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Nanocrystalline copper-tantalum composites

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Title: Nanocrystalline copper-tantalum composites
Author(s): Savage, Howard Scott
Doctoral Committee Chair(s): Rigsbee, J. Michael
Department / Program: Physics, GeneralEngineering, MetallurgyEngineering, Materials Science
Discipline: Physics, GeneralEngineering, MetallurgyEngineering, Materials Science
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): Physics, General Engineering, Metallurgy Engineering, Materials Science
Abstract: This research investigated the physical metallurgy, high temperatures coarsening, and processing/structure relationships for Cu$\sb{\rm 1-x}$Ta$\sb{\rm x}$ (x = $\sim$5 to 20 atomic percent) alloys. These metastable alloys were produced using a plasma assisted physical vapor deposition (PAPVD) process which allowed ion bombardment during alloy deposition. Techniques used for structural and chemical analyses of these alloys include: transmission and scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction, microhardness, and sheet resistance. PAPVD processing parameters varied in this study included: ion bombardment, ion to depositing atom ratio, deposition rate, and alloy composition. Thermal processing variations included: annealing at 800 C for up to 100 hours and at 900 C for up to 10 hours and hot isostatic pressing (HIP) at 900 C for 1 hour and 172 MPa.This research successfully demonstrated that physical vapor deposition processes can "design" the microstructures of metastable Cu$\sb{\rm 1-x}$Ta$\sb{\rm x}$ alloys at the near atomic scale. These alloys consist of an essentially pure Cu matrix with a dispersion of discrete, nanoscale second phase particles. For as-deposited alloys: (1) the Cu matrix morphology was dependent on Ta content and ion bombardment and the film densities increased with decreasing Ta content and increasing ion bombardment and (2) the second phase particles consisted of bcc Ta, fcc Ta, and Ta oxide, the particle size was dependent on Ta content and ion bombardment, and the particles were mainly smaller than 10 nm. For annealed alloys: (1) annealing at 900 C for 10 hours altered only slightly the matrix morphology and showed that the second phase particles are effective at pinning Cu grain boundaries, consistent with the predictions of the Zener model; (2) the second phase particles remained bcc Ta, fcc Ta, and Ta oxide, with sizes still $<$10 nm; (3) oxygen incorporation into the growing coating stabilized the annealed particle sizes; (4) the matrix and second phase morphologies in HIPped alloys coarsened more in regions which underwent greater plastic strains; and, (5) Ta particle coarsening occurred by the Ostwald mechanism (annealed alloys) as well as collisional coalescence (HIPped alloys).
Issue Date: 1991
Type: Text
Language: English
URI: http://hdl.handle.net/2142/23694
Rights Information: Copyright 1991 Savage, Howard Scott
Date Available in IDEALS: 2011-05-07
Identifier in Online Catalog: AAI9136723
OCLC Identifier: (UMI)AAI9136723
 

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