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C Suryanarayana – One of the best experts on this subject based on the ideXlab platform.

  • lattice contraction during amorphization by mechanical Alloying
    Journal of Applied Physics, 2008
    Co-Authors: C Suryanarayana, Satyajeet Sharma
    Abstract:

    Amorphization has been achieved in blended elemental Fe-based multicomponent alloy powders by mechanical Alloying. The effect of Nb addition to the Fe42Ni28Zr10−xNbxB20 alloy in the composition range of 1–6 at. % Nb has been investigated and it was shown that the glass-forming ability (GFA) of the alloys, defined as the milling time required to produce an amorphous phase, improved with Nb addition. The improvement was not regular; the highest GFA was achieved at an Nb level of 2 at. %. Associated with the amorphization process, lattice contraction was noted. The processes of occurrence of the amorphous phase in this alloy system, maximum GFA in the alloy with 2 at. % Nb, and lattice contraction were explained on the basis of the atomic strain model developed first for binary alloys and extended later to ternary and multicomponent alloys, and the change in coordination number with the size ratio of the constituent atoms.

  • mechanical Alloying and milling
    , 2004
    Co-Authors: C Suryanarayana
    Abstract:

    Mechanical Alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of powder contamination has been analyzed and methods have been suggested to avoid/minimize it. The present understanding of the modeling of the MA process has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product phases obtained by MA with those of rapid solisolidification processing, another non-equilibrium processing technique.

  • the science and technology of mechanical Alloying
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001
    Co-Authors: C Suryanarayana, E Ivanov, V V Boldyrev
    Abstract:

    Abstract Mechanical Alloying (MA) is a powder metametallurgy processing technique involving cold welding, fracturing, and rewelding of powder particles in a high-energy ball mill, and has now become an established commercial technique to produce oxide dispersion strengthened (ODS) nickel- and iron-based materials. MA is also capable of synthesizing a variety of metastable phases, and in this respect, the capabilities of MA are similar to those of another important non-equilibrium processing technique, viz., rapid solisolidification processing (RSP). However, the “science” of MA is being investigated only during the past 10 years or so. The technique of mechanochemistry, on the other hand, has had a long history and the materials produced in this way have found a number of technological applications, e.g., in areas such as hydrogen storage materials, heaters, gas absorbers, fertilizers, catalysts, cosmetics, and waste management. The present paper discusses the basic mechanisms of formation of metastable phases (specifically supersaturated solid solutions and amorphous phases) by the technique of MA and these aspects are compared with those of RSP. Additionally, the variety of technological applications of mechanically alloyed products are highlighted.

F H Froes – One of the best experts on this subject based on the ideXlab platform.

  • mechanical Alloying of nb al powders
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 1996
    Co-Authors: Zhixue Peng, C Suryanarayana, F H Froes
    Abstract:

    The effect of mechanical Alloying (MA) on solid solubility extension, nanostructure formation, amorphization, intermetallic compound formation, and the occurrence of a face-centered cubic (fcc) phase in the Nb-Al system has been studied. Solid solubility extension was observed in both the terminal compositions and intermetallic compounds: 15 pct Nb in Al and 60 pct Al in Nb, well beyond the equilibrium and even rapid solisolidification levels (2.4 pct Nb and 25 pct Al, respectively) and increased homogeneity range for the NbAl3 phase. Nanostructured grains formed in all compositions. In the central part of the phase diagram, amorphization occurred predominantly. Only NbAl3, the most stable intermetallic, formed during MA; in most cases, a subsequent anneal was required. On long milling time, an fcc phase, probably a nitride, formed as a result of contamination from the ambient atmosphere.

  • synthesis of intermetallics by mechanical Alloying
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1995
    Co-Authors: F H Froes, C Suryanarayana, K Russell, C G Li
    Abstract:

    Abstract Mechanical Alloying (MA), a solid-state powder processing method, is a “far from equilibrium” synthesis technique which allows the development of novel crystal structures and microstructures, leading to enhanced physical and mechanical properties. The application of MA to the synthesis of intermetallics in the TiAl(Nb), AlFe, NbAl, TiMg, AlZr(Fe) and AlMg systems is presented. The ability to synthesize a variety of alloy phases, including supersaturated solid solutions, nanocrystalline structures, amorphous phases and intermetallic compounds themselves, is discussed. No extension of solubility using MA was observed in the intermetallics studied, unlike the situation using rapid solisolidification (RS). Nanostructured grains were observed in all compositions, their rate of decrease in size and minimum size being related to the following partially interrelated parameters: stability of the intermetallic, grain boundary energy, melting point and the balance between defect creation/recovery. Long-time milling generally resulted in amorphous phase formation largely because of the increase in grain boundary energy per mole with reduced grain size; good agreement with the Miedema model for amorphization was obtained in the AlFe system. Generally, annealing was required to form the intermetallic after MA; however, intermetallics with a large negative enthalpy of formation were detected in the mechanically alloyed condition. Low-temperature compaction allowed the retention of the fine microstructure in the nanometer range, giving an interesting capability to enhance ductility in the normally brittle intermetallics.

  • synthesis of nanocrystalline al5fe2 by mechanical Alloying
    Scripta Metallurgica Et Materialia, 1994
    Co-Authors: D K Mukhopadhyay, C Suryanarayana, F H Froes
    Abstract:

    Mechanical Alloying (MA), a solid state powder processing technique, has been employed to synthesize a variety of alloy phases starting from either blended elemental or prealloyed powders. Recently there have been many investigations on the synthesis of intermetallic compounds by MA. However, in a majority of these cases the synthesis of the intermetallics is achieved only on heat treatment of the MA powders. Only in a few cases is the formation of the intermetallics achieved directly by MA; some of these phases are in the ordered state, although the ordering is far from complete. The purpose of the present paper is to report on the successful direct synthesis of the ordered Al[sub 5]Fe[sub 2] intermetallic by MA starting from blended elemental powders.

V V Boldyrev – One of the best experts on this subject based on the ideXlab platform.

  • the science and technology of mechanical Alloying
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001
    Co-Authors: C Suryanarayana, E Ivanov, V V Boldyrev
    Abstract:

    Abstract Mechanical Alloying (MA) is a powder metallurgy processing technique involving cold welding, fracturing, and rewelding of powder particles in a high-energy ball mill, and has now become an established commercial technique to produce oxide dispersion strengthened (ODS) nickel- and iron-based materials. MA is also capable of synthesizing a variety of metastable phases, and in this respect, the capabilities of MA are similar to those of another important non-equilibrium processing technique, viz., rapid solidification processing (RSP). However, the “science” of MA is being investigated only during the past 10 years or so. The technique of mechanochemistry, on the other hand, has had a long history and the materials produced in this way have found a number of technological applications, e.g., in areas such as hydrogen storage materials, heaters, gas absorbers, fertilizers, catalysts, cosmetics, and waste management. The present paper discusses the basic mechanisms of formation of metastable phases (specifically supersaturated solid solutions and amorphous phases) by the technique of MA and these aspects are compared with those of RSP. Additionally, the variety of technological applications of mechanically alloyed products are highlighted.

  • tribochemical equilibrium in mechanical Alloying of metals
    Journal of Materials Science, 1991
    Co-Authors: K B Gerasimov, A A Gusev, E Y Ivanov, V V Boldyrev
    Abstract:

    The structure of the product in mechanical Alloying depends both on the elemental composition and the milling conditions. An increase of ball energy led to more pronounced crystallinity of the product. Mechanical Alloying at small ball energy leads to the formation of amorphous alloys for Zr-Co and Cu-Ti systems. Demixing of Ti3Cu4 into crystalline TiCu and TiCu4 and demixing of Zr50Co50 into Zr3Co and ZrCo2 was found. The results are explained on the basis of the concept of tribochemical equilibrium.

S Ranganathan – One of the best experts on this subject based on the ideXlab platform.

  • novel materials synthesis by mechanical Alloying milling
    International Materials Reviews, 1998
    Co-Authors: B S Murty, S Ranganathan
    Abstract:

    An account is given of the research that has been carried out on mechanical Alloying/milling (MA/MM) during the past 25 years. Mechanical Alloying, a high energy ball milling process, has established itself as a viable solid state processing route for the synthesis of a variety of equilibrium and non-equilibrium phases and phase mixtures. The process was initially invented for the production of oxide dispersion strengthened (ODS) Ni-base superalloys and later extended to other ODS alloys. The success of MA in producing ODS alloys with better high temperature capabilities in comparison with other processing routes is highlighted. Mechanical Alloying has also been successfully used for extending terminal solid solubilities in many commercially important metallic systems. Many high melting intermetallics that are difficult to prepare by conventional processing techniques could be easily synthesised with homogeneous structure and composition by MA. It has also, over the years, proved itself to be superior to rapid solisolidification processing as a non-equilibrium processing tool. The considerable literature on the synthesis of amorphous, quasicrystalline, and nanocrystalline materials by MA is critically reviewed. The possibility of achieving solid solubility in liquid immiscible systems has made MA a unique process. Reactive milling has opened new avenues for the solid state metallothermic reduction and for the synthesis of nanocrystalline intermetallics and intermetallic matrix composites. Despite numerous efforts, understanding of the process of MA, being far from equilibrium, is far from complete, leaving large scope for further research in this exciting field.

Guy Monteil – One of the best experts on this subject based on the ideXlab platform.

  • Nanoparticles Alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle Alloying
    Nanotechnology, 2017
    Co-Authors: Nikolaos Semaltianos, Rémi Chassagnon, Virginie Moutarlier, Virginie Blondeau-patissier, Mohamed Assoul, Guy Monteil
    Abstract:

    Laser irradiation of a mixture of single-element micro/nanomaterials may lead to their Alloying and fabrication of multi-element structures. In addition to the laser induced Alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced Alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablaablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles Alloying in liquid. Nanoparticles Alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ~405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles Alloying and network formation are also discussed.