Critical Temperature for Ductile-to-Brittle Transition for Metallic Glasses

A comprehensive analysis of plasticity (and toughness) in bulk metallic glasses (BMGs) is presented. Different effects such as: contribution of shear modulus/bulk modulus ratio, structural relaxation, and cooling rate effect are evaluated for Pt57.5Cu14.7Ni5.3P22.5 (Pt-BMG), Pd43Cu27Ni10P20 (Pd-BMG)...

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Bibliographic Details
Published in:AIP conference proceedings 2012-03
Main Authors: Kumar, Golden, Neibecker, Pascal, Schroers, Jan
Format: Article
Language:English
Subjects:
Amorphous materials
Annealing
Cooling rate
Ductile brittle transition
Embrittlement
Palladium
Platinum
Zirconium
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Summary:A comprehensive analysis of plasticity (and toughness) in bulk metallic glasses (BMGs) is presented. Different effects such as: contribution of shear modulus/bulk modulus ratio, structural relaxation, and cooling rate effect are evaluated for Pt57.5Cu14.7Ni5.3P22.5 (Pt-BMG), Pd43Cu27Ni10P20 (Pd-BMG), and Zr44Ti11Ni10Cu10Be25 (Zr-BMG). We introduce a critical temperature, TC, which is an intrinsic feature of a BMG former above which the BMG does not embrittle. We demonstrate that TC/Tg ratio indicates the embrittlement sensitivity of a BMG due to annealing and cooling rate. This ratio is larger than one for Pd-BMG and smaller than one for the Pt-BMG. As a consequence, Pd-BMG is more sensitive to cooling rate and annealing induced embrittlement. In contrast, Pt-BMG does not embrittle during sub-Tg annealing or at practically achievable slow cooling rates. Study of shear modulus/bulk modulus ratio for Pd-BMG and Pt-BMG does not follow the previously proposed critical value for ductile to brittle transition.
ISSN:0094-243X