Effect of Nonequilibrium Defects Due to Phase Transformation on Diffusion in Beta Zirconium

The effect of the hcp(--->)bcc phase transformation on the anomalous diffusion characteristics of bcc zirconium has been investigated in this study. ('113)Sn and ('59)Fe tracers were used to typify the diffusing nature of self- and fast-diffusing atoms. A differential measurement of diffusion in two samples was carried out under very different preannealing conditions but otherwise identical states of diffusion time and temperature. In the first set of experiments, one of the samples was annealed for lengthy periods of time ((TURN) 20-30 hours) at premelting temperatures ((TURN) 1550(DEGREES)C) prior to diffusion (at lower temperature in the bcc phase). This was done in an attempt to decrease the defect concentration produced by the phase transformation. During the second set of experiments, the sample was cycled three times through the phase transformation temperature ((TURN) 890(DEGREES)C) (hcp(--->)bcc(--->)hcp(--->)bcc), with a view to enhance the defect density due to phase changes. In both sets of experiments, the second sample was raised to the diffusion temperature directly. The relative diffusivities of two samples were measured by serial sectioning and counting techniques. Appropriate correction methods were derived, for each set, to identify the proper interface because of the unique sectioning problems encountered.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Metallurgical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Chelluri, Bhanumathi

• Engineering, Metallurgy

Language dc:language

eng

Identifier

(UMI)AAI8114400

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/68649