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2020 Vol. 25, No. 4
Published: 2020-08-15
Engineering and Technology
Theoretical Research
Review
Review
273
Research progress on preparation and application of high-purity rhenium and its compounds
ZHANG Jiarun, LIU Zhiyong, LIU Zhihong, LI Qihou
Rhenium has excellent properties such as high temperature resistance and corrosion resistance, and is widely used in high temperature alloys, aerospace special alloys, petrochemicals and other fields. This article introduces various preparation techniques of high-purity rhenium and its compounds, analyzes the advantages and disadvantages of preparing high-purity ammonium perrhenate by precipitation crystallization, ion exchange, and solvent etraction and its application sitiation, and discusses the research progress of preparing high-purity rhenium powder by hydrogen reduction, plasma, electrolysis, and vapor deposition. The application prospects of rhenium in the field of alloys are outlined.
2020 Vol. 25 (4): 273-279 [
Abstract
] (
666
)
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2092
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Theoretical Research
280
Vertical section of 50Ti-
x
Al-
y
Nb in Ti-Al-Nb system
ZHAO Yun, LIU Libin, YANG Jiajun, ZHANG Ligang
The Ti-Al-Nb ternary alloy samples were prepared by vacuum melting, and then annealed at 1 000, 900, and 800 ℃ for 720, 1 440, and 2 160 h in furnace, respectively. Finally, these samples were quickly quenched to retain the high temperature structure. The vertical section of 50Ti-
x
Al-
y
Nb in Ti-Al-Nb system was studied using X-ray diffraction analysis (XRD), differential thermal analysis (DSC) and electron probe microanalysis (EPMA). This work focused on detecting the change of phase zone in the middle temperature region (800-1 000 ℃). Five three-phase equilibrium zones: σ+β+α
2
, σ+O+α
2
, α
2
+γ+β, α
2
+γ+σ and α
2
+σ+τ; two two-phase equilibrium regions: β+O and α
2
+γ; and two single-phase regions: γ and β have been measured.
2020 Vol. 25 (4): 280-287 [
Abstract
] (
286
)
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593
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288
Molecular dynamics simulation of void evolution and its mechanical response in single-crystal tungsten under extreme strain rate
BAI Xiaodan, CHEN Xun, MA Yunzhu, LIU Wensheng, LIANG Chaoping
Molecular dynamics simulation was used to investigate the void evolution in single-crystal tungsten under uniaxial compression at extreme high strain rate (10
8
-10
11
s
-1
), and the mechanical properties were also tested. The results show that the yield strength and Young’s modulus decrease as a function of void radius. The plastic behavior of tungsten with different radius of void shows similar feature with the increase of strain rate. At $\dot{\varepsilon }$≥5×10
10
s
-1
, the single crystal tungsten is changed into an amorphous structure. The amorphization of tungsten with void is delayed in comparison to perfect tungsten crystal ($\dot{\varepsilon }$≥10
10
s
-1
). At$\dot{\varepsilon }$≤10
10
s
-1
, before amorphization, the evolution of void during deformation the synergic effect of dislocation generation and twinning. The detailed plastic behavior follows: 1) The emission of 1/2[111] dislocation loop. 2) The decomposition of 1/2[111] screw dislocation. 3) The formation of (112)$[\bar{1}\bar{1}1]$twins, 4) the collapse of void.
2020 Vol. 25 (4): 288-295 [
Abstract
] (
456
)
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1119
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Engineering and Technology
296
Effect of milling time on the microstructure and mechanical properties of M2 powder metallurgy high speed steel
YANG Junhao, LIU Rutie, XIONG Xiang, LUAN Huaizhuang, HAO Yanrong, YANG Baozhen, CHEN Jie
The M2 powder metallurgy high speed steel (PM HSS) was prepared with the carbonyl iron powders and carbide powders as raw materials. The powders were mixed via ball milling for 0-72 h, and then compacted by double-action pressing before sintered at 1 205 ℃ for 1h. The effect of the milling time on the carbon content, oxygen content, microstructure and mechanical properties of the M2 PM HSS were studied. The results show that with the increase of milling time, the particle size of the mixed powders decreases, the oxygen content increases significantly, and the carbon content of the M2 PM HSS decreases due to the carbon-thermal reduction. The main phases of M2 PM HSS are Fe, M
6
C, M
2
C and MC. With increasing milling time, metastable M
2
C carbide decreases, while M
6
C and MC carbides increase. Besides, with the increasing of milling time, the grain size of M2 PM HSS and particle size of carbide become finer, the carbide distribution is more uniform, and the relative density, hardness and bending strength of M2 PM HSS increase significantly. After milling for 72 h, the relative density of M2 PM HSS is 99.3%, and the hardness (HRC) and the bending strength are 50.6 and 2 852 MPa, respectively.
2020 Vol. 25 (4): 296-303 [
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] (
482
)
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304
Microstructure and properties of MIM 17-4PH stainless steel prepared by nitrogen sintering process
WANG Yue, LI Ruidi, YUAN Tiechui
MIM 17-4PH stainless steel was prepared at 1 260, 1 290 and 1 305 ℃ using nitrogen sintering technology in the whole process. The microstructure and properties of the stainless steel were tested and analyzed, which were compared with MIM 17-4PH stainless steel prepared by conventional sintering process of vacuum and argon sintering. The results show that the MIM 17-4PH sintering in a nitrogen atmosphere throughout the process facilitates the nitriding effect. Compared to the conventional sintering process with vacuum and argon, the whole sintering process under nitrogen decreases its relative density, while the grains are obviously refined and new microstructure appears. Meanwhile, the content of austenite in sintered stainless steel decreases with the increase of sintering temperature. 1 290 ℃ is the best temperature to make sample possess relatively higher densification, better nitriding effect, refined grain size, and uniform distribution of fine second phase. The nitrogen sintering improves the comprehensive mechanical properties compared with vacuum and argon sintering. The tensile strength increases from 900 MPa to 1 158 MPa. The elongation increases from 6% to about 10%, and cross-sectional hardness (HRC) increases from 20.2 to 28.0.
2020 Vol. 25 (4): 304-311 [
Abstract
] (
584
)
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2041
)
312
Effect of Cr content on high temperature oxidation behavior of porous NiCrMoCu alloys
ZOU Haoran, LI Xide, ZHANG Chuo, YANG Junsheng, HE Yuehui
NiCrMoCu porous material was fabricated by the activation reaction sintering method using Ni, Cr, Mo and Cu element powders as raw materials. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrum (EDS), pore size tester were conducted to characterize the phase composition, pore morphology, element valence, element content and pore structure of porous materials before and after high temperature oxidation at 800 ℃. The results indicate that the oxidation mass gain and the decrease rate of permeability of NiCrMoCu porous materials show a trend of decreasing first and then increasing with the increases of Cr content. When the Cr content attains 35%, and the oxidation time is 20 h, the smallest mass gain is 7.31 mg/cm, and the rate of decrease in permeability is 23.41%. When Cr mass fraction ranges from 10% to 35%, the surface composition of the material is mainly Cr
2
O
3
. The Cr content continues to increase to 40%, its oxidizing substances are mainly Cr
2
O
3
and NiCr
2
O
4
. The addition of alloying element Cr is conducive to the formation of a dense Cr
2
O
3
thin film on the surface, preventing air from continuing to penetrate the alloy substrate to produce oxidation. However, the Cr content continues to increase, the fluffy structure of NiCr
2
O
4
is generated to increase the oxidaion.
2020 Vol. 25 (4): 312-320 [
Abstract
] (
325
)
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542
)
321
Nano-SiC addition on microstructure, mechanical properties and high temperature oxidation resistance of Ti(C,N)-based cermets
GONG Difan, LI Yongxia, YANG Hailin, ZOU Dan, LIU Yanjun
Ti(C,N), WC, Mo
2
C, TaC and Cr
2
C
3
powders were used as the main raw materials, Co and Ni powders were used as binders, and nano-SiC powders with 0-11% volume fraction were added as the reinforcing phase to prepare Ti- (C,N) based cermets. The effect of SiC content on the microstructure, mechanical properties and high temperature oxidation resistance of ceramic materials was studied. The results indicated that a small amount of SiC could not change the original phase structure of the cermet. As SiC content increased, the integrity of the ring phase decreased and the average grain size of the hard phase reduced. Ti(C,N)-based cermet with 5% volume fraction SiC had excellent comprehensive properties, with Rockwell hardness of 88.8 HRA, flexural strength of 2 280 MPa, and fracture toughness of 13.22×10
3
kN∙m
-3/2
. The addition of SiC enhanced the high temperature oxidation resistance of Ti(C,N) based cermets and produced a dense SiO
2
film on the surface.
2020 Vol. 25 (4): 321-329 [
Abstract
] (
363
)
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1087
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330
Effects of LaB
6
addition on densification behavior, microstructure and mechanical properties of Ti(C,N) based cermets
HUANG Jianhua, ZHANG Meimei, KANG Xiyue, LIN Nan, YAN Yan, QIU Song, LIU Yi, HE Yuehui
The traditional powder metallurgy method was used to prepare Ti(C,N)-based cermet materials with different LaB
6
additions. The effects of LaB
6
addition on the densification process, microstructure and mechanical properties of cermets were studied. The results show that the addition of LaB
6
can accelerate the densification of the material, and especially it has a significant effect on increasing the densification rate of the material during the solid phase sintering process. The microstructure of the prepared samples are typical core-shell structures, but with the increase of the amount of LaB
6
addition, the carbon-deficient phase is also increased. At the same time, LaB
6
can promote the solid solution of Ti(C,N) particles into the binder phase, so that the average particle size of the black phase Ti(C,N) in the material decreases. The cermet material added with mass fraction of 0.01% LaB
6
has good mechanical properties, among which the hardness reaches 92.07 HRA, the fracture toughness and bending strength are 12.09 MPa/m
1/2
and 14.785 MPa, respectively.
2020 Vol. 25 (4): 330-337 [
Abstract
] (
392
)
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645
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338
Effect of magnesium aluminate spinel on the microstructures and mechanical properties of 95 alumina ceramics
FANG Haojie, LIU Qiuyu, HE Yiwen, GUO Weiming, ZHANG Xiaoyun, ZHU Linlin, ZENG Chao, LIN Huatai
The effects of 6% magnesium-aluminum spinel (MgAl
2
O
4
) on the microstructures and mechanical properties of 95 alumina (Al
2
O
3
) ceramics sintered at 1 550 ℃ with different holding times (2 h and 4 h) were studied. Scanning electron microscopy and X-ray diffraction were used to observe the ceramic and examine phase assemblage. The results showed that the grain size of Al
2
O
3
ceramics without MgAl
2
O
4
was coarser and have lower density. Prolonging the holding time could increase the density of the ceramics, thereby increasing the hardness of the material. The Vickers hardness with sintered 2 h and 4 h were 12.6±0.4 GPa and 14.7±0.4 GPa, respectively. When 6% MgAl
2
O
4
was added, the grain size of Al
2
O
3
ceramics was decreased, and the relative density was also increased. The hardness were increased to 13.5±0.4 GPa (1 550 ℃/2 h) and 15.5±0.9 GPa (1 550℃/4 h).
2020 Vol. 25 (4): 338-343 [
Abstract
] (
462
)
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344
Densification mechanism of Ti-1Al-8V-5Fe alloy by spark plasma sintering
LI Wenjie, ZENG Fanhao, LI Lei, WANG Ziwei, LIU Honghao, PENG Yirui, GU Yi
TiH
2
, FeV
80
, Al and Fe powders were used as raw materials, and the spark plasma sintering was used to prepare Ti-1Al-8V-5Fe (Ti185) alloys at 800-1 200 ℃ for 10min. The effective stress exponent (
n
) and the densification activation energy (
Q
d
) were evaluated by the sintering densification curve and mature creep model, which were used to study the densification kinetics of Ti185 alloys. The results showed that the alloys were rapidly densified without obvious grain growth at low temperature (800-1 000 ℃). When sintering temperature reached 1 100 ℃, the alloys were slowly densified with obvious grain growth. During sintering at 800-1 000 ℃, the densification stage in the early stage of dwelling had low effective stress exponent
n
and apparent activation energy
Q
d
(
n
=1,
Q
d
=52 kJ/mol), which was the stage of low effective stress, and grain boundary diffusion controlled the densification process of alloys. However, the later stage of dwelling corresponded to a higher effective stress stage, with
n
=3 and
Q
d
=175.7 kJ/mol. The densification mechanism of the alloys was controlled by dislocation climbing.
2020 Vol. 25 (4): 344-351 [
Abstract
] (
422
)
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1195
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352
In vitro histocompatibility of TNZS-based biomaterials
ZHAO Qian
Ti, Nb, Zr, Sn, Cu, Ag and Co powders were used as the raw materials, Ti-24Nb-4Zr-7.9Sn(TNZS), TNZS-5Cu, TNZS-5Ag and TNZS-5Co (mass fraction, %) alloys were prepared by high-energy ball milling, cold pressing and vacuum sintering. SD rat osteoblasts were inoculated in dulbecco’s modified eagle medium (DMEM) with 10% fetal calf serum (FBS) and subcultured, and the cell proliferation, cell adhesion and cytotoxicity experiments were carried out. The results showed that addition of 5% Cu, Ag and Co to TNZS alloys could improve the proliferation of osteoblasts to a certain extent. The surface of TNZS-5Co alloy was the most favorable to promote cell adhesion at the early stage of culture (24 h and 72 h). At the later stage of culture (120 h and 168 h), TNZS-5Cu and TNZS-5Ag alloys were more favorable for the adhesion of osteoblasts. The morphology and elongation of osteoblasts attached to the surface of TNZS-5Ag were the best, followed by TNZS-5Co, while the cell adhesion ability of TNZS and TNZS-5Cu were relatively weak. The cytotoxicity grade of the four materials was level 2, which showed that all of them met the cytotoxicity requirements of the biomedical implant materials.
2020 Vol. 25 (4): 352-357 [
Abstract
] (
337
)
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785
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358
Microstructure and mechanical properties of siliceous rock/A356 composites for construction prepared by spray forming
LI Kui, ZHANG Zhaofang, MA Nan, LI Ming
The A356 aluminum alloys and siliceous rock particles reinforced A356 aluminum matrix composites (mass fraction of siliceous rock particles is 4.5%) were prepared by spray molding. The interface structure, aluminum matrix structure and mechanical properties were compared. The results showed that all of the siliceous rock particles could be captured and uniformly distributed in the aluminum matrix during the spray forming. The siliceous rock particles formed a good mosaic structure in the aluminum matrix, and did not fall off during the double-spray electrolysis. Many dislocations were formed in the area close to the particle/matrix interface. The Si content in the Al matrix near the interface was higher, while the amount of other elements remained unaltered. Compared with A356 aluminum alloy, the tensile strength of siliceous rock/A356 composites increased from 603 MPa to 662 MPa, and the elongation increased from 3.52% to 3.92%. Both of the A356 alloy and siliceous rock/A356 composite were ductile fracture. The tensile fracture surface of siliceous rock/A356 composites was pitted by the pulled-out grains of siliceous rock, and many debris were generated.
2020 Vol. 25 (4): 358-362 [
Abstract
] (
304
)
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688
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