Atomistic studies of dislocations in titanium and titanium-aluminum compound / Alexey Girshick.

Format:

Book

Manuscript

Microformat

Thesis/Dissertation

Author/Creator:

Girshick, Alexey.

Contributor:

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Materials science and engineering.

Materials science and engineering--Penn dissertations.

Local Subjects:

Penn dissertations--Materials science and engineering.

Materials science and engineering--Penn dissertations.

Physical Description:

xxiii, 246 pages : illustrations ; 29 cm

Production:

1997.

Summary:

The main thrust of the research presented in this thesis is atomistic studies of dislocations in crystalline materials using computer modeling. Dislocations affect many properties of materials and control their deformation behavior. The aim of this research is to establish the connection between the core structure of dislocations determined by computer modeling and the experimentally observed deformation modes. This thesis comprises two separate projects, employing similar methodology: studies of dislocations in L1$\sb0$ TiAl and in pure Ti. The former investigation is presented in Section A. Computer simulations were performed by molecular statics method using the Finnis-Sinclair type potential for Ti-Al alloys, which was constructed in the course of this work. The results of this study allowed us to propose an explanation for the deformation behavior of TiAl-based alloys, which has later received both theoretical and experimental support. The second part of the thesis (Section B) is concerned with studies of dislocations in the hcp Ti. The experimentally observed deformation mode in this material is slip in the prism plane, while previous computer modeling studies based on central-force potentials predicted the dominance of the slip in the basal plane. It was suggested that this phenomenon is an indication of strong directional bonding in Ti due to the presence of an unfilled d-band in this element. The study of dislocations and $\gamma$-surfaces were performed using both a central-force Finnis-Sinclair type potential and a bond-order potential, which includes the possible effects of directional bonding. The bond-order potential for Ti was constructed in the course of this work. This was the first application of this recently developed method to studies of extended defects in metals. The results of our study employing the bond-order potential unambiguously show that the prism slip is preferred in Ti. Analogous calculations using the central-force Finnis-Sinclair type potential predict the preference for the basal slip, in agreement with other central-force studies but in disagreement with experiment. Thus we have demonstrated that the prism slip observed in Ti is a consequence of the directional bonding of d-electrons in this material.

Notes:

Thesis (Ph.D. in Materials Science and Engineering) -- University of Pennsylvania, 1997.

Includes bibliographical references.

Local Notes:

University Microfilms order no.: 98-14848.

OCLC:

187456913