MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Evaluation of the Glass-Forming Ability of Nb-Ni-Ti-Zr Quaternary Alloys Using the CALPHAD Approach
Tatsuya TokunagaHiroshi OhtaniMitsuhiro Hasebe
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2007 Volume 48 Issue 7 Pages 1635-1638

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Abstract

The glass-forming ability of Nb-Ni-Ti-Zr quaternary alloys has been evaluated by combining the Calculation of Phase Diagrams method with the Davies-Uhlmann kinetic approach. Time-temperature-transformation (TTT) curves were obtained for steady state nucleation for the calculations, which give the time required for the formation of detectable amounts of a crystalline phase from a supercooled liquid as a function of temperature. Then, the critical cooling rates for glass formation were calculated from the TTT curves. Among the input parameters for the calculation of the TTT curves, the driving force for crystallization of the crystalline phase was derived using the thermodynamic function of each phase formulated in previous studies. The calculations show that the critical cooling rates for Nb40−xyNi60TixZry alloys decrease with increasing Zr content up to 20 mol%Zr. In particular, the calculated values for the Nb10Ni60Ti10Zr20 and Nb5Ni60Ti15Zr20 alloys were around 100 K/s.

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© 2007 The Japan Institute of Metals and Materials
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