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Crystallographic Characteristic of Intermetallic Compounds in Al-Si-Mg Casting Alloys Using Electron Backscatter Diffraction

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Chinese Journal of Mechanical Engineering 2010年第3期23卷 305-311页

作者： ZOU Yongzhi XU Zhengbing HE Juan ZENG Jianmin State Key laboratory of Solidification Processing Northwestern Polytechnical University Xi＇ an 710072 China Key laboratory of nonferrous Materials and New Processing Technology of Ministry of Education Guangxi University Nanning 530004 China

The Al-Si-Mg alloy which can be strengthened by heat treatment is widely applied to the key components of aerospace and aeronautics. Iron-rich intermetallic compounds are well known to be strongly influential on mechanical properties in Al-Si-Mg alloys. But intermetallic compounds in cast Al-Si-Mg alloy intermetallics are often misidentified in previous metallurgical studies. It was described as many different compounds, such as AlFeSi, Al8Fe2Si, Al5（Fe, Mn）3Si2 and so on. For the purpose of solving this problem, the intermetallic compounds in cast Al-Si alloys containing 0.5% Mg were investigated in this study. The iron-rich compounds in Al-Si-Mg casting alloys were characterized by optical microscope（OM）, scanning electron microscope（SEM）, energy dispersive X-ray spectrometer（EDS）, electron backscatter diffraction（EBSD） and X-ray powder diffraction（XRD）. The electron backscatter diffraction patterns were used to assess the crystallographic characteristics of intermetallic compounds. The compound which contains Fe/Mg-rich particles with coarse morphologies was Al8FeMg3Si6 in the alloy by using EBSD. The compound belongs to hexagonal system, space group P6_2m, with the lattice parameter a=0.662 nm, c=0.792 nm. The β-phase is indexed as tetragonal Al3FeSi2, space group I4/mcm, a=0.607 nm and c=0.950 nm. The XRD data indicate that Al8FeMg3Si6 and Al3FeSi2 are present in the microstructure of Al-7Si-Mg alloy, which confirms the identification result of EBSD. The present study identified the iron-rich compound in Al-Si-Mg alloy, which provides a reliable method to identify the intermetallic compounds in short time in Al-Si-Mg alloy. Study results are helpful for identification of complex compounds in alloys.

关键词： Al-Si-Mg alloys intermetallic compound electron backscatter diffraction(EBSD) X-ray powder diffraction(XRD)

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Interface microstructure and formation mechanism of diffusion-bonded joints of TiAl to steel 40Cr

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中国有色金属学会会刊：英文版 2002年第6期12卷 1069-1071页

作者：何鹏冯吉才张炳刚钱乙余 National Key laboratory of Advanced Welding Production Technology Harbin Institute of Technology

TiAl intermetallics was diffusion bonded to steel 40Cr in vacuum furnace. The results show that at the TiAl 40Cr interface the mixture reaction layer of Ti 3Al+FeAl+FeAl 2 is formed close to the TiAl base, TiC layer is formed in the middle and obvious decarbonized layer is formed closest to the steel 40Cr side. The whole reaction process can be divided into three stages. In the first stage, TiC layer is formed at the interface TiAl/40Cr, as well, decarbonized layer occurs on the steel 40Cr side. In the second stage, TiAl, FeAl 2 and FeAl are formed adjacent to TiAl, in the mean, the continuous diffusion of Al atoms from TiAl to 40Cr gives rise to the formation of Ti 3Al. In the last stage, the thickness of each reaction layer increases with bonding time according to a parabolic law. The growth energy Q and the growth velocity K 0 of reaction layer Ti 3Al+FeAl+FeAl 2+TiC in the diffusion bonded joints of the TiAl base alloy to steel 40Cr are 203.017 kJ/mol and 6.074 mm 2/s, respectively, and the growth formula (thickness of reaction layer) is y 2=6.074×10 -6 exp(-203 017.48/ RT)t . By virtue of this formula, the growth of reaction layer Ti 3Al+FeAl+FeAl 2+TiC can be presetted and controlled.

关键词：钛铝金属间化合物 40Cr钢晶间显微组织形成机制

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Recent progress in porous intermetallics:Synthesis mechanism,pore structure,and material properties

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Journal of Materials Science & Technology 2021年第15期74卷 89-104页

作者： Yao Jiang Yuehui He Haiyan Gao State Key laboratory of Powder Metallurgy Central South UniversityChangsha410083China

Intermetallic compounds have the characteristics of long-range ordered structure and combination of metallic and covalent bonds,showing intrinsic brittleness and outstanding performance *** synthesis mechanism,pore structure characterization and material properties of powder metallurgy porous intermetallics are reviewed in this *** with traditional porous materials,porous intermetallics have good thermal impact resistance,machinability,thermal and electrical conductivity similar to metals,as well as good chemical corrosion resistance,rigidity and high-temperature property similar to *** mechanisms of preparation and pore formation of porous intermetallics mainly include four aspects:(1)the physical process based on the interstitial space between the initial particles and its evolution in the subsequent procedures;(2)the chemical combustion process based on the violent reaction between the initial powder components;(3)the reaction kinetics process based on the difference between the diffusion rates of elements;(4)the phase transition process based on the difference between the phase *** characterization parameters to the pore structure description for porous intermetallics include mainly overall porosity,open porosity,permeability,maximum pore size,pore size distribution and tortuosity *** terms of microstructure characterization of porous intermetallics,three-dimensional pore morphology scanning technology has the potential to reveal the internal characteristics of pore *** research on material properties of porous intermetallics mainly focuses on electrochemical catalytic activity,generalized oxidation resistivity at high temperature,resistance against chemical corrosion and mechanical properties,which have obvious advantages over traditional porous *** the field of the development of porous intermetallics,it is expected to expand their applications by further reducing the pore size to the nanoscale

关键词： Intermetallic compound Porous material Preparation mechanism Pore structure Material property

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Microstructures and mechanical properties of Ti3Al/Ni-based superalloy joints arc welded with Ti–Nb and Ti–Ni–Nb filler alloys

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Progress in Natural Science:Materials International 2014年第4期24卷 313-320页

作者： Bingqing Chen Huaping Xiong Bingbing Sun Siyi Tang Borui Du Neng Li laboratory of Welding and Forging Beijing Institute of Aeronautical Materials

Dissimilar joining of Ti3Al-based alloy to Ni-based superalloy has been carried out using gas tungsten arc(GTA) welding technology with Ti–Nb and Ti–Ni–Nb filler *** joint welded with the Ti–Nb filler alloy contained much less interfacial brittle phases than the one using the Ti–Ni–Nb filler *** average room-temperature tensile strength of the joint welded with Ti–Nb was 202 MPa and the strength value of the one welded with Ti–Ni–Nb was 128 *** both fillers,the weak links of the dissimilar joints were the weld/In718 *** presence of TiNi,TiNi3 and Ni3Nb intermetallic compounds in the joint welded with Ti–Ni–Nb induced microcracks at the weld/In718 interface and deteriorated the mechanical properties of the *** the adoption of the Ti–Nb filler alloy decreased the formation tendency of interfacial brittle phases to some extent and thus enhanced the tensile strength of the joint.

关键词： Ti3Al Ni-based superalloy Arc welding Interface intermetallics Mechanical properties

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Microstructure characterization and tensile properties of a Ni-containing TiAl-based alloy with heat treatment

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Rare Metals 2016年第1期35卷 26-34页

作者： Jian-Chao Han Shu-Long Xiao Jing Tian Yu-Yong Chen Li-Juan Xu Xiao-Peng Wang Yi Jia Shou-Zhen Cao School of Materials Science and Engineering Harbin Institute of Technology National Key laboratory of Science and Technology on Precision Heat Processing of Metals Harbin Institute of Technology State Key laboratory of Advanced Welding and Joining Harbin Institute of Technology

The effects of Ni addition on solidification micro structure and tensile properties of Ti-48Al-2Cr-2Nb alloy were investigated using differential scanning calorimetry（DSC）,X-ray diffraction（XRD）,scanning electron microscopy（SEM） equipped with energy-dispersive spectroscope（EDS） and transmission electron microscopy（TEM）.Results show that with 3 at%Ni addition,the as-cast micro structure is mainly composed of fine lamellar colonies（~50 μm）,γ grains and Ni-ridied τ_3 *** heat treatment at 1380℃,the Ni-containing alloy is characterized by fine fully lamellar micro structure（~90 μm）.The heat-treated Ni-containing specimen exhibits superior room temperature tensile properties than other *** tensile properties are discussed in light of the microstructure evolution and role of Ni-riched τ_3 phase.

关键词： TiAl-based intermetallics Solidificationmicrostructure Heat treatment Phase transformation Tensile properties

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Inherent Shear-Dilatation Coexistence in Metallic Glass

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Chinese Physics Letters 2009年第1期26卷 190-193页

作者：蒋敏强江思跃戴兰宏 State Key laboratory of nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 State Key laboratory of Explosion Science and Technology Bei3ing Institute of Technology Beijing 100081

Shear deformation can induce normal stress or hydrostatic stress in metallic glasses [Nature Mater. 2 （2003） 449, intermetallics 14 （2006） 1033]. We perform the bulk deformation of three-dimensional Cu46Zr54 metallic glass （MG） and Cu single crystal model systems using molecular dynamics simulation. The results indicate that hydrostatic stress can incur shear stress in MG, but not in crystal. The resultant pronounced asymmetry between tension and compression originates from this inherent shear-dilatation coexistence in MG.

关键词： field emission molybdenum dioxide enhancement factor

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Undercooling and rapid solidification of Nb-Si eutectic alloys studied by long drop tube

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中国有色金属学会会刊：英文版 2006年第A02期16卷 89-92页

作者：王育人董树勇魏炳忱李维火 National Microgravity laboratory Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

Niobium-silicide alloys have great potential for high temperature turbine applications. The two-phase Nb/Nb5Si3 in situ composites exhibit a good balance in mechanical properties. Using the 52 in drop tube, the effect of undercooling and rapid solidification on the solidification process and micro-structural characterization of Nb-Si eutectic alloy was studied. The microstructures of the Nb-Si composites were investigated by optics microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometry (EDS). Up to 480 K, deep undercooling of the Nb-Si eutectic samples was successfully obtained, which corresponds to 25% of the liquidus temperature. Contrasting to the conventional microstructure usually found in the Nb-Si eutectic alloy, the microstructure of the undercooled sample is divided into the fine and coarse regions. The most commonly observed microstructure is Nb+Nb5Si3, and the Nb3Si phase is not be found. The change of coarseness of microstructure is due to different cooling rates during and after recalescence. The large undercooling is sufficient to completely bypass the high temperature phase field.

关键词：冷却过度快速凝固 Nb-Si共晶合金长滴管金属间化合物

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Replacement with Each Other of Ti and Zr in the intermetallics of Al-(Si-)Ti-Zr Alloys

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Journal of Materials Science & Technology 2013年第3期29卷 291-296页

作者： Tong Gao Xiangfa Liu Key laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of EducationShandong University

The structures and compositions of Ti and Zr rich phases in ternary Al-Ti-Zr and quaternary Al-Si-Ti-Zr systems were investigated by energy dispersive spectroscopy and X-ray diffraction. The additions of Ti and Zr were changed. It was found that Ti and Zr can replace each other in the Ti and Zr rich phases of Al-（Si-）Ti- Zr alloys. Compositions of the phases have been measured as a function of Ti and Zr additions. The content of Ti （Zr） in the phases increases with its addition in the alloys. Besides, the increase of Ti content can result in a decrease of lattice parameters. Microhardness of the phases in Al-18Si-xTi-yZr alloys changes with composition evolution. Moreover, the microhardness is higher than that of the intermetallics of ternary Al-Si-Ti and AI-Si-Zr alloys, due to the distortion of crystal structure caused by the replacement of Ti and Zr.

关键词： Replacement Composition Lattice parameters Microhardness

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A novel heat-resistant Al–Si–Cu–Ni–Mg base material synergistically strengthened by Ni-rich intermetallics and nano-AlN_p microskeletons

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Journal of Materials Science & Technology 2019年第3期35卷 306-312页

作者： Kaiqi Hu Qingfei Xu Xia Ma Qianqian Sun Tong Gao Xiangfa Liu Key laboratory for Liquid–Solid Structural Evolution and Processing of Materials Ministry of Education Shandong University

In this work, nano-AlN particle(nano-AlN_p) microskeletons were introduced into an Al–Si–Cu–Ni–Mg alloy by Al–8 AlN master alloy in which the nano-AlN_p reinforcements connect with each other to form three-dimensional networks. It is found that these nano-AlN_p microskeletons mainly distribute in the binary Al–Si eutectic zones resulting in flaky eutectic Si phases being modified to particulates. Meanwhile,the microskeletons strengthen the matrix synergistically with semi-continuous Ni-rich intermetallics in three dimensions. The tensile mechanical properties, micro-hardness and thermal expansion properties of the alloy at different temperatures are significantly improved. Especially, the ultimate tensile strength(UTS) at 350℃ increases from 85MPa to 106MPa, rising by 24.7%, which is ascribed to nano-AlN_p microskeletons assisting intermetallics with undertaking mechanical loading, and to the modification of eutectic Si phases to reduce the stress concentration at elevated temperatures.

关键词： Al–Si alloy Heat-resistant Al alloy Mechanical properties at high temperatures Nano-AlN_p microskeletons

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High-entropy L1_(2)-Pt(FeCoNiCuZn)_(3) intermetallics for ultrastable oxygen reduction reaction

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Journal of Energy Chemistry 2023年第11期86卷 158-166,I0004页

作者： Qian Zhang Tao Shen Min Song Shuang Wang Jialin Zhang Xiao Huang Shanfu Lu Deli Wang Key laboratory of Material Chemistry for Energy Conversion and Storage(Huazhong University of Science and Technology) Ministry of EducationHubei Key Laboratory of Material Chemistry and Service FailureSchool of Chemistry and Chemical EngineeringHuazhong University of Science and TechnologyWuhan 430074HubeiChina Beijing Key laboratory of Bio-inspired Energy Materials and Devices School of Space and EnvironmentBeihang UniversityBeijing 100191China

Enhancing the stability of Pt-based electrocatalysts for the sluggish cathodic oxygen reduction reaction(ORR)is critical for proton exchange membrane fuel cells(PEMFCs).Herein,high-entropy intermetallic(HEI)L1_(2)-Pt(FeCoNiCuZn)3is designed for durable ORR *** from the unique HEI structure and the enhanced intermetallic phase stability,Pt(FeCoNiCuZn)3/C nanoparticles demonstrate significantly improved stability over Pt/C and PtCu_(3)/C *** Pt(FeCoNiCuZn)3/C exhibits a negligible decay of the half-wave potential during 30,000 potential cycles from 0.6 to 1.0 V,whereas Pt/C and PtCu_(3)/C are negatively shifted by 46 and 36 m V,*** after 10,000 cycles at potential up to 1.5 V,the mass activity of Pt(FeCoNiCuZn)3/C still shows~70%*** evidenced by the structural characterizations,the HEI structure of Pt(FeCoNiCuZn)3/C is well maintained,while PtCu_(3)/C nanoparticles undergo severe Cu leaching and particle *** addition,when assembled Pt(FeCoNiCuZn)3/C as the cathode in high-temperature PEMFC of 160℃,the H_(2)-O_(2)fuel cell delivers almost no degradation even after operating for 150 h,demonstrating the potential for fuel cell *** work provides a facile design strategy for the development of high-performance ultrastable electrocatalysts.

关键词： High-entropy intermetallics Pt-based electrocatalysts Oxygen reduction reaction High stability

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