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Stochastic studies of dislocation mo...

Deo, Chaitanya Suresh.

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Stochastic studies of dislocation mobility in BCC alloys.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Stochastic studies of dislocation mobility in BCC alloys./
Author:	Deo, Chaitanya Suresh.
Description:	193 p.
Notes:	Source: Dissertation Abstracts International, Volume: 64-09, Section: B, page: 4591.
Contained By:	Dissertation Abstracts International64-09B.
Subject:	Engineering, Materials Science. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3106046

Stochastic studies of dislocation mobility in BCC alloys.
Deo, Chaitanya Suresh.

Stochastic studies of dislocation mobility in BCC alloys. - 193 p.

Source: Dissertation Abstracts International, Volume: 64-09, Section: B, page: 4591.

Thesis (Ph.D.)--University of Michigan, 2003.

The interaction of dislocations and solute atoms is key to understanding crystal plasticity in alloys. I present a kinetic Monte Carlo (kMC) simulation of the glide of a screw dislocation in the presence of substitutional atoms. The dislocation motion is represented by the kink diffusion model, which explicitly includes double kink nucleation, kink migration and kink-kink annihilation. The rates at which these unit processes occur are calculated using parameters obtained through ab initio and molecular dynamics simulations. Nucleation of a stable double kink on a dislocation takes a long time leading to inefficient simulations. I present a novel method to integrate over the initial sub-critical double kink formation events. The method involves calculation of the first passage time for a temporally homogenous discrete state Markov process. Such an approach may be used in other situations involving the consideration of fast events in kMC simulations, which may otherwise lead to computational bottlenecks. Incorporation of such a first passage time analysis is key to efficient simulations in the present case. Simulations at several solute concentrations and a range of stresses and temperatures are performed for the case of a screw dislocation in bcc tantalum and molybdenum. The effects of the operating parameters such as the temperature and applied stress on the velocity of the dislocation are represented as mobility laws. Effect of different types of short- and long-range solute dislocation interactions on these mobility laws is studied by the kMC simulations. These mobility laws can then be used in Dislocation Dynamics (DD) simulations that parameterize the dependence of dislocation velocity on operating parameters and solute concentrations in alloys. Thus, the kMC method described here can be employed to bridge the length and time scales between the atomic scale simulations that operate on the order of pico-seconds and large scale dislocation dynamics simulations of crystal plasticity.Subjects--Topical Terms:

1017759
Engineering, Materials Science.

Stochastic studies of dislocation mobility in BCC alloys.
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100 1 $a Deo, Chaitanya Suresh. $3 1951958
245 1 0 $a Stochastic studies of dislocation mobility in BCC alloys.
300 $a 193 p.
500 $a Source: Dissertation Abstracts International, Volume: 64-09, Section: B, page: 4591.
500 $a Chair: David J. Srolovitz.
502 $a Thesis (Ph.D.)--University of Michigan, 2003.
520 $a The interaction of dislocations and solute atoms is key to understanding crystal plasticity in alloys. I present a kinetic Monte Carlo (kMC) simulation of the glide of a screw dislocation in the presence of substitutional atoms. The dislocation motion is represented by the kink diffusion model, which explicitly includes double kink nucleation, kink migration and kink-kink annihilation. The rates at which these unit processes occur are calculated using parameters obtained through ab initio and molecular dynamics simulations. Nucleation of a stable double kink on a dislocation takes a long time leading to inefficient simulations. I present a novel method to integrate over the initial sub-critical double kink formation events. The method involves calculation of the first passage time for a temporally homogenous discrete state Markov process. Such an approach may be used in other situations involving the consideration of fast events in kMC simulations, which may otherwise lead to computational bottlenecks. Incorporation of such a first passage time analysis is key to efficient simulations in the present case. Simulations at several solute concentrations and a range of stresses and temperatures are performed for the case of a screw dislocation in bcc tantalum and molybdenum. The effects of the operating parameters such as the temperature and applied stress on the velocity of the dislocation are represented as mobility laws. Effect of different types of short- and long-range solute dislocation interactions on these mobility laws is studied by the kMC simulations. These mobility laws can then be used in Dislocation Dynamics (DD) simulations that parameterize the dependence of dislocation velocity on operating parameters and solute concentrations in alloys. Thus, the kMC method described here can be employed to bridge the length and time scales between the atomic scale simulations that operate on the order of pico-seconds and large scale dislocation dynamics simulations of crystal plasticity.
590 $a School code: 0127.
650 4 $a Engineering, Materials Science. $3 1017759
650 4 $a Engineering, Metallurgy. $3 1023648
690 $a 0794
690 $a 0743
710 2 0 $a University of Michigan. $3 777416
773 0 $t Dissertation Abstracts International $g 64-09B.
790 1 0 $a Srolovitz, David J., $e advisor
790 $a 0127
791 $a Ph.D.
792 $a 2003
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3106046