Bulk Metallic Glasses XIV: Poster Session
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Hahn Choo, University of Tennessee; Yanfei Gao, University of Tennessee; Yunfeng Shi, Rensselaer Polytechnic Institute; Xie Xie, The University of Tennessee; Gongyao Wang, The University of Tennessee; Jianzhong Jiang, Zhejiang University

Tuesday 6:00 PM
February 28, 2017
Room: Hall B1
Location: San Diego Convention Ctr

L-24: Deformation Behavior of a Ti-Zr-based Bulk Metallic Glass Matrix Composite: Kevin Kaufmann1; Laura Andersen1; Kenneth Vecchio1; 1University of California, San Diego
    Research efforts into bulk metallic glasses have emphasized improving their mechanical properties via a variety of methods, one of which is the introduction of a ductile crystalline phase. This presentation will focus on controlling the volume fraction of the crystalline phase of in a bulk metallic glass matrix composite based on the system: Ti-Zr-Nb-Cu-Be-Sn, via composition and cooling rate control, and characterizing the impact of the degree of crystallinity on strain rate sensitivity and deformation mechanism. Bulk samples were fabricated via arc melting and subsequent suction casting. The resultant microstructures were investigated via optical microscopy and electron backscatter diffraction (EBSD). The dynamic behavior and fracture toughness were subsequently studied to determine if strain rate sensitivity is introduced due to the presence of the crystalline phase. This work serves to advance the understanding of bulk metallic glass matrix composites, particularly rate sensitivity, leading to optimized mechanical performance, and improved intrinsic toughness.

L-25: Effect of Annealing on the Magnetic Properties of Fe-based Amorphous Alloys: Song Yi Kim1; HyeRyeong On1; A Young Lee1; Hyun Ah Kim1; Min Ha Lee1; 1Kitech
    In this study, the effect of annealing on the soft-magnetic properties of Fe-based amorphous has been investigated with the crystallization of amorphous phase. Fe-based amorphous alloy and annealed samples were fabricated by Arc melting, melt-spinning and followed heat treatment at 450~500℃. The as-prepared amorphous ribbons were analyzed by DSC to observe crystallization behavior. Annealed ribbon samples were characterized by X-ray diffraction using X-ray diffractometer with Cu-Kα radiation. Magnetic properties were measured by a vibration sample magnetometer. The saturated magnetic flux density of the ribbon increased up to 2.5T by annealing compared with the of amorphous ribbon before annealing due to nucleation of α-Fe phase.

L-26: Micro-imprinting of High Strength Hf-based Bulk Metallic Glass Using by Athermal Method: Song Yi Kim1; Min Ha Lee1; 1Korea Institute of Industrial Technology
    We presents that micrometer scale patterning of a typical brittle metallic glass alloy and transferring patterns on Cu foil and another metallic glass by imprinting technique. As demonstrated by experiments in current study, it is possible by cold-plastic forming which can show good micro-viscous deformability at room temperature without thermal energy. Plastic forming of high strength metallic glass alloys at room temperature resulting from the homogeneous flow of typical brittle metallic glass alloy is very important when considering engineering applications.

L-27: Phase Separation in Cu47.5Zr48Al4Co0.5 Bulk Metallic Glass: William Rainforth1; Haiyun Wang1; 1The University of Sheffield
    Liquid phase separation as a strategy to develop bulk metallic glass with large plasticity, has been studied in several systems, including CuZr-based BMG system. It was stated that structural heterogeneity could not only lead to multiplication of shear bands, but also could block the propagation of shear bands during deformation. In most circumstances, phase separation can be introduced into the system by adding alloying elements with a positive enthalpy of mixing with other constituents. Co has a small positive enthalpy of mixing with Cu (ΔHCo-Cu=+6kJ/mol) and has a large negative enthalpy of mixing with Zr (ΔHCo-Zr=-41kJ/mol). Thus, it is probable that this will induce phase separation in Cu-Zr-Al-Co quaternary system. Liquid phase separation in Cu47.5Zr48Al4Co0.5 was investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM) and nanoindentation. Phase separation and CuZr B2 phase results in enhanced plasticity and work hardening.

L-28: Solid-state Amorphization of W-containing Alloy Powders: Young Jun Kwon1; Christopher A Schuh2; Hoon Kwon1; Ki Sub Cho1; 1Kookmin University; 2MIT
    An alloy comprising nanocrystals of W embedded within an amorphous matrix was prepared by high-energy ball milling. When the powder samples were heated into the super-cooled liquid region of the amorphous matrix, the remaining, crystalline portions of the sample were found to fully amorphize. This result was found to be closely related to carbon diffusion within the powder, and amorphization of the W nanocrystals was analyzed in terms of the energetic difference between C-supersaturated W and the relaxed structure, as well as the constraints of kinetics

L-30: The Effects of Nitrogen Addition on the Magnetic Properties of Fe-based Amorphous Alloy: HyeRyeong Oh1; Minha Lee1; SONGYI Kim1; A-Young Lee1; Gyu Hyeon Park1; Hyun-ah Kim1; Jongryoul Kim2; 1KITECH; 2Hanyang University
    The magnetic properties of amorphous soft magnetic materials are attracted in the industrial application by their high magnetic saturation, low coercivity, and high permeability. The demand of amorphous soft magnetic materials has also increased dramatically and continuously in various IT industrial products, for example electromagnetic shielding and near field communication. In current study, effect of addition of nonmetallic elements such as Nitrogen, Boron, Phosphorous on Fe-based amorphous alloys in presented. The Fe-based amorphous alloy is good candidate materials due to the high saturation magnetic flux density. The magnetic property of Fe-based amorphous alloy was improved with increasing Nitrogen concentration by reducing magneto crystalline anisotropy and suppressing crystal grain growth. The Fe based alloy ribbon containing Nitrogen prepared by melt-spinning. The amorphous structure was analyzed by X-ray diffraction and the soft magnetic property was examined by vibrating sample magnetometer.

L-31: Thermal Induced Reversible Devitrification in Zr-Pt Binary Alloy: Hyun Ah Kim1; A Young Lee1; Hye Ryeong Oh1; Gyu Hyeon Park1; Song Yi Kim1; Ryan T. Ott2; Do Hyang Kim3; Min Ha Lee1; 1Korea Institute of Industrial Technology; 2Ames Laboratory (USDOE); 3Yonsei University
    Amorphous phases can be obtained by the liquid quenching technique based on the rapid cooling at a rate which is sufficient to bypass nucleation of crystalline phase. Crystallization due to devitrify of amorphous structure during the thermal annealing is common phenomenon because of the thermodynamic stability. However it was recently observed that amorphous phase can be formed by a solid state reaction of pure polycrystalline metals under isothermal conditions. In current study, unlike other typical metallic glassy alloys which show annealing induced devitrification, we report the annealing induced vitrification (or reversible devitrification) in amorphous ZrPt binary melt spun ribbons with effect of critical cooling rate on the formation of metastable phase. This reversible devitrification is clearly represented in a ZrPt alloy which transformed into amorphous structure from metastable nanocrystals due to the decomposition of quenched in metastable crystalline phase by the annealing process.

L-33: Extending the Realm of Glass Transition Temperature and Strength Relation in Metallic Glasses: Hehsang Ahn1; Jinwoo Kim1; Soyeon Kim1; Eun Soo Park1; 1Seoul National University
    The drawback in low thermal stability of metallic glasses has limited their applications as structural materials despite their high strength, wear and corrosion resistance. Glass transition temperature (Tg), which represents the thermal stability of a metallic glass, generally have a linear correlation with the yield strength (σy) of the alloy. Thus, the alloy design for the ascent of Tg to extremely high temperature is an effective way for developing a strong and thermally stable metallic glass. Here, we developed novel refractory metal-based metallic glasses with high Tg over 1000 K and σy exceeding 5 GPa. The Tg and σy of the alloys were evaluated precisely by thermomechanical analysis and nanomechanical test, respectively. These unique metallic glasses lighten the unexplored realm of Tgy relation in metallic glasses, and have a large potential for applications in extremely harsh environment, such as a high-temperature wear-resistant coating materials.

L-34: Viscous Flow Densification during Spark Plasma Sintering of Fe Based Amorphous Alloy Powder: Tanaji Paul1; Sandip Harimkar1; 1Oklahoma State University
    Spark plasma sintering of Fe48Cr15Mo14Y2C15B6 amorphous alloy powder close to its glass transition temperature (Tg = 575 oC) at a high heating rate of 100 oCmin-1 led to enhanced viscous flow with simultaneous plastic deformation under applied pressure. This resulted in near fully dense compacts while higher temperatures increased stiffening with consequent reduction in densification rate. Following, two discrete stages of densification were revealed with viscous flow confirmed to be the mass transport mechanism upto 585 oC where a maximum densification rate of 0.0011 s-1 was attained. The estimated activation energy, 94.0 kJmol-1 was smaller than during non-isothermal viscous flow in the as cast alloy. Considering the role of heating rate on the above, investigations with 50, 100 and 150 oCmin-1 revealed a steady decrease not only in the temperatures of onset, end and maximum rates of densification but also in the activation energy from 76.2 to 55.2 kJmol-1.

L-35: Comparative Analysis of the Tribological Behavior of Hf-BMGs and Hf-crystalline Alloys: Manuel Abad1; Luke Mortimer1; Phil Meagher1; David Browne1; 1University College Dublin
    The use of bulk metallic glasses (BMG) in advanced material applications is known to improve the mechanical performance providing high strength and hardness values and relatively low Young’s modulus. The tribological properties of Zr-BMGs have been of great interest during the last few years; however, the tribological behavior of Hf-BMGs has not been reported yet. The synthesis, characterization and mechanical and tribological properties of different Hf-alloys are shown in this work. The selected samples, Hf58Cu20Ni16Ti6 and Hf48Cu29Ni10Al13, have been prepared by suction casting in an arc melter. The samples before and after the tribological tests were characterized by XRD, SEM and TEM. The mechanical properties were studied by means of Vickers Hardness. The friction coefficient and wear rates were evaluated and the debris was studied. A comparison of the obtained results based on the original amorphous or crystalline structure was made.