Nanoscale self-organization in irradiated ternary alloys

Zhang, Xuan

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https://hdl.handle.net/2142/72996 Copy

Description

Title

Nanoscale self-organization in irradiated ternary alloys

Author(s)

Zhang, Xuan

Issue Date

2015-01-21

Director of Research (if dissertation) or Advisor (if thesis)

• Bellon, Pascal
• Averback, Robert S.

Doctoral Committee Chair(s)

Bellon, Pascal

Committee Member(s)

• Averback, Robert S.
• Zuo, Jian-Min
• Dillon, Shen J.

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Metal
• Alloy
• Nanoscale
• Self-organization
• Irradiation
• Transmission Electron Microscopy (TEM)
• Monte Carlo simulation

Abstract

Microstructural stability of nanostructured alloys under harsh environments such as high temperatures and high dose irradiation is a primary concern in the deployment of those materials for engineering applications. This thesis work explores several pathways to stabilize nanostructures in Cu-based ternary alloy systems, which contain a very small fraction of refractory alloying element (W) that is highly immiscible with Cu. Three systems with distinct interaction energies have been investigated. 1) In the Cu-Nb-W system, where Nb is moderately immiscible with Cu but is miscible with W, very stable Nb-rich core/W-rich shell nanoprecipitates form upon annealing, as a result of the competition between thermodynamics and kinetics of Nb and W in Cu. When samples are first subjected to room temperature irradiation, however, W-rich core/Nb-rich shell nanoprecipitates form instead. These nanoprecipitates display even stronger resistance to thermal coarsening, which is rationalized by the very high trapping efficiency of ramified W cores for Nb atoms. 2) In the Cu-Ag-W system, where Ag is moderately immiscible with Cu and is highly immiscible with W, compositional patterning, as a steady state of the system under irradiation, can be extended to much higher temperatures by first using room temperature irradiation to introduce W nanoprecipitates, which then serve as sinks for point defects during elevated temperature irradiation. 3) In the Cu-Ni-W system, where Ni is miscible with Cu with a small positive heat of mixing but tends to form compound with W, irradiation-induced W nanoprecipitates force the Ni atoms out of solution during annealing, forming Nb-W compound, and the system evolves towards the same steady state during room temperature irradiation, regardless of the initial state. The work contains both experimental and computational studies.

Graduation Semester

2014-12

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http://hdl.handle.net/2142/72996

Copyright and License Information

Copyright 2014 Xuan Zhang

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