A Simple Physically Based Phenomenological Model for the Strengthening/Softening Behavior of Nanotwinned Copper

2015 ◽  
Vol 82 (12) ◽  
Author(s):  
X. Zhang ◽  
A. E. Romanov ◽  
E. C. Aifantis
Keyword(s):  
Grain Size ◽  
Constitutive Equation ◽  
Phenomenological Model ◽  
Temperature Effects ◽  
Atomistic Simulations ◽  
Gradient Plasticity ◽  
Size Dependent ◽  
Softening Behavior ◽  
Physically Based ◽  
Twin Thickness

A robust phenomenological model based on a modified size-dependent Voce-type constitutive equation is proposed to describe the dependence of strength on twin thickness, for nanotwinned copper (nt-Cu) polycrystals, in agreement with experiments and related atomistic simulations. A gradient plasticity argument is employed to determine the critical nanotwin thickness where the transition from Hall–Petch (HP) hardening to inverse Hall–Petch (IHP) softening occurs. Strain rate and temperature effects are also discussed. The proposed constitutive equation may be used for engineering design purposes by controlling the interplay between grain size and twin thickness.

Quasi Drift and Quasi Diffusion: A Grain size Dependent Polysilicon Tft Model

1999 ◽  
Vol 557 ◽  
Author(s):  
W. Eccleston
Keyword(s):  
Grain Size ◽  
Crystalline Silicon ◽  
Electrical Characteristics ◽  
High Current ◽  
Field Effect Mobility ◽  
Physical Processes ◽  
Potential Barriers ◽  
Size Dependent ◽  
Physically Based ◽  
Polysilicon Tft

AbstractMost of the models for Thin Film Transistors take no account of the way that electrons move across grain boundaries. The purpose of this work is to produce an analytical model, physically based, that takes account of both the change in height of the potential barriers that separate the grains, and the change of carrier density in the grains with gate voltage. The high current and subthreshold regions are treated. The model enables the change of field effect mobility with grain size and temperature to be determined. Two closed form expressions are provided which should be of value to both device and circuit designers, as well as providing insight to the physical processes occurring in such devices. They form a close analogy with the electrical characteristics of MOSFETs on crystalline silicon, diffusion and drift being replaced by quasi-diffusion and primary quasi-drift.

Grain-Size-Dependent Grain Boundary Deformation during Yielding in Nanocrystalline Materials Using Atomistic Simulations

JOM ◽  
2020 ◽  
Vol 72 (4) ◽  
pp. 1745-1754 ◽  
Author(s):  
Satish S. Rajaram ◽  
Ankit Gupta ◽  
Gregory B. Thompson ◽  
Jacob Gruber ◽  
Andrei Jablokow ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Atomistic Simulations ◽  
Size Dependent ◽  
Boundary Deformation

Gradient plasticity used for modeling extrinsic and intrinsic size effects in the torsion of Au microwires

2016 ◽  
Vol 25 (1-2) ◽  
pp. 53-56
Author(s):  
Xiaokun Wei ◽  
Avraam Konstantinidis ◽  
Chengzhi Qi ◽  
Elias Aifantis
Keyword(s):  
Grain Size ◽  
Sample Size ◽  
Plasticity Theory ◽  
Length Scale ◽  
Gradient Plasticity ◽  
Internal Length ◽  
Size Dependent ◽  
Internal Length Scale ◽  
Model Size ◽  
Phenomenological Coefficients

AbstractThe gradient plasticity theory proposed by Aifantis and coworkers has been successfully used to model size effect phenomena at the microscale and nanoscale, by introducing into the formulation an internal length scale associated with the phenomenological coefficients of the gradient plasticity model. In this paper, Aifantis’ gradient plasticity theory is applied to model the sample size-dependent torsion of thin wires, with a strain-dependent internal length scale as well as grain size dependence based on the Hall-Petch relationship. This study reveals that internal length scale is related with sample size and grain size, with such a connection determined by the ductility of the material.

Grain-size-dependent gas-sensing properties of TiO2 nanomaterials

2015 ◽  
Vol 211 ◽  
pp. 67-76 ◽  
Author(s):  
B. Lyson-Sypien ◽  
M. Radecka ◽  
M. Rekas ◽  
K. Swierczek ◽  
K. Michalow-Mauke ◽  
...  
Keyword(s):  
Grain Size ◽  
Gas Sensing ◽  
Sensing Properties ◽  
Size Dependent ◽  
Gas Sensing Properties ◽  
Tio2 Nanomaterials

Controlling Grain Size in Oxide Ceramics for Optimization of Strength and Wear Resistance

2012 ◽  
Vol 715-716 ◽  
pp. 703-710
Author(s):  
W.M. Rainforth ◽  
P. Zeng ◽  
L. Ma
Keyword(s):  
Grain Size ◽  
Sliding Wear ◽  
Second Phase ◽  
Alumina Ceramics ◽  
Size Dependent ◽  
Mild Wear ◽  
Accumulation Mechanism ◽  
Wear Transition ◽  
Magnitude Increase ◽  
Zirconia Toughened Alumina

t is well known that alumina ceramics undergo a time dependent wear transition during sliding wear. The transition, which is associated with 1-2 orders of magnitude increase in specific wear rate, involves a change from mild wear to intergranular fracture. The transition is strongly grain size dependent, with the time to the transition decreasing with grain size. However, there is a minimum grain size that can be achieved in fully dense alumina using commercially viable processing. Alternative strategies for reducing grain size and increasing toughness are through the addition of a fine second phase, with SiC and ZrO2being the most promising. The resultant composite not only has finer grain size, but also exhibits additional toughening mechanisms. This paper reports on the microstructural control in alumina, zirconia toughened alumina and alumina-silicon carbide composites. The grain size and residual stress distribution are related to the damage accumulation mechanism that occur during frictional contact, in particular the surface specific dislocation activity.

Modelling Discontinuous Dynamic Recrystallization Using a Physically-Based Model for Nucleation

2012 ◽  
Vol 715-716 ◽  
pp. 492-497 ◽  
Author(s):  
Darren G. Cram ◽  
Hatem S. Zurob ◽  
Yves J.M. Bréchet ◽  
Christopher R. Hutchinson
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Growth Models ◽  
Peak Stress ◽  
Physically Based Model ◽  
Size Evolution ◽  
Model Predictions ◽  
Physically Based ◽  
Pure Cu ◽  
State Stress

A physically-based model for nucleation during discontinuous dynamic recrystallization (DDRX) has been developed and is coupled with polyphase plasticity and grain growth models to predict the macroscopic stress and grain size evolution during straining. The nucleation model is based on a recent description for static recrystallization and considers the dynamically evolving substructure size. Model predictions are compared with literature results on DDRX in pure Cu as a function of initial grain size, deformation temperature and strain-rate. The characteristic DRX features such as single to multiple peak stress transitions and convergence towards a steady-state stress and grain size are quantitatively reproduced by the model.

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