Atomistic Theory of Bulk Metallic Glass Formation

2002 ◽  
Vol 754 ◽  
Author(s):  
T. Egami
Keyword(s):  
Glass Transition ◽  
Metallic Glass ◽  
Cooling Rate ◽  
Bulk Metallic Glass ◽  
Glass Formation ◽  
Dynamics Simulation ◽  
Necessary Condition ◽  
Atomic Transport ◽  
Strong Repulsion ◽  
First Time

ABSTRACTBulk metallic glass can be formed only when the critical cooling rate for glass formation is reduced to 100–2 K/sec. However, a cooling rate achievable with molecular dynamics simulation is higher by many orders of magnitude, so the gap has to be abridged by analytical theories. We propose a theory of bulk metallic glass formation based upon our early theories of glass formation composition. The critical concepts include the idea of local glass transition, distributed local glass transition temperatures and coincident local fluctuation for atomic transport. Strong repulsion between small atoms was recognized for the first time as the necessary condition for bulk glass formation.

Effect of Compositional Short Range Order on Glass Formation in Binary Metallic System

2002 ◽  
Vol 754 ◽  
Author(s):  
Hao Chen ◽  
Mahadevan Khantha ◽  
Takeshi Egami
Keyword(s):  
Glass Transition ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Glass Formation ◽  
Short Range ◽  
Short Range Order ◽  
Glass Forming Ability ◽  
Range Order ◽  
Dynamics Simulation ◽  
Glass Forming

ABSTRACTMolecular Dynamics simulation was carried out to study the glass transition and crystallization in the metal-metalloid binary system with pair-wise potentials. The results show that a repulsive potential between metalloid (small) atoms increases the glass forming ability. The observation is consistent with the recent theory of bulk metallic glass formation through local glass transition and nano-glass formation. The theory predicted that the compositional short-range order (CSRO) prevents the small atom pairing so as to increase the glass forming ability (GFA). The present results demonstrate the important role of CSRO in bulk metallic glass formation.

Fabrication of ternary Mg–Cu–Gd bulk metallic glass with high glass-forming ability under air atmosphere

2003 ◽  
Vol 18 (7) ◽  
pp. 1502-1504 ◽  
Author(s):  
H. Men ◽  
D. H. Kim
Keyword(s):  
Metallic Glass ◽  
Cooling Rate ◽  
Bulk Metallic Glass ◽  
Glass Formation ◽  
Glass Forming Ability ◽  
Casting Method ◽  
Glass Forming ◽  
Air Atmosphere ◽  
Mold Casting ◽  
Order Of Magnitude

A new Mg65Cu25Gd10 alloy having significantly improved glass-forming ability (GFA) has been developed. In this article, we show that the ternary Mg65Cu25Gd10 bulk metallic glass with diameter of at least 8 mm can successfully be fabricated by a conventional Cu-mold casting method in air atmosphere. The critical cooling rate for glass formation was estimated on the order of magnitude of approximately 1 K/s. When compared with the GFA of Mg65Cu25Y10 alloy, the significantly improved GFA of Mg65Cu25Gd10 alloy cannot be explained by ΔTx and Trg values.

Critical cooling rate for Fe48Cr15Mo14Y2C15B6 bulk metallic glass formation

2006 ◽  
Vol 14 (8-9) ◽  
pp. 898-902 ◽  
Author(s):  
K. Hildal ◽  
N. Sekido ◽  
J.H. Perepezko
Keyword(s):  
Metallic Glass ◽  
Cooling Rate ◽  
Bulk Metallic Glass ◽  
Glass Formation ◽  
Critical Cooling Rate

The influence of the cooling rate on bulk metallic glass formation in Mg80Cu15Y5 and Mg80Cu10Y10

2010 ◽  
Vol 45 (23) ◽  
pp. 6365-6373 ◽  
Author(s):  
M. Regev ◽  
H. Rosenson ◽  
Z. Koren ◽  
A. Katz-Demyanetz
Keyword(s):  
Metallic Glass ◽  
Cooling Rate ◽  
Bulk Metallic Glass ◽  
Glass Formation

scholarly journals Effects of Annealing on Enthalpy Recovery and Nanomechanical Behaviors of a La-Based Bulk Metallic Glass

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 579
Author(s):  
Ting Shi ◽  
Lanping Huang ◽  
Song Li
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Structural Relaxation ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Nanoindentation Measurement

Structural relaxation and nanomechanical behaviors of La65Al14Ni5Co5Cu9.2Ag1.8 bulk metallic glass (BMG) with a low glass transition temperature during annealing have been investigated by calorimetry and nanoindentation measurement. The enthalpy release of this metallic glass is deduced by annealing near glass transition. When annealed below glass transition temperature for 5 min, the recovered enthalpy increases with annealing temperature and reaches the maximum value at 403 K. After annealed in supercooled liquid region, the recovered enthalpy obviously decreases. For a given annealing at 393 K, the relaxation behaviors of La-based BMG can be well described by the Kohlrausch-Williams-Watts (KWW) function. The hardness, Young’s modulus, and serrated flow are sensitive to structural relaxation of this metallic glass, which can be well explained by the theory of solid-like region and liquid-like region. The decrease of ductility and the enhancement of homogeneity can be ascribed to the transformation from liquid-like region into solid-like region and the reduction of the shear transition zone (STZ).

A deep eutectic point in quaternary Zr–Ti–Ni–Cu system and bulk metallic glass formation near the eutectic point

2012 ◽  
Vol 21 (1) ◽  
pp. 67-74 ◽  
Author(s):  
D.M. Lee ◽  
J.H. Sun ◽  
D.H. Kang ◽  
S.Y. Shin ◽  
G. Welsch ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Glass Formation ◽  
Eutectic Point

Effect of cooling rate on the bending plasticity of Zr55Al10Ni5Cu30 bulk metallic glass

2012 ◽  
Vol 527 ◽  
pp. 36-39 ◽  
Author(s):  
Y. Hu ◽  
H.H. Yan ◽  
T. Lin ◽  
J.F. Li ◽  
Y.H. Zhou
Keyword(s):  
Metallic Glass ◽  
Cooling Rate ◽  
Bulk Metallic Glass

Strong Liquid Behavior of Zr-Ti-Cu-Ni-Be Bulk Metallic Glass Forming Alloys

1996 ◽  
Vol 455 ◽  
Author(s):  
Ralf Busch ◽  
Andreas Masuhr ◽  
Eric Bakke ◽  
William L. Johnson
Keyword(s):  
Glass Transition ◽  
Melting Point ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Supercooled Liquid ◽  
Glass Transition Region ◽  
Glass Forming ◽  
Liquid Behavior ◽  
Metallic Liquids ◽  
Microscopic Origin

ABSTRACTThe viscosities of the Zr46.75Ti8.25Cu7.5Ni10Be27.5 and the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass forming liquids was determined from the melting point down to the glass transition in the entire temperature range of the supercooled liquid. The temperature dependence of the viscosity in the supercooled liquid obeys the Vogel-Fulcher-Tammann (VFT) relation. The fragility index D is about 20 for both alloys and the ratio between glass transition temperature and VFT temperature is found to be 1.5. A comparison with other glass forming systems shows that these bulk metallic glass formers are strong liquids comparable to sodium silicate glass. Furthermore, they are the strongest among metallic glass forming liquids. This behavior is a main contributing factor to the glass forming ability since it implicates a higher viscosity from the melting point down to the glass transition compared to other metallic liquids. Thus, the kinetics in the supercooled liquid is sluggish and yields a low critical cooling rate for glass formation. The relaxation behavior in the glass transition region of the alloys is consistent with their strong glassy nature as reflected by a stretching exponent that is close to 0.8. The microscopic origin of the strong liquid behavior of bulk metallic glass formers is discussed.

scholarly journals Virtual Development of Process Parameters for Bulk Metallic Glass Formation in Laser-Based Powder Bed Fusion

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 450
Author(s):  
Johan Lindwall ◽  
Andreas Lundbäck ◽  
Jithin James Marattukalam ◽  
Anders Ericsson
Keyword(s):  
Additive Manufacturing ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Process Parameters ◽  
Glass Formation ◽  
Laser Power ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Scanning Strategies ◽  
Hatch Spacing

The development of process parameters and scanning strategies for bulk metallic glass formation during additive manufacturing is time-consuming and costly. It typically involves trials with varying settings and destructive testing to evaluate the final phase structure of the experimental samples. In this study, we present an alternative method by modelling to predict the influence of the process parameters on the crystalline phase evolution during laser-based powder bed fusion (PBF-LB). The methodology is demonstrated by performing simulations, varying the following parameters: laser power, hatch spacing and hatch length. The results are compared in terms of crystalline volume fraction, crystal number density and mean crystal radius after scanning five consecutive layers. The result from the simulation shows an identical trend for the predicted crystalline phase fraction compared to the experimental estimates. It is shown that a low laser power, large hatch spacing and long hatch lengths are beneficial for glass formation during PBF-LB. The absolute values show an offset though, over-predicted by the numerical model. The method can indicate favourable parameter settings and be a complementary tool in the development of scanning strategies and processing parameters for additive manufacturing of bulk metallic glass.

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