Title page for ETD etd-04262004-153825


Type of Document Dissertation
Author Hyde, Brian
URN etd-04262004-153825
Title Effects of Carbon on Fracture Mechanisms in Nanocrystalline BCC Iron - Atomistic Simulations
Degree PhD
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Farkas, Diana Committee Chair
Batra, Romesh C. Committee Member
Corcoran, Sean Gerald Committee Member
Kampe, Stephen L. Committee Member
Reynolds, William T. Jr. Committee Member
Keywords
  • fracture
  • Metals
  • grain boundaries
  • atomistic simulations
  • C
  • Fe
Date of Defense 2004-04-20
Availability unrestricted
Abstract
Atomistic computer simulations were performed using embedded atom method interatomic potentials in α-Fe with impurities and defects. The effects of intergranular carbon on fracture toughness and the mechanisms of fracture were investigated. It was found that as the average grain size changes the dominant energy release mechanism also changes. Because of this the role of the intergranular carbon changes and these mechanisms compete affecting the fracture toughness differently with changing grain size.

Grain boundary accommodation mechanisms are seen to be dominant in the fracture of nanocrystalline α-Fe. To supplement this work we investigate grain boundary sliding using the Σ = 5,(310)[001] symmetrical tilt grain boundary. We observe that in this special boundary sliding is governed by grain boundary dislocation activity with Burgers vectors belonging to the DSC lattice. The sliding process was found to occur through the nucleation and glide of partial grain boundary dislocations, with a secondary grain boundary structure playing an important role in the sliding process. Interstitial impurities and vacancies were introduced in the grain boundary to study their role as nucleation sites for the grain boundary dislocations. While vacancies and H interstitials act as preferred nucleation sites, C interstitials do not.

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