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2025 Vol. 30, No. 5
Published: 2025-10-15
Engineering and Technology
Theoretical Research
Theoretical Research
387
Physical properties of B
12
RE (RE=Sc, Y) under different pressures: a first-principles study
MENG Jiali, CHEN Zeyu, CUI Zhihao, XI Yongqi, PANG Qiyuan, ZHENG Shaolong, TAO Xiaoma
DOI: 10.19976/j.cnki.43-1448/TF.2025009
This study systematically investigated the thermodynamic, mechanical, and electronic structure properties of B
12
Sc and B
12
Y under pressures ranging from 0 GPa to 50 GPa via first-principles calculations. The results indicate that the calculated lattice constants and formation enthalpies are all consistent with existing literature data. The calculated elastic constants of B
12
Sc and B
12
Y satisfy the mechanical stability criteria for cubic crystals. With increasing pressure, the elastic constants
C
11
,
C
12
, and
C
44
increase with different rates,
C
12
exhibits the largest increase, followed by
C
11
, and then
C
44
. Meanwhile, the bulk modulus shows the most significant increase with increasing pressure, followed by elastic modulus, then by shear modulus. The Vickers hardness of B
12
Sc and B
12
Y at ambient pressure are 32.45 and 36.34, respectively, suggesting their potential as strengthening phases in Mg alloys. The sound velocities, Debye temperatures, and lattice thermal conductivities increase with rising pressure, the Debye temperatures of B
12
Sc and B
12
Y are 1 336.6 K and 1 233.2 K at 0 GPa, respectively, indicating high melting points and strong interatomic interactions in these compounds. Both B
12
Sc and B
12
Y exhibit metallic behavior, with covalent bonds formed between B and B atoms, providing strong interatomic interactions that contribute to their high Debye temperatures and hardness.
2025 Vol. 30 (5): 387-394 [
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] (
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Engineering and Technology
395
Microstructure and deformation mechanism of (Fe
45
Mn
35
Co
10
Cr
10
)
99
C
1
high-entropy alloy by laser powder bed fusion
LI Xianglong, GENG Zhaowen, CHEN Chao, LUO Jinru, ZHOU Kechao
DOI: 10.19976/j.cnki.43-1448/TF.2025026
FeMnCoCrC high-entropy alloys were fabricated using laser powder bed fusion (LPBF) from pre-alloyed (Fe
45
Mn
35
Co
10
Cr
10
)
99
C
1
gas-atomized powder. The effects of LPBF process parameters on the microstructure and mechanical properties of the alloy were investigated by scanning electron microscope, transmission electron microscope, X-ray diffractometer, and room-temperature tensile test, with the aim of elucidating the underlying deformation mechanisms. The results indicate that the FeMnCoCrC high-entropy alloy exhibits a stable single-phase FCC structure, with randomly oriented grains and no significant texture. Furthermore, rich dislocation cell structures formed during the LPBF process, while no carbide precipitation is observed. The alloy fabricated under the optimal parameters (laser power of 120 W and scanning speed of 400 mm/s) demonstrates a enhanced yield strength while maintaining good elongation, achieving a yield strength of 603 MPa, a tensile strength of 850 MPa, and an elongation of 44.0%. The plastic deformation mechanism of the FeMnCoCrC high-entropy alloy is primarily governed by dislocation slip and twinning-induced plasticity, which collectively contribute to a sustained work-hardening capacity. In contrast, the martensite-induced plasticity mechanism is completely suppressed during deformation.
2025 Vol. 30 (5): 395-404 [
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] (
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405
Fluorescence detection of deep-seated stresses inside La
2
Zr
2
O
7
/YSZ double-ceramic thermal barrier coatings
BAI Yibo, DING Chengyun, CHU Qianqian, LI Wensheng, CHENG Bo
DOI: 10.19976/j.cnki.43-1448/TF.2025013
Thermal barrier coatings (TBCs) are extensively utilized in the metal hot-end components of aircraft engines. The primary cause of delamination failure of TBCs ceramic layers is deep-seated stresses in the ceramic layer. The present study focuses on the La
2
Zr
2
O
7
/YSZ double-ceramic thermal barrier coating system, which operates at higher temperatures. In the YSZ layer, a Y
2
O
3
:Eu
3+
fluorescent stress-responsive units were identified, and sintering experiments at 1 300 ℃ were conducted on TBCs. The deep-seated residual stress of TBCs was calculated by combining the Eu
3+
fluorescence-stress response equation, and the fluorescence migration mechanism was explained through density functional theory calculations. The results indicate that the detection depth of the stress-responsive unit can reach 100 μm, and the deep layers of TBCs undergo a transition between compressive and tensile stresses. Stress can to induce lattice distortion in the Y
2
O
3
:Eu
3+
fluorescent stress-responsive unit, leading to changes in its electronic cloud structure, and ultimately resulting in regular changes in optical properties.
2025 Vol. 30 (5): 405-413 [
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] (
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414
Microstructure and mechanical properties of GH3536 alloy by laser powder bed fusion
LIANG Shengxiang, LI Ruidi, YUAN Tiechui, ZHANG Yi, MA Xin, HUANG Min
DOI: 10.19976/j.cnki.43-1448/TF.2025032
GH3536 alloy exhibits stable performance at elevated temperatures and is extensively utilized in high-temperature resistant components, including eddy current devices and engine blades. In this research, GH3536 alloy blocks were fabricated using laser powder bed fusion with partitioned block rotating scanning. The surface microstructure of the alloy was analyzed through scanning electron microscope and electron backscatter diffraction. Additionally, the mechanical properties and microhardness of the printed alloy were evaluated at room temperature. The results indicate that GH3536 alloy exhibits a limited number of pores and microcracks. Furthermore, a distinct microstructural difference is observed between the horizontal surface (
XOY
plane) and the constructed surface (
XOZ
plane). The
XOY
plane displays parallel scanning tracks, whereas the
XOZ
plane reveals melt pools, and the grains are fine and the dislocation density is relatively high at the melt pool boundaries. The room temperature tensile strengths of the alloy parallel to the
XOY
direction and the
XOZ
direction are 878 MPa and 762 MPa, respectively, and the elongation rates are 32% and 42%, respectively. There are a large number of small dimples at the tensile fracture. The microhardness (HV
0.2
) for the
XOY
and
XOZ
planes are 308 and 299, respectively.
2025 Vol. 30 (5): 414-423 [
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] (
)
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424
Dynamic hot forging preparation of textured Si
3
N
4
ceramics with high performance
DU Xuanhao, YAO Shu, FAN Jianye, GUO Huimin, CAI Silong, ZHAO Yulong, ZHAO Ke, LIU Jinling, LIU Dianguang
DOI: 10.19976/j.cnki.43-1448/TF.2025028
Si
3
N
4
ceramics exhibit excellent mechanical properties due to their strong covalent bonding characteristics, however, this characteristic makes them difficult to secondary process, severely limiting their widespread industrial applications. In this study, dynamic hot forging (DHF) technology was employed to process commercial Si
3
N
4
ceramics, the effects of hot forging temperature on the microstructure and mechanical properties of materials were studied. The results indicate that under a dynamic pressure of (60±5) MPa and a hot forging temperature of 1 800 ℃, the Si
3
N
4
ceramics exhibit optimal mechanical properties, with a hardness of 13.84 GPa, a fracture toughness of 6.88 MPa·m
1/2
, and a bending strength reaching 925 MPa. All performance metrics significantly surpassing those of the original samples. This performance enhancement is primarily attributed to two key factors: firstly, the elimination of defects such as pores during the hot forging process, and secondly, the structural texturing effect induced by dynamic pressure. The DHF technology developed in this study provides an effective new method for the secondary processing and strengthening of high-performance difficult-to-machine ceramic materials.
2025 Vol. 30 (5): 424-432 [
Abstract
] (
)
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433
Effects of heat treatment on microstructure and thermo-mechanical properties of thin-layered C/C composites
LI Haimei, LIU Zaidong, QIAO Zhiwei, YE Zhiyong, LIU Junwen, LI Zhiqiang, WEI Yanbin, YU Wenhao, LONG Quanyuan, LU Li, WEN Qingbo, WANG Yalei, XIONG Xiang
DOI: 10.19976/j.cnki.43-1448/TF.2025042
In this study, thin-layered C/C composites with a spread-stitching architecture were prepared by chemical vapor deposition. The effects of high-temperature heat treatment on the microstructure, mechanical and thermal expansion properties of the C/C composites were systematically investigated. The results indicate that high-temperature heat treatment leads to a reduction of shear strength at interface between the carbon fiber and pyrolytic carbon, while simultaneously enhancing the degree of graphitization in both materials. After high-temperature heat treatment, the tensile strength of the C/C composites increases from 112.3 MPa to 195.3 MPa, which is primarily attributed to the weakened interfacial shear strength. In contrast, the compressive strength decreases from 300.0 MPa to 121.6 MPa, mainly due to the degradation of interlaminar bonding strength, with interlayer delamination identified as the dominant failure mode. Furthermore, the enhanced graphitization degree of the C/C composites after high-temperature heat treatment is demonstrated to be the primary factor governing the increase in modulus and the reduction in the coefficient of thermal expansion of the composites.
2025 Vol. 30 (5): 433-445 [
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] (
)
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)
446
Compressive properties of selective laser melted 316L stainless steel gradient lattice structures
WANG Xiaokang, WU Liguang, YE Jianbo, HU Yaowu, LIU Hui, CAI Gaoshen
DOI: 10.19976/j.cnki.43-1448/TF.2025040
Lattice structures are increasingly utilized in aerospace, automotive manufacturing, and biomedical fields due to their advantages of lightweight construction, excellent sound insulation, high specific strength, high specific stiffness, and superior vibration absorption properties. To investigate the relationship between gradient strategies and the mechanical response of gradient lattice structures, this study designed gradient lattice structures with different gradient strategies and fabricated corresponding specimens using selective laser melting technology. The compressive properties of these structures were systematically investigated through a combined approach of simulation and experimental validation. The results indicate that during compression, the nodes of the lattice cells serve as primary stress concentration locations. Uniform structures, unidirectional gradient structures, and bidirectional gradient structures exhibit distinct deformation behaviors. Gradient lattice structures exhibit higher elastic modulus, yield strength, compressive strength, and plateau stress compared to uniform structures. Furthermore, bidirectional gradient structures demonstrate superior mechanical properties over unidirectional gradient structures and superior energy absorption performance compared to both uniform and unidirectional gradient structures. This study provides technical support for predicting the compressive response of diverse gradient lattice structures.
2025 Vol. 30 (5): 446-455 [
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] (
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456
Regulatory mechanisms of Na
2
CO
3
and NaCl on the micro-nano morphology of CeO
2
in the flux method
YANG Zhipeng, GAN Xueping, LIU Ronghui
DOI: 10.19976/j.cnki.43-1448/TF.2025046
As an economically viable material with extensive applications, morphology regulation of CeO
2
has remained a critical challenge. This study developed a flux method for spheroidizing blocky CeO
2
, with systematic investigation into the regulatory mechanisms of Na
2
CO
3
, NaCl, and their composite fluxes on CeO
2
morphology. The results reveal flux type and concentration can significantly affect the spheroidization process of CeO
2
. Na
2
CO
3
facilitates micro-scale (~5 μm) quasi-spherical particle evolution above 900 ℃ through chemically activated mechanisms combining Na⁺ lattice intercalation and oxygen vacancy compensation. Optimized spherical CeO
2
with sphericity index 0.80 is achieved at 1 000 ℃ when mass ratio of Na
2
CO
3
and raw materials is 1.8∶10. Comparatively, NaCl-dominated systems generate nano-sized particles (500-800 nm) via physical fluxing effects but exhibit pronounced agglomeration. The composite flux system demonstrate antagonistic interactions between components, leading to degraded sphericity relative to single-component counterparts. This work confirms that process regulation can overcome intrinsic limitations of conventional solid-phase method morphology control. The Na
2
CO
3
-dominated system features operational simplicity, cost-effectiveness, and superior particle dispersibility, offering a scalable pathway for industrial synthesis of spherical CeO
2
with precisely tunable diameters (1-10 μm).
2025 Vol. 30 (5): 456-470 [
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] (
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