scholarly journals Small Atom Diffusion and Breakdown on Stokes-Einstein Relation in the Supercooled Liquid State of Zr-Ti-Cu-Ni-Be Alloys

1996 ◽  
Vol 455 ◽  
Author(s):  
U. Geyer ◽  
S. Schneider ◽  
Y. Qiu ◽  
M.-P. Macht ◽  
T. A. Tombrello ◽  
...  
Keyword(s):  
Liquid State ◽  
Diffusion Mechanism ◽  
Supercooled Liquid ◽  
Einstein Relation ◽  
Viscosity Data ◽  
Atom Diffusion ◽  
Glass Forming ◽  
Supercooled Liquid State ◽  
Liquid States ◽  
Arrhenius Expression

ABSTRACTBe diffusivity data in the bulk metallic glass forming alloys Zr41.2Ti13.8Cu12.5Ni10Be22.5 and Zr46.7Ti8.3Cu7.5Ni10Be27.5 are reported for temperatures between 530K and 710K, extending up to 80K into the supercooled liquid states of the alloys. At the glass transition temperature, Tg, a change in temperature dependence of the data is observed in both alloys, and above Tg the diffusivity increases faster with temperature than below. The data in the supercooled liquid can be described by a modified Arrhenius expression containing the communal entropy of the supercooled liquid and based on a diffusion mechanism suggested earlier. The comparison with viscosity data in the supercooled liquid state of Zr46.7Ti8.3Cu7.5Ni10Be27.5 reveals a breakdown of the Stokes- Einstein relation, whereas D(T) and η(T) follow a relation close to van den Beu-kel's. The breakdown of the Stokes- Einstein relation indicates a cooperative diffusion mechanism in the supercooled liquid state of the ZrTiCuNiBe alloys.

scholarly journals Small atom diffusion and breakdown of the Stokes–Einstein relation in the supercooled liquid state of the Zr46.7Ti8.3Cu7.5Ni10Be27.5 alloy

1996 ◽  
Vol 69 (17) ◽  
pp. 2492-2494 ◽  
Author(s):  
U. Geyer ◽  
W. L. Johnson ◽  
S. Schneider ◽  
Y. Qiu ◽  
T. A. Tombrello ◽  
...  
Keyword(s):  
Liquid State ◽  
Supercooled Liquid ◽  
Einstein Relation ◽  
Atom Diffusion ◽  
Supercooled Liquid State ◽  
Small Atom

scholarly journals Diffusion in Metallic Glasses and Supercooled Melts

2000 ◽  
Vol 644 ◽  
Author(s):  
F. Faupel ◽  
K. Rätzke ◽  
H. Ehmler ◽  
P. Klugkist ◽  
V. Zöllmer ◽  
...  
Keyword(s):  
Glass Transition ◽  
Metallic Glasses ◽  
Liquid State ◽  
Mode Coupling ◽  
Structural Changes ◽  
Diffusion Mechanism ◽  
Supercooled Liquid ◽  
Kirkendall Effect ◽  
Dynamic Simulations ◽  
Supercooled Liquid State

AbstractDiffusion in metallic glasses and in the supercooled liquid state is of considerable interest not only from the technological point of view but also in terms of fundamental science, particularly in connection with the glass transition. Within the framework of the mode coupling theory the glass transition is a kinetic phenomenon characterized by the arrest of viscous flow at a critical temperature Tc well above the calorimetric glass transition temperature Tg. Below Tc the theory predicts cooperative hopping processes. We present results from isotope effect measurements which indeed confirm the highly collective nature of diffusion in metallic glasses and suggest cooperative hopping processes to be closely related to the universal low-frequency excitations as observed in recent molecular dynamic simulations. In accord with the mode coupling scenario these cooperative hopping processes are also observed in the supercooled liquid state of the new bulk metallic glasses well above Tg. The reported kink in the Arrhenius plot for diffusion of various elements is shown to be related to structural changes above Tg, e.g., an increase in free volume as probed by positron annihilation, but not to a change in the diffusion mechanism. Measurements of the activation volume of diffusion indicate that, depending on the structure of the glass, cooperative hopping may take place without assistance of thermally generated defects or via delocalized thermal defects. Moreover, we provide evidence of the existence of an opposite Kirkendall effect in interdiffusion between certain amorphous alloys that combine slow diffusion via thermal defects and fast direct diffusion.

In Situ Observation of Solidification of Bulk Metallic Glass Forming Alloys from Supercooled Liquid by Using High Energy X-Ray Diffraction Combined with Levitation Techniques

2010 ◽  
Vol 638-642 ◽  
pp. 1677-1682 ◽  
Author(s):  
Masahito Watanabe ◽  
Akitoshi Mizuno ◽  
Toshihiko Akimoto ◽  
Shinji Kohara
Keyword(s):  
Liquid State ◽  
Supercooled Liquid ◽  
High Energy ◽  
In Situ Observation ◽  
X Ray Diffraction ◽  
Phase Selection ◽  
X Ray ◽  
Glass Forming ◽  
Supercooled Liquid State

It is well known that multi-component alloys form bulk metallic glasses (BMGs) from the supercooled liquid state without rapid quenching. However, the mechanism of phase selection between crystal and glass states has not been fully clarified. To obtain an insight into the glass-forming processes, we carried out in-situ observation on the solidification of Zr-based BMG-forming alloys from its supercooled liquids by time-resolved X-ray diffraction combined with the conical nozzle levitation (CNL) technique to achieve a containerless melting. For Zr-based alloys, we succeeded in detecting the X-ray diffraction patterns during glass formation from the supercooled liquid state as well as the crystallization from the liquid state. Furthermore we performed the precise structure analysis of supercooled state of Zr-based binary liquids. Based on the liquid structure and in-situ observation results, we discussed about the phase selection mechanism between crystal and glass states.

Micro mold filling kinetics of metallic glasses in supercooled liquid state

2013 ◽  
Vol 113 (10) ◽  
pp. 104505 ◽  
Author(s):  
J. Ma ◽  
L. S. Huo ◽  
D. Q. Zhao ◽  
W. H. Wang
Keyword(s):  
Metallic Glasses ◽  
Liquid State ◽  
Supercooled Liquid ◽  
Mold Filling ◽  
Supercooled Liquid State ◽  
Kinetics Of
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