Bulk Metallic Glasses XVIII: Structures and Mechanical Properties
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Yanfei Gao, University of Tennessee-Knoxville; Hahn Choo, University of Tennessee; Yunfeng Shi, Rensselaer Polytechnic Institute; Robert Maass, Federal Institute of Materials Research and Testing (BAM); Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical
Thursday 8:30 AM
March 18, 2021
Room: RM 7
Location: TMS2021 Virtual
Session Chair: Jamie Kruzic, University of New South Wales; Xie Xie, FCA US LLC
8:30 AM Invited
Microstructure - Fracture Toughness Relationships in Bulk Metallic Glasses: Jamie Kruzic1; Bosong Li1; Bernd Gludovatz1; Anna Ceguerra2; Keita Nomoto1; Simon Ringer2; Shenghui Xie3; Sergio Scudino4; 1University of New South Wales; 2The University of Sydney; 3Shenzhen University; 4IFW Dresden
Cold rolling and cryogenic thermal cycling were used to create heterogeneous glassy microstructures in Zr-based bulk metallic glasses (BMGs). Thermal cycling raised the fracture toughness of a Zr-Cu-Ni-Al-Nb BMG by promoting plastic deformation and stable crack growth. Microhardness mapping revealed a microstructure of hard and soft domains (~63 μm × 105 μm), and thermal cycling heterogeneously softened the hard domains while the soft domains remained unchanged. Multi-directional cold rolling samples prior to thermal cycling reduced the scatter in fracture toughness. One-directional (1-D) cold rolling of a Zr-Ti-Cu-Ni-Al BMG induced both hardening and softening in the microstructure with a heterogeneous distribution that depended on the rolling orientation. Accordingly, considerable anisotropy was found for the fracture toughness of the 1-D rolled samples. Transmission electron microscopy, synchrotron x-ray, and atom probe microscopy studies are underway to understand the nanostructural nature of the observed hard and soft microstructure heterogeneities.
8:55 AM Invited
Structural Heterogeneities Dictate Strength and Fracture Toughness in a Zr-based Metallic Glass: Bernd Gludovatz1; Lisa Krämer2; Bosong Li1; Anton Hohenwarter3; Jamie Kruzic1; 1UNSW Sydney; 2ESI-Leoben; 3Montanuniversität Leoben
The excellent combination of properties like high strength, low stiffness, and large elastic strain limits make bulk-metallic glasses (BMGs) candidate materials for many structural applications. Major drawbacks for their use in engineering fields are highly variable fracture toughness values and limited ductilities. Here, we will show how precise heat-treatments and structural modifications through high-pressure torsion (HPT) can be used to specifically tailor the microstructure of the glass Zr52.5Cu17.9Ni14.6Al10Ti5 (Vitreloy 105). Using maps of small load Vickers hardness indents we identify soft and hard regions in the glass and correlate their distribution with the material’s stress-strain behavior in tension. We furthermore identify clearly distinguishable failure characteristics in fracture toughness tests using the as-cast, annealed and HPT-deformed samples. Our results clearly indicate the potential of thermo-mechanical processing to alter the mechanical properties of metallic glasses and provide a pathway to improved damage tolerance in these materials.
9:20 AM Invited
Mechanical Behavior and Phase Stability of Ductile Metallic Glass Nanoparticles: Wendy Gu1; Mehrdad Kiani1; Abhinav Parakh1; 1Stanford University
The properties of metallic glasses are highly dependent on fabrication and processing methods. Here, we use colloidal synthesis to make nickel-boron metallic glass nanoparticles with tunable size, composition and mechanical behavior. These nanoparticles are found to have high ductility and homogeneous deformation at room temperature. In situ transmission electron microscopy compression testing reveals that nanoparticles either deform homogeneously, or through a slowly propagating slip event reminiscent of shear banding. Scanning electron microscope compression testing shows that nanoparticles of 89 to 263 nm in size show an inverse size effect, in which larger nanoparticles are more likely to exhibit homogeneous deformation, while smaller nanoparticles are more likely to exhibit shear banding. Phase stability at high pressure are investigated by placing nanoparticles inside of a diamond anvil cell, compressing the particles to ~10 GPa pressure and performing in-situ X-ray diffraction. At elevated pressures, the nanoparticles form a hexagonal close-packed crystalline phase.
9:45 AM Invited
Microscopic Description of Plasticity, Relaxation and Rejuvenation Using Anelastic Relaxation Spectra: Michael Atzmon1; Tianjiao Lei2; Luis Rangel DaCosta3; 1University of Michigan; 2University of California, Irvine; 3University of California, Berkeley
Metallic glasses can exist in many structural states, with variable properties. While the fictive temperature or enthalpy are useful parameters that describe those states, they don’t describe them uniquely. At the same fictive temperature, different behavior, e.g., enthalpy, deformation or magnetic properties, is observed. Using anelastic relaxation measurements over ~10 orders of magnitude of time, we obtain time constant spectra, which contain a wealth of information. They contain distinct peaks, fitted well by a model of thermally activated shear transformation zones, exhibiting a quantized hierarchy of shear transformation zones (STZs). Both alpha and beta relaxation are part of this hierarchy, but correspond to different nanoscale domains or different local STZ compositions. Furthermore, in contrast to common assertions, the alpha relaxation is not intrinsically irreversible – rather, it is fully reversible at small strain. The results will be used to provide microscopic descriptions of rejuvenation and plasticity. Funding: NSF Grant DMR-1708043
10:10 AM
Competing Effects of Topology and Chemical Bonding on Mechanical Properties of Metallic Glasses: Vrishank Jambur1; Chaiyapat Tangpatjaroen1; Jianqi Xi1; Meng Gao1; John Perepezko1; Izabela Szlufarska1; 1University of Wisconsin - Madison
While minor alloying is used extensively to manipulate mechanical properties of metallic glasses (MGs), a mechanistic understanding of this effect is still lacking. Presently, minor alloying effects on mechanical properties are explained in terms of the effect of the alloying elements on the packing efficiency of atoms and topological order without much emphasis on the effect of chemical interactions between the atoms. Using nanoindentation experiments and atomistic simulations, we demonstrate that minor alloying Al-Sm MGs with transition metals can increase their mechanical strength by changing the strength of chemical bonds alone. We show that this strengthening is distinct from changes in topological order and in fact it can occur despite the fact that the alloying element decreases topological order. This finding demonstrates that the effects of topology and chemistry on mechanical properties of MGs can compete with each other and that they should be understood as separate, sometimes competing mechanisms.