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Emerging Evidence of a Second Glass Phase in Strong to Ultra-Fragile Bulk Metallic Glass-Forming Liquids


Corona, Sydney Lea (2022) Emerging Evidence of a Second Glass Phase in Strong to Ultra-Fragile Bulk Metallic Glass-Forming Liquids. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9bvb-2d78.


This thesis compiles three experimental works that provide evidence for distinct bulk metallic glass (BMG) phases across a range of kinetic fragilities. Motivated by An et al.’s computational discovery of a secondary heterogeneous glass phase in pure Ag and binary AgCu and CuZr, the thesis reports the distinct glass phases in the high and ultra-high fragile regime with a tunable Pt80-XCuXP20 system, and the kinetically strong Ni71.4Cr5.64Nb3.46P16.5B3 (Ni208) BMG.

The high-fragility work utilizes direct measurement techniques for liquid configurational enthalpy as a function of temperature on anneal-equilibrated samples (Chapter 2). An apparent first-order glass-melting transition is revealed across kinetic fragilities ranging from m = 60 to over 90. The glass-melting temperature, Tgm, traverses up the ∆T region with increasing Cu content, X. A further experimental study of PtCuP explored the traditional and second glass phases to determine if they are in fact equivalent to the two glasses of An et al. (Chapter 3). Hardness data reveal that while the high-fragility samples grow the second glass during anneal, it forms in the ultra-fragile samples on quenching. Further, this apparent glass-melting transition is visible via traditional thermodynamic methods in ultra-fragile samples. For X = 20, where Tgm is in the inaccessible ∆T region, rapid capacitive discharge heating visualizes Tgm as well.

Investigation of a kinetically stronger Ni-based BMG connects the presence of the secondary glass to the embrittlement transition in Ni208 (Chapter 4). Inclusions are only present in embrittled samples, and are suppressed to lower temperatures when the initial melt is overheated above a critical toughening temperature. The inclusions show a heterogeneous structure and 30% increased hardness, similar to the computational Ag secondary glass phase.

These works provide compelling evidence for the existence of a secondary glass phase across the spectrum from strong to ultra-fragile glasses, and validates the initial computational discovery. This proves to be a significant work, as it presents direct experimental evidence of a novel phenomenon in metallic liquids, and presents a new solid-like glass phase.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Bulk Metallic Glass; BMG; Angell Kinetic Fragility; Strong; Tough; Fragile; notch fracture toughness; indentation; Calorimetry; Mechanics; Secondary Glass Phase; G-Phase; L-Phase; Inclusions;
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Johnson, William Lewis (advisor)
  • Samwer, Konrad (co-advisor)
Thesis Committee:
  • Fultz, Brent T. (chair)
  • Johnson, William Lewis
  • Samwer, Konrad
  • Goddard, William A., III
  • Schwab, Keith C.
Defense Date:28 April 2022
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Record Number:CaltechTHESIS:04132022-221839497
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 2. adapted for Chapter 4. adapted for Chapter 4.
Corona, Sydney Lea0000-0002-4962-619X
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14545
Deposited By: Sydney Corona
Deposited On:02 Jun 2022 19:51
Last Modified:08 May 2024 16:35

Thesis Files

[img] PDF (Full thesis) - Final Version
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[img] MS Excel (Supplemental Material including raw data for figures throughout the thesis.) - Supplemental Material
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