Understanding the Origin of Glass Forming Ability in Metallic Glasses

Author: Hoff, Andrew Taylor

Year: 2018

Degree: Dissertation (Ph.D.)

Advisor: Johnson, William Lewis

Committee Members: Fultz, Brent T.; Faber, Katherine T.; Greer, Julia R.; Johnson, William Lewis

Option: Materials Science

DOI: 10.7907/Z7Y5-0B62

Abstract

The glass forming ability of metallic glasses has been one of their most studied yet least understood properties. Crystal nucleation in a recently development Ni-based metallic glass was studied by undercooling in a DSC under a variety of conditions and showed stochastic very deep undercooling behavior. The glass forming ability of a family of Ni-based alloys was analyzed and was found to depend only on two experimentally accessible factors, the reduced glass transition temperature and the liquid fragility. Neutron scattering experiments showed that in two model glass formers vibrational entropy had essentially no change through the glass transition, demonstrating that the change in entropy through the glass transition is due almost entirely to configurational entropy. The configurational enthalpy of a pair of recently developed Pt-based metallic glasses show almost no change in the undercooled liquid between the liquidus and TTT-nose, demonstrating the inability of current models to explain the thermodynamics of supercooled liquids.

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