Novel precipitate structures in alloys under irradiation

Shu, Shipeng

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https://hdl.handle.net/2142/88942 Copy

Description

Title

Novel precipitate structures in alloys under irradiation

Author(s)

Shu, Shipeng

Issue Date

2015-08-27

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

Bellon, Pascal

Doctoral Committee Chair(s)

Bellon, Pascal

Committee Member(s)

• Averback, Robert S
• Trinkle, Dallas R
• Zhang, Yang

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• self-organization
• irradiation

Abstract

We investigate the fundamentals of precipitate stability under energetic particle irradiation, towards the goal of better controlling the microstructures of driven alloys. First we focus on an irradiation-induced precipitatewithin- precipitate structure, which is referred to as “cherry-pit” structure. We show by computer simulation and analytical modeling that the formation of cherry-pit structure is a special instance of compositional patterning, and that the conditions for compositional patterning and the formation of cherry-pit structures are related, but different from each other. Then we develop a new kinetic Monte Carlo model, which includes the generation, recombination, and sink elimination of irradiation-induced point defects, as well as ballistic mixing. With this tool we explore the possibility of using point-defect sinks to alter the temperature range where compositional patterns are stable. This novel approach for optimizing radiation-resistant materials is then tested experimentally using a Cu-Ag-W model alloy. Lastly we show that the addition of a high density of W nanoparticles dramatically alters the coarsening behavior of precipitate-hardened Cu-Ag alloys. First, the nanoparticles suppress precipitate growth, but far more surprisingly they induce non-equilibrium Ag wetting layers on grain boundaries. This observation is explained using kinetic Monte Carlo simulations, which show that caging of Ag precipitates by the W nanoparticles suppresses their growth and drives the formation of the wetting layers.

Graduation Semester

2015-12

Type of Resource

text

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http://hdl.handle.net/2142/88942

Copyright and License Information

Copyright 2015 Shipeng Shu

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