Theoretical strength and prediction of structural defects in metallic glasses

2019 ◽  
Vol 100 (2) ◽  
Author(s):  
Zhukun Zhou ◽  
Hao Wang ◽  
Mo Li
Keyword(s):  
Metallic Glasses ◽  
Theoretical Strength ◽  
Structural Defects

Mössbauer study of structural defects in metallic glasses

1987 ◽  
Vol 35 (1-4) ◽  
pp. 659-662 ◽  
Author(s):  
Ajay Gupta ◽  
R. P. Verma ◽  
S. N. Kane ◽  
S. Lal
Keyword(s):  
Metallic Glasses ◽  
Structural Defects ◽  
Mössbauer Study

Point Defects, Recovery Kinetics and Ordering in Irradiated Bulk Metallic Glasses

2007 ◽  
Vol 1048 ◽  
Author(s):  
Yuri Petrusenko ◽  
Alexander Bakai ◽  
Valeriy Borysenko ◽  
Dmitro Barankov ◽  
Oleksandr Astakhov ◽  
...  
Keyword(s):  
Point Defects ◽  
Metallic Glasses ◽  
Electrical Resistance ◽  
Amorphous Solids ◽  
Structural Defects ◽  
Thermally Activated ◽  
Local Ordering ◽  
Defect Mobility ◽  
Kinetics Of ◽  
Thermally Activated Process

AbstractThe problem of structural properties and structural defects of amorphous solids is still of vital importance. To make clear whether stable point defects exist in metallic glasses (MGs) or not, we have studied the accumulation and recovery kinetics of radiation defects in ZrTiCuNiBe and ZrTiCuNiAl bulk MGs irradiated with 2.5 MeV electrons at T ∼ 80 K. The electrical resistance measurements of the irradiated samples were performed. The recovery spectrum of irradiation-induced electrical resistance was measured for the 85–300 K temperature range. The most important result of the recovery experiments is that they clearly show the annealing stages for the irradiated samples. Two annealing peaks located at T∼150 K and T∼225 K are resolved for ZrTiCuNiBe glass. Similar peaks are also revealed for ZrTiCuNiAl. It can be concluded from the data that the defect mobility is a thermally activated process, and that the activation energy is not as high as that for vacancies in crystalline alloys. Thus, the data obtained testify in favor of the structure with “perfect” local ordering of atoms. It should be noted that this property is basic in the formulation of the polycluster model of amorphous solids.

Intrinsic structural defects on medium range in metallic glasses

2016 ◽  
Vol 75 ◽  
pp. 36-41 ◽  
Author(s):  
X. Huang ◽  
Z. Ling ◽  
Y.J. Wang ◽  
L.H. Dai
Keyword(s):  
Metallic Glasses ◽  
Structural Defects ◽  
Medium Range

Granulation of Bulk Metallic Glass Forming Alloys as a Feedstock for Thermoplastic Forming and their Compaction into Bulk Samples

2016 ◽  
Vol 879 ◽  
pp. 589-594 ◽  
Author(s):  
David Geissler ◽  
Jacob Grosse ◽  
Sven Donath ◽  
David Ehinger ◽  
Mihai Stoica ◽  
...  
Keyword(s):  
Metallic Glasses ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Supercooled Liquid ◽  
Amorphous Structure ◽  
Supercooled Liquid Region ◽  
Structural Defects ◽  
Liquid Region ◽  
Brittle Behavior ◽  
Technological Approach

The various technologically important properties of metallic glasses are intimately connected to their amorphous structure that lacks the archetypical structural defects of polycrystalline metals and alloys, i.e. dislocations and grain boundaries. However, the amorphous structure also limits the application potential of this class of materials because of a macroscopically brittle behavior and size limitations. Consequently, with some exceptions, at least one dimension for technological products is limited to a few millimeters or even less. With the presented technological approach this drawback will be addressed. Our first results on several alloys show that with a dedicated instrumentation amorphous granulates can be successfully produced. By hot pressing in the supercooled liquid region, these granulates can be compacted into bulk shapes in the cm range. Further, due to the low viscosity of the supercooled liquid state, this technology disposes of a high formability. It is demonstrated that not only compact samples but also complex shapes in near net shape geometry can be produced. Results on the mechanical properties and microstructure will be discussed and related to important processing issues. Even though this technological approach does not directly address the second drawback of bulk metallic glasses, i.e. catastrophic failure due to highly localized shear bands, it is believed that this route offers possible pathways to improve this issue as well and, most important, to offer a technological route for implementing bulk metallic glasses into products of rather arbitrary shape and larger size.

Effect of Structural Defects, Surface Irregularities, and Quenched-In Defects on Corrosion of Zr-Based Metallic Glasses

2009 ◽  
Vol 40 (5) ◽  
pp. 1131-1141 ◽  
Author(s):  
B. Vishwanadh ◽  
Geogy J. Abraham ◽  
Jagannath ◽  
S. Neogy ◽  
R. S. Dutta ◽  
...  
Keyword(s):  
Metallic Glasses ◽  
Structural Defects ◽  
Surface Irregularities

scholarly journals Flow units as dynamic defects in metallic glassy materials

2018 ◽  
Vol 6 (2) ◽  
pp. 304-323 ◽  
Author(s):  
Zheng Wang ◽  
Wei-Hua Wang
Keyword(s):  
Metallic Glasses ◽  
Primary Objective ◽  
Structural Defects ◽  
Flow Units ◽  
Flow Response ◽  
Open Questions ◽  
Unit Model ◽  
Response To Stress ◽  
Glassy Materials ◽  
Atomic Flow

Abstract In a crystalline material, structural defects such as dislocations or twins are well defined and largely determine the mechanical and other properties of the material. For metallic glass (MG) with unique properties in the absence of a long-range lattice, intensive efforts have focused on the search for similar ‘defects’. The primary objective has been the elucidation of the flow mechanism of MGs. However, their atomistic mechanism of mechanical deformation and atomic flow response to stress, temperature, and failure, have proven to be challenging. In this paper, we briefly review the state-of-the-art studies on the dynamic defects in metallic glasses from the perspective of flow units. The characteristics, activation and evolution processes of flow units as well as their correlation with mechanical properties, including plasticity, strength, fracture, and dynamic relaxation, are introduced. We show that flow units that are similar to structural defects such as dislocations are crucial in the optimization and design of metallic glassy materials via the thermal, mechanical and high-pressure tailoring of these units. In this report, the relevant issues and open questions with regard to the flow unit model are also introduced and discussed.

Transmission electron microscopy of composite materials

1988 ◽  
Vol 46 ◽  
pp. 1012-1015
Author(s):  
K.P.D. Lagerlof
Keyword(s):  
Composite Materials ◽  
Physical Properties ◽  
Structural Defects ◽  
Structural Composites ◽  
Multiphase Materials ◽  
Structural Reinforcement ◽  
Transmission Electron ◽  
Reinforced Fiber ◽  
Particulate Reinforced Composites ◽  
Definition Of

Although most materials contain more than one phase, and thus are multiphase materials, the definition of composite materials is commonly used to describe those materials containing more than one phase deliberately added to obtain certain desired physical properties. Composite materials are often classified according to their application, i.e. structural composites and electronic composites, but may also be classified according to the type of compounds making up the composite, i.e. metal/ceramic, ceramic/ceramie and metal/semiconductor composites. For structural composites it is also common to refer to the type of structural reinforcement; whisker-reinforced, fiber-reinforced, or particulate reinforced composites [1-4].For all types of composite materials, it is of fundamental importance to understand the relationship between the microstructure and the observed physical properties, and it is therefore vital to properly characterize the microstructure. The interfaces separating the different phases comprising the composite are of particular interest to understand. In structural composites the interface is often the weakest part, where fracture will nucleate, and in electronic composites structural defects at or near the interface will affect the critical electronic properties.

On the Shape of Field-Ion Emitters

1976 ◽  
Vol 34 ◽  
pp. 520-521
Author(s):  
H.C. Eaton ◽  
B.N. Ranganathan ◽  
T.W. Burwinkle ◽  
R. J. Bayuzick ◽  
J.J. Hren
Keyword(s):  
Grain Boundary ◽  
Spherical Shape ◽  
Theoretical Strength ◽  
Evaporation Process ◽  
Field Evaporation ◽  
Geometric Information ◽  
Field Ion Microscopy ◽  
Considerable Error ◽  
True Shape ◽  
Ion Microscopy

The shape of the emitter is of cardinal importance to field-ion microscopy. First, the field evaporation process itself is closely related to the initial tip shape. Secondly, the imaging stress, which is near the theoretical strength of the material and intrinsic to the imaging process, cannot be characterized without knowledge of the emitter shape. Finally, the problem of obtaining quantitative geometric information from the micrograph cannot be solved without knowing the shape. Previously published grain-boundary topographies were obtained employing an assumption of a spherical shape (1). The present investigation shows that the true shape deviates as much as 100 Å from sphericity and boundary reconstructions contain considerable error as a result.Our present procedures for obtaining tip shape may be summarized as follows. An empirical projection, D=f(θ), is obtained by digitizing the positions of poles on a field-ion micrograph.

Sign in / Sign up

Export Citation Format

Share Document