Plastic Instability Due to Collective Dislocation Effect in Portevin-Le Châtelier Effect and Dislocation Nucleation

Two manifestations of plastic instability, the Portevin-Le Châtelier (PLC) effect and the cooperative nucleation of dislocation loops, have been studied. In the experimental part of the work, two creep-type mechanical tests have been conducted on a Cu-10at.%Al single crystal and a Mg single crystal to study the plastic instability in the PLC effect and dislocation nucleation respectively. The deformation modes of Cu-10at.%Al single crystal at different temperatures or loading conditions have been further studied by optical microscope and transmission electron microscope observations. The distribution of solute atoms around a moving dislocation has been obtained for a finite system. The dynamic interaction between the diffusing solute atoms and a moving dislocation has been studied using the Kinetic Monte Carlo (KMC) simulation of tensile and creep tests. The importance of dislocation interaction in the plastic instability of the PLC effect has also been studied by using a multi-dislocation system. In the study of the cooperative dislocation nucleation, a new method has been developed to calculate the image stress in a finite sample, which has been subsequently used to calculate the mean field stress responsible for the constructive dislocation interaction between nucleating dislocation loops.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science and Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Gu, Xuemin

Contributors dc:contributor

• Bellon, Pascal

• Engineering, Metallurgy

Language dc:language

eng

Identifier

(MiAaPQ)AAI3223602

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/82779