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microstructure characterization and Fracture Toughness of Laves Phase-Based Cr–Nb–Ti Alloys

Acta Metallurgica Sinica(English Letters) 2015年第4期28卷 514-520页

作者： Yun-Long Xue Shuang-Ming Li Hong Zhong Lai-Ping Li Heng-Zhi Fu State Key Laboratory of Solidification Processing Northwestern Polytechnical University Northwest Institute for Non-Ferrous Metal Research

Three Laves phase-based alloys with nominal compositions of Cr2Nb-xTi （x = 20, 30, 40, in at%） have been prepared through vacuum non-consumable arc melting. The results show that the microstructures of Cr2Nb-（20, 30） Ti alloys are composed of the primary Laves phase C15-Cr2（Nb,Ti） and bcc solid solution phase, while the microstructure of Cr2Nb-40Ti alloy is developed with the eutectic phases C15-Cr2（Nb,Ti）/bcc solid solution. The measured fracture toughness of ternary Laves phase C15-Cr2（Nb,Ti） is about 3.0 MPa m1/2, much larger than 1.4 MPa m1/2 for binary Laves phase Cr2Nb. Meanwhile, the fracture toughness of Cr2Nb-xTi （x = 20, 30, 40） alloys increases with increasing Ti content and reaches 10.6 MPa m1/2 in Cr2Nb-40Ti alloy. The eutectic microstructure and addition of Ti in Cr2Nb are found to be effective in toughening Laves phase-based alloys.

关键词： Laves phase-based alloys microstructure characterization Fracture toughness Crackpropagation Fracture

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microstructure characterization in a sensitized Al-Mg-Mn-Zn alloy

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Rare Metals 2018年第2期37卷 129-135页

作者： Chun-Yan Meng Di Zhang Ping-Ping Liu Lin-Zhong Zhuang Ji-Shan Zhang State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing School of Materials Science and Engineering University of Science and Technology Beijing

Alloying elements, present in the aluminum solid solution or the precipitates, influence the corrosion resistance of A1-Mg-Mn-Zn alloys. In this study, sensi- tizing treatment was applied to an A1-Mg-Mn-Zn alloy to modify the precipitation at the grain boundaries or in the grains. Transmission electron microscopy （TEM） and scanning electron microscope （SEM） were used to characterize various second-phase particles and determine their orientation relationship with the A1 matrix. After sensitizing treatment, z-phase （Mg32（Al, Zn）49） is observed to precipitate along the grain boundaries in a coarser size, producing a discontinuous grain boundary precipitate structure. In addition, Mn-rich particles are found to form with various shapes, such as global, plate and rhombus.

关键词： Al-Mg-Mn-Zn alloy Mg32（A1, Zn）49 phase A16（Mn, Fe） phase microstructure characterization

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microstructure characterization of localized corrosion wear of Cr/Cr₂N+ a-C:H/a-C:H:Cr multilayer coatings on carbon fiber composites

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BULLETIN OF THE POLISH ACADEMY OF SCIENCES-TECHNICAL SCIENCES 2017年第2期65卷 171-177页

作者： Janusz, M. Major, L. Lackner, J. M. Grysakowski, B. Krawiec, H. Polish Acad Sci Inst Met & Mat Sci 25 Reymonta St PL-30059 Krakow Poland Inst Surface Technol & Photon 94 Leobner St A-8712 Niklasdorf Austria Univ Sci & Technol Fac Foundry Engn 23 Reymonta St PL-30059 Krakow Poland

The use of carbon fiber composites (CFC) for different applications is widespread. Carbon-based materials show, however, significant oxidative degradation in air. Modern materials are subjected to aggressive, corrosive environment. This type of environment may strongly reduce their mechanical properties. For the protection of CFC, it was necessary to apply coatings to the composite surface. In the presented paper, a chromium/chromium nitride (Cr/Cr2N) multilayer structure has been selected as the inner part. The outer part of the coating was a hydrogenated amorphous carbon (a-C:H), gradually implanted by Cr nanocrystals. The application of transmission electron microscopy (TEM) indicated that the proposed deposition method allowed the formation of a Cr/Cr2N multilayer of A = 150 nm, topped with a-C11+ Cr23C6 composite of a varied carbides density. The micro-hardness of the deposited coatings was up to 14 GPa (at a load of 2 and 5 mN). The microstructure of the deposited coatings was described in detail by means of TEM in the authors recently published paper Ill This paper is a continuation thereof, aimed at describing microstructure changes after a localized corrosion process. In order to study localized corrosion in coatings, particularly in metallic (Cr) interlayers, the potential measurements and voltammetry experiments were performed in a Ringer solution. The open-circuit potential reaches stable values after a sufficient time period. The results indicated that the presence of a-C:H+Cr23C6, the outer part of the coating, speeds up the localized corrosion process in Cr interlayers in the inner part of a coating.

关键词： nano-composite multilayer coatings micro-corrosion carbon-fiber composites microstructure characterization TEM

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Process optimization, microstructure characterization, and mechanical properties of Al-Mg-Sc-Zr alloys prepared via laser powder bed fusion

Additive Manufacturing Frontiers

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Additive Manufacturing Frontiers 2025年第1期4卷

作者： Nie, Yunfei Wu, Haibin Tang, Qian Yi, Hao Qin, Changliang Wang, Binsheng Li, Zhonghua Li, Kun Han, Quanquan State Key Laboratory of Mechanical Transmissions Chongqing University Chongqing 400044 China School of Mechanical Engineering North University of China Taiyuan 030051 China Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education Centre for Additive Manufacturing School of Mechanical Engineering Shandong University Jinan 250061 China

Aluminum alloys manufactured using traditional processes are increasingly unable to meet the high flexibility and performance requirements of modern engineering. In this study, Al-Mg-Sc-Zr alloys were manufactured via laser powder bed fusion (LPBF) to obtain high-performance aluminum alloys. To this end, process parameter optimization and heat treatment were adopted. The optimal process parameters were determined by initially analyzing the relative density and defect distribution under varying energy densities. The sample obtained under the optimal process parameters exhibited a relative density of 99.84 %. Subsequently, the corresponding phase compositions, microstructures, and mechanical performance of the as-fabricated specimens were determined using the optimal process parameters before and after heat treatment. The microstructures of the samples showed typical equiaxed columnar bimodal grain structures, with Al₃(Sc,Zr) precipitates detected. The samples exhibited no significant anisotropy before and after heat treatment, while the grain orientation differences were dominated by high-angle grain boundaries. The mechanical properties of all the samples were characterized using tensile and hardness tests. The yield strength, ultimate tensile strength, and elongation of the sample were 475.0 MPa, 508.2 MPa, and 8.3 %, respectively. Overall, samples with high density, low porosity, high strength, and high plasticity were obtained by process parameter optimization and appropriate heat treatment. © 2025

关键词： Al-Mg-Sc-Zr alloy Laser powder bed fusion Mechanical properties microstructure characterization Processing optimization

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microstructure characterization of nanocrystalline Ni₃C synthesized by high-energy ball milling

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JOURNAL OF ALLOYS AND COMPOUNDS 2009年第1-2期479卷 193-200页

作者： Ghosh, B. Dutta, H. Pradhan, S. K. Univ Burdwan Dept Phys Burdwan 713104 W Bengal India Vivekananda Coll Dept Phys Burdwan 713103 W Bengal India

Preparation of a metal carbide by a conventional route requires a huge instrumentation regarding melting the metal and graphite under vacuum at a very high temperature. However, mechanical alloying process is a very useful method for the fabrication of high melting point materials like metal carbides, which additionally produce nanocrystalline structure with improved properties. This article reports the microstructure characterization of nanocrystalline Ni3C synthesized at room temperature by mechanical milling of Ni and graphite powders under inert atmosphere. The stoichiometric Ni3C phase is formed after 5 h of milling. microstructure of the prepared materials is characterized in terms of lattice imperfections, primarily by analyzing the X-ray powder diffraction data, employing both Warren-Averbach's method of line profile analysis and Rietveld's structure refinement method. The phase transformation kinetics studied by the Rietveld method reveals that the graphite powder becomes amorphous at the early stage of milling and then diffuses into Ni matrix and a Ni-C solid solution is formed within 1 h of milling. The high-resolution electron microscopy reveals that the Ni3C phase is initiated as a thin shell on Ni-C core within 2 h of milling and becomes stoichiometric in composition within 5 h of milling. Electron microscopy observations agree well with the X-ray measurement of particle size (similar to 9 nm) of Ni3C phase in 5 h milled sample and Ni-Ni3C core shell structure in 3 h milled sample. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Nanocrystalline Ni3C Ball milling XRD microstructure characterization HRTEM

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microstructure characterization and thermal stability of TC11/Ti₂AlNb joints during thermal exposure

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MATERIALS characterization 2018年 145卷 461-472页

作者： Xie, B. C. Qin, C. Ning, Y. Q. Zhou, C. Yao, Z. K. Northwestern Polytech Univ Sch Mat Sci & Engn Xian 710072 Shaanxi Peoples R China Beifang Univ Nationalities Sch Mat Sci & Engn Yinchuan 750021 Peoples R China

TC11/Ti(2)AINb welding joints undergoing hot deformation were thermally exposed at the range of 500-700 degrees C for 100, 200 and 500 h. In present research, typical microstructures of five different zones of the joints were investigated, fusion zone, two interfaces and two base alloys included. The microstructures of fusion zone, Ti(2)AINb-based alloy and the interface between them were characterized by the coarsening of O phase during thermal exposure, while those of TC11 alloy and the interface between it and fusion zone featured the coarsening of alpha(s) phase. The transformation from B2 to beta and O phase was stifled below 600 degrees C and Ti2AlNb-based alloy thus was verified to be stable at this temperature range. alpha(s) phase was stable during exposure at 500 degrees C. When exposed above 600 C, alpha(s) phase coarsened by at least 52% with the extension of holding time. Due to the low thermal stability of alpha(s) phase compared with that of O phase, the fracture position of the samples tested at room temperature moved from fusion zone to TC11 alloy when temperature rose. In spite of different thermal exposure conditions, the samples tested at 300 and 500 degrees C all fractured at TC11 alloy for the severe coarsening of alpha(s) phase. The decrease of interfacial area resulting from the coarsening of O and alpha(s) phases facilitated the dislocation slipping and the strength of joints thus deteriorated. The mechanical properties of TC11/Ti2AlNb joints measured at room temperature, 300 and 500 degrees C were all correlated with the lamellar thickness of O and alpha(s) phases.

关键词： TC11/Ti(2)AINb joint Thermal exposure microstructure characterization Thermal stability Dual-alloy disc

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microstructure characterization by X-Ray Computed Tomography of C/C-SiC Ceramic Composites Fabricated with Different Carbon Fiber Architectures

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APPLIED COMPOSITE MATERIALS 2019年第4期26卷 1247-1260页

作者： Wan, Fan Pirzada, Talha J. Liu, Rongjun Wang, Yanfei Zhang, Changrui Marrow, Thomas James Natl Univ Def Technol Coll Aerosp Sci & Engn Changsha 410073 Hunan Peoples R China Univ Oxford Dept Mat Oxford OX1 3PH England

The microstructure morphologies have been characterized by high resolution laboratory X-ray computed tomography in Carbon Fiber Reinforced Carbon and Silicon Carbide (C/C-SiC) ceramic composites fabricated by Gaseous Silicon Infiltration (GSI) from C/C preforms of three different architectures: 3D stitched cloth fabric;3D orthogonal woven fabric;and needled short-cut felt. Each composites' microstructure was influenced by the structure of the C/C preform. By incorporating tomography with gravimetric analysis, the 3D distribution of the SiC was visualized, showing a connected SiC network in the needled short-cut felt, and more heterogeneous SiC formation on the surfaces of the fiber bundles in the stitched and woven fabrics. The needled short-cut felt provided the largest contact surface for the GSI reaction and generated similar to 56% volume fraction of SiC, which is almost twice and three times that achieved in the stitched and woven fabrics respectively. Differences in the open and closed pore distributions were also measured by mercury intrusion porosimetry and tomography.

关键词： Carbon fiber architecture C/C-SiC composite microstructure characterization X-ray computed tomography Mercury intrusion porosimetry

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microstructure characterization of high energy ball-milled nanocrystallineV₂O₅ by Rietveld analysis

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MATERIALS CHEMISTRY AND PHYSICS 2003年第3期77卷 868-877页

作者： Dutta, H Pradhan, SK Univ Burdwan Dept Phys Burdwan 713104 W Bengal India

Nanocrystalline vanadium pentoxide has been processed with high energy planetary ball-mill at two different ball-to-powder mass ratio (BPMR) for different lengths of time (0-35 h). microstructure characterization of ball-milled samples is made by employing Rietveld's X-ray powder structure refinement analysis in terms of lattice imperfections. The particle sizes and lattice strain values are found to be anisotropic. The plastic deformation induced in the process of ball-milling caused a massive decrease in particle size and increase in lattice strain within 15 min of milling, and a saturation of particle size of similar to6.5 nm is reached within 10 h of milling. The shape of milled particle is presumed to be parallelepiped and the influence of BPMR predominated in initial size reduction. The initial change in intensities of two major X-ray reflections is found to be due to insignificant change in atomic coordinates on the event of severe high energy impact. The peak broadening at initial stage of milling is due to fracture of particles, but later (after particle size saturation), dominated by increase in anisotropic lattice strains particularly along [0 0 1]. (C) 2002 Elsevier Science B.V All rights reserved.

关键词： microstructure characterization ball-to-powder mass ratio rietveld analysis V2O5 ball-milling

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microstructure characterization and evaluation of mechanical properties in 2A97 aluminum-lithium alloys welded by stationary shoulder friction stir welding

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JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T 2022年 16卷 416-432页

作者： Sun, G. D. Zhou, L. Liu, Y. N. Yang, H. F. Jiang, J. T. Li, G. A. Harbin Inst Technol State Key Lab Adv Welding & Joining Harbin 150001 Peoples R China Harbin Inst Technol Weihai Shandong Prov Key Lab Special Welding Technol Weihai 264209 Peoples R China Harbin Inst Technol Sch Mat Sci & Engn Harbin 150001 Peoples R China AVCC Beijing Inst Aeronaut Mat Beijing 100095 Peoples R China

2A97 Al-Li alloy joints with the thickness of 1.5 mm were fabricated by stationary shoulder friction stir welding (SSFSW) under rotational speeds of 600-1000 rpm and a fixed welding speed of 200 mm/min. As the rotational speeds increased, the grain sizes of the nugget zone (NZ) kept almost constant with the presence of zigzag defects. The electron back-scattered diffraction (EBSD) analysis suggested that the initial crystal orientation with near < 001 >parallel to TD and < 001 > kWD textural components exhibited weaker anisotropy induced by the severe shearing deformation. The dynamic recrystallization (DRX) mechanisms were clarified in the transition from low-angle grain boundaries (LAGBs) to high-angle grain boundaries (HAGBs). In contrast to the conventional FSW joints of Al-Li alloys, the dis-persions were indexed as Al11Cu5Mn3, Al2Cu within the grains, and Al-Cu-Mn-Zn phase at the grain boundaries in the SSFSW joints. The T-1, delta'/beta' and theta' precipitates were detected in the base metal (BM), and the theta' precipitates were dissolved in the heat affected zone (HAZ). However, those strengthening precipitates were absent in the NZ. The variation of the ultimate tensile strength first increased and then decreased with the increasing rota-tional speeds. Moreover, the joint obtained at a rotational speed of 1000 rpm exhibited the best combination of strength and ductility. The defect-free joints failed in the thermo-mechanically affected zone (TMAZ), which corresponded to the hardness minima posi-tions (HMP). However, an abnormal fracture occurred in the NZ due to the presence of weak-bonding areas and curved band structures. (c) 2021 The Authors. Published by Elsevier B.V.

关键词： Aluminum-lithium alloys SSFSW microstructure characterization Mechanical properties

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microstructure characterization of IG110 and reactor pebble graphite using synchrotron micro X-ray diffraction 2D maps

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SURFACE AND INTERFACE ANALYSIS 2021年第1期53卷 90-99页

作者： He, Zhoutong Zhang, Can Tang, Hui Liu, Ming Marsden, Barry J. Zhou, Xingtai Chinese Acad Sci Shanghai Inst Appl Phys Shanghai 201800 Peoples R China Univ Manchester Sch MACE Nucl Graphite Res Grp Manchester M13 9LP Lancs England

Knowledge about the microstructure of nuclear graphite is critical to the understanding of its irradiation behavior in the reactor. Using micro X-ray diffraction (mu XRD) two-dimensional (2D) maps, the crystallite character of IG110 and reactor pebble graphite was characterized at the submillimeter range with a spatial resolution of about 5 mu m. Various structures in the nuclear graphite were identified by comparing the X-ray diffraction peak intensity, position, and full width at half maximum (FWHM) 2D maps. The two-peak feature of the FWHM histograms seen in pebble graphite may be related to the raw coke and natural graphite used as raw materials. With these results, it can be concluded that the mu XRD 2D map is an effective method to characterize the microstructure of nuclear graphite.

关键词： micro X-ray diffraction 2D maps microstructure characterization molten salt reactor nuclear graphite

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