title: Accessing thermoplastic processing windows in metallic glasses using rapid capacitive discharge.
abstract: The ability of the rapid-capacitive discharge approach to access optimal viscosity ranges in metallic glasses for thermoplastic processing is explored. Using high-speed thermal imaging, the heating uniformity and stability against crystallization of Zr35Ti30Cu7.5Be27.5 metallic glass heated deeply into the supercooled region is investigated. The method enables homogeneous volumetric heating of bulk samples throughout the entire supercooled liquid region at high rates (~10(5) K/s) sufficient to bypass crystallization throughout. The crystallization onsets at temperatures in the vicinity of the "crystallization nose" were identified and a Time-Temperature-Transformation diagram is constructed, revealing a "critical heating rate" for the metallic glass of ~1000 K/s. Thermoplastic process windows in the optimal viscosity range of 10(0)-10(4) Pa · s are identified, being confined between the glass relaxation and the eutectic crystallization transition. Within this process window, near-net forging of a fine precision metallic glass part is demonstrated.
authors.affiliation: Keck Engineering Laboratories, California Institute of Technology, Pasadena, CA 91125.
authors.forename: Georg
authors.initials: G
authors.lastname: Kaltenboeck
authors.affiliation: Keck Engineering Laboratories, California Institute of Technology, Pasadena, CA 91125.
authors.forename: Thomas
authors.initials: T
authors.lastname: Harris
authors.affiliation: Keck Engineering Laboratories, California Institute of Technology, Pasadena, CA 91125.
authors.forename: Kerry
authors.initials: K
authors.lastname: Sun
authors.affiliation: Keck Engineering Laboratories, California Institute of Technology, Pasadena, CA 91125.
authors.forename: Thomas
authors.initials: T
authors.lastname: Tran
authors.affiliation: Keck Engineering Laboratories, California Institute of Technology, Pasadena, CA 91125.
authors.forename: Gregory
authors.initials: G
authors.lastname: Chang
authors.affiliation: Keck Engineering Laboratories, California Institute of Technology, Pasadena, CA 91125.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Schramm
authors.affiliation: Keck Engineering Laboratories, California Institute of Technology, Pasadena, CA 91125.
authors.forename: Marios D
authors.initials: MD
authors.lastname: Demetriou
authors.affiliation: Keck Engineering Laboratories, California Institute of Technology, Pasadena, CA 91125.
authors.forename: William L
authors.initials: WL
authors.lastname: Johnson