Brittle and Ductile Character of Amorphous Solids

2016 ◽  
Vol 8 (3) ◽  
pp. 485-498
Author(s):  
Miguel Lagos ◽  
Raj Das
Keyword(s):  
Glass Transition ◽  
Plastic Flow ◽  
Metallic Glasses ◽  
Bulk Material ◽  
Amorphous Solids ◽  
Amorphous Structure ◽  
Atomic Scale ◽  
Brittle Solid ◽  
Disordered Structure ◽  
The Difference

Abstract.Common silicate glasses are among the most brittle of the materials. However, on warming beyond the glass transition temperature Tg glass transforms into one of the most plastic known materials. Bulk metallic glasses exhibit similar phenomenology, indicating that it rests on the disordered structure instead on the nature of the chemical bonds. The micromechanics of a solid with bulk amorphous structure is examined in order to determine the most basic conditions the system must satisfy to be able of plastic flow. The equations for the macroscopic flow, consistent with the constrictions imposed at the atomic scale, prove that a randomly structured bulk material must be either a brittle solid or a liquid, but not a ductile solid. The theory permits to identify a single parameter determining the difference between the brittle solid and the liquid. However, the system is able of perfect ductility if the plastic flow proceeds in two dimensional plane layers that concentrate the strain. Insight is gained on the nature of the glass transition, and the phase occurring between glass transition and melting.

Critical growth and energy barriers of atomic-scale plastic flow units in metallic glasses

2021 ◽  
Vol 202 ◽  
pp. 114033
Author(s):  
J.H. Yu ◽  
L.Q. Shen ◽  
D. Şopu ◽  
B.A. Sun ◽  
W.H. Wang
Keyword(s):  
Plastic Flow ◽  
Metallic Glasses ◽  
Critical Growth ◽  
Atomic Scale ◽  
Energy Barriers ◽  
Flow Units

scholarly journals Synthesis and Properties of Bulk Metallic Glasses in Pd-Ni-P and Pd-Cu-P Alloys

1996 ◽  
Vol 455 ◽  
Author(s):  
Y. He ◽  
R. B. Schwarz
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Composition Range ◽  
Wide Composition Range ◽  
Upper Limit ◽  
Ternary Alloy Systems ◽  
The Difference ◽  
Thermal Stability Of

ABSTRACTBulk amorphous Pd-Ni-P and Pd-Cu-P alloy rods with diameters ranging from 7 to 25 mm have been synthesized over a wide composition range using a fluxing technique. For most bulk amorphous Pd-Ni-P alloys, the difference ΔT = Tx - Tg between the crystallization temperature Tx and the glass transition temperature Tg is larger than 90 K, while for bulk amorphous Pd-Cu-P alloys, ΔT varies from 27 to 73 K. Pd40Ni40P20 has the highest glass formability, and 300-gram bulk amorphous cylinders, 25 mm in diameter and 50 mm in length, can be easily produced. This size, however, is not an upper limit. The paper presents the glass formation ranges for both ternary alloy systems and data on the thermal stability of the amorphous alloys, as well as their specific heat, density, and elastic properties.

Inhomogeneous Amorphous Structure of Bulk Metallic Glasses Examined from Structural Relaxation Kinetics

2010 ◽  
Vol 638-642 ◽  
pp. 1632-1636 ◽  
Author(s):  
Osami Haruyama ◽  
R. Wada ◽  
M. Kohda ◽  
Yokoyama Yoshihiko ◽  
Nobuyuki Nishiyama ◽  
...  
Keyword(s):  
Metallic Glasses ◽  
Structural Relaxation ◽  
Bulk Metallic Glasses ◽  
Amorphous Structure ◽  
Relaxation Behavior ◽  
Volume Relaxation ◽  
Wide Range ◽  
The Difference ◽  
Fragile Glass ◽  
Kinetics Of

The kinetics of structural relaxation in fragile glass former, Pd46Cu35.5P18.5 BMG, and strong glass former, Zr50Cu40Al10 BMG, was investigated by volume relaxation. The former exhibited a relaxation phenomenon that is well understood by the local topological instability model, while the latter showed monotonous relaxation behavior over a wide range down to Tg-60 K. The discrepancy may be closely related to the difference in the fragility of both glasses.

scholarly journals Nanoglass and Nanocrystallization Reactions in Metallic Glasses

2021 ◽  
Vol 8 ◽  
Author(s):  
John H Perepezko ◽  
Meng Gao ◽  
Jun-Qiang Wang
Keyword(s):  
Glass Transition ◽  
Metallic Glass ◽  
Metallic Glasses ◽  
Annealing Treatment ◽  
Supercooled Liquid ◽  
The Novel ◽  
Dsc Measurements ◽  
The Difference ◽  
The Stability ◽  
New Strategies

Strategies to change the properties of metallic glass by controlling the crystallization and the glass transition behavior are essential in promoting the application of these materials. Aside from changing the composition approaches to stabilize the glass and frustrate the nucleation and growth of crystals, new strategies at a fixed glass composition are of special interest. In this review, some recent work is summarized on new strategies to tune the properties of metallic glasses without changing composition. First, the nanocrystallization strategy is introduced that is based on the nanocrystallized microstructures such as those that develop in marginal Al-based metallic glasses. The heterogeneous and transient nucleation effects in the nanocrystallization reactions in Al-based metallic glasses are systematically investigated and can be assessed by the determination of delay time based on Flash DSC measurements. These results provide a basis to understand the strong effect of minor alloying additions on the onset of primary Al nanocrystallization and to design the novel Al-based composites with improved properties. Secondly, by an optimal annealing treatment, a liquid-cooled Au-based metallic glass can achieve very high kinetic stability to yield a large increase in glass transition temperature of 28 K and this is 3-5 times larger than the increase usually reported. The measured enthalpy decrease is about 50% of the difference between the as-cooled glass and the equilibrium crystalline state and reaches the extrapolated enthalpy of the supercooled liquid. Finally, the nano-glass strategy makes an Au-based nanoglass show ultrastable kinetic characters at low heating rate (e.g., 300 K/s) compared to a melt-spun ribbon, which is attributed to the kinetic constraint effect of nanoglobular interfaces. These results indicate that the nanoglass microstructure can act to increase metallic glass stability and provide another mechanism for the synthesis of ultrastable glass. These developments open new opportunities to improve the stability and properties and largely increase the application potentials of metallic glasses.

The Role of Disorder and the Elastic Robustness of Bulk Metallic Glasses

2012 ◽  
Vol 1520 ◽  
Author(s):  
P. M. Derlet ◽  
R. Maaß
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Plastic Flow ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Structural Transformations ◽  
Linear Temperature Dependence ◽  
Thermally Activated ◽  
Deformation Properties

ABSTRACTDespite significant atomic-scale heterogeneity, bulk metallic glasses well below their glass transition temperature exhibit a surprisingly robust elastic regime and a sharp elastic-to-plastic transition with a yield stress that depends approximately linearly on temperature. The present work attempts to understand these features within the framework of thermally activated plasticity. The presented statistical thermal activation model, in which the number of available structural transformations scales exponentially with system size, results in two distinct temperature regimes of deformation. At temperatures close to the glass transition temperature thermally activated Newtonian plastic flow emerges, whilst at lower temperatures the deformation properties fundamentally change due to the eventual kinetic freezing of the available structural transformations. In this regime, a linear temperature dependence emerges for the stress which characterises the elastic to plastic transition. For both regimes the transition to macroscopic plastic flow corresponds to a transition from a barrier energy dominated to a barrier entropy dominated statistics. The work concludes by discussing the possible influence that kinetic freezing might have on the low temperature heterogeneous and high temperature homogeneous plasticity of bulk metallic glasses.

scholarly journals Damage Characteristics of Zr-Based Metallic Glasses under Helium Ions Irradiation

2016 ◽  
Vol 849 ◽  
pp. 22-27
Author(s):  
Feng Jiang Li ◽  
Jian Shuo Xing ◽  
Zi Qiang Zhao ◽  
Bing Chen Wei
Keyword(s):  
Metallic Glasses ◽  
Volume Concentration ◽  
High Strength ◽  
Amorphous Structure ◽  
Helium Ions ◽  
Damage Characteristics ◽  
Disordered Structure ◽  
Structures And Properties ◽  
Partial Crystallization ◽  
Irradiation Resistance

Metallic glasses (MGs) exhibit extremely high strength and superior resistance to corrosion. They are also supposed to be resistant against displacive irradiation due to their inherent disordered structure, and thereby are viewed as potential candidates for applications in irradiation environments. However, the structures and properties evolution of metallic glasses, especially bulk metallic glasses (BMGs), under irradiation has not been fully understood up to now. In this work, the structural stability and damage characteristics of a Zr-based BMG under helium ions irradiation environment were investigated. Meanwhile, the effect of structural relaxation and crystallization on the irradiation response of the BMG was also studied. Results show that the BMG reserves the amorphous structure within the studied range of fluence, and exhibits better irradiation resistance compared to that of the crystalline alloys. In our opinion, the initial free volume concentration affects the damage morphology of the BMG, while partial crystallization will lead to significantly embrittlement under irradiation.

Images and Applications of Ion Explosion Spike Pits

1990 ◽  
Vol 48 (1) ◽  
pp. 584-585
Author(s):  
P. Fraundorf ◽  
J. Tentschert
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Bulk Material ◽  
Coulomb Repulsion ◽  
The Body ◽  
Atomic Scale ◽  
Early Solar System ◽  
Transmission Electron ◽  
Nuclear Particle ◽  
Particle Tracks

Since the discovery of their etchability in the early 1960‘s, nuclear particle tracks in insulators have had a diverse and exciting history of application to problems ranging from the selective filtration of cancer cells from blood to the detection of 244Pu in the early solar system. Their usefulness stems from the fact that they are comprised of a very thin (e.g. 20-40Å) damage core which etches more rapidly than does the bulk material. In fact, because in many insulators tracks are subject to radiolysis damage (beam annealing) in the transmission electron microscope, the body of knowledge concerning etched tracks far outweighs that associated with latent (unetched) tracks in the transmission electron microscope.With the development of scanned probe microscopies with lateral resolutions on the near atomic scale, a closer look at the structure of unetched nuclear particle tracks, particularly at their point of interface with solid surfaces, is now warranted and we think possible. The ion explosion spike model of track formation, described loosely, suggests that a burst of ionization along the path of a charged particle in an insulator creates an electrostatically unstable array of adjacent ions which eject one another by Coulomb repulsion from substitutional into interstitial sites. Regardless of the mechanism, the ejection process which acts to displace atoms along the track core seems likely to operate at track entry and exit surfaces, with the added feature of mass loss at those surfaces as well. In other words, we predict pits whose size is comparable to the track core width.

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