检索结果-南通市图书馆

Microstructure and microsegregation of directionally solidified Ti–45Al–8Nb alloy with different solidification rates

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2016年第1期35卷 70-76页

作者： Xiang-Jun Xu Lin Song Xiao-Ou Jin Dong-Dong Han Xin Wang Jun-Pin Lin Materials and Chemistry School Zhongyuan University of Technology State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing School of Architecture and Engineering Heilongjiang University

Microstructure and microsegregation of directionally solidified Ti-45Al-8Nb alloy were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and electron probe microanalyzer（EPMA）.For the alloy solidified at the solidification rates（v） ranging from 10 to 400 μm·s^（-1）,the microstructure of the mushy zone exhibits a cellular-dendritic structure at lower growth rate（v=10-50 μm·s^（-1）） and a typical dendritic morphology at higher growth rate（v = 100-400 μm·s^（-1））.The relationship between primary dendrite arm spacing（λ_1）and v is λ_1=1.08×10~3v^（-0.35）.Al and Nb elements segregate at interdendritic zone and in the dendritic core,respectively.In solid of mushy zone,a relatively flat concentration profile is observed for the typical dendrite structure,and Nb enriches in B2 phase induced by β→α＋βtransformation.The content of B2 phase is hardly affected by v.The extent of microsegregation in steady-state zone decreases at a lower growth rate because holding the samples at higher temperature after solidification for a long time can homogenize the solid effectively.

关键词： Nb-containing TiAl alloy Solidification Microstructure microsegregation

Formation process and mechanical properties in selective laser melted multi-principal-element alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第2期133卷 12-22页

作者： Jing Peng Jia Li Bin Liu Jian Wang Haotian Chen Hui Feng Xin Zeng Heng Duan Yuankui Cao Junyang He Peter K.Liaw Qihong Fang State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China State Key Laboratory of Porous Metal Materials Northwest Institute for Nonferrous Metal ResearchXi’an 710016China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996USA

Additive manufacturing is believed to open up a new era in precise microfabrication,and the dynamic microstructure evolution during the process as well as the experiment-simulation correlated study is conducted on a prototype multi-principal-element alloys FeCrNi fabricated using selective laser melting(SLM).Experimental results reveal that columnar crystals grow across the cladding layers and the dense cellular structures develop in the filled crystal.At the micron scale,all constituent elements are evenly distributed,while at the near-atomic scale,Cr element is obviously segregated.Simulation results at the atomic scale illustrate that i)the solid-liquid interface during the grain growth changes from horizontal to arc due to the radial temperature gradient;ii)the precipitates,microscale voids,and stacking faults also form dynamically as a result of the thermal gradient,leading to the residual stress in the SLMed structure.In addition,we established a microstructure-based physical model based on atomic simulation,which indicates that strong interface strengthening exists in the tensile deformation.The present work provides an atomic-scale understanding of the microstructural evolution in the SLM process through the combination of experiment and simulation.

关键词： Selective laser melting Multi-principal-element alloys Cellular structure microsegregation Grain growth Mechanical properties

Effect of cerium on microstructure,eutectic carbides and Laves phase in electroslag remelted 15Cr-22Ni-1Nb austenitic heat-resistant steel

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research(International) 2023年第2期30卷 338-349页

作者： Xin Zhu Cheng-bin Shi Shi-jun Wang Peng Lan Jing Li State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing(USTB)Beijing100083China School of Metallurgical and Ecological Engineering University of Science and Technology Beijing(USTB)Beijing100083China

The dendrites,eutectic carbides,Laves phase and microsegregation of alloying element in electroslag remelted 15Cr-22Ni-1Nb austenitic heat-resistant steel with varying cerium contents were studied.The liquidus and solidus temperatures of the steel were determined to reveal the effect of cerium on solidification temperature interval and local solidification time of the steel.The secondary dendrite arm spacing decreases from 57.10 to 40.18μm with increasing the cerium content from 0 to 0.0630 wt.%.The eutectic NbC and Laves phase in as-cast ingots exhibit blocky and honeycomb morphology,respectively.The area fractions and sizes of eutectic NbC and Laves phase in as-cast ingots decrease with the increase in cerium content.The atomic percentage of Laves phase-forming element(Ni,Nb,Cr,Mo and Si)decreases with the increase in cerium content of the steel.The microsegregation of Mo,Ni,Si,Cr and Nb decreases with increasing the cerium content,which is favorable to reducing both the amount and sizes of eutectic NbC and Laves phase in as-cast ingots.The solidification temperature interval and local solidification time of the steel decrease as the cerium content is increased from 0 to 0.0630 wt.%,which inhibits the growth of dendrites,eutectic NbC and Laves phase.

关键词： Heat-resistant steel Rare earth cerium Eutectic NbC Laves phase microsegregation Solidification characteristics

Quantitative effects of phase transition on solute partition coefficient,inclusion precipitation, and microsegregation for high-sulfur steel solidification

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2019年第10期35卷 2383-2395页

作者： Lintao Gui Mujun Long Shixin Wu Zhihua Dong Dengfu Chen Yunwei Huang Huamei Duan Levente Vitos State Key Laboratory of Coal Mine Disaster Dynamics and Control College of Materials Science and EngineeringChongqing UniversityChongqing400044China Department of Materials Science and Engineering KTH Royal Institute of TechnologyStockholm10044Sweden Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials Chongqing UniversityChongqing400044China

Segregation and inclusion precipitation are the common behaviours of steel solidification, which are resulted from the redistribution and diffusion of the solute elements at the solid-liquid interface. The effect of the phase transition of high-sulfur free-cutting steel is quantified in the present work for the solute partition coefficient(ki), inclusion precipitation, and microsegregation by establishing a coupling model of microsegregation and inclusion precipitation, wherein the quantified dependencies of ki in terms of temperature, phase and carbon(C) content were applied. Results showed that the solidification temperature range and phase transition of high-sulfur steel that under different solidification paths and C contents were quite different, leading to differences in ki and eventually in microsegregation. kC,kP, and kS were mainly affected by phase composition and kSi was primarily by temperature, while kMn depended on both phase composition and temperature during solidification. Increasing the C content within the interval 0.07-0.48 wt%, the ‘proportion of the δ phase maintained temperature region during solidification’(Pδ), kave Pand kave S(kiave, the average value of the ki across the whole stages of solidification)decreased monotonically, whereas kave Cincreased linearly. The peritectic reaction impacted on the phase composition and ki, leading to the change in microsegregation. Such effect of the peritectic reaction was more significant at the last stage of solidification. When the Pδ was between 75% and 100%(corresponding to 0.07-0.16 wt% C), the solidification path resulted in a greater effect on the microsegregation of solutes C, P, and S because of the peritectic reaction. The microsegregation of solutes Mn and S were comprehensively influenced by kMn, kS and Mn S precipitation as well. The studies would help reveal the solute redistribution at the solid-liquid interface, and improve the segregation of high-sulfur steel by controlling the solidification and precipitation in practice.

关键词： Phase transition microsegregation Solute partition coefficient Inclusion precipitation High-sulfur steel

Simulation of the Dendrite Morphology and microsegregation in Solidification of Al–Cu–Mg Aluminum Alloys

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2015年第2期28卷 173-181页

作者： Rui Chen Qing-Yan Xu Bai-Cheng Liu Key Laboratory for Advanced Materials Processing Technology Ministry of Education School of Materials Science and Engineering Tsinghua University

Since most typical alloys in industrial applications are multicomponent with three or more components, and various CA models proposed in the past mainly focus on the binary alloys, a two-dimensional modified cellular automaton model allowing for the quantitatively predicting dendrite growth of multicomponent alloys in the low P6clet number regime is presented. The elimination of the mesh-induced anisotropy is achieved by adopting a modified virtual front tracking method. A new efficient method based on the lever rule is applied to calculate the solid fraction increment of the interfacial cells. The thermodynamic data such as liquidus temperature, the partition coefficients, and the slope of liquidus surface, needed for determining the dynamics of dendrite growth, are obtained by coupling with PanEngine. This model is applied to simulate the dendrite morphology and microsegregation of A1-Cu-Mg temary alloy both for single and multi- dendrites growth. The simulated results demonstrate that the difference of the concentration distribution profiles ahead of the dendrite tip for each alloying element mainly results from the different partition coefficients and solute diffusion coefficients. Comparison with the prediction of analytical model is carded out and it reveals the correctness of the model. Consequently, the difference in interdendritic microsegregation behavior of different components is analyzed.

关键词： Cellular automaton Multicomponent Dendrite growth microsegregation

Revisiting dynamics and models of microsegregation during polycrystalline solidification of binary alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第15期74卷 155-167页

作者： Tongzhao Gong Yun Chen Shanshan Li Yanfei Cao Dianzhong Li Xing-Qiu Chen Guillaume Reinhart Henri Nguyen-Thi Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei230026China Aix Marseille Univ Universite de ToulonCNRSIM2NPMarseilleFrance

microsegregation formed during solidification is of great importance to material properties.The conventional Lever rule and Scheil equation are widely used to predict solute segregation.However,these models always fail to predict the exact solute concentration at a high solid fraction because of theoretical assumptions.Here,the dynamics of microsegregation during polycrystalline solidification of refined Al-Cu alloy is studied via two-and three-dimensional quantitative phase-field simulations.Simulations with different grain refinement level,cooling rate,and solid diffusion coefficient demonstrate that solute segregation at the end of solidification(i.***.when the solid fraction is close to unit)is not strongly correlated to the grain morphology and back diffusion.These independences are in accordance with the Scheil equation which only relates to the solid fraction,but the model predicts a much higher liquid concentration than simulations.Accordingly,based on the quantitative phase-field simulations,a new analytical microsegregation model is derived.Unlike the Scheil equation or the Lever rule that respectively overestimates or underestimates the liquid concentration,the present model predicts the liquid concentration in a pretty good agreement with phase-field simulations,particularly at the late solidification stage.

关键词： microsegregation Grain refinement Cooling rate Back diffusion Phase-field method

Modeling solidification structure evolution and microsegregation under pressure condition

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2006年第6期13卷 516-522页

作者： Qiang Li Qiaoyi Guo Rongde Li School of Materials Science and Engineering Shenyang University of Technology Shenyang 110023 China Fundamental School Shenyang Ligong University Shenyang 110168 China

Solidification microstructure and microsegregation were simulated under a constant pressure condition using the cellular automaton method. First, a single dendrite evolution was simulated and compared under pressure condition and under normal condition, respectively. The solidification microstructure and microsegregation were then simulated. Through simulation, it may be concluded that if the growth direction of the dendrite is parallel to the pressure direction, dendrite growth will be hindered. On the other hand, pressure has no influence on the dendrite evolution. However, when two dendrites grow in close contact, solute enrichment occurs in the dendrites, which hinders the growth of the dendrites. In addition, the solute is preferentially enriched along the pressure direction.

关键词： dendrite microsegregation pressure condition modeling

Alloy solidification: Assessment and improvement of an easy-to-apply model

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第35期130卷 1-11页

作者： H.Liu Y.Liu S.L.Lu Y.Zhang H.Chen Y.Chen M.Qian School of Materials Science and Engineering Southwest Jiaotong UniversityChengdu 610031China Centre for Additive Manufacturing School of EngineeringRMIT UniversityMelbourneVIC 3000Australia School of Materials Science and Engineering Sichuan UniversityChengdu 610065China

It has been a central task of solidification research to predict solute microsegregation. Apart from the Lever rule and the Scheil-Gulliver equation, which concern two extreme cases, a long list of microsegregation models has been proposed. However, the use of these models often requires essential experimental input information, e.g., the secondary dendrite arm spacing(λ), cooling rate( ˙T) or actual solidification range(△T). This requirement disables these models for alloy solidification with no measured values for λ,˙T and △T. Furthermore, not all of these required experimental data are easily obtainable. It is therefore highly desirable to have an easy-to-apply predictive model that is independent of experimental input,akin to the Lever rule or Scheil-Gulliver model. Gong, Chen, and co-workers have recently proposed such a model, referred to as the Gong-Chen model, by averaging the solid fractions(f_(s)) of the Lever rule and Scheil-Gulliver model as the actual solid fraction. We provide a systematic assessment of this model versus established solidification microsegregation models and address a latent deficiency of the model, i.e.,it allows the Lever rule solid fraction fsto be greater than one(f_(s)> 1). It is shown that the Gong-Chen model can serve as a generic model for alloy solidification until fsreaches about 0.9, beyond which(f_(s)> 0.9) its applicability is dictated by both the equilibrium solute partition coefcient(k) and the solute diffusion coefcient in the solid(Ds), which has been tabulated in detail.

关键词： Solidification microsegregation Solute Back diffusion Eutectic formation

Multi-scale dendritic patterns sequentially superimposed in a primary semi-solid matrix

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第12期107卷 26-33页

作者： Xiaoping Ma Dianzhong Li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesWenhua Road No.72Shenyang 110016PR China

The principle and control for solidification present crucial challenges.Through in situ and real time observation on the solidification of M50 bearing steel,here we discovered that the base of conventional dendritic arms is constituted by a primary semi-solid matrix.Due to the superimposition of temperature fluctuations from the large to the subtle scale,multi-scale dendritic patterns will sequentially emerge and evolve in the primary semi-solid matrix.These findings redefine the essence of multi-scale dendrites as the multi-scale segregation patterns in the primary semi-solid matrix,reconstitute the time and space sequence in the formation of multi-scale dendrites,and reveal the superimposition of temperature fluctuation as the driving principle.These new understandings will fundamentally influence the solidification field.These results also indicate important engineering applications,such as designing multi-scale dendrites,controlling the dendritic segregation and eliminating the detrimental eutectics.

关键词： Solidification Dendrite Microstructures microsegregation Macrosegregation