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https://hdl.handle.net/2142/22759
Description
Title
Radiation damage in nickel(3) aluminum
Author(s)
Bui, Tho Xuan
Issue Date
1995
Doctoral Committee Chair(s)
Robertson, Ian M.
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Condensed Matter
Engineering, Metallurgy
Engineering, Materials Science
Language
eng
Abstract
The ordered intermetallic Ni$\sb3$Al was used in two series of experiments that were designed to elucidate both fundamental and practical aspects of radiation damage. The first is a Transmission Electron Microscopy investigation of cascade damage under heavy ion irradiation; the second is a radiation induced segregation study. For the first topic, the cascade generated damage structure (namely, disordered zones and dislocation loops) were examined as a function of ion mass (Ar$\sp+$, Kr$\sp+$, Xe$\sp+$), ion energy (30 and 50 keV), and irradiation temperature (30, 300, 350 and 400K). At room temperature and at constant ion energy, the average size of the disordered zones increases with increasing ion mass. At room temperature and at constant ion mass, the zone size increases with increasing energy; but only for the heavier Xe+ ions. At 30K, for the same ion mass and ion energy, the size of the disordered zones was smaller than at room temperature. When the irradiation temperature was increased to 400K, the disordered zone size was also found to be smaller than that obtained from the room temperature irradiations. The zones were found to increase in size with increasing ion mass, similar to the trend observed with the room temperature irradiation.
For all irradiation temperatures, the dislocation loop yield shows the same trends as the disordered zone size: the yield increases with increasing energy and increasing ion mass. The loop yield is also lower for irradiations at 30K and 400K than at 300K and 350K. It was found that while there is a correlation between the size of the disordered zones, larger disordered zones did not necessarily produce larger dislocation loops. An interpretation of these results in terms of current computer modeling for the formation of disordered zones and dislocation loops will be presented.
Surface segregation studies using Auger electron spectroscopy were performed in order to investigate the effects of Radiation Induced Segregation (RIS) on Ni$\sb3$Al. The results showed that Ni$\sb3$Al has a strong resistance to RIS. TEM analysis of the microstructure under irradiation suggests that the resistance to segregation is due to a dense and stable dislocation network that exists within the irradiated region throughout the temperature range at which RIS is expected to occur. This dislocation network competes against the surface as a point defect sink, preventing the long-range migration of point defects that is necessary for RIS to occur. The nature of the dislocation network suggests a strong influence of ordering energy on the stability of the dislocations.
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