title: Sink property of metallic glass free surfaces.
abstract: When heated to a temperature close to glass transition temperature, metallic glasses (MGs) begin to crystallize. Under deformation or particle irradiation, crystallization occurs at even lower temperatures. Hence, phase instability represents an application limit for MGs. Here, we report that MG membranes of a few nanometers thickness exhibit properties different from their bulk MG counterparts. The study uses in situ transmission electron microscopy with concurrent heavy ion irradiation and annealing to observe crystallization behaviors of MGs. For relatively thick membranes, ion irradiations introduce excessive free volumes and thus induce nanocrystal formation at a temperature linearly decreasing with increasing ion fluences. For ultra-thin membranes, however, the critical temperature to initiate crystallization is about 100 K higher than the bulk glass transition temperature. Molecular dynamics simulations indicate that this effect is due to the sink property of the surfaces which can effectively remove excessive free volumes. These findings suggest that nanostructured MGs having a higher surface to volume ratio are expected to have higher crystallization resistance, which could pave new paths for materials applications in harsh environments requiring higher stabilities.
authors.affiliation: 1] Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843, USA [2] Department of Materials Science &Engineering, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Shao
authors.affiliation: School of Physics, Peking University, Beijing 100871, P.R. China.
authors.forename: Engang
authors.initials: E
authors.lastname: Fu
authors.affiliation: Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Lloyd
authors.initials: L
authors.lastname: Price
authors.affiliation: Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Di
authors.initials: D
authors.lastname: Chen
authors.affiliation: Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Tianyi
authors.initials: T
authors.lastname: Chen
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Xie
authors.affiliation: School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
authors.forename: Don A
authors.initials: DA
authors.lastname: Lucca