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Special Issue "Advances in Bulk Metallic Glasses"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 October 2011)

Special Issue Editors

Guest Editor
Prof. Dr. Alain R. Yavari

Euronano-SIMaP, Institut Polytechnique de Grenoble (INPG), 1130 rue de la Piscine, BP 75, 38402 Saint-Martin-d'Hères, France
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Guest Editor
Dr. Konstantinos Georgarakis

WPI-AIMR, Tohoku University, Japan; Euronano-SIMaP-INP Grenoble, 1130 rue de la Piscine, BP 75, 38402 Saint-Martin-d'Hères, France
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Special Issue Information

Dear Colleagues,

Bulk metallic glasses (BMGs) are currently on the cutting edge of Materials Science research. Easy bulk glass forming alloys are usually multicomponent eutectic or near eutectic liquid compositions with high viscosities and depressed melting temperatures that result in reduced critical cooling rates required for suppression of crystal formation.

For about two decades after the discovery of the first glassy alloy quenched from the liquid in 1960, the critical cooling rate for suppression of crystallisation was extremely high (of the order of 106 K/s), limiting the sample dimensions to less than 100 μm and restricting applications to a few areas such as magnetic devices and sensors. In the 80’s, an improvement of the maximum size of glassy specimens had been achieved for few alloys using fluxing techniques, bringing down the critical cooling rates to about 104K/s. However, the trend changed in the early 90’s and bulk metallic glasses emerged as an important and promising new class of materials. Since then, a large number of bulk alloys has been quenched to a glassy state with thickness reaching several centimeters and critical cooling rates sometimes as low as 1 K/s. This dramatic improvement in the glass formability was related to alloys having three main features, i.e. multi-component systems, significant atomic size ratios above 12% between their components and negative heats of mixing.

The disordered atomic structure of bulk metallic glasses results in various remarkable properties, such as high mechanical strength up to 5 GPa, elasticity up to 2% strain, good corrosion and wear resistance and excellent soft magnetic properties. The combination of their unique properties with their good formability through viscous flow in the supercooled liquid state, and their near-net-shape casting ability has led to several new applications including reinforcement for high-performance sports equipment, micromotors, springs, armor devices, biomedical implants and ornaments. However, the field of bulk metallic glasses is believed to possess high potential for further development.

Prof. Dr. Alain. R. Yavari
Dr. Konstantinos Georgarakis
Guest Editors

Keywords

  • supercooled liquids
  • amorphous metals
  • glass-forming ability
  • liquid alloys
  • rapid quenching
  • copper mold casting
  • fluxing
  • critical cooling rate
  • glass transition
  • eutectic alloys

Related Special Issue

Published Papers (3 papers)

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Research

Open AccessArticle Structural and Mechanical Characterization of Zr58.5Ti8.2Cu14.2Ni11.4Al7.7 Bulk Metallic Glass
Materials 2012, 5(1), 1-11; doi:10.3390/ma5010001
Received: 1 November 2011 / Revised: 7 December 2011 / Accepted: 14 December 2011 / Published: 22 December 2011
Cited by 5 | PDF Full-text (3126 KB) | HTML Full-text | XML Full-text
Abstract
Thermal stability, structure and mechanical properties of the multi-component Zr58.5Ti8.2Cu14.2Ni11.4Al7.7 bulk metallic glass have been studied in detail. The glassy material displays good thermal stability against crystallization and a fairly large supercooled liquid region
[...] Read more.
Thermal stability, structure and mechanical properties of the multi-component Zr58.5Ti8.2Cu14.2Ni11.4Al7.7 bulk metallic glass have been studied in detail. The glassy material displays good thermal stability against crystallization and a fairly large supercooled liquid region of 52 K. During heating, the alloy transforms into a metastable icosahedral quasicrystalline phase in the first stage of crystallization. At high temperatures, the quasicrystalline phase undergoes a transformation to form tetragonal and cubic NiZr2-type phases. Room-temperature compression tests of the as-cast sample show good mechanical properties, namely, high compressive strength of about 1,630 MPa and fracture strain of 3.3%. This is combined with a density of 6.32 g/cm3 and values of Poisson’s ratio and Young’s modulus of 0.377 and 77 GPa, respectively. The mechanical properties of the glass can be further improved by cold rolling. The compressive strength rises to 1,780 MPa and the fracture strain increases to 8.3% for the material cold-rolled to a diameter reduction of 10%. Full article
(This article belongs to the Special Issue Advances in Bulk Metallic Glasses)
Open AccessArticle Non-Isothermal Kinetic Analysis of the Crystallization of Metallic Glasses Using the Master Curve Method
Materials 2011, 4(12), 2231-2243; doi:10.3390/ma4122231
Received: 27 October 2011 / Revised: 12 December 2011 / Accepted: 14 December 2011 / Published: 20 December 2011
Cited by 8 | PDF Full-text (2142 KB) | HTML Full-text | XML Full-text
Abstract
The non-isothermal transformation rate curves of metallic glasses are analyzed with the Master Curve method grounded in the Kolmogorov-Johnson-Mehl-Avrami theory. The method is applied to the study of two different metallic glasses determining the activation energy of the transformation and the experimental kinetic
[...] Read more.
The non-isothermal transformation rate curves of metallic glasses are analyzed with the Master Curve method grounded in the Kolmogorov-Johnson-Mehl-Avrami theory. The method is applied to the study of two different metallic glasses determining the activation energy of the transformation and the experimental kinetic function that is analyzed using Avrami kinetics. The analysis of the crystallization of Cu47Ti33Zr11Ni8Si1 metallic glassy powders gives Ea = 3.8 eV, in good agreement with the calculation by other methods, and a transformation initiated by an accelerating nucleation and diffusion-controlled growth. The other studied alloy is a Nanoperm-type Fe77Nb7B15Cu1 metallic glass with a primary crystallization of bcc-Fe. An activation energy of Ea = 5.7 eV is obtained from the Master Curve analysis. It is shown that the use of Avrami kinetics is not able to explain the crystallization mechanisms in this alloy giving an Avrami exponent of n = 1. Full article
(This article belongs to the Special Issue Advances in Bulk Metallic Glasses)
Open AccessArticle Thermodynamic Origin of the Vitreous Transition
Materials 2011, 4(5), 869-892; doi:10.3390/ma4050869
Received: 22 March 2011 / Revised: 19 April 2011 / Accepted: 5 May 2011 / Published: 9 May 2011
Cited by 4 | PDF Full-text (547 KB) | HTML Full-text | XML Full-text
Abstract
The vitreous transition is characterized by a freezing of atomic degrees of freedom at a temperature Tg depending on the heating and cooling rates. A kinetic origin is generally attributed to this phenomenon instead of a thermodynamic one which we develop here.
[...] Read more.
The vitreous transition is characterized by a freezing of atomic degrees of freedom at a temperature Tg depending on the heating and cooling rates. A kinetic origin is generally attributed to this phenomenon instead of a thermodynamic one which we develop here. Completed homogeneous nucleation laws reflecting the energy saving due to Fermi energy equalization of nascent crystals and their melt are used. They are applied to bulk metallic glasses and extended to inorganic glasses and polymers. A transition T*g among various Tg corresponds to a crystal homogeneous nucleation temperature, leading to a preliminary formation of a cluster distribution during the relaxation time preceding the long steady-state nucleation time of crystals in small samples. The thermally-activated energy barrier ΔG*2ls/kBT at T*g for homogeneous nucleation is nearly the same in all glass-forming melts and determined by similar values of viscosity and a thermally-activated diffusion barrier from melt to cluster. The glass transition T*g is a material constant and a linear function of the energy saving associated with charge transfers from nascent clusters to the melt. The vitreous transition and the melting temperatures alone are used to predict the free-volume disappearance temperature equal to the Vogel-Fulcher-Tammann temperature of fragile glass-forming melts, in agreement with many viscosity measurements. The reversible thermodynamic vitreous transition is determined by the disappearance temperature T*g of the fully-relaxed enthalpy Hr that is not time dependent; the observed specific heat jump at T*g is equal to the proportionality coefficient of Hr with (T*g − Ta) for T ≤ T*g as expected from the enthalpy excess stored by a quenched undercooled melt at the annealing temperature Ta and relaxed towards an equilibrium vitreous state. However, the heat flux measurements found in literature over the last 50 years only gave an out-of-equilibrium Tg since the enthalpy is continuous at T*g without visible heat jump. Full article
(This article belongs to the Special Issue Advances in Bulk Metallic Glasses)
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