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INTERMEDIA TETEMPERATURE STRESS ANOMALY IN B_2 ALLOYS: WITH SPECIAL ATTENTION TO THE CASE OF IRON aluminides

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中国有色金属学会会刊：英文版 1999年第S1期9卷 157-168页

作者： D.G.Morris Institute of Structural Metallurgy, University of Neuchtel, 2000 Neuchtel, Switzerland

The iron aluminides show anomalous stress peaks at temperatures of the order of 400～600 ℃, irrespective of whether the crystal structure is B2 type or DO 3 type. Such features will be examined on the basis of thermally activated dislocation processes, considering the influence of test parameters such as temperature and strain rate, and material parameters such as crystal composition and orientation. Detailed analyses of deformation modes by slip step studies, transmission electron microscopy examinations of dislocation structures, and texture studies will also be considered. Observations of dislocation structures are clearly of great interest for suggesting the possible models of deformation, but suffer from two major weaknesses: the post mortem structures in samples deformed at high temperature may not be the same as those producing plasticity; almost all possible hypotheses for strengthening can find support from such observations, since almost all imaginable dislocation configurations can be found with sufficient diligence by the researcher. Strengthening at intermediate temperatures in DO 3 and B2 ordered iron aluminides will be analysed here, making combined use of observations of deformation structures and examinations of the influence of varying the deformation parameters.

关键词： Iron aluminides B2 alloys stress anomaly

MICROSTRUCTURAL EVOLUTION AND MECHANISMS OF SUPERPLASTICITY IN LARGE GRAINED IRON aluminides

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中国有色金属学会会刊：英文版 1999年第S1期9卷 228-239页

作者： Dongliang Lin (T.L.Lin) and Yi Liu Open Laboratory of Education Ministry of China for High Temperature Materials Tests, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030, China

The superplastic behavior has been found in Fe 3Al and FeAl alloys with grain sizes of 100～600 μm. The large grained Fe 3Al and FeAl alloys exhibit all deformation characteristics of conventional fine grain size superplastic alloys. However, superplastic behavior was found in large grained iron aluminides without the usual prerequisites for the superplasticity of a fine grain size and grain boundary sliding. The metallographic examinations have shown that average grain size of large grained iron aluminides decreased during superplastic deformation. Transmission electron microscopy (TEM) observations have shown that there were a great number of subgrain boundaries which formed a network and among which the proportion of low and high angle boundaries increased with the increase of strain. The observed superplastic phenomenon is explained by continuous recovery and recrystallization. During superplastic deformation, an unstable subgrain network forms and these subboundaries absorb gliding dislocations and transform into low and high angle grain boundaries. A dislocation gliding and climb process accommodated by subboundary sliding, migration and rotation, allows the superplastic flow to proceed.

关键词： iron aluminides superplasticity mechanism microstructural evolution dislocation gliding dislocation climb superplastic flow

Bulk Al–Al_3Zr composite prepared by mechanical alloying and hot extrusion for high-temperature applications

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International Journal of Minerals,Metallurgy and Materials 2017年第8期24卷 937-942页

作者： E.Pourkhorshid M.H.Enayati S.Sabooni F.Karimzadeh M.H.Paydar Department of Materials Engineering Isfahan University of Technology Department of Materials Science and Engineering School of Engineering Shiraz University

Bulk Al/Al_3Zr composite was prepared by a combination of mechanical alloying(MA) and hot extrusion processes. Elemental Al and Zr powders were milled for up to 10 h and heat treated at 600℃ for 1 h to form stable Al_3Zr. The prepared Al_3Zr powder was then mixed with the pure Al powder to produce an Al–Al_3Zr composite. The composite powder was finally consolidated by hot extrusion at 550℃. The mechanical properties of consolidated samples were evaluated by hardness and tension tests at room and elevated temperatures. The results show that annealing of the 10-h-milled powder at 600℃ for 1 h led to the formation of a stable Al_3Zr phase. Differential scanning calorimetry(DSC) results confirmed that the formation of Al_3Zr began with the nucleation of a metastable phase, which subsequently transformed to the stable tetragonal Al_3Zr structure. The tension yield strength of the Al-10wt%Al_3Zr composite was determined to be 103 MPa, which is approximately twice that for pure Al(53 MPa). The yield stress of the Al/Al_3Zr composite at 300℃ is just 10% lower than that at room temperature, which demonstrates the strong potential for the prepared composite to be used in high-temperature structural applications.

关键词： aluminum matrix nanocomposites mechanical alloying hot extrusion aluminides powder metallurgy

CREEP OF A POLYCRYSTALLINE NEAR γ-TiAl Alloy WITH A LAMELLAR MICROSTRUCTURE

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Acta Metallurgica Sinica(English Letters) 1996年第6期9卷 565-570页

作者： WR. Chen J.Triantafillou J. Beddoes and L. Zhao(Dept. of Mech. & Aero. Eng.,Carleton University, Ottawa,Canada Structures, Materials & Propulsion Laboratory,National Research Council, Ottawa, Canada ) Carleton Univ Ottawa Canada

Creep of a polycrystalline near γ-TiAl alloy in two fully lamellar conditions is presented. A lamellar structure with fine interface spacing and planar grain boundaries provides improved creep resistance. The lamellar structure with wide interface spacing and interlocked grain boundaries has <1/2 the creep life, five times the minimum strain rate and greater tertiary *** strain is accommodated by dislocation motion in soft grains, but the strain rate is controlled by hard grains. The resistance to fracture is controlled by the grain boundary morphology, with planar boundaries causing intergranular *** maximize the creep resistance of near γ-TiAl with a lamellar microstructure requires narrow lamellar interface spacing and interlocked lamellae along grain boundaries.

关键词： creep,γ-TiAl titanium aluminides lamellar structure

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Fe_3Al BASED ALLOYS

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Acta Metallurgica Sinica(English Letters) 1995年第Z1期8卷 393-404页

作者： D.G. MORRIS(Institute of Structural Metallurgy, Avenue de Bellevaux 51, University of Neuchatel, 2000 NEUCHATEL, SWITZERLAND) Univ of Neuchatel Switzerland

The promise for industrial applications offered by iron aluminides is today restricted by insufficient ductility at room temperature and mediocre strength and creep resistance at high temperatures. The tendency to embrittlement in the presence of hydrogen or water vapour limits the ductility even more. The atomic arrangements in binary and alloyed variants are examined here and related to the difficulties of dislocation propagation at room and at high temperatures. In this way the influence of intrinsic structure and alloying modifications on mechanical behaviour can be understood. Possibilities for further improving properties through structure control are considered.

关键词： Intermetallics aluminides Order Anti-phase boundaries Dislocation structures,Anomalous strengthening Solute hardening.

Phase and Microstructure Properties of Laser Cladding NiAl Intermetallic Compound Coating at Elevated Temperature

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稀有金属材料与工程 2012年第S1期41卷 116-119页

作者： Yu Youjun Zhou Jiansong Yang Lianbin Chen Jianmin Zhou Huidi Chun, Guo Wang Lingqian Chinese Acad Sci Lanzhou Inst Chem Phys State Key Lab Solid Lubricat Lanzhou 730000 Peoples R China Chinese Acad Sci Grad Univ Beijing 100049 Peoples R China NW Normal Univ Coll Chem & Chem Engn Lanzhou 730070 Peoples R China

The phase and microstructure properties of laser cladding single phase NiAl coating at elevated temperature of 800 °C were investigated by means of XRD,SEM,and *** was found that Ni3Al phase with a fine equiaxial microstructure precipitated along NiAl grain boundaries via the solid-state diffusion of Ni atoms during heating *** and Ni3Al phases have a commonzone *** phase and microstructure evolutions of NiAl during heating process can acquire well understand the diffusion behavior of laser cladding NiAl intermetallic compound coating and provide better guidance on its production and practical use.

关键词： nickel aluminides intermetallic compounds coating phase and microstructure evolution

INTERMETALLIC ALLOYS AND COMPOSITES FOR THE 21ST CENTURY: A BASIC ENERGY SCIENCES PROGRAM OF THE U. S. DEPARTMENT OF ENERGY

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中国有色金属学会会刊：英文版 1999年第S1期9卷 355-363页

作者： Alan L. Dragoo Division of Materials Sciences, Office of Basic Energy Sciences, U.S.Department of Energy, Germantown, MD 2087-1290, U.S.A.

Progress has been made in intermetallic alloys over the past decade and a half, but intermetallics remain a relatively unexplored class of materials for energy applications. Hence, they offer considerable opportunities both for scientific research on fundamental structural property processing relationships and for technological development. The Department of Energy supports a program of scientific research on intermetallic alloys such as the nickel and iron aluminides and is establishing new research efforts in silicides and Laves phases through the program of the Division of Materials Sciences, of the Office of Basic Energy Sciences. Areas of research include theory and materials simulation, microalloying, high resolution sudies of structure and composition, mechanical properties, point defects and dislocation mechanics, phase transformations, and processing. Research is conducted through programs at the Department of Energy National Laboratories and through grants to academic and industrial *** results from Division of Materials Sciences programs have provided the basis and transportation. In addition, a cooperative effort between research groups has been established as a project on intermetallic materials under the Center of Excellence in Synthesis and Processing of Advanced Materials.

关键词： intermetallics energy applications nickel aluminides iron aluminides silicides Laves phases

The Synthesis and Characterization of Arc Melted Fe1-xAlxAlloys

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Journal of Applied Mathematics and Physics 2013年第2期1卷 4-8页

作者： Sandeep Rajan Rajni Shukla Anil Kumar Anupam Vyas Ranjeet Kumar Brajpuriya Department of Physics Amity University Haryana Gurgaon India. Department of Physics Deenbandhu Chhotu Ram University of Science & Technology Sonipat India

The paper presents correlation study on a series of Fe1-xAlx alloy samples prepared by arc melting. All the samples show crystalline structure, irrespective of the Al content and are textured mainly along (110) direction. The particle size decreases rapidly with x particularly after x > 0.3. The corresponding magnetic measurements were obtained at room temperature using a VSM, with a maximum applied field of 14 kOe. The results show that the ferromagnetic state of the samples disappears with x, and becomes paramagnetic for alloys with x ≥ 0.4. It is also found that coercivity (Hc) and resistivity increase with x. The results were interpreted in terms of continuous change in their electronic structure i.e. overlap of the electron wave functions of the magnetic atoms with the Al electron wave function.

关键词： Transition Metal aluminides Magnetization and Electronic Properties