Activation volume in heterogeneous deformation of Mg65Cu12.5Ni12.5(Ce75La25)10 metallic glass

2015 ◽  
Vol 118 (20) ◽  
pp. 204302 ◽  
Author(s):  
Nicolas Thurieau ◽  
Loïc Perrière ◽  
Mathilde Laurent-Brocq ◽  
Yannick Champion
Keyword(s):  
Metallic Glass ◽  
Activation Volume ◽  
Heterogeneous Deformation

Change in Activation Volume for Plastic Deformation of Zr-based Bulk Metallic Glass following Annealing

2007 ◽  
Vol 1048 ◽  
Author(s):  
Jonathan B. Puthoff ◽  
Donald S. Stone ◽  
Hongbo Cao ◽  
Paul M. Voyles
Keyword(s):  
Plastic Deformation ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Activation Volume ◽  
Cast Alloy ◽  
Transformation Zone ◽  
Alloy Hardness ◽  
Shear Transformation ◽  
Shear Transformation Zone ◽  
The Individual

AbstractWe performed nanoindentation creep experiments on the bulk metallic glass Zr54Cu38Al8 in an effort to measure the scale of the individual deformation events responsible for plastic deformation. From a nanoindentation creep experiment, we can determine V*, the activation volume, which we interpret as the volume of a shear transformation zone (STZ) multiplied by the shear strain undergone by the STZ during thermal activation. For the as-cast alloy hardness, H, is 5.33 ± 0.06 GPa, and V* is 87 ± 5 Å3. The alloy was then annealed near Tg for 24 hr and retested. No crystallization occurred during annealing as verified by XRD and TEM. Following annealing H increased to 7.36 ± 0.08 GPa and V* increased to 160 ± 10 Å3. We interpret the change in V* as arising from an increase in the number of atoms involved in the STZ.

scholarly journals Analysis on Degradation in Creep Strength of 9Cr-W Martensitic Steel

2021 ◽  
Vol 10 (1) ◽  
pp. 1
Author(s):  
Manabu TAMURA
Keyword(s):  
Activation Volume ◽  
Martensitic Steel ◽  
Rupture Strength ◽  
Early Stage ◽  
Laves Phase ◽  
Creep Mechanism ◽  
Steel Grades ◽  
Time Parameters ◽  
Heterogeneous Deformation

In order to clarify the creep mechanism of high Cr martensitic steel, creep curves of 9Cr-1W and 9Cr-4W steels were analyzed applying an exponential law to the temperature, stress, and time parameters. The activation energy, Q, the activation volume, V, and the Larson-Miller constant, C, are obtained as functions of creep strain. At the beginning of creep, sub-grain boundary strengthening by swept dislocations out of sub-grains occurs followed by strengthening due to the rearrangement of M23C6 and the precipitation of Laves phase. After Q reaches a peak, heterogeneous recovery and subsequent heterogeneous deformation begin at an early stage of transient creep in the vicinity of some weakest boundaries due to coarsening of the precipitates, which triggers the unexpected degradation in strength due to the accelerating coarsening of precipitates. Stabilizing not only M23C6 but also Laves phase is important to mitigate the degradation of rupture strength of martensitic steel. The above creep mechanism for martensitic steel can be applicable to the explanation for the degradation in long term rupture strength of high Cr martensitic steel, Grades 91 and 92.

scholarly journals Correlation between High Temperature Deformation and β Relaxation in LaCe-Based Metallic Glass

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 833 ◽  
Author(s):  
Yinghong Chen ◽  
Jichao Qiao
Keyword(s):  
Glass Transition ◽  
High Temperature ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Strain Rate ◽  
Activation Volume ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Β Relaxation

High-temperature deformation around the glass transition temperature Tg and the dynamic mechanical behavior of La30Ce30Al15Co25 metallic glass were investigated. According to dynamic mechanical analysis (DMA) results, La30Ce30Al15Co25 metallic glass exhibits a pronounced slow β relaxation process. In parallel, strain-rate jump experiments around the glass transition temperature were performed in a wide range of strain rate ranges. The apparent viscosity shows a strong dependence on temperature and strain rate, which reflects the transition from non-Newtonian to Newtonian flow. At low strain or high temperature, a transition was observed from a non-Newtonian viscous flow to Newtonian viscous flow. It was found that the activation volume during plastic deformation of La30Ce30Al15Co25 metallic glass is higher than that of other metallic glasses. Higher values of activation volume in La30Ce30Al15Co25 metallic glass may be attributed to existence of a pronounced slow β relaxation. It is reasonable to conclude that slow β relaxation in La30Ce30Al15Co25 metallic glass corresponds to the “soft” regions (structural heterogeneities) in metallic glass.

Structural analysis of a binary metallic glass model. I. — The Pd80Si20 alloy

1985 ◽  
Vol 46 (2) ◽  
pp. 235-241 ◽  
Author(s):  
F. Lançon ◽  
L. Billard ◽  
J. Laugier ◽  
A. Chamberod
Keyword(s):  
Structural Analysis ◽  
Metallic Glass ◽  
Glass Model

Under Pressure: Mechanochemical Effects on Structure and Ion Conduction in the Sodium-Ion Solid Electrolyte Na3PS4

2020 ◽  
Author(s):  
Theodosios Famprikis ◽  
O. Ulas Kudu ◽  
James Dawson ◽  
Pieremanuele Canepa ◽  
François Fauth ◽  
...  
Keyword(s):  
Ionic Conductivity ◽  
Mechanochemical Synthesis ◽  
Activation Volume ◽  
External Pressure ◽  
Sodium Ion ◽  
Variable Pressure ◽  
Ion Conductor ◽  
Ceramic Synthesis ◽  
Solid State Batteries ◽  
Fast Ion

<div> <p>Fast-ion conductors are critical to the development of solid-state batteries. The effects of mechanochemical synthesis that lead to increased ionic conductivity in an archetypical sodium-ion conductor Na<sub>3</sub>PS<sub>4</sub> are not fully understood. We present here a comprehensive analysis based on diffraction (Bragg, pair distribution function), spectroscopy (impedance, Raman, NMR, INS) and <i>ab-initio</i> simulations aimed at elucidating the synthesis-property relationships in Na<sub>3</sub>PS<sub>4</sub>. We consolidate previously reported interpretations about the local structure of ball-milled samples, underlining the sodium disorder and showing that a local tetragonal framework more accurately describes the structure than the originally proposed cubic one. Through variable-pressure impedance spectroscopy measurements, we report for the first time the activation volume for Na<sup>+</sup> migration in Na<sub>3</sub>PS<sub>4</sub>, which is ~30% higher for the ball-milled samples. Moreover, we show that the effect of ball-milling on increasing the ionic conductivity of Na<sub>3</sub>PS<sub>4</sub> to ~10<sup>-4</sup> S/cm can be reproduced by applying external pressure on a sample from conventional high temperature ceramic synthesis. We conclude that the key effects of mechanochemical synthesis on the properties of solid electrolytes can be analyzed and understood in terms of pressure, strain and activation volume.</p> </div>

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