Bulk Metallic Glasses XVII: Structures and Characterization
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 2:00 PM
February 27, 2020
Room: Marina Ballroom G
Location: Marriott Marquis Hotel
Session Chair: Takeshi Egami, University of Tennessee; Jamie Kruzic, University of New South Wales (UNSW Sydney)
2:00 PM Invited
High Pressure Quenched Metallic Glasses: Wojciech Dmowski1; Stanislaw Gierlotka2; Geunhee Yoo3; Hui Wang1; Yoshihiko Yokoyama4; Eun Soo Park3; Takeshi Egami5; 1University of Tennessee; 2Polish Academy of Science; 3Seoul National University; 4Tohoku University; 5Oak Ridge National Laboratiry
High Pressure Quenched (HPQ) glasses are prepared by quenching from the supercooled liquid under hydrostatic pressure and decompression at RT. The HPQ samples have a different structure and higher density, and mirror the pressure induced structure in the liquid state. The data suggest that pressure induces a phase transition in the supercooled liquid. HPQ glass sample transforms back to the structure, quenched without pressure by annealing near Tg. Volume expansion studies show volume relaxation upon reaching Tg. The HPQ glasses exhibit larger value of Young modulus and microhardness revealed by nanoindentation and static compression examinations. Interestingly the yield stress is also increased. The DSC studies suggest high activation volume during transformation from the HPQ structure to the “equilibrium” glass. TEM examination of the partially crystallized samples reveal unexpected microstructures induced by crystallization under pressure.Supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Science and Engineering Division.
2:20 PM Invited
Microstructural, Mechanical and Thermal Characterization of Mg65Ni25Y5M5 (M= Si, B, La) Amorphous Alloy by Melt Spinning: Celal Kursun1; Dan Thoma1; John Perepezko1; 1University of Wisconsin, Madison
Mg65Ni25Y5M5 (M= Si, B, La) alloys were synthesized by melt spinning at a wheel speed of 55 ms-1. Structural evolutions, thermal behaviors and mechanical properties of these alloys were systematically characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), flash differential scanning calorimetry (Flash DSC) and Vickers microhardness (HV). The XRD, SEM and TEM results revealed that the melt spun ribbons have an amorphous structure. According to Flash DSC results, the amorphous Mg65Ni25Y5M5 (M= Si, B, La) alloys exhibited a distinct glass transition temperature (𝑇𝑔) and a wide supercooled liquid region (Δ𝑇𝑥 = 𝑇𝑥 − 𝑇𝑔) before crystallization. The 𝑇𝑔 ranges from 199-223 ˚C for the different M components and Δ𝑇𝑥 ranges from 61-72 ˚C. The microhardness of the as-quenched ribbons was measured in the range of 315 HV – 336.8 HV.
2:40 PM Invited
Role of Heterogeneous Microstructure Modifications in Affecting Fracture Toughness of Zr-based Bulk Metallic Glasses: Jamie Kruzic1; Bosong Li1; Bernd Gludovatz1; Anna Ceguerra2; Keita Nomoto1; Simon Ringer2; Shenghui Xie3; Sergio Scudino4; 1University of New South Wales; 2University of Sydney; 3Shenzhen University; 4IFW Dresden
Cold rolling and cryogenic thermal cycling were used to manipulate heterogeneous glassy microstructures and fracture toughness in Zr-based BMGs. Thermal cycling raised the fracture toughness of a Zr-Cu-Ni-Al-Nb BMG by promoting plastic deformation and stable crack growth, with the most significant increase occurring in the first 20 thermal cycles. 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 apparently unchanged. Two-dimensional cold rolling the samples prior to thermal cycling reduced the scatter in fracture toughness compared to as-cast thermal cycled samples. One-dimensional cold rolling of a Zr-Ti-Cu-Ni-Al BMG was found to induce both heterogeneous hardening and softening in the microstructure, and create considerable anisotropy to the fracture toughness. Transmission electron and atom probe microscopy studies are underway to understand the nanostructural nature of the observed heterogeneities.
3:00 PM
X-ray Diffraction Study of the Local Topological Rearrangement and Plasticity of Bulk Metallic Glasses: Hui Wang1; Wojciech Dmowski1; Zengquan Wang1; Yoshihiko Yokoyama2; Hongbin Bei3; Takeshi Egami1; 1University of Tennessee; 2Tohoku University; 3Oak Ridge National Laboratory
The study of the room temperature (RT) plasticity of bulk metallic glasses (BMGs) is essential since the RT plasticity is Achilles' Heels of BMGs that limits their applications. Due to the intrinsic disordered structure, contrary to the well-defined defects in crystalline materials such as dislocations, the defects in metallic glasses (MGs) are just qualitatively described. It’s well established that “elastic” deformation of BMG is locally heterogenous and non-affine because of the local topological rearrangement (LTR) which is related to the emerging shear transformation zones (STZs) that control the nature of the plastic deformation during yielding. In this paper, the LTR is quantified by the local plasticity parameter, ε_0/ε_∞ , proposed through the in-situ high-energy X-ray diffraction of BMGs under compression and the anisotropic pair distribution function (PDF) analysis. The correlation between the microscopic structural correspondence of the elastic deformation and the macroscopic plastic behavior of BMGs is established.
3:20 PM Break
3:40 PM
Local Dynamics in Metallic Liquids Studied by Inelastic Neutron Scattering: Zengquan Wang1; Wojciech Dmowski1; Hui Wang1; Takeshi Egami1; 1University of Tennessee
Local dynamics in liquid metals has been poorly understood when compared to their crystalline counterparts. For instance, the atomistic origin of the viscous behavior is not well elucidated, even though viscosity is one of the most basic properties for liquids. In this research, inelastic neutron scattering (INS) experiments were carried out on various metallic liquid droplets (including single, binary, and complex BMG forming liquids), using an electro-static levitator, at different temperatures at SNS. The dynamic structure function S(Q,E) and the Van Hove correlation function G(r,t) were then obtained. Compared with MD simulation results, the local configuration change was analyzed based on distinct G(r,t) and proved as the elementary excitation in high temperature metallic liquids, thus controlling their shear viscosity. Also, self diffusion behaviors were analyzed based on self G(r,t). A comprehensive understanding of the local dynamics was made in various metallic liquids.
4:00 PM
Mechanical Deformation of Iron-based in situ Metallic Glass Matrix Composites: Arash Yazdani1; Darren Dewitt1; Wei Huang2; Günther W.H. Höhne3; Scott T. Misture4; Javier E. Garay1; David Kisailus2; Olivia Graeve1; 1University of California, San Diego; 2University of California, Riverside; 3Ulm University; 4Alfred University
SAM2×5 is an amorphous steel with a chemical composition of Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. In this study, dense samples were prepared using the spark plasma sintering technique at varying temperatures ranging from 615 to 675°C. Room and high temperature X-ray diffraction results showed that increasing the SPS temperature resulted in the devitrification of mainly carbide-based phases from the amorphous matrix. TEM observations showed that crystalline phases with sizes of less than 20 nm are uniformly distributed within the amorphous matrix. The crystallinity of the sintered samples was calculated using a novel differential scanning calorimetry-based technique, spanning from 21 wt.% to 82 wt.%. The average macro- and micro-compressive strength values ranged between 1.7 and 2.2 GPa, respectively, and were independent of sintering temperature. Moreover, brittle fracture along with formation of shear bands were identified as the failure mechanism.
4:20 PM Invited
Atomic Structural Features Hidden in Structure Factor of Metallic Alloy Liquids: Chae Woo Ryu1; Wojciech Dmowski1; Takeshi Egami1; 1University of Tennessee
Disordered atomic structures in metallic liquids and glasses are difficult to characterize for their structural features owing to the absence of long ranged translational periodicity. To unravel an enigmatic problem, neutron and X-ray diffraction experiments of metallic glasses have been carried out, it is therefore anticipated that the first diffraction peak of the structure factor, S(Q), carries significant information about order in metallic glasses. In the present study, we use high energy X-ray scattering and electro-static levitation in combination with molecular dynamics simulation and suggest that the shape of the first peak of S(Q) of metallic alloy liquids show specific features in the structure of a system. We found that the first peak shape of S(Q) reflects diversity in atomic sizes, structural coherence length, and the closeness to the ideal glass state, which allows us to understand the inherent nature of structural disorder in metallic system.
4:40 PM Cancelled
Glass-forming Ability and Atomic Packing Structure of Al-TM-RE Amorphous Alloys: Jinfu Li1; 1Shanghai Jiao Tong University
Al-TM-RE (TM—transition metals, RE—rare earth elements) amorphous alloys with high Al contents (>80at.%) exhibit high strength in combination with good ductility and corrosion, which make them promising as structural materials. In this paper, the glass-forming ability (GFA) of the alloys with TM=Ni, Co and RE= La, Y, Ce, Gd, Dy was carefully determined by suction casting wedge-shaped samples under identical conditions and the atomic packing structure was studied using the extended X-ray absorption fine structure (EXAFS) technique. It is found the optimal glass-forming composition varies with the type of TM but seldom influenced by the type of RE. Unlike Ni-centered clusters that connect each other through sharing faces and edges, Co-centered clusters tend to share vertexes and edges with the surrounding clusters, due to which more Al atoms are required for the optimal glass-forming composition of Al-Co-RE systems.