hardness and wear resistance of the valve seat material matrix W6Mo5Cr4V2, Fe-Mo and Co-Cr-Mo hard particles. When quenching at 1 140-1 260 ℃, Fe-Mo and Co-Cr-Mo hard particles diffuse obviously. The effect of quenching on carbides in copper-covered areas is small. There are more undissolved and larger size carbides in the covering area. When the quenching temperature is 1 220 ℃, the microhardness (HV) of the matrix material, Fe-Mo and Co-Cr-Mo hard particles are 528, 892 and 632 respectively. Tempering temperature has little effect on hardness of the valve seat. The highest hardness can be obtained when the tempering temperature is 520 ℃. The seat with hardness (HRC) of 49.2 and wear quantity of 0.029 5 g are obtained at quenching temperature of 1 220 ℃, tempering temperature of 520 ℃ and tempering number of 3.
2018 Vol. 23 (1): 9-16 [
Abstract
] (
364
)
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17
Effects of carbon source and synthesized temperature on the morphology and phase composition of nano-sized ZrC powders prepared by carbothermal reduction method
ZENG Guang, YANG Xin, SU Zhean, CHEN Lei, FANG Cunqian, HUANG Qizhong
ZrC nano-crystals and 2D-nanosheet ZrC were synthesized by carbothermal reduction method using glucose and graphene as carbon source and zirconium acetate as zirconium source. The effects of carbon source and the synthesized temperature on morphology and phase composition of ZrC were investigated. The results show that using glucose as carbon source, ZrC is formed initially at 1 400 ℃ and completely transformed to ZrC nano-crystals at 1 600 ℃ with the sizes in the range of 140-200 nm. Using graphene as carbon source, ZrC 2D-nanosheet is synthesized at 1 600 ℃ with the thickness of 240 nm. Graphene not only offers carbon source, but also serves as a template for the precipitation of ZrO
2
and growing of ZrC 2D-nanosheet in the carbothermal reduction.
2018 Vol. 23 (1): 17-24 [
Abstract
] (
389
)
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1366
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25
Microstructure and low cycle fatigue behavior of P/M nickel-based superalloy
WU Chengxin, WANG Zi, JIANG Liang
A new Ni based powder metallurgy superalloy was prepared by hot isostatic pressing, hot extrusion (HE) and 1 130 ℃/1 h heat treatment using Ni based alloy powder as raw material. The low cycle fatigue behavior including the microstructure of the pristine alloy, cyclic stress response and fracture morphology of the alloy were studied by a LCF test under atmospheric environment at 750 ℃. The results indicate that the previous particle boundary (PPB) appears after hot isostatic pressing, which is mainly consisted of coarse γ′ and fine carbon oxides. After HE and heat treatment, PPB disappears and grains refine to 7.5 μm. There are three types of γ′ phase after heat treatment, coarse γ′ phase on boundary, nearly spherical medium size γ′ phase and dispersed fine spherical γ′ phase intragranular. The low cycle fatigue fracture mode of the alloy is mainly intergranular fracture, and the grain surface of the fracture surface has different degree of oxidation.
2018 Vol. 23 (1): 25-31 [
Abstract
] (
332
)
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647
)
32
Effect of powder loading on mechanical properties of metal injection molding 17-4PH stainless steel
YU Jian, LI Yimin, LI Dongyang, LI Xing
The binder composition POM (polyformaldehyde) in the injection molded 17-4PH stainless steel body was catalytically degreased under nitric acid atmosphere, and then thermal degreasing and sintering were carried out in a vacuum sintering furnace. The effects of powder loading and catalytic degreasing time on the catalytic degreasing rate were studied, and the effects of powder loading on the microstructure, density and tensile strength of sintered products were also studied. The results show that the microstructure of the sintered products is composed of austenite and a small amount of ferrite. With increasing the powder loading from 55.1% to 65.7%, the catalytic degreasing rate of the sintered sample decreases from 7.8% to 5.2%; the density increases from 7.56 g/cm
3
to 7.66 g/cm
3
, and the tensile strength increases from 1 076 MPa to 1 204 MPa. With increasing the thermal retention time from 30 min to 90 min at 130 ℃, the catalytic degreasing rate increases from 4.9% to 6.7%. When the thermal retention time in the range of 90-150 min, the catalytic degreasing rate stabilise at about 6.7%. With the powder loading of 65.7%, the POM in the binder can be completely removed by 90min catalytic degreasing. The degreasing rate reaches 87%, and the injection blank forms a complete communicating channel.
2018 Vol. 23 (1): 32-37 [
Abstract
] (
339
)
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(560 KB) (
525
)
38
Spin coating process and photocatalytic activities of modified graphene thin film
SUN Shiqing, ZHENG Yanyin, GU Baoshan, GUO Dong, QIN Sen, FU Kai
Modified graphene dispersion was prepared by the modified Hummer method, and the modified graphene film was prepared on the glass substrate by spin coating method. The effects of low speed (600-800 r/min), medium speed (1 000-2 000 r/min), high speed (3 000-5 000 r/min), dropping time (10-30 s), acceleration (100-700 r/(min·s)) and pH value (4-11) on the adhesion of the thin graphene film were studied, and the optimized spin coating process parameterts were obtained. The modified graphene and its film were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy, Raman spectroscopy and laser confocal spectroscopy. The effect of the modified graphene film on the degradation of methylene blue in visible light was emphasically studied, and the photocatalytic principle of visible light was preliminarily revealed. The results show that the modified graphene film with the optimum adhesion can be obtained by rotating the modified graphene dispersion whose pH value is 7 and the dripping time is 20 s at the low speed of 800 r/min for 60 s at first, the medium speed of 1500 r/min for 30 s, and the high speed 4000 r/min for 60 s at last, with an acceleration rate of 100 r/(min∙s). The modified graphene film exists the maximum absorption peak at 421 nm in the visible wavelength band. The visible photo degradation rate of methylene blue by the modified graphene film is 34.4% for 4 h. Its catalytic principle is that the graphene film generats a strong oxidant • OH in the visible light, which can gradually degrade methylene blue and other pollutants into carbon dioxide and water, then the purpose of degradation is ultimately achieved.
2018 Vol. 23 (1): 38-46 [
Abstract
] (
327
)
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841
)
47
Effectts of heat treatment process on microstructure and mechanical property of IN713C alloy prepared by injection molding
XIE Xiaohui, WU Wei, PAN Donghua, YANG Zhongchen, LU Renwei, LI Duxin
IN713C alloy was prepared through metal injection molding using IN713C pre-alloyed gas atomized powder as raw powder, after solution treatment at 1 150, 1 175 and 1 120 ℃, and then aging at 760, 850 and 930 ℃. The microstructure and phase composition of the alloy were observed and analyzed by scanning electron microscopy (SEM) and energy spectrometer. The hardness and tensile strength of the alloy in temper state were determined. The results show that the γ′ precipitation phase in cooling phase decreases when the solution temperature continue to increase over a certain value. The hardness and tensile strength of the alloy reaches to 42.4 HRC and 1 175.9 MPa respectively when solid solution at 1 175 ℃. When aging at 760 ℃, the hardness and tensile strength reaches 43.6HRC and 1 223.7MPa respectively. When the aging temperature is above 760 ℃, γ′ phase size become coarser due to larger lattice mismatch; with increasing aging treatment temperature, γ′ phase the size increases, the quantity of γ′ phase and the volume fraction of the strengthening phase decrease, and the hardness and tensile strength of the alloy decrease. The optimal heat treatment process of IN713C in this study is 1 175 ℃2 h/AC+760 ℃16 h/AC.
2018 Vol. 23 (1): 47-53 [
Abstract
] (
330
)
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669
)
54
Effects of cold rolling deformation and baking treatment on microstructure and properties of CTP aluminum plate
JIA Guangze, HUANG Yuanchun, LIU Yu, XIAO Zhengbing
The 1060CTP aluminum plates were treated by different rolling systems and two different baking treatments of 220 ℃×10 min and 280 ℃×5 min. The effects of cold deformation and baking treatment on the microstructure, electrolytic corrosion properties and mechanical properties of CTP aluminum plates were studied through the polarization curves, microhardness, tensile property test, SEM and metallographic observation. The experimental results show that the grain size is larger than that of the first pass, and the larger the first sub-pressure, the finer the grain size. The aluminum plates have small and uniform crystal grains, and the corrosion and mechanical properties are better when the first reduction rate is 58.2%. The aluminum plate base is sensitive to the temperature during the baking process, and the high temperature baking treatment makes the strength of the aluminum base decrease sharply, while the elongation increase correspondingly. After baking at 280 ℃×5 min, the dimple size is more uniform, the depth is deeper, so the plasticity is better, and the resistance to printing is higher.
2018 Vol. 23 (1): 54-62 [
Abstract
] (
279
)
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(1487 KB) (
674
)
63
Effect of Fe on hydrogen evolution performance of Ni-based Ni-S alloy coating electrode
RAN Min, WU Yihui, HE Hanwei
Ni-Fe-S three elemental alloy coating was prepared on nickel foil by electrodeposition method on the basis of preparation of Ni-S alloy electrode and adding ferrous sulfate into the bath. The electrode surface morphology, phase composition, and valence state of elements were respectively analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy(XPS). The electro-catalytic hydrogen evolution performance and corrosion resistance of the coating electrode in KOH electrolyte were tested by electrochemical workstation, and compared with Ni-S alloy coating electrode. The results show that the surface of Ni-Fe-S coating electrode is composed of many tumor-like protrusions with rich surface structure, while the addition of Fe element can improve the amorphous degrees of alloy coating and corrosion resistance in alkaline electrolyte. Hydrogen evolution over potential of Ni-Fe-S electrode is reduced by 128 mV (36.6%) compared with Ni-S electrode. It indicates that Ni-Fe-S electrode has superior performance of catalytic hydrogen evolution.
2018 Vol. 23 (1): 63-69 [
Abstract
] (
357
)
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1857
)
70
Impact abrasive wear resistance of a new type of sintered high chromium cast iron
LU Ruiqing, XIAO Ping’an, SONG Jianyong, GU Jinghong, ZHANG Ting, LI Xiaoying
The wear resistance of sintered, cast hypereutectic high chromium cast iron and TM52 steel bonded carbide under different impact energy conditions were compared. The development of the wear surface and the micro-crack of the sub-surface were analyzed by scanning electron microscopy (SEM). The wear mechanism was also discussed. The results show that the high chromium cast iron prepared by liquid phase sintering has excellent impact abrasive wear resistance. Under the medium and low impact energy conditions, the wear resistance of sintered high chromium cast iron is significantly better than that of TM52 (4 to 10 times).Under the medium and high impact work conditions, the wear resistance increases more than 10 times compared to that of casting high chromium cast iron. The wear mechanism of sintered high chromium cast iron is mainly micro-cutting, as well as fatigue wear and brittle fragmentation under the high-energy impact work. The short rod-like M
7
C
3
-type carbides in sintered high chromium cast iron yield small split and stress concentration on metal matrix, while the martensite-based matrix with high strength and toughness, can effectively support and maintain a uniform dispersion of carbides and block micro-cracks initiation and expansion.
2018 Vol. 23 (1): 70-77 [
Abstract
] (
408
)
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(1 KB)
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(687 KB) (
768
)
78
Crystal structure and dielectric properties of complex perovskite Ba[(Co
1-
x
Mg
x
)
1/3
Nb
2/3
]O
3
microwave ceramics
LIU Liang, HUANG Zonglian, XIAO Ya, CHENG Lijin, LIU Shaojun
Ba[(Co
1-
x
Mg
x
)
1/3
Nb
2/3
]O
3
(0.0≤
x
≤0.4) microwave ceramics were prepared by the conventional solid reaction method. The relationship between the B site 1:2 ordering and microwave dielectric properties of Mg-doped Ba(Co
1/3
Nb
2/3
)O
3
microwave ceramics were clarified using dielectric performance test XRD, Raman and TEM. The results show that the
Q
∙
f
of Mg-doped Ba(Co
1/3
Nb
2/3
)O
3
ceramics is increased because the B site 1:2 ordering degree is enhanced. The highest ordering degree of the ceramics doped with
x
=0.2 is obtained at 1 420 ℃. After annealing at 1 300 ℃ for 24 h, the ordering degree of 1:2 in B site is further improved, and the second phase is eliminated. Microwave properties with
ε
r
=30.94,
Q
∙
f
=63 161 GHz,
τ
f
=4.1 ppm/℃ comparable to those of conventional Ta based composites perovskite microwave ceramics are obtained.
2018 Vol. 23 (1): 78-84 [
Abstract
] (
314
)
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(1 KB)
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(444 KB) (
1025
)
85
Corrosion resistance of porous Ti
3
(Si,Al)C
2
intermetallics in hydrochloric acid solution
WANG Zhonghe, KANG Jian’gang, ZHANG Huibin, LIU Xinli, HE Yuehui, JIANG Yao
Porous Ti
3
(Si,Al)C
2
intermetallic compounds was fabricated by the powder metallurgy method using Ti, Si, Al and graphite powders as raw materials. It was a potential material with premium structure and properties. In this paper, corrosion kinetic curves, change of pore structure, surface morphology and Tafel polarization curves were measured in HCl solution (a%=0.001, 0.01, 0.1 and 1 mol/L at 20 ℃) to assess the corrosion resistance properties of porous Ti
3
(Si,Al)C
2
intermetallic compounds compared with porous Ti. The results show that the corrosion behavior of Ti
3
(Si,Al)C
2
obeys the rule of parabolic, and the lowest mass loss of porous Ti
3
(Si,Al)C
2
is in HCL solution of 0.001 mol/L, about 29% of that of porous Ti. Porous configuration of Ti
3
(Si,Al)C
2
is stable in acid environment. The change of maximum pore size and permeability of Ti
3
(Si,Al)C
2
are 1.06%, 9.4% respectively in HCL solution of 0.001 mol/L, and keep stable with the increase of acidity. The results of polarization curves of Ti
3
(Si,Al)C
2
show that the free corrosion potential declines and the corrosion current density increases with the increase of acidity. The best result of free corrosion potential and corrosion current density of porous Ti
3
(Si,Al)C
2
are 161 mV and 7.802×10
-4
mA·cm
-2
respectively in HCL solution of 0.01 mol/L. Porous Ti
3
(Si,Al)C
2
exhibits excellent hydrochloric acid corrosion resistively.
2018 Vol. 23 (1): 85-93 [
Abstract
] (
346
)
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(1 KB)
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(1119 KB) (
585
)
94
Equivalent thermal conductivity of composites reinforced by carbon fiber with 2.5D fabric based on unit cell
LI Hui, DU Jianhua, WANG Haoxu
The microstructure model of carbon fiber bundles and the unit cell structure model of the composites reinforced by carbon fiber with 2.5D fabric were established by finite element method. The equivalent thermal conductivity of carbon fiber bundles and composites in steady thermal conditions were calculated. The effects of carbon fiber diameter and the space between two carbon fibers on the thermal conductivity in axial and radial direction of carbon fiber bundles and in thickness direction of the composites were investigated. The results show that, the thermal conductivity of the carbon matrix is between the radial thermal conductivity and the axial thermal conductivity of carbon fiber. With increasing the carbon fiber diameter, the axial thermal conductivity of the carbon fiber bundles increases, the radial thermal conductivity and the thermal conductivity of the composites in thickness direction decrease. With increasing the space between two carbon fibers, the axial thermal conductivity of the carbon fiber bundles decreases, the radial thermal conductivity and the thermal conductivity of the composites in thickness direction increase.
2018 Vol. 23 (1): 94-100 [
Abstract
] (
441
)
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(1 KB)
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(569 KB) (
1034
)
101
Synthesis and photocatalytic property of SiO
2
nanopowder coated by Cu/Ag-doped TiO
2
GUAN Renfa, XIAO Ya, LIU Qiming, LIU Shaojun
The TiO
2
-coated SiO
2
(TCS) nanocatalysts with about 12 nm thickness coating and high dipersity were synthesized by the sol-gel method. Based on the previous experiment, the photocatalytic efficiency of TCS catalysts was enhanced notably by doping Cu and Ag. The effects of coating and doping on the structure and photocatalytic activity of TiO
2
and the relative mechanism were investigated by XRD, XPS, UV-vis and the photocatalytic degradation experiment of methyl orange. The results show that, the Ti—O—Si bonds between the interface of TiO
2
and SiO
2
have an impact on the crystallization process of TiO
2
and restrain the growth of the grains. Cu
2
O-TiO
2
-SiO
2
composite powder with excellent performance can be synthesized by controlling the experimental conditions. The reinforcement mechanism of doping Cu can be ascribed to the modification of Cu
2
O semiconductor to TiO
2
. The increasing of photocatalytic property is related to the oxygen vacancy and Cu
2
O particles. Doping Ag cannot change the width of the forbidden band but can improve the intensity of light absorption, and the photocatalytic degradation efficiency is 95.7% after doping 1.0%Ag.
2018 Vol. 23 (1): 101-109 [
Abstract
] (
322
)
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(1 KB)
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(754 KB) (
1590
)
110
Tribological behaviors and reliability life of Cu-based friction materials for space applications in vacuum at room temperature
ZHONG Aiwen, YAO Pingping, XIAO Yelong, ZHOU Haibin, FAN Kunyang, GONG Taimin, LING Pan, LIU Chao
The friction and wear characteristics of Cu-based powder metallurgy friction materials were evaluated on a space friction testing machine at high load (400 N) in vacuum at room temperature. The reliability life and wear mechanism of friction materials were investigated and revealed respectively. The experimental results show that there are three stages during the friction process. At the first stage, the friction coefficient increases from 0.28 to 0.61, and the abrasive wear is the dominant wear mechanism. In the second stage, the friction coefficient remains steadily (~0.61), and the dominant wear mechanism is the mixture of abrasive wear and adhesive wear. At the third stage, the friction coefficient begins to decrease. The dominant wear mechanism transforms to be the mixture adhesive wear and severe fatigue wear, leading to the material failure. During the test, the stability friction coefficient keeps up 0.9. The friction pairs can meet the demand of indexing mechanism and space manipulator in vacuum at room temperature.
2018 Vol. 23 (1): 110-118 [
Abstract
] (
365
)
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(1 KB)
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(970 KB) (
505
)
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