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2022 Vol. 27, No. 5
Published: 2022-10-15
Engineering and Technology
Theoretical Research
Theoretical Research
453
Molecular dynamics simulation of shear deformation of gradient nanostructured polycrystalline aluminum
HUANG Qianru, LIU Jianghui, KONG Yi, DU Yong
DOI: 10.19976/j.cnki.43-1448/TF.2022020
Gradient nanopolycrystalline structured metals are receiving increasing attention due to their unique plastic deformation mechanism and possible mechanical property enhancement. In this paper, the effect of different gradient nanostructures on the shear deformation behavior is investigated using a molecular dynamics approach. By comparing the dislocation evolution and atomic structure of grains during shear deformation of different gradient nanostructures, it is found that the deformation mechanisms of different gradient nanostructures are basically the same in the initial and intermediate stages of shear deformation process, with a large number of dislocations moving and accumulating at the grain boundaries, and then passing through the grain boundaries and finally releasing at the grain surface. In the middle and later stages of the deformation process, the different gradient nanostructures behave differently. For structures with higher shear strength, there is no shear band through multiple grains after shear deformation, and some of the coarse grains are broken into several smaller grains due to the large difference between grain orientation and shear direction and grain rotation, while the fine grains do not change significantly. The shear strength of the smaller structures is seriously affected by the shear bands formed during shear deformation due to dislocation plugging and release and interconnection of grain boundaries.
2022 Vol. 27 (5): 453-459 [
Abstract
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1465
)
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460
Thermodynamic investigation of the Ag-Cu-Co system
MAO Xueliang, LI Xiaojing, LIU Shuhong, DU Yong
DOI: 10.19976/j.cnki.43-1448/TF.2022036
Phase constituents of the Ag-Cu-Co alloys in as-cast and annealed at 400 ℃ and 650 ℃ were studied by inductively coupled plasma optical emission spectrometer (ICP-OES), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that no ternary compound is observed in this work. At 400 ℃, the maximum solubility of Cu and Co in FCC(Ag), Ag and Co in FCC(Cu) and Ag and Cu in HCP(Co) are determined to be 10.08% and 1.43%, 2.37% and 0.98%, as well as 0.22% and 4.15% (mole fraction, %, the same below), respectively. While at 650 ℃, the maximum solubility of Cu and Co in FCC(Ag), Ag and Co in FCC(Cu) and Ag and Cu in FCC(Co) are determined to be 15.74% and 0.97%, 3.69% and 4.47% as well as 0.15% and 7.48%, respectively. Thermodynamic database of the Ag-Cu-Co system is extrapolated from the reported thermodynamic description of the three sub-binary systems of Ag-Cu, Ag-Co and Cu-Co in literature, based on the CALPHAD (calculation of phase diagram) approach. Using the presently obtained database, the isothermal sections at 400 ℃ and 650 ℃, the liquidus projection as well as the solidification path of the Ag-Cu-Co system are calculated. The reasonable agreement between the calculations and measurement indicates the accuracy of the thermodynamic description of the Ag-Cu-Co system obtained by extrapolation using the CALPHAD approach.
2022 Vol. 27 (5): 460-470 [
Abstract
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594
)
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Engineering and Technology
471
Effect of Ti powder activation on preparation of Ti(C,N) powder by carbothermal reduction and nitridation
XIE Junlong, LI Kaihua, YE Jinwen
DOI: 10.19976/j.cnki.43-1448/TF.2022026
The kinetics and phase evolution of Ti(C,N) formation process by-carbothermal reduction and nitridation of titania (TiO
2
), carbon and tailing Ti powder as activator were investigated using TG/DSC, XRD. The Kissinger- Akahira-Sunose (KAS) method was used to calculate the activation energies that Ti
3
O
5
reacted to form Ti(C,N) in the system without adding and adding tailing Ti powder, which were (5 053.34±683.64) kJ/mol and (4 485.46±687.33) kJ/mol respectively. The result indicated that tailing Ti could effectively reduce the activation energy of the carbothermal reduction and nitridation reaction; the phase evolution study of the process showed that Ti reacted with TiO
2
to form Ti
4
O
7
at 800 ℃, which directly surpassed the Ti
n
O
2
n
-1
(
n
>4),a series of intermediate phase transformation process, single-phase Ti(C,N) could be obtained by holding at 1 400 ℃ for 0.5 h; Finally, the oxygen content of 0.34%, the free carbon content of 0.33% and high-quality Ti(C,N) powder with a particle size of 1-2 μm was prepared at 1 750 ℃ for 4 h.
2022 Vol. 27 (5): 471-477 [
Abstract
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391
)
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771
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478
High-temperature stability of microstructure and properties of Cu-Cr-Nb-Ce alloy fabricated by selective laser melting
AI Yongkang, LIU Zuming, ZHANG Yazhou, YE Shupeng, LI jian
DOI: 10.19976/j.cnki.43-1448/TF.2022024
Cu-Cr-Nb-Ce alloy was fabricated by selective laser melting (SLM). The high-temperature stability of microstructure, mechanical properity and electrical conductivity of Cu-Cr-Nb-Ce alloy was studied by high-temperature heat treatment at 1 000 ℃. The results show that the matrix mocrostructure of the XY plane (perpendicular to the build direction) of the as-SLMed Cu-Cr-Nb-Ce alloy is composed of long columnar grains in the center of the molten pool and fine equiaxed grains distributed along the boundary of the molten pool. The two kinds of grains are staggered and the average grain size is 28.3 μm. The second phase are the nanoscale Cr
2
Nb phases dispersed in the matrix. After heat treatment at 1 000 ℃ for 10, 50 and 100 h, the overall morphology of the grains does not change obviously, but the grains grow and the average size of grain increases by 8.5%, 18.7% and 27.2%, respectively; The average size Cr
2
Nb phase grows from 29.5 nm to 348.6 nm, 524.9 nm and 589.4 nm respectively, and the maximum size reaches 1-3 μm. In addition, Cr
2
Nb phases in heat-treated specimens are more densely along the grain boundary. The hardness (HV) of the alloy decreases significantly from 126 to 84, 79 and 75 respectively; while the electrical conductivity increases significantly from 18.5%IACS to 54.6%IACS after heat treatment for 10 h, whereas no significant progress is observed with extension of the heat treatment time.
2022 Vol. 27 (5): 478-487 [
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489
)
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638
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488
Effects of Mo on the microstructure and properties of WC-(8Co, 2Ni) cemented carbide
GUO Juhua, LI Bin, HE Rengui, WANG Jianying, LOU Jia, LIU Yanjun, LI Yongxia, YANG Hailin
DOI: 10.19976/j.cnki.43-1448/TF.2021099
In this work, the WC-(8Co,2Ni)-
x
Mo (
x
=0, 0.5, 1.0, 1.5, mass fraction,%) composite powders were successfully prepared by chemical coating method, and then the WC-(8Co,2Ni)-
x
Mo cemented carbides were fabricated by vacuum sintering method. The microstructure and phase composition of precursors and composite powders were studied. The effects of Mo on the microstructure, mechanical properties and corrosion resistance of WC-(8Co,2Ni) cemented carbide were investigated. The results show that the Mo in the WC-(8Co,2Ni)-
x
Mo composite powders is uniformly distributed on the surface of the WC particles. The WC-(8Co,2Ni)-
x
Mo cemented carbides are density, and have no obvious pores, WC and binder distribute uniformly. As the mass fraction of Mo increases from 0 to 1.5%, the average grain size of WC decreases from 1.6 μm to 1.1 μm. The hardness (HRA) of the alloy increases from (87.3±0.1) to (88.3±0.2), and the bending strength decreases from (2 890±27) MPa to (2 560±29) MPa. The low conductivity Mo-containing passivation film is formed during the corrosion process, so the corrosion resistance of the alloys is significantly improved.
2022 Vol. 27 (5): 488-497 [
Abstract
] (
543
)
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849
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498
Fracture failure behavior and dynamic recrystallization of pure tungsten under deformation at ultra-high strain rates
CHEN Xun, HUANG Yufeng, ZHANG Lei, CHEN Boshan, LIU Wensheng, MA Yunzhu
DOI: 10.19976/j.cnki.43-1448/TF.2022027
The laser shock loading technique was used to achieve dynamic load on powder metallurgy sintered and molten tungsten at ultra-high strain rates. Polycrystalline tungsten’s damage characteristics and microstructure were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). And the effects of holes on the failure behavior and dynamic recrystallization (DRX) mechanism of polycrystalline tungsten was investigated. The results show that fracture along the grain still dominates the failure mode of polycrystalline tungsten at ultra-high strain rates. Holes at grain boundaries and inside grains become the origin of fracture failure of the material under dynamic loading. The reflection of shock waves by the holes causes a continuous concentration of stress around the holes. Many dislocations form and tangle, resulting in a rapid increase in deformation storage energy. Sintered tungsten exhibits numerous equiaxed recrystallization after shock loading at higher shock pressure. The degree of recrystallization decreases as the shock wave decays with thickness.
2022 Vol. 27 (5): 498-508 [
Abstract
] (
687
)
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(2450 KB) (
850
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509
Corrosion resistance, in-vitro degradation and osteogenic properties of AZ91D alloy modified by Mg-Fe-LDH coating
JING Shaohui, ZHOU Jixiang, ZHAO Dapeng, WU Hong
DOI: 10.19976/j.cnki.43-1448/TF.2022031
In order to meet the clinical requirements for corrosion resistance and osteogenesis of magnesium-based metal implants, the dense and uniform Mg-Fe-layered double hydroxide (Fe-LDH) coatings were prepared on the AZ91D Mg alloy matrix by hydrothermal method and the Fe-LDH/AZ91D samples were obtained. Electrochemical and hydrogen evolution experiments were performed to explore the effects of coatings on corrosion resistance and its in-vitro performance. Combining CCK-8 and in-vitro mineralization experiments, the biocompatibility and osteogenic properties of Fe-LDH/AZ91D were studied. The results show that the existence of the Fe-LDH coating establishes a barrier between AZ91D and the corrosive liquid and improves the corrosion resistance of the alloy. The corrosion inhibition efficiency of the modified magnesium alloy reaches 92.76%. After immersion in PBS for 14 days, the mass loss rate of AZ91D (40.59%) is almost 1.6 times that of Fe-LDH/AZ91D (25.16%), and the corrosion rate (4.14 mm/a) is about twice that of Fe-LDH/AZ91D (2.13 mm/a). The leaching solutions with different Fe-LDH/AZ91D volume fractions have good cell compatibility and can maintain the osteogenic activity of the cells, reaching the same level as the control group.
2022 Vol. 27 (5): 509-518 [
Abstract
] (
428
)
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610
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519
Microstructure and corrosion properties of Cr and Zr microalloyed ultra-high strength Al-Zn-Mg-Cu-Yb as-cast alloy
XU Yongxiang, FANG Huachan, DUAN Zhiying, ZHANG Zhuo, WANG Jiayu, ZHU Mengzhen, ZHU Kai, XIAO Peng
DOI: 10.19976/j.cnki.43-1448/TF.2022041
Cr and Zr microalloyed Al-Zn-Mg-Cu-Yb alloys were prepared by ingot metallurgy. The precipitation characteristics of solidified crystalline phase in Cr or Zr microalloyed Al-Zn-Mg-Cu-Yb alloys and its influence mechanism on the corrosion behavior of the as-cast alloys were studied by electrochemical test and static corrosion experiment, combined with the observation and analysis of X-ray diffraction, optical microscope, scanning electron microscope and transmission electron microscope. The results show that the dendrites of the three as-cast Al-Zn-Mg-Cu-Yb alloys are mainly composed of Al
2
CuMg (
S
phase), Al
8
Cu
4
Yb and Mg(Zn,Cu,Al)
2
(
Sigma
phase). The addition of Cr or Zr leads to the increase of Cu content in
Sigma
phase, the increase of potential of
Sigma
phase and the decrease of potential difference between dendrites and aluminum matrix, which can improve the corrosion properties of the as-cast alloys. Compared with Al-Zn-Mg-Cu-Yb and Al-Zn-Mg-Cu-Yb-Cr alloys, Al-Zn-Mg-Cu-Yb-Zr alloy has higher corrosion resistance, and the corrosion form changes from intergranular corrosion to uniform corrosion.
2022 Vol. 27 (5): 519-531 [
Abstract
] (
448
)
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(1229 KB) (
737
)
532
Microstructure and properties of WC-Co pellet-strengthened high entropy alloy composite hard coatings prepared by laser cladding
LAN Yang, MA Qingyuan, YANG Zihan, ZHANG Wenhui, PENG Yingbo, ZHENG Jun, ZHANG Wei, LIU Huiren, XU Xiongliang
DOI: 10.19976/j.cnki.43-1448/TF.2022046
WC and WC-Co spherulite hard phases were added to FeCoCrNiMo
0.15
high entropy alloy powder respectively, and WC/HEA and WC-Co/HEA high entropy alloy composite coatings prepared on 304 stainless steel substrate by laser cladding method, respectively. The microstructure, hardness, wear resistance and corrosion resistance of the two composite coatings were studied and compared with the properties of the Ni60/WC composite coatings prepared by vacuum diffusion welding. The results show that the WC particles in the WC-Co/HEA coating have high sphericity and few pores and cracks. Adding Co element can effectively avoid the decomposition of WC during the laser cladding process. The average microhardness (HV) of WC/HEA and WC-Co/HEA composite coatings are both above 800 MPa. The average microhardness (882.55 MPa) of WC-Co/HEA coating is higher than that of WC/HEA coating hardness (817.27 MPa), and the average friction factor (0.40) of WC-Co/HEA coating is slightly lower than that of the WC/HEA coating (0.46). Compared with Ni60/WC coating, HEA-based coating has better retention and wet tability to WC, which can reduce the interfacial reaction between coating and WC, so the microhardness of WC-Co/HEA composite coating, friction and wear performance, corrosion resistance are better than that of Ni60/WC and WC/HEA coatings.
2022 Vol. 27 (5): 532-541 [
Abstract
] (
505
)
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712
)
542
Microstructure evolution of continuous alumina fiber under tensile sintering
PENG Shaoheng, YAO Shuwei, WANG Juan, LIU Wensheng, MA Yunzhu
DOI: 10.19976/j.cnki.43-1448/TF.2022038
Continuous alumina fibers were prepared using sol-gel dry spinning-high temperature sintering method. During the pre-sintering and high-temperature sintering of the precursor fibers, the self-designed tensioning sintering device was used to apply axial tension to the fibers. The effects of tension on the thermal decomposition, phase transformation, structural evolution and properties of alumina fibers during the sintering process were investigated by characterizing the morphology, composition and structure of alumina fibers and comparing with the fibers sintered freely (without tension).The results show that the application of tension during sintering can significantly increase the straightness of pre-sintered and sintered fibers, and promote the decomposition and removal of residues in precursor fibers. Tensile sintering can inhibit the axial shrinkage of fibers, increase the radial shrinkage, and promote the transformation of γ-Al
2
O
3
to α-Al
2
O
3
. Tensile sintering can also improve the grain morphology and pore distribution of fibers, promote grain growth and shrinkage, and removal of intergranular pores, and promote the densification of fibers. Compared with free sintering, the application of 0.9 MPa axial tension during sintering increases the average tensile strength of alumina fibers sintered at 1500 ℃ for 3 min by 231%, from 0.35 GPa to 1.16 GPa.
2022 Vol. 27 (5): 542-549 [
Abstract
] (
625
)
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964
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550
Adsorption performance of acid scarlet GR by γ-AlOOH prepared with hydrothermal method
LÜ Fengcheng, WANG Ding, LI Zhonglin, LI Yuping, LI Yibing, HE Guixiang
DOI: 10.19976/j.cnki.43-1448/TF.2022052
Using aluminum sulfate octadecahydrate as the aluminum source and urea as the precipitant, the γ-AlOOH adsorbent was prepared by hydrothermal synthesis. The microstructure, morphology and adsorption performance of γ-AlOOH were analyzed and tested by X-ray diffractometer (XRD), scanning electron microscope (SEM) and N
2
adsorption-desorption method. The effects of adsorption time, initial pH and initial mass concentration of acidic scarlet GR solution on the adsorption performance of acid scarlet GR by γ-AlOOH were studied as well. The results show that the γ-AlOOH adsorbent has a core-shell micron-flower hierarchical structure with high purity, a specific surface area of 205.07 m
2
/g, and an average pore size of 3.07 nm. When the initial mass concentration of the acid scarlet GR solution is 300 mg/L, the volume is 200 mL, the pH value is 2, and the temperature is 25 ℃, the adsorption amount of acid scarlet GR by 1 g γ-AlOOH reaches 470.65 mg, the removal rate is 78.44%. The adsorption kinetics of the adsorption process conforms to the pseudo-second-order kinetic model, and the adsorption thermodynamics conforms to the Langmuir thermodynamic model. After 8 cycles of adsorption, the adsorption amount of acid scarlet GR by 1 g γ-AlOOH regenerated adsorbent in 300 mg/L acid scarlet GR solution can still reach 422.57 mg, and the removal rate is 70.43%.
2022 Vol. 27 (5): 550-558 [
Abstract
] (
401
)
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(682 KB) (
611
)
559
Measurement of the sphericity and satellity of 3D printing metal powder by imaging particle size analysis——with argument on GB/T39251—2020
LIU Wenli, YANG Zhenghong, WANG Xinquan
DOI: 10.19976/j.cnki.43-1448/TF.2022021
The particle size and shape characteristics of 3D printed spherical metal powder have a great influence on the properties of formed parts. Therefore, it is very important to explore appropriate particle size and shape parameters to control the quality of 3D printing spherical metal powder. Mixing the coarse and fine particle size of 3D printing metal powder in a certain proportion can effectively improve the product strength and quality on the surface. In fact, the traditional laser diffraction method is difficult to distinguish the multi particle groups of powder samples, while the image particle sizing analysis an easy solution. The sphericity and satellitized degree of 3D printing powder are the focus of particle shape research, but the sphericity is actually distinguished by three corresponding levels of shape including macroshape, mesoshape and microshape, which isdifficultto be completely characterized by a certain parameter. In this paper, the instrument (Occhio 500nano XY) and method of measuring particle size by imaging method are proposed for 3D printing spherical metal powder, and compared with the traditional laser diffraction method. It is proposed that Bluntness and Outgrowth index, two unique quantitative microshape parameters are the most suitable evaluation parameters for the sphericity of 3D printing metal powder which were described the meaning and indicated the discrimination. It is proved that Bluntness is one of the most sensitive sphericity characterization parameters, and Outgrowth index can reflect the satellitized degree of spherical particles quantitatively. However, the circularity recommended by
2022 Vol. 27 (5): 559-568 [
Abstract
] (
760
)
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1933
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