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Designing Rules of Laser-Clad high-Entropy Alloy Coatings with Simple Solid Solution Phases

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Acta Metallurgica Sinica(English Letters) 2020年第8期33卷 1064-1076页

作者： Yongfei Juan Jiao Zhang Yongbing Dai Qing Dong Yanfeng Han shanghai key Lab of advanced high-temperature materials and precision forming Shanghai Jiao Tong UniversityShanghai 200240China

The criteria of process parameters(μ≤4),atomic size difference(ε≤5.8,δ≤11 andα≤2),thermodynamic(-14.5≤△Hmix≤6.5 andΩ≥1.8)in the prediction of the phase stability for laser-clad high-entropy alloy coatings are studied in ***,the criteria of valence electron concentration(VEC)applied to distinguish the stability of different solid solution phases are as follows:VEChigh-entropy alloy coatings quite *** other modified criteria(δ,α,△Hmix,Ω,VEC)are proved to be different from those of the high-entropy alloys synthesized by the traditional casting and smelting processes.

关键词： high-entropy alloys Laser cladding Phase stability Criteria

A review on prediction of casting defects in steel ingots:from macrosegregation to multi-defect model

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Journal of Iron and Steel Research International 2022年第12期29卷 1901-1914页

作者： Jun Li Xiao-wei Xu Neng Ren Ming-xu Xia Jian-guo Li School of materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China shanghai key laboratory of advanced high-temperature materials and precision forming Shanghai 200240China

Due to the nature of the solute redistribution,the reduction in the solidification rate with time in a square root relationship,and the multiphase melt flow during the solidification,casting defects such as macrosegregation,shrinkage cavity,and porosity will inevitably occur in the steel ingot and intensify with the increase in ingot *** defects directly affect the performance of the final product and severely restrict the choice of subsequent thermal processing methods and process ***,the solidification defects including macrosegregation,shrinkage/porosity,and inclusions encountered in the preparation of large steel ingots and their formation mechanisms were *** development progress and the latest development of the macrosegregation model for steel ingots were introduced in detail,especially the latest progress in the coupling prediction of macrosegregation and shrinkage as well as macrosegregation and *** methods to reduce macrosegregation of ingots were discussed as ***,a new casting method called layered casting was introduced in *** method can effectively improve the uniformity of the macrostructure and reduce the macrosegregation of the large ingots and therefore is a promising method for preparing large ingots with high homogeneity.

关键词： Steel ingot Macrosegregation Numerical modeling Multiphase model Solidification defect

Atomic scale visualizations of low-angle grain boundary mediated plasticity by coupled dislocation climb and glide in nanoporous gold

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Nano Research 2023年第2期16卷 2622-2629页

作者： Shufen Chu Junnan Jiang Xiaoran Zhao Baode Sun Pan Liu shanghai key laboratory of advanced high-temperature materials and precision forming State Key Laboratory of Metal Matrix CompositesSchool of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Grain boundaries(GBs),as a prevalent structural characteristic,play a crucial role in the deformation of nanoporous metals with nanosized grains and ***,the fundamental understanding of GB-mediated deformation is still lacking because the plastic behavior of discrete ligaments involving GBs remains to be ***,we report atomic scale visualizations of coupled GB dislocation climb and glide in nanoporous gold ligaments with low-angle GBs via in situ tensile straining inside a Cs-corrected transmission electron *** zig-zag motion paths of GB dislocations are precisely determined by real-time tracking of the movements of dislocation *** concurrent climb and glide of the dislocation arrays are confined to a narrow GB region,greatly enhancing GB diffusion in the bicrystal *** findings of coupled dislocation climb and glide shine a light on the room-temperature deformation of nanoporous metals and provide a time-dependent atomic-level physical image for GB engineering.

关键词： nanoporous gold dislocation climb dislocation glide low-angle grain boundaries

Integration of Electrical Properties and Polarization Loss Modulation on Atomic Fe–N‑RGO for Boosting Electromagnetic Wave Absorption

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Nano-Micro Letters 2025年第2期17卷 517-532页

作者： Kaili Zhang Yuefeng Yan Zhen Wang Guansheng Ma Dechang Jia Xiaoxiao Huang Yu Zhou State key laboratory of precision Welding&Joining of materials and Structures Harbin Institute of TechnologyHarbin 150001People’s Republic of China School of materials Science and Engineering Harbin Institute of TechnologyHarbin 150001People’s Republic of China MIIT key laboratory of advanced Structural‑Functional Integration materials&Green Manufacturing Technology Harbin Institute of TechnologyHarbin 150001People’s Republic of China

Developing effective strategies to regulate graphene’s conduction loss and polarization has become a key to expanding its application in the electromagnetic wave absorption(EMWA)*** on the unique energy band structure of graphene,regulating its bandgap and electrical properties by introducing heteroatoms is considered a feasible ***,metal-nitrogen doping reduced graphene oxide(M–N-RGO)was prepared by embedding a series of single metal atoms M–N_(4) sites(M=Mn,Fe,Co,Ni,Cu,Zn,Nb,Cd,and Sn)in RGO using an N-coordination atom-assisted *** composites had adjustable conductivity and polarization to optimize dielectric loss and impedance matching for efficient EMWA *** results showed that the minimum reflection loss(RL_(min))of Fe–N-RGO reaches−74.05 dB(2.0 mm)and the maximum effective absorption bandwidth(EAB_(max))is 7.05 GHz(1.89 mm)even with a low filler loading of only 1 wt%.Combined with X-ray absorption spectra(XAFS),atomic force microscopy,and density functional theory calculation analysis,the Fe–N_(4) can be used as the polarization center to increase dipole polarization,interface polarization and defect-induced polarization due to d-p orbital hybridization and structural ***,electron migration within the Fe further leads to conduction loss,thereby synergistically promoting energy *** study demonstrates the effectiveness of metal-nitrogen doping in regulating the graphene′s dielectric properties,which provides an important basis for further investigation of the loss mechanism.

关键词： Electromagnetic wave absorption Fe-N-RGO Dipole polarization Conduction loss Impedance matching

Effects of a high magnetic field on single-phase interface evolution,additional interfacial energy and nucleation undercooling in Al-based alloy

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Journal of materials Science & Technology 2023年第23期154卷 43-53页

作者： Lin Wang Zhipeng Long Long Hou Song Yan Baode Sun Xi Li shanghai key Lab of advanced high-temperature materials and precision forming Shanghai Jiao Tong University Shanghai 200240 China State key laboratory of advanced Special Steels Shanghai University Shanghai 200072 China

The effects of a high magnetic field on the evolution of the single-phase interface and the liquid-solid interface energy in Al-Cu alloy were investigated *** is found that the application of the magnetic field has a significant promotion effect on the migration of liquid droplets,accelerating the formation of the single-phase *** should be attributed to the thermoelectric(TE)magnetic convection in the droplets which has enhanced the diffusion and increased the migration speed of liquid ***,the effect of the high magnetic field on the solid-liquid interface energy is analyzed by an improved grain boundary groove(GBG)*** average solid-liquid interface energy of theα-Al/Al-Cu and Al2Cu/Al-Cu systems increases and decreases with the increase of the magnetic field,*** above experiment results are well explained based on the formation and interaction of the magnetic dipole at the solid-liquid ***,experimental results reveal that the magnetic-field-induced interface energy increases and decreases the nucleation undercooling of the Al-30wt.%Cu alloy and Al-35wt.%Cu alloy,*** studying the effect of the magnetic-field-induced interface energy on the nucleation undercooling,the understanding of the interface energy-induced nucleation undercooling deepens.

关键词： high magnetic field Interface energy Nucleation undercooling Grain boundary groove

Steady-State Creep Behavior of Super304H Austenitic Steel at Elevated temperatures

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Acta Metallurgica Sinica(English Letters) 2015年第11期28卷 1336-1343页

作者： Ping Ou Long Li Xing-Fei Xie Jian Sun shanghai key laboratory of advanced high-temperature materials and precision forming School of Materials Science and EngineeringShanghai Jiaotong University School of materials Science and Engineering Jiangxi University of Science and Technology

Creep behavior of Super304H austenitic steel has been investigated at elevated temperatures of 923-973 K and at applied stress of 190-210 MPa. The results show that the apparent stress exponent and activation energy in the creep deformation range from 16.2 to 27.4 and from 602.1 to 769.3 kJ/mol at different temperatures, respectively. These high values imply the presence of a threshold stress due to an interaction between the dislocations and Cu-rich precipitates during creep deformation. The creep mechanism is associated with the dislocation climbing governed by the matrix lattice diffusion. The origin of the threshold stress is mainly attributed to the coherency strain induced in the matrix by Cu-rich precipitates. The theoretically estimated threshold stresses from Cu-rich precipitates agree reasonably with the experi- mental results.

关键词： Super304H steel Cu-rich precipitate Creep Threshold stress

Premature failure induced by non-equilibrium grain-boundary tantalum segregation in air-plasma sprayed ZrO_(2)-YO_(1.5)-TaO_(2.5)thermal barrier coatings

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International Journal of Minerals,Metallurgy and materials 2022年第12期29卷 2189-2200页

作者： Yao Yao Di Wu Xiaofeng Zhao Fan Yang shanghai key laboratory of advanced high temperature materials and precision forming Shanghai Jiao Tong UniversityShanghai 200240China School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

ZrO_(2)-YO_(1.5)-TaO_(2.5)(ZYTO)is a promising top-coat material for thermal barrier coatings(TBCs).The bulk properties of ZYTO have been reported by several studies,but its performances as TBCs are less-well *** this work,ZYTO TBCs were prepared by air plasma spraying(APS)and their thermal cycling performances were investigated at 1150℃.Despite of the good bulk properties,APS ZYTO TBCs present an extremely short thermal fatigue *** is attributed to the non-equilibrium grain-boundary segregation of TaO_(2.5) induced by limited solubility and rapid quenching during APS process,resulting in a tetragonal(t)to cubic(c)and metastable-tetragonal(tm)phase transformation in ZYTO *** volume shrinkage(~0.74vol%)of phase transformation leads to many cracks at the c/tm phase boundaries after *** the other hand,the formation of cubic phase with massive grain-boundary Ta segregation induces a large intergranular embrittlement and a weak bonding strength(~5.3 MPa),resulting in the premature failure of the ZYTO TBCs.

关键词： thermal barrier coatings air plasma spray tantalum segregation phase transformation

Effect of Needle Coke on Gas Permeability of Ceramic Casting Molds

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Journal of shanghai Jiaotong university(Science) 2018年第S1期23卷 124-131页

作者： WANG Feia ZHU Guolianga LI Feia SUN Baode shanghai key laboratory of advanced high-temperature materials and precision forming The State key laboratory of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai 200240China

The permeability of a new investment casting mold system prepared by adding needle cokes has been investigated in this work. The permeability tests of the molds were carried out at the temperature of 25—1 200?*** results showed that the addition of needle cork could significally increase the permeability of the molds by a factor of about 4 because the burning of needle cokes increased the porosities of the molds. Meanwhile, the needle coke modified molds exhibited higher green strength and greater thickness both on flat section and at sharp edges compared with the full fused silica mold. Taking account of the mold thickness, the needle coke modified molds had increased adjusted fracture load(AFL) by a factor of about 2 at the test temperature of 25—1 200?C. The addition of needle coke significally improved the permeability of the molds during both autoclaving and casting,and optimized the correlation between the permeability and green strength of the molds.

关键词： permeability mold needle coke strength investment casting

A first-principles study of displacive β to ω transition in Ti-V alloys

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Progress in Natural Science:materials International 2017年第6期27卷 703-708页

作者： Wei Mei Jian Sun Yufeng Wen shanghai key laboratory of advanced high-temperature materials and precision forming School of Materials Science and Engineering Shanghai Jiao Tong University School of Mathematical Sciences & Physics Jinggangshan University

The ground state properties of β and ω phases in Ti-(0–30 at%)V alloys were calculated, and subsequently thermodynamics and energy barriers of the displacive β to ω transition were investigated by first-principles. The results show that the lattice parameters of β and ω phases decreases with increasing V content in Ti-V alloys. The principal lattice strains for the β to ω transition are highly compositional dependent, and the volume variation decreases with increasing V content. The mechanical stability of the ω phase increases initially at the V content around 10 at% and then decreases with increasing V content. Based on the quasiharmonic Debye model, a metastable diffusionless phase diagram has been established, showing that the ω phase is thermodynamically more stable than the β phase at room temperature, anticipating a spontaneous transition from β to ω phases in Ti-V alloys. The calculations of energy pathways indicate that there is an energy barrier during the displacive βto ω transition in Ti-V alloys at temperatures from 100 to 500 K, but not at 0 K.

关键词： Elastic property Phase transition Ti-V alloys First-principles