Amorphous Alloys as a Promising Class of Functional Materials. Pt. 1: Manufacturing Methods, Structure, Physical and Mechanical Properties

Study on the damage of Zr63.5Cu23Al9Fe4.5 amorphous and crystalline alloys by Fe, He ions beam irradiation

Electrocatalytic behaviour of Ni-base amorphous alloys

Formation ability, thermal stability, and mechanical properties of the Zr50Cu34Al8Ag8 amorphous alloys prepared by different mold materials

In order investigate the structural dependence of defect formation during irradiation, amorphous Fe79B16Si5 alloy and crystalline FeBSi alloy were irradiated by 300 keV helium ions at room temperature. Positron annihilation lifetimes observed for the unirradiated amorphous and the crystalline FeBSi alloys were nearly equal, i.e., 124.4±0.3 ps and 124.6±0.2 ps, respectively. The S parameters of the Doppler-broadening of annihilation radiation measured using a positron beam were also similar for the unirradited amorphous and crystalline FeBSi alloys. It means that the positron annihilation at the free volume in amorphous Fe79B16Si5 alloy is not prominent. The Doppler-broadening S parameter increased after the helium irradiation. This phenomenon was more pronounced in the amorphous FeBSi alloy. It suggests that the atoms are more easily displaced in amorphous alloy than in crystalline alloy during irradiation.

1. General Topics.- Proteins and Glasses.- Fractals and Localization.- Relation between Microstructure, Transport and Optical Properties in Composite Materials.- Comments on the Mode Coupling Theory of the Liquid Glass transition.- Computer Simulation Studies of Atomic Structure and Dynamics Relevant to Liquid and Amorphous Alloys.- On Surface Properties of the Classical One-Component Plasma.- 2. Structure of Liquids.- Relations between Atomic Arrangement and Electronic Structure in Liquid Metals and Alloys.- Liquid Structure and Freezing of Metals and Molten Salts.- The Structure of Liquid Binary Alloys.- Glass Transition in Simple Molten Salts.- Local Order at the Manganese Sites in Ionic Solutions by XANES.- "Bond"-Orientational Short Range Order in Liquid Aluminium.- 3. Structure of Amorphous Materials.- Atomic Short Range Order in Amorphous Materials.- Electronically Driven Structural Effects in Liquid and Amorphous Metals and Alloys.- The Origin of Microstructures of Rapidly Solidified Alloys.- Disorder in Metals - Selected Problems.- Defects in Amorphous Alloys.- Superconducting and Structural Properties of Amorphous Zr (Ni,Mo,W)-Alloys.- 4. Dynamics of Liquids and Amorphous Materials.- Atomic Motions in Liquids.- Experimental Studies of Atomic Motions in Liquid Metals.- Atomic Dynamics in Binary Liquids with Attractive A-B Interaction.- Transition from Gaussian to Dispersive Atomic Transport in Amorphous Materials.- Interaction Effects in Liquids with Low Electron Densities.- Nuclear iQuadrupolar Relaxation and Thermodynamics in Liquid Ternary Alloys.- Single Particle Motion in Liquid Sodium.- 5. Electronic Properties of Liquid and Amorphous Materials.- Electronic Structure and Transport in Amorphous and Liquid Metals.- Electronic Structure of Metallic Glasses - Bulk and Surface Properties.- Fluid Metals at High Temperatures.- Low Temperature Transport Properties: The Electrical Resistivity of some Amorphous Alloys.- Amorphous Metals at High Pressure.- Electron Localization in the Liquid Tl-Te-System as seen by Bi-Impurity.- Temperature Dependence of the Hall-Effect in some Amorphous Transition Metal Alloys.- Magnetoresistance Studies of Amorphous FeZr Alloys.- Magnetoconductivity of MgZn Metallic Glasses at Low Temperatures.- Optical Properties of Pt-Si Glasses.- Electrical Resistivity of Liquid Rare Earth-Transition Alloys of Nickel with Lanthanum and Cerium.- 6. Production of Amorphous Materials.- Formation of Non-Crystalline Metallic Alloys with and without Rapid Quenching.- Materials Amorphized by Laser Irradiation.- How to Produce Well-Defined Amorphous Alloys.- Ion Implantation and Amorphisation in Metallic Systems.- Surface Amorphous Alloys Obtained by Ion-Mixing.- Organometallic Glass-Forming Materials and their Structure.- Bulk Amorphous Metals by Solid State Reaction.

Metallic glasses have been a promising class of materials since their discovery in the 1960s. Indeed, remarkable chemical, mechanical and physical properties have attracted considerable attention, and several excellent reviews are available. Moreover, the special group of glass forming alloys known as the bulk metallic glasses (BMG) become amorphous solids even at relatively low cooling rates, allowing them to be cast in large cross sections, opening the scope of potential applications to include bulk forms and net shape structural applications. Recent studies have been reported for new bulk metallic glasses produced with lower cooling rates, from 0.1 to several hundred K/s. Some of the application products of BMGs include sporting goods, high performance springs and medical devices. Several rapid solidification techniques, including melt-spinning, atomization and surface melting have been developed to produce amorphous alloys. The aim of all these methods is to solidify the liquid phase rapidly enough to suppress the nucleation and growth of crystalline phases. Furthermore, the production of amorphous/crystalline composite (ACC) materials by partial crystallization of amorphous precursor has recently given rise to materials that provide better mechanical and magnetic properties than the monolithic amorphous or crystalline alloys. In addition, these advances illustrate the broad untapped potentialmore » of using the glassy state as an intermediate stage in the processing of new materials and nanostructures. These advances underlie the necessity of investigations on prediction and control of phase stability and microstructural dynamics during both solidification and devitrification processes. This research presented in this dissertation is mainly focused on Cu-Zr and Cu-Zr-Al alloy systems. The Cu-Zr binary system has high glass forming ability in a wide compositional range (35-70 at.% Cu). Thereby, Cu-Zr based alloys have attracted much attention according to fundamental research on the behaviors of glass forming alloys. Further motivation arising from the application of this system as a basis for many BMGs and ACC materials; the Cu-Zr system warrants this attention and offers great potential for the development of new materials. However, the prediction and control of microstructural evolution during devitrification remains challenging because of the complex devitrification behavior of the Cu-Zr binary alloy which is arising from the competition of metastable and stable phases and diversity of crystal structures. This dissertation details a systematic fundamental investigation into the mechanisms and kinetics of the various crystallization transformation processes involved in the overall devitrification response of Cu-Zr and Cu-Zr-Al glasses. Various isothermal and nonisothermal treatments are employed, and the structural response is characterized using bulk X-ray and thermal analysis methods as well as nanoscale microscopic analysis methods, revealing structural and chemical details down to the atomic-scale. By carefully combining techniques such as differential scanning calorimetry (DSC), in-situ synchrotron high energy X-ray diffraction (HEXRD), and transmission electron microscopy (TEM) to quantify the characterization transformations, this research has uncovered numerous details concerning the atomistic mechanisms of crystallization and has provided much new understanding related to the dominant phases, the overall reaction sequences, and the rate-controlling mechanisms. As such this work represents a substantial step forward in understanding these transformations and provides a clear framework for further progress toward ultimate application of controlled devitrification processing for the production of new materials with remarkable properties.« less

Determination of the free energy of metastable crystalline and amorphous NbCo alloys and its application to metastable phase formation

Amorphous alloys are a group of novel mechanical and functional materials that possess remarkably improved properties, such as mechanical property, wear property, anti-corrosion property, magnetic property and catalytic property, compared with those of their crystalline counterparts. The interactions between amorphous alloys and hydrogen can lead to various interesting physical and chemical phenomena, and also important applications. Typically, some amorphous alloys can store more hydrogen with faster kinetics than their crystalline counterparts due to the disordered atomic structures, which make them promising candidates for hydrogen storage. Hydrogen induced optical transformation in amorphous alloy film with thickness on a nanoscale makes them suitable for developing optical switchable windows. Hydrogen could be used as a sensitive probe to study the atomic structures of amorphous alloys. Amorphous alloys, whose structures are similar to defects in crystalline alloys (vacancies, dislocations, boundaries, ect.), are a group of suitable objects to study the interactions between hydrogen and defects. Amorphous alloys are also promising membranes materials for industrial hydrogen gas purification. Micro-alloying by hydrogenation could enhance the plasticity and glass-forming ability of amorphous alloy.In this review, recent research progress of interactions between amorphous alloys and hydrogen are summarized from two main aspects: fundamental research and practical applications. In the aspect of fundamental research, we firstly review the recent study on hydrogen in the amorphous alloy, including the hydrogen concentration and distribution, hydrogen occupancy type and geometric size, hydrogen diffusion and thermodynamics and other relevant physical and chemical issues. Secondly, the studies on the effects of hydrogenation on thermal stability, magnetic property and internal friction of amorphous alloys, together with some discussion on the corresponding mechanisms are summarized. Thirdly, hydrogen embrittlement of amorphous alloy and the corresponding prevention techniques, together with the studies of the interactions between hydrogen and defects in crystalline materials such as vacancies, dislocations and boundaries in material, are also involved. In the aspect of practical applications, we firstly review recent advances in amorphous hydrogen storage alloys, focusing on transition metal based amorphous alloys and Mg based alloys. Secondly, amorphous alloy films for hydrogen purification, hydrogen sensors and optical switchable windows are reviewed. Thirdly, some positive influences introduced by hydrogenation on amorphous alloys are discussed, typically on enhancing plasticity and glass-forming ability. Besides the above, hydrogen induced amorphization on crystalline alloy, the use of amorphous alloy for preparing nanocrystalline hydrogen storage materials, and using hydrogenation to crack bulk amorphous alloys to produce amorphous alloys powders are also discussed. In the last section of this review, we try to give our own viewpoint of the future perspectives of relevant researches and applications of interactions between hydrogen and amorphous alloys.

Metallic glasses have been a promising class of materials since their discovery in the 1960s. Indeed, remarkable chemical, mechanical and physical properties have attracted considerable attention, and several excellent reviews are available. Moreover, the special group of glass forming alloys known as the bulk metallic glasses (BMG) become amorphous solids even at relatively low cooling rates, allowing them to be cast in large cross sections, opening the scope of potential applications to include bulk forms and net shape structural applications. Recent studies have been reported for new bulk metallic glasses produced with lower cooling rates, from 0.1 to several hundred K/s. Some of the application products of BMGs include sporting goods, high performance springs and medical devices. Several rapid solidification techniques, including melt-spinning, atomization and surface melting have been developed to produce amorphous alloys. The aim of all these methods is to solidify the liquid phase rapidly enough to suppress the nucleation and growth of crystalline phases. Furthermore, the production of amorphous/crystalline composite (ACC) materials by partial crystallization of amorphous precursor has recently given rise to materials that provide better mechanical and magnetic properties than the monolithic amorphous or crystalline alloys. In addition, these advances illustrate the broad untapped potential of using the glassy state as an intermediate stage in the processing of new materials and nanostructures. These advances underlie the necessity of investigations on prediction and control of phase stability and microstructural dynamics during both solidification and devitrification processes. This research presented in this dissertation is mainly focused on Cu-Zr and Cu-Zr-Al alloy systems. The Cu-Zr binary system has high glass forming ability in a wide compositional range (35-70 at.% Cu). Thereby, Cu-Zr based alloys have attracted much attention according to fundamental research on the behaviors of glass forming alloys. Further motivation arising from the application of this system as a basis for many BMGs and ACC materials; the Cu-Zr system warrants this attention and offers great potential for the development of new materials. However, the prediction and control of microstructural evolution during devitrification remains challenging because of the complex devitrification behavior of the Cu-Zr binary alloy which is arising from the competition of metastable and stable phases and diversity of crystal structures. This dissertation details a systematic fundamental investigation into the mechanisms and kinetics of the various crystallization transformation processes involved in the overall devitrification response of Cu-Zr and Cu-Zr-Al glasses. Various isothermal and nonisothermal treatments are employed, and the structural response is characterized using bulk X-ray and thermal analysis methods as well as nanoscale microscopic analysis methods, revealing structural and chemical details down to the atomic-scale. By carefully combining techniques such as differential scanning calorimetry (DSC), in-situ synchrotron high energy X-ray diffraction (HEXRD), and transmission electron microscopy (TEM) to quantify the characterization transformations, this research has uncovered numerous details concerning the atomistic mechanisms of crystallization and has provided much new understanding related to the dominant phases, the overall reaction sequences, and the rate-controlling mechanisms. As such this work represents a substantial step forward in understanding these transformations and provides a clear framework for further progress toward ultimate application of controlled devitrification processing for the production of new materials with remarkable properties.

Shear band evolution and mechanical behavior of cold-rolled Zr-based amorphous alloy sheets: An in-situ study

Wetting of Ni-based amorphous and crystalline alloys by Sn and Sn-based solders

Shape memory effect in metallic glasses

Oxidation behavior of a Zr–Cu–Al–Ni amorphous alloy in air at 300–425 °C

Some applications of NMR to the study of magnetically-ordered materials with emphasis on the short-range order in (Fe-B)-based crystalline and amorphous alloys

Since the amorphous state is not thermodynamically stable, it is known that this state easily transfers to a more stable state when annealed at temperatures sufficiently low that crystallization does not occur. This transfer process has now been interpreted in terms of structural relaxation. The structural relaxation is frequently described by two categories of a topological short-range ordering (TSRO) process and a chemical short-range ordering (CSRO) process [1]. The TSRO process involves irreversible structural change via highly collective atomic rearrangements with the annihilation of density fluctuation and stress relief in the as-quenched specimen [2, 3]. On the other hand, the anneal-induced reversible relaxation behaviour is also well documented in some amorphous alloys [4] and it is considered to be the atomic rearrangement between specific constituent elements. Such reversible relaxation behaviour in amorphous alloys is mainly attributed to the CSRO process [5]. Regarding the structural change due to lowtemperature annealing, much reliable information has been obtained using X-ray and neutron diffraction [6, 7]. These results clearly indicate that a highly disordered frozen-in structure, which is metastable in amorphous alloys prepared by rapid quenching from the melt, relaxes structurally owing to low-temperature annealing and the atoms occupy more stable positions in the disordered atomic arrangement. Thus, we now have sufficiently reliable information about the TSRO process [2, 3]. However, these structural studies have still had relatively little impact on the CSRO process due to low temperature annealing, because the available structural data are very limited for the individual chemical constituents in amorphous alloys. The use of anomalous X-ray scattering may bring about a significant breakthrough in this subject by obtaining the environmental structure around a specific element in amorphous alloys. The main purpose of this work is to present the results on the structural change of amorphous Pd41Ni41Si18 alloy due to low-temperature annealing by applying anomalous X-ray scattering (AXS) at the Ni K absorption edge, coupled with ordinary Xray diffraction data. Amorphous ribbons were prepared by the meltspinning method with a single copper roller in a purified Ar atmosphere. The ribbon shape was about 30 μm in thickness and 2 mm in width. The quality of samples was tested by X-ray diffraction and differential scanning calorimetry (DSC). The samples were annealed at 603 K for 330 s to reduce partially the excess free volume. It may be worth mentioning that the crystallization temperature was estimated to be 668 K, defined as a departure from the base line of the DSC thermogram taken with a heating rate of 0.33 K sy1 and the present annealing condition was determined from the temperature– time–transformation diagram determined from electrical resistance measurements. Ordinary X-ray scattering profiles of the 2θ range between 5 and 1308 were obtained by Mo Kα radiation with a pyrolitic grade monochromator in the diffraction beam path. AXS experiments were carried out with the synchrotron radiation source at Photon Factory of the National Laboratory for High Energy Physics in Japan. The X-ray energies of 8.032 or 8.307 keV, which are 300 and 25 eV below the Ni K absorption edge, were selected by the double Si(1 1 1) monochromator. The energy resolution of the monochromator is about 7 eV [8]. The 2θ range was varied from 10 to 1408. The experimental details including data processing have been reported previously [9, 10]. It must be stressed that special effort has been paid to reduce the statistical fluctuation in the AXS measurements by accumulating at least 1:5 3 105 counts so as to maintain a statistical error of less than 0.3%. Fig. 1 shows the interference functions, Qi(Q)as (solid curve) and Qi(Q)an (dotted curve), obtained from ordinary X-ray scattering for as-quenched and annealed samples together with the difference, Q i(Q) ˆ Qi(Q)an y Qi(Q)as. Fig. 2a represents the reduced radial density function, G(r), which is given by Fourier transformation of Qi(Q), for both asquenched and annealed samples. In the case of the