Structural changes and stress state effects during inhomogeneous flow of metallic glasses

2006 ◽  
Vol 54 (3) ◽  
pp. 327-332 ◽  
Author(s):  
K FLORES
Keyword(s):  
Stress State ◽  
Metallic Glasses ◽  
Structural Changes ◽  
Inhomogeneous Flow

A survey of instrumented indentation studies on metallic glasses

2004 ◽  
Vol 19 (1) ◽  
pp. 46-57 ◽  
Author(s):  
C.A. Schuh ◽  
T.G. Nieh
Keyword(s):  
Metallic Glasses ◽  
Structural Changes ◽  
Shear Banding ◽  
Depth Sensing ◽  
Future Directions ◽  
Fundamental Physics ◽  
New Approach ◽  
The Past ◽  
Rate Dependent

The development of instrumented nanoindentation equipment has occurred concurrently with the discovery of many new families of bulk metallic glass during the past decade. While indentation testing has long been used to assess the mechanical properties of metallic glasses, depth-sensing capabilities offer a new approach to study the fundamental physics behind glass deformation. This article is a succinct review of the research to date on the indentation of metallic glasses. In addition to standard hardness measurements, the onset of plasticity in metallic glasses is reviewed as well as the role of shear banding in indentation, structural changes beneath the indenter, and rate-dependent effects measured by nanoindentation. The article concludes with perspectives about the future directions for nanocontact studies on metallic glasses.

scholarly journals Specific Features of Structure Transformation and Properties of Amorphous-Nanocrystalline Alloys

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 358 ◽  
Author(s):  
Alexandr Aronin ◽  
Galina Abrosimova
Keyword(s):  
Amorphous Phase ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Structural Changes ◽  
Shear Bands ◽  
Component Composition ◽  
Amorphous Structure ◽  
Structure Evolution ◽  
Current State ◽  
Heterogeneous Phase

This work is devoted to a brief overview of the structure and properties of amorphous-nanocrystalline metallic alloys. It presents the current state of studies of the structure evolution of amorphous alloys and the formation of nanoglasses and nanocrystals in metallic glasses. Structural changes occurring during heating and deformation are considered. The transformation of a homogeneous amorphous phase into a heterogeneous phase, the dependence of the scale of inhomogeneities on the component composition, and the conditions of external influences are considered. The crystallization processes of the amorphous phase, such as the homogeneous and heterogeneous nucleation of crystals, are considered. Particular attention is paid to a volume mismatch compensation on the crystallization processes. The effect of changes in the amorphous structure on the forming crystalline structure is shown. The mechanical properties in the structure in and around shear bands are discussed. The possibility of controlling the structure of fully or partially crystallized samples is analyzed for creating new materials with the required physical properties.

Structural changes and physical properties of Fe–Ni-based metallic glasses rapidly heated by pulsed electrical currents

1991 ◽  
Vol 6 (5) ◽  
pp. 1028-1034 ◽  
Author(s):  
L. Zaluski ◽  
A. Zaluska ◽  
M. Kopcewicz ◽  
R. Schulz
Keyword(s):  
Heat Treatment ◽  
Magnetic Properties ◽  
Metallic Glasses ◽  
Structural Changes ◽  
Annealing Treatment ◽  
Electrical Current ◽  
Liquid Nitrogen Temperature ◽  
Alpha Phase ◽  
Thermal Spike ◽  
Electrical Currents

Fe–Ni–Si–B metallic glasses have been annealed and crystallized using short electrical current pulses. Two types of electrical heat treatment have been used. The first one is an isothermal annealing treatment using a very high initial heating rate while the second one is a thermal spike applied on an amorphous sample held at various initial temperatures. The microstructure of the alloys after heat treatment has been characterized by x-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy. The thermal and magnetic properties of the samples measured by DSC and hysteresis loop tracer have been studied after the various heat treatments and correlated with the microstructure of the alloys. The crystallization at high temperatures produces the gamma phase only, while at low temperatures, a mixture of the gamma and alpha phases (the alpha phase being predominant) is usually observed. The samples initially held at liquid nitrogen temperature and heat treated with a thermal spike remain amorphous and show improved magnetic properties (lower coercive field and higher induction at saturation) without loss of ductility.

scholarly journals Nanoscale strength distribution in amorphous versus crystalline metals

2010 ◽  
Vol 25 (12) ◽  
pp. 2251-2263 ◽  
Author(s):  
C.E. Packard ◽  
O. Franke ◽  
E.R. Homer ◽  
C.A. Schuh
Keyword(s):  
Yield Point ◽  
Metallic Glasses ◽  
Structural Changes ◽  
Thermal Fluctuations ◽  
Strength Distribution ◽  
Future Research ◽  
Transformation Zone ◽  
Crystalline Materials ◽  
Plastic Yield

Low-load nanoindentation can be used to assess not only the plastic yield point, but the distribution of yield points in a material. This paper reviews measurements of the so-called nanoscale strength distribution (NSD) on two classes of materials: crystals and metallic glasses. In each case, the yield point has a significant spread (10–50% of the mean normalized stress), but the origins of the distribution are shown to be very different in the two materials classes. In crystalline materials the NSD can arise from thermal fluctuations and is attended by significant rate and temperature dependence. In metallic glasses well below their glass-transition temperature, the NSD is reflective of fluctuations in the sampled structure and is not very sensitive to rate or temperature. Computer simulations using shear transformation zone dynamics are used to separate the effects of thermal and structural fluctuations in metallic glasses, and support the latter as dominating the NSD of those materials at low temperatures. Finally, the role of the NSD as a window on structural changes due to annealing or prior deformation is discussed as a direction for future research on metallic glasses in particular.

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