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Fracture toughness and fatigue-crack propagation in a Zr–Ti–Ni–Cu–Be bulk metallic glass

Gilbert, C. J. and Ritchie, R. O. and Johnson, W. L. (1997) Fracture toughness and fatigue-crack propagation in a Zr–Ti–Ni–Cu–Be bulk metallic glass. Applied Physics Letters, 71 (4). pp. 476-478. ISSN 0003-6951. http://resolver.caltech.edu/CaltechAUTHORS:GILapl97

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Abstract

The recent development of metallic alloy systems which can be processed with an amorphous structure over large dimensions, specifically to form metallic glasses at low cooling rates (similar to 10 K/s), has permitted novel measurements of important mechanical properties. These include, for example, fatigue-crack growth and fracture toughness behavior, representing the conditions governing the subcritical and critical propagation of cracks in these structures. In the present study, bulk plates of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy, machined into 7 mm wide, 38 mm thick compact-tension specimens and fatigue precracked following standard procedures, revealed fracture toughnesses in the fully amorphous structure of K(lc)similar to 55 MPa root m, i.e., comparable with that of a high-strength steel or aluminum ahoy. However, partial and full crystallization, e.g., following thermal exposure at 633 K or more, was found to result in a drastic reduction in fracture toughness to similar to 1 MPa root m, i.e., comparable with silica glass. The fully amorphous alloy was also found to be susceptible to fatigue-crack growth under cyclic loading, with growth-rate properties comparable to that of ductile crystalline metallic alloys, such as high-strength steels or aluminum alloys; no such fatigue was seen in the partially or fully crystallized alloys which behaved like very brittle ceramics. Possible micromechanical mechanisms for such behavior are discussed.


Item Type:Article
Additional Information:©1997 American Institute of Physics. Received 28 April 1997; accepted 28 May 1997. This work was supported by the Air Force Office of Scientific Research. Thanks are also due to Dr. A. Peker and Dr. M. Tenhover of Amorphous Technologies International, Corporation for their support and for supplying the material.
Subject Keywords:ZIRCONIUM ALLOYS; TITANIUM ALLOYS; NICKEL ALLOYS; COPPER ALLOYS; BERYLLIUM ALLOYS; CRACK PROPAGATION; FRACTURE MECHANICS; METALLIC GLASSES; AMORPHOUS STATE; CRYSTALLIZATION
Record Number:CaltechAUTHORS:GILapl97
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:GILapl97
Alternative URL:http://dx.doi.org/10.1063/1.119610
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3451
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:07 Jun 2006
Last Modified:26 Dec 2012 08:54

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