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2023 Vol. 28, No. 5
Published: 2023-10-15
Engineering and Technology
Engineering and Technology
413
Effects of Yb addition on microstructure and properties of Al-Zn-Mg-Cu-Zr-Cr alloy
DUAN Zhiying, ZHANG Qianqian, FANG Zhou, FANG Huachan, ZHANG Zhuo, CHEN Kanghua
DOI: 10.19976/j.cnki.43-1448/TF.2023021
Two kinds of Al-Zn-Mg-Cu alloys adding Zr, Cr elements and Zr, Cr and Yb clements were prepared by the melting and casting method, respectively. Optical microscopy, transmission electron microscopy, and scanning electron microscopy were used to observe the microstructure of these alloys, and mechanical and corrosion properties were also tested. The results show that AlZnMgCu-Zr-Cr-Yb alloy maintains a fibrous structure dominated by small angular grain boundaries after solid solution treatment, which is attributed to the precipitation of a large number of fine and diffuse (Al,Cr)
3
(Zr,Yb) phases of 10-20 nm, which can hinder dislocation and grain boundary migration and thus significantly inhibit matrix recrystallisation. The addition of Yb can increase the hardness, strength, elongation, and fracture toughness of the alloy, with the fracture toughness increases from 24.2 MPa·m
1/2
to 32.4 MPa·m
1/2
. The resistances to stress corrosion, intergranular corrosion, and exfoliation corrosion all increase at the same time, with the threshold stress intensity factor for stress corrosion cracking (
K
ISCC
) increases from 10.6 MPa·m
1/2
to 17.0 MPa·m
1/2
. The intergranular corrosion depth decreases, the exfoliation susceptibility reduces and the exfoliation grade lowers from EB+ to EA.
2023 Vol. 28 (5): 413-426 [
Abstract
] (
1098
)
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427
Two-step hydrothermal preparing nanoflower-like Ni
3
Fe/Ni
3
S
2
high-efficiency electrocatalysts to enhance oxygen evolution reaction in alkaline media
CHEN Yuxiang, HE Hanwei
DOI: 10.19976/j.cnki.43-1448/TF.2023039
Ni
3
Fe/Ni
3
S
2
oxygen evolution catalysts were synthesized by two-step hydrothermal method using Fe(NO
3
)
3
·9H
2
O and Na
2
S·9H
2
O as Fe source and S source, respectively, and nickel mesh (NM) as the Ni source and support substrate. The microstructure and morphology of the catalysts were analyzed by XRD, XPS, SEM, and TEM, and the electrochemical properties were tested by an electrochemical workstation. The results demonstrate that the Ni
3
Fe/Ni
3
S
2
catalyst synthesized by the two-step hydrothermal method has rich three-dimensional nanoflower morphology, which enhances the spatial utilization of the catalyst. Ni
3
S
2
exposes a high refractive index $\{\bar{2}10\}$. crystalline surface, which contributes to the synergistic effect with the (111) crystalline surface of Ni
3
Fe to enhance the catalytic activity. The oxygen evolution overpotential is 229 mV at a current density of 10 mA/cm
2
in 1 mol/L KOH (25 ℃), the overpotential is 335 mV for a current density of 600 mA/cm
2
in 5.35 mol/L KOH (80 ℃), and the decay rate of the overpotential is only 2.39% after 6 000 cyclic voltammetry cycles. It demonstrates that the catalyst has good oxygene evolution performance and stability.
2023 Vol. 28 (5): 427-437 [
Abstract
] (
462
)
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438
Potassium-doped O3-type layered oxide cathode material and its performance
WEI Shubing, HE Yongju, CAO Xinxin, LIANG Shuquan
DOI: 10.19976/j.cnki.43-1448/TF.2023049
K doped O3-type Na
0.9-
x
K
x
Cu
0.22
Fe
0.30
Mn
0.48
O
2
(
x
=0, 0.05, 0.1) cathode materials were prepared by simple solid phase method. The structural stabilities and electrochemical properties of the materials were analyzed and studied by X-ray diffractometer, scanning electron microscope, transmission electron microscope, and electrochemical experiment. The results show that K doping can enhance the structural stability, the Na
+
diffusion rate and electrochemical reversibility are also significantly improved. The O3→P3 phase transition occurs earlier and faster, which has a positive effect on improving the energy efficiency of O3-type cathode materials. The O3-type Na
0.85
K
0.05
Cu
0.22
Fe
0.30
Mn
0.48
O
2
cathode material possesses excellent cycle stability, which can deliver a capacity retention of 88.6% after 150 cycles at 0.5 C. K doping is low-cost and simple to operate, which can help to promote the industrialization of stable high-performance sodium ion batteries.
2023 Vol. 28 (5): 438-447 [
Abstract
] (
442
)
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843
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448
Effects of annealing on microstructure and mechanical properties of powder metallurgy hot rolled CoCrFeNiC
0.05
high-entropy alloy sheet
ZHANG Yangfan, ZHOU Rui, TAO Hui, LI Huizhong, LIANG Xiaopeng
DOI: 10.19976/j.cnki.43-1448/TF.2023050
The pre-alloyed powder was prepared by gas atomization method with Cr, Co, Fe, Ni simple substance and Cr
3
C
2
as raw materials. CoCrFeNiC
0.05
high-entropy alloy was prepared by hot isostatic pressing, and the alloy was hot rolled and annealed. The effects of annealing on the microstructure and mechanical properties of powder metallurgy hot rolled CoCrFeNiC
0.05
high-entropy alloy sheet were systematically studied by X-ray diffraction, optical microscope, scanning electron microscope, transmission electron microscope, electron backscatter diffraction, Vickers hardness, and tensile testing. The results show that the grains are equiaxed in hot isotactic pressed alloy but transform to elongated morphology after hot rolling. The hot rolled sheet exhibits a strong F-type texture, and twins and submicron Cr
23
C
6
typed carbide are observed. After annealing treatment at 800 ℃, the alloy undergoes complete recrystallization. Hot rolling combining with moderate temperature annealing (500 ℃) is an effective approach to achieving good comprehensive mechanical properties for CoCrFeNiC
0.05
high-entropy alloy, with yield strength of 961 MPa, tensile strength of 1 023 MPa, and elongation of 13.6%.
2023 Vol. 28 (5): 448-455 [
Abstract
] (
266
)
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532
)
456
High temperature oxidation behavior of Nb-particle reinforced Ti-45Al-5Nb-0.3W alloy
HUANG Jiani, LI Huizhong, LIANG Xiaopeng, CHE Yixuan
DOI: 10.19976/j.cnki.43-1448/TF.2023051
Ti-45Al-5Nb-0.3W (mole fraction) alloy (Nb
p
/TiAl alloy) toughened by 2%Nb particles was prepared by hot isostatic pressing. After heat treatment at 1 280 ℃ for 24 h, the elements diffused fully, and the Nb-rich region transformed into the lamellar structure and γ grains. The phase composition and oxide film structure of the alloy before and after oxidation were studied by optical microscope, X-ray diffraction, scanning electron microscope, energy spectrometer, and electron probe microanalysis, and the oxidation mechanism of Nb
p
/TiAl alloy was revealed. The results show that the oxidation kinetics curves of Nb
p
/TiAl alloy during isothermal oxidation at 800, 850, and 900 ℃ are parabolic, and the mass increments per unit area after 100 h oxidation are 3.32, 7.36 and 17.27 g/m
2
, respectively. A protective oxide film is formed on the alloy surface with multi-layer structure of TiO
2
/Al
2
O
3
/(Al
2
O
3
+ TiO
2
+NbO)/(TiN+Ti
2
AlN+AlNb
2
), which can effectively inhibit the diffusion of O element in the alloy and improve the oxidation resistance of TiAl alloy.
2023 Vol. 28 (5): 456-464 [
Abstract
] (
230
)
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359
)
465
Effects of annealing temperature on the microstructure and mechanical properties of Ni/Cu explosive composite plates
CHEN Huijie, LI Huizhong, LIANG Xiaopeng, LU Yuchen, ZENG Zhiheng
DOI: 10.19976/j.cnki.43-1448/TF.2023052
Ni/Cu laminated composite plates were fabricated by explosive welding. The effects of annealing temperature on the microstructure and mechanical properties of Ni/Cu composite plates were studied by optical microscope, scanning electron microscope, electron probe, and energy spectrometer, as well as tensile, shear, and hardness tests. The results show that with the increase of annealing temperature, the grain size of Ni and Cu matrix on both sides of the interface of the composite plate increases, and the thickness of the interface element diffusion layer increases. When the annealing temperature is 600 ℃, the thickness of the element diffusion layer reaches 5.82 μm. The hardness distribution of the composite plate after annealing at 200 ℃ has little change compared with that of the explosive state. When the annealing temperatures are 400 ℃ and 600 ℃, the hardness (HV1) at the interface are 65.1 and 66.1, respectively, which are significantly lower than that in the explosive state (160.2). The tensile strength of the composite plates in explosive state and after annealing at 200, 400, and 600 ℃ are 351.6, 305.9, 281.7, and 284.8 MPa, respectively, with elongation of 2.6%, 7.8%, 39.1%, and 39.4%.When the annealing temperature is 400 ℃, the shear strength of the composite plate reaches the maximum value of 191.3 MPa, which is 17.5 MPa higher than that of the explosive state.
2023 Vol. 28 (5): 465-472 [
Abstract
] (
407
)
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640
)
473
Effects of thermal exposure on microstructure and properties of Al-Li alloy with different aging treatments
ZHANG Shuying, JIANG Bo, XIAO Pan
DOI: 10.19976/j.cnki.43-1448/TF.2023053
The effects of thermal exposure on microstructure and properties of 2A97 Al-Li alloy in different aging states were studied by means of scanning electron microscope, X-ray diffraction, transmission electron microscope, and hardness test. The results show that the phase types and morphologies of T6 and T8 alloys are similar after thermal exposure. With the increase of thermal exposure temperature, θʹ phase (Al
2
Cu) coarsens and decreases in quantity, T
1
phase (Al
2
CuLi) changes to equilibrium phase, and the thermal stability of the alloy deteriorates. Different from T8 alloy, the strengthening phase in T6 alloy is not only T
1
and θʹ phases, but also cubic phase, but the strengthening effect of this phase is much lower than that of T
1
and θʹ phases. After exposure at 200 ℃, the quantity of cubic phase increases, and after exposure at 300 ℃, it redissolves into the matrix. Therefore, the thermal stability of T6 alloy after low temperature thermal exposure is better than that of T8 alloy, but the thermal stability of the two aging state alloys after high temperature thermal exposure is basically the same. The hardness of T8 alloy is significantly higher than that of T6 alloy, and the hardness decrease of T8 alloy is greater than that of T6 after low temperature thermal exposure. However, the hardness decrease of the two alloys after high temperature thermal exposure is basically the same.
2023 Vol. 28 (5): 473-480 [
Abstract
] (
309
)
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(901 KB) (
567
)
481
Preparation, microstructure and properties of Nb phase plasticized TiAl/Nb composites with core-shell structure
SHEN Jingyuan, HU Lianxi, WANG Haoyang
DOI: 10.19976/j.cnki.43-1448/TF.2023054
In response to the challenges of the low plasticity at room temperature and difficulty in meeting engineering applications in traditional γ-TiAl alloys, this paper proposed Nb phase plasticized TiAl/Nb composites with core-shell structure, and systematically studied the preparation technology and mechanical properities of the composites. The results show that complete encapsulation of large-sized γ-TiAl atomized powder by fine Nb particle can be achieved after 120 h ball milling at the speed of 200 r/min. Subsequently, a densified core-shell structure with controllable plasticized phase can be obtained after vacuum hot pressing at 1 200 ℃/1 h, under 40 MPa. The prepared TiAl/Nb composites exhibit high strength and good plasticity with the yield strength of 971.5 MPa, compressive strength of 2 337.7 MPa, and fracture strain of 31.7% at room temperature. The high strength and excellent plasticity of the composites are attributed to the ductile β-Nb phase which facilitates coordinated deformation between matrix phase colonies, which thereby enhancing the continuous deformation capacity of the integral bulk materials.
2023 Vol. 28 (5): 481-489 [
Abstract
] (
267
)
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537
)
490
Effect of preparation process on corrosion resistance properties of powder metallurgy FeCrNi medium entropy alloy
HU Haixia, LIU Yong, HUANG Qianli
DOI: 10.19976/j.cnki.43-1448/TF.2023061
FeCrNi medium entropy alloys were prepared by canned hot extrusion and hot press sintering technology, respectively. The effects of preparation process on microstructure and corrosion resistance of FeCrNi alloy were studied. The results show that the average grain size of FeCrNi medium entropy alloy prepared by hot extrusion is 13 μm with coarse annealing twins, while the average grain size of FeCrNi medium entropy alloy prepared by hot press sintering is smaller, and the average grain size is 6 μm. FeCrNi medium entropy alloy prepared by hot press sintering shows good corrosion resistance in 0.5 mol/L H
2
SO
4
+2×10
-6
mol/L HF solution, that is a higher breakdown potential (0.979 V), a lower corrosion current density (7.68×10
-6
A/cm
2
), and a wider passive zone Δ
E
(1.011 V). Cr element in the passive film of FeCrNi by hot extrusion is mainly in the form of Cr(OH)
3
, while Cr element in the passive film of FeCrNi by hot press sintering is mainly in the form of Cr
2
O
3
. This is because the high density grain boundaries of the fine crystal structure provide more diffusion channels for Cr, and then promote the formation of Cr
2
O
3
in the passive film, and improve the stability and corrosion resistance of the passive film.
2023 Vol. 28 (5): 490-499 [
Abstract
] (
338
)
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1108
)
500
Microstructure and mechanical properties of dense Al
2
O
3
-ZrO
2
composite ceramic via flash sintering treatment
YAO Shu, LIU Dianguang, ZHAO Ke, LIU Jinling
DOI: 10.19976/j.cnki.43-1448/TF.2023065
Dense Al
2
O
3
-ZrO
2
composite ceramics were prepared by pressureless sintering using α-Al
2
O
3
and yttria stabilized zirconia powders as raw materials, conducting heat treatment under critical electric field, and the microstructure and mechanical properties of the composite ceramics were investigated. Results indicate that the onset temperature of flash sintering for sintered dense Al
2
O
3
-ZrO
2
composite ceramic is 308 ℃ under an electric field of 900 V/cm. Al
2
O
3
-ZrO
2
eutectic zone is in-situ synthesized in the dense Al
2
O
3
-ZrO
2
composite ceramic using flash sintering at 1 200 ℃ and 700 V/cm. The flash sintered ceramic is divided into three zones: composite zone, transition zone, and eutectic zone. In the composite zone, the Al
2
O
3
and ZrO
2
phases are irregular shapes and uniformly distributed, where there is similar microstructure to the sintered ceramic. In the transition zone, the abnormal grain growth is observed, and the coarse Al
2
O
3
and ZrO
2
phases are evenly distributed. In the eutectic zone, it possesses the typical microstructure of Al
2
O
3
-ZrO
2
eutectic ceramic. The Vickers hardness and toughness of eutectic zone are 17.94 GPa and 3.51 MPa·m
1/2
, respectively, which are comparable to those of Al
2
O
3
-ZrO
2
eutectic ceramic fabricated by directional solidification technique.
2023 Vol. 28 (5): 500-508 [
Abstract
] (
210
)
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510
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