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Title: Volume conservation in bulk metallic glasses

Abstract

We report that the excess molar volumes of mixing for ~30 metalloid-free bulk metallic glasses (BMGs) are essentially zero, indicating that the original volumes of "mechanically mixed" constituent elemental metals are conserved after glass formation. This is attributed to the lack of solute-solute bonds and the ideal-mixing nature of solvent-solute bonding upon amorphization. The hard-sphere atomic packing fractions of most of these BMGs are found to be ~0.74, comparable to the maximum packing efficiency for close-packed structures. These findings provide a new perspective for understanding amorphous structures.

Authors:
 [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
Work for Others (WFO)
OSTI Identifier:
983533
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 91; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BONDING; EFFICIENCY; GLASS; METALLIC GLASSES; metallic glasses; atomic structure

Citation Formats

Ma, Dong, Stoica, Alexandru Dan, and Wang, Xun-Li. Volume conservation in bulk metallic glasses. United States: N. p., 2007. Web. doi:10.1063/1.2751595.
Ma, Dong, Stoica, Alexandru Dan, & Wang, Xun-Li. Volume conservation in bulk metallic glasses. United States. doi:10.1063/1.2751595.
Ma, Dong, Stoica, Alexandru Dan, and Wang, Xun-Li. Mon . "Volume conservation in bulk metallic glasses". United States. doi:10.1063/1.2751595.
@article{osti_983533,
title = {Volume conservation in bulk metallic glasses},
author = {Ma, Dong and Stoica, Alexandru Dan and Wang, Xun-Li},
abstractNote = {We report that the excess molar volumes of mixing for ~30 metalloid-free bulk metallic glasses (BMGs) are essentially zero, indicating that the original volumes of "mechanically mixed" constituent elemental metals are conserved after glass formation. This is attributed to the lack of solute-solute bonds and the ideal-mixing nature of solvent-solute bonding upon amorphization. The hard-sphere atomic packing fractions of most of these BMGs are found to be ~0.74, comparable to the maximum packing efficiency for close-packed structures. These findings provide a new perspective for understanding amorphous structures.},
doi = {10.1063/1.2751595},
journal = {Applied Physics Letters},
number = 2,
volume = 91,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
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  • For production of micro components in large numbers, forging is an interesting and challenging process. The conventional metals like silver, steel and aluminum often require multi-step processes, but high productivity and increased strength justify the investment. As an alternative, bulk metallic glasses will at elevated temperatures behave like a highly viscous liquid, which can easily form even complicated geometries in 1 step. The strengths and limitations of forming the 2 materials are analyzed for a micro 3D component in a silver alloy and an Mg-Cu-Y BMG.
  • Results of calorimetric, differential thermal analysis, and structural measurements are presented for a series of bulk metallic glass forming compositions in the Zr[endash]Ti[endash]Cu[endash]Ni[endash]Be alloy system. The calorimetric data for five alloys, prepared along the tie line between phase separating and nonphase separating compositions, show that the transition from phase separating to nonphase separating behavior is smooth. The bulk glasses near the center of the tie line exhibit large supercooled liquid regions: [Delta]T[approx]135 K, the largest known for a bulk metallic glass. [copyright] [ital 1999 American Institute of Physics.]
  • Formation of bulk metallic glass in quaternary Ti--Zr--Cu--Ni alloys by relatively slow cooling from the melt is reported. Thick strips of metallic glass were obtained by the method of metal mold casting. The glass forming ability of the quaternary alloys exceeds that of binary or ternary alloys containing the same elements due to the complexity of the system. The best glass forming alloys such as Ti{sub 34}Zr{sub 11}Cu{sub 47}Ni{sub 8} can be cast to at least 4-mm-thick amorphous strips. The critical cooling rate for glass formation is of the order of 250 K/s or less, at least two orders ofmore » magnitude lower than that of the best ternary alloys. The glass transition, crystallization, and melting behavior of the alloys were studied by differential scanning calorimetry. The amorphous alloys exhibit a significant undercooled liquid region between the glass transition and first crystallization event. The glass forming ability of these alloys, as determined by the critical cooling rate, exceeds what is expected based on the reduced glass transition temperature. It is also found that the glass forming ability for alloys of similar reduced glass transition temperature can differ by two orders of magnitude as defined by critical cooling rates. The origins of the difference in glass forming ability of the alloys are discussed. It is found that when large composition redistribution accompanies crystallization, glass formation is enhanced. The excellent glass forming ability of alloys such as Ti{sub 34}Zr{sub 11}Cu{sub 47}Ni{sub 8} is a result of simultaneously minimizing the nucleation rate of the competing crystalline phases. The ternary/quaternary Laves phase (MgZn{sub 2} type) shows the greatest ease of nucleation and plays a key role in determining the optimum compositions for glass formation. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.« less
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