Effects of Irradiation and Thermal Annealing on the Mechanical and Microstructural Properties of Bulk Metallic Glasses

Author

Jamieson Brechtl, University of Tennessee

Orcid ID

http://orcid.org/0000-0002-1739-4283

Date of Award

8-2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Energy Science and Engineering

Major Professor

Steven Zinkle

Committee Members

Peter Liaw, Maik Lang, Kurt Sickafus

Abstract

A series of ion irradiation and annealing experiments have been performed on Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ “BAM-11” and Cu₆₀Zr₂₀Hf₁₀Ti₁₀ bulk metallic glass (BMG) specimens to evaluate their irradiation- and temperature-induced microstructural and mechanical property evolution. These experiments covered four main themes, namely, ion irradiation, neutron irradiation, thermal annealing, and helium implantation. For the ion irradiations, samples were exposed to 9 MeV Ni and 5.5 MeV C ions at temperatures ranging from room temperature to 360 ^oC. For the Ni ion irradiations the samples were exposed to midrange (~1.5 m depth) doses of 0.5 and 10 displacements per atom (dpa), while the C ion irradiations samples were irradiated to a midrange dose of 0.5 dpa. For the neutron irradiations, samples were irradiated by neutrons (E > 0.1 MeV) at ~70 ^oC to fluences of 1.4 × 10²⁰ n/cm² and 1.4 × 10²¹ n/cm² (doses of 0.1 and 1 dpa). Thermal annealing experiments involved heating the samples to various temperatures ranging from 25 - 770 ^oC. For the helium implantation experiments, amorphous and partially crystallized BMGs were exposed to helium fluences of 2 × 10¹⁵ and 5 × 10¹⁵ cm^-2 . The mechanical property and microstructural characterization included nanoindentation, compression testing, bend testing, Xray diffraction (XRD), neutron diffraction, thermal desorption analysis (TDS), and nuclear reaction analysis. From the experiments, several important conclusions were obtained. The results of the XRD and nanoindentation characterizations of the ion irradiated and thermal annealed specimens indicate good stability during irradiation at 25 to 290 ^oC up to at least 10 dpa but suggest that the BAM-11 BMG is not suitable for irradiation environments where temperatures exceed 300 ^oC for prolonged periods of time. As for the neutron irradiation and thermal annealing experiments, significant softening was observed in the sample irradiated by neutrons, while postirradiation annealing led to a marked increase in hardening. Neutron diffraction results indicated vi that primary knock-on events caused rejuvenation (disordering) while annealing resulted in structural relaxation. The results of the TDS experiments found that for the lower He implantation fluence, He desorbed more quickly in the partially crystallized alloy, indicating a structural effect on the mobility of He.

Recommended Citation

Brechtl, Jamieson, "Effects of Irradiation and Thermal Annealing on the Mechanical and Microstructural Properties of Bulk Metallic Glasses. " PhD diss., University of Tennessee, 2019.
https://trace.tennessee.edu/utk_graddiss/5949