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2020 Vol. 25, No. 1
Published: 2020-02-15
Engineering and Technology
Theoretical Research
Theoretical Research
1
First-principles calculations study and experimental results of L1
2
-structured Al
3
(Yb,Zr) precipitate
CHEN Zhuo, FANG Huachan, ZHU Changjun, ZHU Jiamin
The formation energy and lattice constant of L1
2
-structured Al
3
Zr, Al
3
Sc, Al
3
Yb, Al
3
(Sc
0.5
,Zr
0.5
), Al
3
(Yb
0.5
,Zr
0.5
) compounds were calculated from first-principles based on plane-wave pseudopotential method. The calculated results indicate that the L1
2
-structured Al
3
(Yb
0.5
,Zr
0.5
) phase is thermodynamically stable and easy to precipitate coherently in Al matrix. With the results of TEM, high-density of coherent, L1
2
-structured Al
3
(Yb,Zr) precipitates with 20-80 nm are precipitated in as-homogenized Al-Zr-Yb alloy, among them, core Zr-riched Al
3
(Yb,Zr) and core Yb-riched Al
3
(Yb,Zr) phases have obvious shell-core structure. Uniform and high density precipitation of L1
2
-structured Al
3
(Yb,Zr) causes an improvement of precipitation-hardened effect and inhibit-recrystallization ability, compared to L1
2
-structured Al
3
Zr precipitates in pure aluminum.
2020 Vol. 25 (1): 1-10 [
Abstract
] (
435
)
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Engineering and Technology
11
Effects of Ti(C
0.7
N
0.3
) addition on the microstructure and properties of (Ti,W,Ta)C-Mo-Ni cermets
LIN Shaojiang, CHEN Xiao, XIONG Weihao
The Ti(C,N)-based cermet materials were prepared by powder metallurgy using (Ti,W,Ta) C and Ti(C
0.7
N
0.3
) as hard phase materials. The effect of Ti(C
0.7
N
0.3
) additions on the microstructures and properties of (Ti,W,Ta)C-Mo-Ni cermets has been studied. The results indicate that the microstructure of (Ti,W,Ta)C-Mo-Ni cermets consist of black core-grey rim structure and white core-grey rim structure. The black cores is Ti(C
0.7
N
0.3
) particle and the white cores is (Ti,W,Ta)C particles. With increasing Ti(C
0.7
N
0.3
) addition, black cores increase and the rims become thinner. Adding Ti (C
0.7
N
0.3
) solid solution has little effect on the hardness of (Ti,W,Ta)C-Mo-Ni cermets, while the bending strength increases first and then decreases with the increase of Ti(C
0.7
N
0.3
). When the Ti(C
0.7
N
0.3
) content is 40%, the optimal properties of (Ti,W,Ta)C-Ti(C
0.7
N
0.3
)-Mo-Ni cermets is obtained, the hardness (HRA) is 90.3 and the bending strength is 1 748 MPa, respectively.
2020 Vol. 25 (1): 11-15 [
Abstract
] (
339
)
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16
Effect of cryogenic rolling and aging heat treatment on microstructure and properties of Al-Zn-Mg aluminum alloy
CHEN Songyi, LIU Qiang, CHEN Kanghua, HUANG Lanping
The Al-Zn-Mg alloy sheets were aged by CR (cryogenic rolling)+480h natural aging, CR+100 ℃/12 h aging, CR+100 ℃/80 h aging and 100 ℃/107 h aging treatment for solution-quenched sheets without CR, respectively. The hardness and room temperature tensile properties of the alloys were determined,and exfoliation corrosion (EXCO) and electrochemical corrosion were carried out. The morphology and microstructure of Al-Zn-Mg alloys were observed by optical microscope, scanning electron microscope and transmission electron microscope. The effects of cryogenic rolling and different aging treatment (natural aging and different time artificial aging) on the micro-structure and properties of Al-Zn-Mg alloys were studied. The results show that the EXCO resistance and electrochemical corrosion resistance of CR+480 h natural aging and CR+100 ℃/12 h ageing treated alloys are worse than those of solution-quenched alloys treated directly at 100 ℃/107 h. The main reason is the formation of submicron, fibrous and high dislocation density ultrafine grains during cryogenic rolling. CR+100 ℃/80 h aging treatment alloy has better exfoliation corrosion resistance and electrochemical corrosion properties due to the formation of high density dislocations during cryogenic rolling, and coarse and discontinuous grain boundary precipitates are formed after subsequent 100 ℃/80 h aging treatment. In addition, the ultra-fine grain structure with high dislocation density was formed after cryogenic rolling, which significantly accelerated the aging hardening response.
2020 Vol. 25 (1): 16-26 [
Abstract
] (
474
)
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)
27
Effect of solution-aging treatment on the microstructure and properties of selective laser melted CoCrWMo alloys
BAN Le, HUANG Jiahao, MAO Weidong, WU Yuanbiao, XIAO Zhiyu
The selective laser melted (SLM) CoCrWMo alloys were solution treated at 1 200 ℃ for 1 h, and then aged at 600, 700, 750, 800 and 900 ℃ for 10 h respectively. The effects of solution-aging treatment on the microstructure and properties of the alloy were studied. The results show that the SLM CoCrWMo alloy is composed of FCC γ phase and HCP ε phase martensite. The transformation from γ phase (FCC phase) to ε phase (HCP phase) occurs during solution- aging treatment. The content of ε phase martensite increases with increasing the aging temperature, M
23
C
6
(M=Cr,Mo,W) precipitated at the same time. In the alloy aged at 750 ℃, the proportion of ε phase is 77%, indicating that aging treatment can promote the transformation of FCC→HCP martensite. The microhardness of all aged alloys is significantly higher than that of solid solution alloys. The strength of the alloy aged at 750 ℃ is improved while the elongation is taken into account, the tensile strength and yield strength are 1 076 MPa and 820.8 MPa respectively, and the elongation reaches 10.5%.
2020 Vol. 25 (1): 27-34 [
Abstract
] (
374
)
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1521
)
35
Effect of TiN content on microstructure and properties of WC-TiC-TaC-8%Co cemented carbide
WANG Yanjie, LIU Yong, YANG Xinyu
Using TiN as N source, WC-TiC-TaC-8.0Co cemented carbide with β-Delamination gradient was prepared by one-step sintering with traditional powder metallurgy method. The microstructure of the alloy was observed and analyzed by means of scanning electron microscope, the effect of TiN addition on the microstructure, the thickness of β-layer, physical and mechanical properties was studied, and cutting test was also carried out. The results show that the density, coercive force, hardness and other physical properties of the alloy have no obvious variation with the increase of TiN content (mass fraction, the same below) in the range of 0-2.0%, but the thickness of β-layer obviously increases. With increasing TiN content from 0.5% to 2.0%, the corresponding thickness of cubic carbide free layer increases from 0 to 32.7 μm. The cutting test results show that the TiN content of 1.0%, cemented carbides has the excellent comprehensive properties of wear resistance and impact resistance after coating.
2020 Vol. 25 (1): 35-39 [
Abstract
] (
361
)
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(1 KB)
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(376 KB) (
1027
)
40
Effect of temperature of coprecipitation on properties of LMA precursors for thermal barrier coatings
LIU Dongmei, LI Chao
LaMgAl
11
O
19
precursor powder for thermal barrier coating was prepared by co-precipitation method (precipitation temperature 80 ℃, precipitation pH value 10.5). The influence of calcining temperature on its microstructure, half-peak full width and spectral strength was tested and analyzed. The results showed that the powder has MgAl
2
O
4
, LaAlO
3
and La
2
O
3
three phases after calcining at 1 100 ℃. As the calcining temperature rise to 1 500 ℃, the LaMgAl
11
O
19
phase is abtained. The particle size of LaMgAl
11
O
19
is between 3 and 5 μm and its thickness is 0.5 to 1.0 μm. When the calcination temperature continues to rise, the electron binding energy of Mg1s, O1s, La3d and Al2p fluctuates and shifts significantly towards the high-energy end. At 1 500 ℃, the electron binding energies of Mg, La and Al all increased. The main electron peaks of O1s, La3d, Mg2p and Al2p were formed on the XPS spectrogram, and Mg, La and Al were oxidized. LaMgAl
11
O
19
crystal has formed a layered structure with interlaced structure, which is obviously anisotropic. As the calcination temperature rises to 1 300 ℃, the number of La
2
O
3
bonds gradually decreases.
2020 Vol. 25 (1): 40-44 [
Abstract
] (
313
)
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(1 KB)
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(365 KB) (
658
)
45
Effect of Ti content on microstructure and properties of Ti-MoSi
2
composite material
HAO Yanan, FAN Jinglian, LU Qiong, WANG Yuanyuan
Using MoSi
2
powders and Ti powders as raw materials, four groups of Ti-MoSi
2
composites with Ti content (mass fraction, %) of 40%, 50%, 60% and 70% were prepared by spark plasma sintering, respectively, and the microstructure, density, hardness and fracture toughness of the material were analyzed and tested. The results show that, the four groups of Ti-MoSi
2
composites all appear core-shell structure. Ti-MoSi
2
composites are mainly composed of Ti
5
Si
3
and Mo
3
Si. When the addition amount of Ti increases to 70%, Ti elementary phase appears in the sample. With increasing Ti content, the density and microhardness of Ti-MoSi
2
decrease, and the fracture toughness increases gradually. The density of Ti-MoSi
2
composites in the four groups is 5.54, 5.34, 5.24 and 5.16 g/cm
3
, Vickers hardness is 8.54, 8.22, 8.13 and 8.02 GPa, and fracture toughness is 7.02, 10.36, 11.62 and 24.52 MPa∙m
1/2
, respectively.
2020 Vol. 25 (1): 45-50 [
Abstract
] (
416
)
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662
)
51
Effect of grinding method on properties of steel slag powder
DUAN Siyu, LI Xi, MA Zhuohui, LIAO Hongqiang, CHENG Fangqin
Making the steel slag into powder by the mechanical comminuting process and applying it to the building materials production is an effective way of the steel slag recycling. The steel slag was ground mechanically by a ball mill and a supersonic steam-jet crusher, respectively. The particle size distribution, chemical composition, mineral composition and the activity index of the steel slag powder obtained by the two kinds of grinding methods were compared and analyzed. In addition, the grinding efficiency and energy consumption of the above two grinding methods were also analyzed. The results show that, in comparison steel slag obtained by ball mill, the particle size (
D
50
: 2.06 μm) of the steel slag obtained by the supersonic steam mill is smaller, and the particle size distribution range is narrower, and the particle is more uniform. Obvious chemical component segregation occurs in the steel slag obtained by the supersonic steam-jet crusher, and more Ca and Si elements are enriched in the steel slag with smaller size particles, which is more conducive to the appearance of its gelling activity. Compared with the ball mill, the supersonic steam mill has higher grinding efficiency and lower energy consumption, and it is more suitable for the steel slag grinding.
2020 Vol. 25 (1): 51-57 [
Abstract
] (
392
)
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1050
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58
Effects of C/N atomic ratio in raw materials on the microstructure and properties of Ti(C,N)-based cermets
CUI Yanming, ZHANG Li, HUANG Long, LIU Tao, LIANG Yan, WU Houping, XIONG Xiangjun
Three kinds of TiCN-25WC-10TaC-2Mo
2
C-7Ni-7Co cermets were prepared from TiCN powders with different C/N ratio, i.e., Ti(C
0.4
,N
0.6
), Ti(C
0.5
, N
0.5
) and Ti(C
0.7
,N
0.3
). The effects of C/N atomic ratio on the microstructure, hardness, transverse rupture strength, Palmqvist toughness, magnetic properties and corrosion resistance of TiCN-based cermets were investigated. The observation and analysis results show that there is a M
6
C type decarburization phase (η phase) in the cermet with Ti(C
0.4
,N
0.6
) as the raw material, which results in a substantially decrease in transverse rupture strength and toughness. Microstructure of the cermet prepared from Ti(C
0.7
,N
0.3
) raw material shows a typical weak core-rim structure, which is accompanied by the best mechanical properties, i.e., 15.61 GPa for HV30, 2 294 MPa for transverse rupture strength and 11.29 MN•m
-3/2
for Palmqvist toughness. With the decrease of C/N ratio in the TiCN raw material, the coercivity force and relative magnetic saturation of cermet decrease rapidly. The results of electrochemical corrosion experiments in H
2
SO
4
solution with pH=1 show that the corrosion resistance of cermets prepared from Ti(C
0.4
,N
0.6
) and Ti(C
0.5
,N
0.5
) is similar, and the corrosion resistance of cermets prepared from Ti(C
0.7
,N
0.3
) is significantly decreased.
2020 Vol. 25 (1): 58-64 [
Abstract
] (
423
)
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(1 KB)
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1337
)
65
Microstructure and frictional wear performance of Fe-Mo-V-C alloy coating prepared by laser cladding
ZHANG Lei, CHEN Xiaoming, SU Jianhao, ZHANG Kai, CHEN Kuan, ZHAO Jian
Fe-Mo-V-C alloy coatings were prepared on the 45
#
steel by laser cladding technique with coaxial powder-feeding. The phase compositions, microstructure and element distribution were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (DES). In addition, the microhardness and friction and wear property of coatings were tested by Vickers hardness tester and dry sliding friction and wear tester, and the wear mechanism was analyzed. The results show that Fe-Mo-V-C alloy coating prepared by laser cladding is mainly composed of α-Fe and Fe-based alloy, including (α-Fe,Ni), Fe
4
V and Fe
0.7
Mo
0.3
, intermetallic compounds including VC, V
8
C
7
, VB and Fe
3
C, and eutectic phase composed of Fe-based metal and Fe
3
C. The microtructure of coating is compact and uniform, and the fine and hard particles in the matrix are dispersive, homogeneous and extensive. The average hardness of coating at 1 600 W is as high as 1 020 HV
0.2
, and its wear resistance is 14 times of the substrate. The dispersion strengthening of VC particles leads to high hardness, and it works as pinning effect and wear-resistant skeleton during the wear process, which greatly improves the wear resistance of Fe-based coating.
2020 Vol. 25 (1): 65-71 [
Abstract
] (
370
)
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(1 KB)
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72
Microstructure and mechanical properties of oxide dispersion strengthened Fe-based alloy prepared by spark plasma sintering
DUAN Qinglong, LIU Zuming, HUANG Liqing, GUO Yang, SU Pengfei, CHEN Shiqi
Oxide dispersion strengthened (ODS) steels was fabricated by gas atomized and ball milling powders via spark plasma sintering (SPS) at 900-1 100 ℃, hot rolling and annealing. Microstructure and mechanical properties of these alloys were investigated by means of X-ray diffraction (XRD), metallographic analysis (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and mechanical testing such as micro-hardness and tensile testing. The results show that sintering temperature, hot rolling and heat treatment can greatly affect the microstructure and properties of ODS iron-based alloys. With the increase of sintering temperature, the original particle interface is gradually eliminated, the porosity of the alloy decreased, the density is increased, the tensile strength and microhardness increase. The tensile strength of the alloys sintered at 900, 1 000 and 1 100 ℃ are 191, 392 and 814 MPa respectively. After rolling and annealing, the tensile strength and elongation of steel sintered at 900 ℃ increase. After rolling, the tensile strength of the alloy sintered at 1 100 ℃ increases to 1 003 MPa, and the elongation is 6.48%. After heat treatment, the tensile strength decreases to 915 MPa, and the total elongation increases to 9.77%.
2020 Vol. 25 (1): 72-78 [
Abstract
] (
389
)
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(1 KB)
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(1151 KB) (
616
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79
Effect of holding time on properties of loess-based inorganic ceramic membrane supports
LI Dachuan, TONG Zhi, HUANG Kaipei, WANG Jiayue, ZHOU Guangrui
The inorganic ceramic membrane supports with Luochuan loess as aggregate, SDBS as sintering aid were prepared by extrusion-molding and solid particle sintering method. The effect of the holding time on the properties of ceramic membrane supports was mainly studied. The crystal phase, microscopic morphology, porosity, flexural strength, acid-base corrosion rate and pure water permeability of ceramic supports were characterized by testing methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury intrusion method, three-point bending method, mass loss method, self-made pure water flux measurement device. The results show that with the holding time increasing, the pure water flux of the support increases first and then decreases, the bending strength continues to increase, the corrosion resistance increases gradually, the liquid phase increases gradually, and the grains tend to mature and complete. The pure water flux, flextural strength, average pore throat radius, acid and alkali corrosion rate of the support sintered at 1 050 ℃ for 20 h are 2 570.47 L/(m
2
∙h∙MPa), 38.91 MPa, 2.39 μm, 0.18% and 0.17% respectively, indicating that the support can be used as an inorganic ceramic membrane carrier for use in the field of water treatment.
2020 Vol. 25 (1): 79-85 [
Abstract
] (
362
)
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(1 KB)
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529
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86
Design of trapezoidal liner of ball mill based on bonding theory
CHU Liang, DONG Weimin, GONG Meng
For the ball mill for grinding, the lifting bars with the same height (numbered 20-20) and 3 kinds of lifting bars with different heights (numbered 20-18, 20-16, and 20-14) were designed. A four-dimensional modeling software Solid Edge was used to model those different types of ball mill lifting bars, and then the model was imported into EDEM to calculate the number of fractures of the BPM bond in the ore model and the cumulative energy received by the lifting bar and the cylinder, to study the effect of liner design on ball mill grinding efficiency and the wear of ball mill. The results show that compared with the model equipped with contour lifting bars (20-20), the number of BPM bond fractures of the ore model in the models equipped with high-and-low lifting bars(20-18, 20-16, 20-14) is higher, that is, the grinding efficiency is higher. Among them, the number of BPM bond breaks of the ore in the model 20-14 is increased by 11.3%, and the crushing effect is the best. Compared with the model 20-20, the cumulative energy of the lift bar and the cylinder of the model 20-18 and the model 20-14 are reduced by 18.6% and 28.1%, respectively, and the wear of the lift bar and the cylinder is reduced. However, the cumulative energy of the model 20-16 and the wear of the ball mill increase.
2020 Vol. 25 (1): 86-90 [
Abstract
] (
310
)
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(1 KB)
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(369 KB) (
511
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