Structural and Mechanical Property Investigation of Metallic Glasses

Amir Rezvan

Research output: ThesisDoctoral Thesis

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The structure-mechanical property relationships of bulk metallic glass (BMG) systems are assessed at various testing domains. By applying a series of materials science concepts, extensive characterization is achieved conveying information about thermo-mechanically driven structural relaxation and crystallization behavior in specific groups of advanced glassy multicomponent systems. In detail, the following studies of selected groups of alloys were carried out: The influence of severe plastic deformation (SPD) prompted by high-pressure torsion (HPT) and isothermal heat treatment (HT) below the glass transition on the structure-property relationships of Cu46Zr46Al8 BMG is investigated separately and alternately in reference to the as-cast state. Controlled crystallization is attained through HT, and HPT was employed afterwards to disperse crystals throughout the glassy matrix. The dispersion of the second phase enhances the thermomechanical stability around the super cooled liquid region. The viscoelastic behavior of four different bulk metallic glass BMG systems, i.e., Cu46Zr46Al8, Cu44Zr44Al8Co4, Cu44Zr44Al8Hf4, and Cu44Zr44Al8Co2Hf2, was investigated concerning its deformation-mode dependence via dynamic mechanical analysis (DMA) in 3-point bending (TPB), tension, and torsion modes. Crystallization decreases the viscoelastic contribution, whereas plastic deformation leads to an increase in atomic mobility. Compared to Cu46Zr46Al8, 4 at. % Co addition in the Cu46¿x/2Zr46¿x/2Al8Cox amorphous alloy leads to a glass showing relatively higher thermomechanical stability around its glass transition. Ti40Zr10Cu36Pd14 BMG is envisioned as an oral implant material and its performance was evaluated in comparison with the gold standard Ti¿6Al¿4V implant material. DMA showed that these materials can be thermomechanically shaped into implants. High-resolution transmission microscopy and X-ray photoelectron spectroscopy revealed the formation of a 15 nm thin copper oxide layer on Ti40Zr10Cu36Pd14 BMG. Unlike titanium oxide formed on Ti¿6Al¿4V, copper oxide is hydrophobic, and its formation reduces the surface wettability. A lower surface colonization of bacteria is confirmed by field emission scanning electron microscopy and fluorescent images. The prospects of Ti40Zr10Cu36Pd14 BMG as oral implant material are advanced in the aspects of processing and structure-dependent mechanical performance. Insights into possible processing routes are provided, where high-temperature compression molding via an optimized process was adopted to both evaluate the thermoplastic net-shaping kinetics and tune the specific properties of the alloy. Processed BMGs and BMG composites of the same composition exhibit improved thermomechanical stability, from which high strength retention at temperatures, compared to the cast glass, by above 100 K higher is registered via dynamic mechanical analysis.
Translated title of the contributionStrukturelle und Mechanische Eigenschaftsuntersuchung von Metallischen Gläsern
Original languageEnglish
Awarding Institution
  • Montanuniversität
  • Bera, Supriya, Assessor B (external), External person
  • Eckert, Jürgen, Supervisor (internal)
  • Sifferlinger, Nikolaus August, Co-Supervisor (internal)
  • Stockinger, Martin, Assessor A (internal)
Publication statusPublished - 2023

Bibliographical note

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  • Bulk metallic glasses
  • Structure
  • Deformation
  • Mechanical properties
  • Viscoelastic behavior
  • Oral implant
  • Bioactivity

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