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Title: Computer simulations of martensitic transition in zirconium
Author: Pinsook, Udomsilp
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1999
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The martensitic transition in zirconium is a first order solid-to-solid transition which transforms from body-centred-cubic (bcc) to hexagonal close-packed (hcp) structure. By using a Finnis-Sinclair type many-body potential derived for zirconium and molecular dynamics (MD) methods, a large number of simulations have been studied with the implementation of Nosé-Hoover thermostat and Parrinello-Raman scheme. We found that the transition is a result of the instability of a transverse N-point phonon in the bcc lattice which can be stabilised by the large fluctuation of the anharmonic effect above the transition temperature via extra vibrational entropy. The transition temperature in our calculations is 1,333K. With the concept of 'local atomic structure', the microstructure can be studied at the atomic level. The kinetics of the transition is dominated by the strain energy. Stripes of (10?1) twins are formed as a consequence. The twins contain some stacking faults. Stacking faults play a major role in the splitting of partial dislocations in twins. After the martensitic microstructure is deformed, we found that the twinning deformation occurs by the aid of partial dislocations and the interchange of neighbouring atoms. The interchange of neighbouring atoms leads to the term 'plastic atoms'. We believe that these plastic atoms cause a microscopic irreversible process and the absent of the shape memory effect in zirconium.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available