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Discovering the ultralow thermal conductive A_(2)B_(2)O_(7)-type high-entropy oxides through the hybrid knowle dge-assiste d data-driven machine learning

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Journal of Materials Science & Technology 2024年第1期168卷 131-142页

作者： Ying Zhang Ke Ren William Yi Wang Xingyu Gao Ruihao Yuan Jun Wang Yiguang Wang Haifeng Song Xiubing liang jinshan li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Innovation Center NPU ChongqingChongqing 401135China Institute of Advanced Structure Technology Beijing Institute of TechnologyHaidian DistrictBeijing 100081China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Defense Innovation Institute Academy of Military Sciences of the PLA of ChinaBeijing 100071China

Lattice engineering and distortion have been considered one kind of effective strategies for discovering advanced materials.The instinct chemical flexibility of high-entropy oxides(HEOs)motivates/accelerates to tailor the target properties through phase transformations and lattice distortion.Here,a hybrid knowledge-assisted data-driven machine learning(ML)strategy is utilized to discover the A_(2)B_(2)O_(7)-type HEOs with low thermal conductivity(κ)through 17 rare-earth(RE=Sc,Y,La-Lu)solutes optimized A-site.A designing routine integrating the ML and high throughput first principles has been proposed to predict the key physical parameter(KPPs)correlated to the targetedκof advanced HEOs.Among the smart-designed 6188(5RE_(0.2))_(2)Zr_(2)O_(7)HEOs,the best candidates are addressed and validated by the princi-ples of severe lattice distortion and local phase transformation,which effectively reduceκby the strong multi-phonon scattering and weak interatomic interactions.Particularly,(Sc_(0.2)Y_(0.2)La_(0.2)Ce_(0.2)Pr_(0.2))_(2)Zr_(2)O_(7)with predictedκbelow 1.59 Wm^(−1)K^(−1)is selected to be verified,which matches well with the ex-perimentalκ=1.69 Wm^(−1)K^(−1)at 300 K and could be further decreased to 0.14 Wm^(−1)K^(−1)at 1473 K.Moreover,the coupling effects of lattice vibrations and charges on heat transfer are revealed by the cross-validations of various models,indicating that the weak bonds with low electronegativity and few bond-ing charge density and the lattice distortion(r∗)identified by cation radius ratio(r A/r B)should be the KPPs to decreaseκefficiently.This work supports an intelligent designing strategy with limited atomic and electronic KPPs to accelerate the development of advanced multi-component HEOs with proper-ties/performance at multi-scales.

关键词： High-entropy oxides Thermal conductivity Pyrochlore Key physical parameter First-Principles

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Magnetic field intensity dependent microstructure evolution and recrystallization behavior in a Co-B eutectic alloy

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Journal of Materials Science & Technology 2023年第7期138卷 93-107页

作者： Fan Bu Yiyuan Zhang Haoxiang liu Jun Wang Eric Beaugnon jinshan li Yixuan He State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Center of Advanced Lubrication and Seal Materials Northwestern Polytechnical UniversityXi’an 710072China Collaborative Innovation Center of NPU Shanghai 201108China Institute of Superconducting Materials and Applied Technology Northwestern Polytechnical UniversityXi’an 710072China Univ.Grenoble Alpes INSA ToulouseUniversity Toulouse Paul SabatierEMFLCNRSLNCMIGrenoble 38000France

Systematic understanding on the magnetic field intensity dependent microstructure evolution and re-crystallization behavior in a Co-B eutectic alloy under a constant undercooling(ΔT≈100 K)were carried out.Absent of the magnetic field,the comparable size of divorced FCC-Co and Co_(3)B eutectic ellipsoidal grains coexist with a few regular lamellas.When the magnetic field is less than 15 T,the elongated primary FCC-Co dendrites parallel to the magnetic field with the dispersed FCC-Co nano-particles em-bedded within the Co_(3)B matrix occupy the inter-dendrite regions.Once the magnetic field increases to 20 T,the FCC-Co/Co_(2)B anomalous eutectic colonies dominate.The formation mechanism of Co_(2)B phase is discussed from several aspects of the competitive nucleation,the chemical redistribution induced by the thermomagnetic-induced convection and magnetic dipole interaction,and the strain-induced trans-formation.Furthermore,the application of magnetic field is found to promote recrystallization,proved by the lower density of misorientation,the appearance of FCC-Co annealed twins and more Co_(3)B sub-grains.This work could further enrich our knowledge about the magnetic-dependent microstructure evolution and recrystallization process in the undercooled Co-B system and provide guidance for controlling the microstructures and properties under extreme conditions.

关键词： Magnetic field Undercooled solidification Microstructure evolution Recrystallization Co-B alloy

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Formation mechanism ofγtwins inβ-solidifedγ-TiAl alloys

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Journal of Materials Science & Technology 2022年第10期105卷 164-171页

作者： Yan liu jinshan li Bin Tang William Yi Wang Minjie Lai Lei Zhu Hongchao Kou State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China

Defects,such as stacking faults(SF)and twins,play a crucial role in stabilizing the order phase and improving the mechanical properties for engineering alloys.The formation mechanism of theγtwins from α_(2)-platelets within β_(0) areas was analyzed at atomic-scale by atomic-resolution high-angle annular dark-feld scanning transmission electron microscopy(HADDF-STEM).The growth faults(ABABCBC)were formed in α_(2)-platelets,yielding a local D0_(19)→L1_(0)(α_(2)→γ)phase transformation.During the annealing process,the growth faults can be rearranged intoγ(ABCABC)and γ^(T)(ACBACB)platelets via the slipping of Shockley partial dislocations 1/3[1010]and 1/3[1010],respectively.The γ and γ^(T) can merge intoγtwins by accident during growing.The interface steps between α_(2) and γ platelets implied that this transformation is a diffusion-controlled defect migration process.The present work provides profound insight towards the formation mechanism ofγtwins,contributing to microstructure controlling and performance improving for TiAl alloys.

关键词： γtwins Titanium aluminides Stacking faults Phase transformation Decomposition

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HFIP-catalyzed highly diastereoselective formal[4+2]cyclization to synthesize difluorinated multisubstituted chromans using difluoroenoxysilanes as C2 synthons

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Chinese Chemical Letters 2022年第6期33卷 3007-3011页

作者： jinshan li Wenxue Xi Saimei liu Yaqi Yang Jianguo Yang Hanfeng Ding Zhiming Wang Advanced Research Institute and Department of Chemistry Taizhou UniversityTaizhou 318000China Department of Chemistry Zhejiang Sci-Tech UniversityHangzhou 310018China Department of Chemistry Zhejiang UniversityHangzhou 310058China

A hexafluoroisopropanol(HFIP)-catalyzed highly diastereoselective formal[4+2]cyclization between ortho-hydroxyphenyl para-quinone methides and difluoroenoxysilanes is developed.This tandem protocol provides a simple and straightforward approach to assemble diverse multiply functionalized difluorinated chromans with high to excellent diastereoselectivity by employing difluoroenoxysilane as a new C2 synthon.

关键词： Difluorinated chromans [4+2]Cyclization Difluoroenoxysilanes HFIP catalysis Diastereoselectivity

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Heterogeneous precipitate microstructure in titanium alloys for simultaneous improvement of strength and ductility

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Journal of Materials Science & Technology 2022年第29期124卷 150-163页

作者： Mengyuan Hao Pei li Xuexiong li Tianlong Zhang Dong Wang Qiaoyan Sun libin liu jinshan li Yuyou Cui Rui Yang Dongsheng Xu Frontier Institute of Science and Technology State Key Laboratory for Mechanical Behavior of MaterialsXi’an Jiaotong UniversityXi’an 710049China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering Central South UniversityChangsha 410083China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Thermal Power Research Institute Co.Ltd. Xi’an 710032China

The design of alloys with simultaneous high strength and high ductility is still a difficult challenge.Here,we propose a new approach to designing multi-phase alloys with a synergistic combination of strength and ductility by engineering heterogeneous precipitate microstructures through the activation of different transformation mechanisms.Using a two-phase titanium alloy as an example,phase field simulations are carried out firstly to design heat treatment schedules that involve both conventional nucleation and growth and non-conventional pseudospinodal decomposition mechanisms,and the calculated microstructures have been evaluated by crystal plasticity finite element modeling.According to simulations,we then set a two-step heat treatment to produce bimodalα+βmicrostructure in Ti-10V-2Fe-3Al.Further mechanical testing shows that the ductility of the alloy is increased by~50%and the strength is increased by~10%as compared to its unimodal counterpart.Our work may provide a general way to improve the mechanical properties of alloys through multiscale microstructure design.

关键词： Titanium alloys Phase field simulation Crystal plasticity finite element Two-step aging Pseudospinodal decomposition mechanisms Multiscale heterogeneous microstructure

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Microstructure Evolution and Its Effect on Mechanical Properties in an Electron Beam Weldedβ-Solidified TiAl Alloy

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Acta Metallurgica Sinica(English Letters) 2023年第10期36卷 1619-1629页

作者： Songkuan Zhao Bin Tang Guoming Zheng Mengqi Zhang Wei Chen Tong Zhao Beibei Wei Lei Zhu jinshan li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China Chongqing Innovation Center Northwestern Polytechnical UniversityChongqing401135China AVIC Manufacturing Technology Institute Beijing100024China Shaanxi Key Laboratory of Electrical Materials and Infiltration Technology School of Materials Science and EngineeringXi’an University of TechnologyXi’an710048China

TiAl alloys are susceptible to cracks during electron beam welding because their limited ductility cannot accommodate the stress generated under fast cooling rate.In this work,pre-heating and post-heating via defocused electron beam were used to obtain well-welded joints without cracks.Lower crack sensitivity of joints was attributed to the microstructure evolution to obtain more ability of stress accommodation with the increasing heating beam current and heating time.Long-time pre-heating of 5 min and post-heating of 12 min led to reduced volume fraction of residualβ0 phase with the growth ofα2/γlamellar colonies in the fusion zone(FZ).The refined microstructure of FZ contributed to the highest hardness of the FZ,and the fracture happened at the base material(BM)in tensile tests,indicating that the tensile properties of the welding seam surpassed that of the BM.This work provides an effective way to obtain TiAl joints with better mechanical properties of the welding seam than that of the BM,which is a breakthrough in the welding of TiAl alloys.

关键词： TiAl alloys Electron beam welding Microstructure Phase transformation Mechanical properties

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Creep anisotropy behavior,deformation mechanism,and its efficient suppression method in Inconel 625 superalloy

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Journal of Materials Science & Technology 2023年第2期133卷 58-76页

作者： Xudong liu Jiangkun Fan Kai Cao Fulong Chen Ruihao Yuan Degui liu Bin Tang Hongchao Kou jinshan li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Innovation Center NPU·ChongqingChongqing 401135China AVIC Manufacturing Technology Institute Beijing 100024China

Mill products,such as sheets,usually show obvious anisotropy in their mechanical properties,which greatly affects both their applications and workability.In this study,the orientation-dependent tensile and creep behaviors of Inconel 625 alloy sheets with weak local textures were systematically investigated at 650°C.The results showed that Inconel 625 superalloy exhibits nearly isotropic tensile properties;how-ever,obvious creep anisotropy appears when loading along different directions.Creep life in the rolling direction(150±5 h)was approximately 4.5 times longer than in the transverse direction(33±1 h).Se-vere creep anisotropy was found to be determined by two aspects:(i)the change in deformation mecha-nisms along the rolling direction(a combination of boundary sliding,dislocation slipping,and twinning)and the transverse direction(dislocation slipping).Stronger impingement of slip bands on grain bound-aries accelerated intergranular crack initiation and propagation during loading along the transverse direc-tion,which resulted in a short creep life.(ii)The differences in strain compatibility at grain boundaries(i.e.,creep loading along the transverse direction resulted in the initial grains forming strong Brass,Cu,and S textures).Creep cracks preferentially nucleated at the junctions between Cu/Brass texture grains,as these interfaces exhibit the worst strain compatibility(Luster-Morris parameter m≤0.22).Furthermore,pre-stress aging(PSA)treatment is proposed as an efficient method to suppress creep anisotropy.The discrepancy rate of creep life was found to be reduced by nearly 50%after PSA treatment.

关键词： Nickel superalloys Creep anisotropy Deformation mechanisms Texture Pre-stress aging

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The microstructure evolution and phase transformation behavior of a β-solidifying γ-TiAl alloy during creep

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Progress in Natural Science:Materials International 2023年第2期33卷 193-202页

作者： Yan liu jinshan li Bin Tang William Yi Wang Yudong Chu Lei Zhu Weiqing Bi Xiaofei Chen Hongchao Kou State Key Laboratory of Solidification Processing Northwestern Polytechnical University Chongqing Innovation Center Northwestern Polytechnical University

The microstructural evolution and creep behavior of the Ti-43.5Al–4Nb–1Mo-0.1B alloy have been investigated by scanning electron microscope(SEM) and transmission electron microscope(TEM). The excellent creep property was obtained with a fully lamellar(FL) microstructure containing the least grain boundary βophase(GB-βo).TEM results revealed that after creep testing the α2→βophase transformation was observed in the FL microstructure. The formation βophase is associated with the accumulation of Mo element, which is confirmed by the energy-dispersive X-ray spectroscopy(EDS). Moreover, the formation of βoprecipitation in α2lamellae effectively decreased the generation of dislocations in(α2/γ) lamellae, thereby improving the creep resistance. For the near gamma(NG) microstructure of the as-forged sample, a large number of dislocations and dislocation tangles were observed in the globular γ phase(γ-glob), which are considered to be the dominant creep mechanism. Moreover,the ellipsoidal ωophase was observed in the GB-βophase, accompanying with dislocations and sub-boundaries formation. In sum, the excellent creep property of the β-solidifying γ-Ti Al alloy is attributed to the fine FL structure with a small amount of GB-βophase and the formation of βoprecipitation in(α2/γ) lamellae.

关键词： TiAl alloys Creep behavior Microstructure evolution TEM Phase transformation

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Effect of long-term aging treatment on the tensile strength and ductility of GH 605 superalloy

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Progress in Natural Science:Materials International 2022年第3期32卷 375-384页

作者： Yixuan He Xudong liu Chenxu Xing Zhangchi Bian Qing Zhou Jun Wang Haifeng Wang jinshan li State Key Laboratory of Solidification Processing Northwestern Polytechnical University Center of Advanced Lubrication and Seal Materials Northwestern Polytechnical University National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of Technology Harbin

Aging treatment is an effective way to optimize the mechanical properties of Co-based superalloys. In this study,commercial GH 605 superalloy was subjected to aging treatment at 650℃ in a wide time range up to 1000 h. The effects of aging time on the tensile characteristics, microstructure evolution and mechanical properties were systematically investigated at room temperature(RT) and 900℃. The results showed that the volume fractions of M6C and M23C6carbide increased with the aging time. After long-term aging treatment, the yield strength(YS) at RT was enhanced from 490.3 MPa to 805.9 MPa, while the alloy still had high tensile ductility(above 20%).Microscopic observations by transmission electron microscopy(TEM) indicated that the strengthening mechanism was related to carbide precipitation inside the grains and the change in the dislocation slipping mode. Moreover,long-term aging treatment can increase the elongation from 24.1% to 47.3% at 900℃ accompanied by a slight increase of YS from 299.3 MPa to 313.9 MPa. Based on detailed microstructure analysis the strengthening mechanism can be attributed to the refined grains as well as carbide precipitation inside the grains and around the grain boundaries.

关键词： GH 605 superalloy Long-term aging treatment Carbide Strengthening mechanism

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门体分流结扎术治疗新生儿先天性肝外门体分流2例

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中华小儿外科杂志 2024年第5期45卷 455-457页

作者：张金山李龙首都儿科研究所普外科中国医学科学院小儿外科微创诊疗创新单元(2021RU015)北京100020

患儿1,女,母孕5个月时超声检查发现门静脉纤细,生后2 d超声发现门静脉-下腔静脉分流。腹部增强CT检查发现门静脉主干与下腔静脉间存在异常分流(图1),诊断为Ⅱ型Abernethy畸形[1]。超声显示异常分流血管直径4.2 mm,血流速度约为0.44 m/s... 详细信息

患儿1,女,母孕5个月时超声检查发现门静脉纤细,生后2 d超声发现门静脉-下腔静脉分流。腹部增强CT检查发现门静脉主干与下腔静脉间存在异常分流(图1),诊断为Ⅱ型Abernethy畸形[1]。超声显示异常分流血管直径4.2 mm,血流速度约为0.44 m/s,显著高于门静脉主干的直径(3.4 mm)和血流速度(0.21 m/s)。血氨明显升高,达60.32µmol/L(正常值:11~40µmol/L)。血生化显示天冬氨酸转氨酶(56.5 U/L)、γ-谷氨酰转肽酶(177 U/L)、总胆红素(223.5µmol/L)、直接胆红素(12.7µmol/L)和总胆汁酸(11.8µmol/L)均明显升高。对于存在临床症状(包括高氨血症、黄疸和肝损伤)或分流量较大(一般分流>30%出现临床症状)的患儿需手术治疗或介入治疗[2-4]。因此,该患儿于生后10 d接受手术治疗。

关键词：门静脉主干门体分流直接胆红素血管直径总胆汁酸结扎术下腔静脉血流速度

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