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Published June 14, 2004 | public
Journal Article Open

Overheating threshold and its effect on time–temperature-transformation diagrams of zirconium based bulk metallic glasses


A pronounced effect of overheating is observed on the crystallization behavior for the three zirconium-based bulk metallic glasses: Zr41.2Ti13.8Cu12.5Ni10Be22.5, Zr57Cu15.4Ni12.6Al10Nb5, and Zr52.5Cu17.9Ni14.6Al10Ti5. A threshold overheating temperature is found for each of the three alloys, above which there is a drastic increase in the undercooling level and the crystallization times. Time–temperature-transformation (TTT) diagrams were measured for the three alloys by overheating above their respective threshold temperatures. The TTT curves for Zr41.2Ti13.8Cu12.5Ni10Be22.5 and Zr57Cu15.4Ni12.6Al10Nb5 are very similar in shape and scale with their respective glass transition temperatures, suggesting that system-specific properties do not play a crucial role in defining crystallization kinetics in these alloys. The critical cooling rates to vitrify the alloys as determined from the TTT curves are about 2 K/s for Zr41.2Ti13.8Cu12.5Ni10Be22.5 and 10 K/s for Zr57Cu15.4Ni12.6Al10Nb5. The measurements were conducted in a high-vacuum electrostatic levitator.

Additional Information

©2004 American Institute of Physics. (Received 23 February 2004; accepted 21 April 2004; published online 28 May 2004) This work was carried out at California Institute of Technology under a contract with the National Aeronautical and Space Administration ~Grant No. NAG8-1744!. The authors wish to thank Dr Haein Choi-Yim for providing the Vit1 samples.


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