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24. Amorphous Mg-based metal foams with ductile hollow spheres.

Author

Brothers, A. H., Dunand, D. C., Zheng, Q., and Xu, J.

Subjects
*LIQUID metals, *METALLIC glasses, *AMORPHOUS substances, *ABSORPTION, *PHYSICS
Abstract

To date, high compressive ductility and energy absorption have been achieved in amorphous metal foams based on high-toughness Pd- and Zr-based metallic glasses and are known to result from two extrinsic toughening mechanisms: bending of struts and shear band arrest by pores. We study here a syntactic amorphous metallic foam produced by infiltration of a bed of hollow crystalline iron spheres with a low-toughness Mg-based metallic glass (Mg60Cu21Ag7Gd12). After quenching to vitrify the matrix, this foam exhibits much higher compressive failure strain and energy absorption than the monolithic metallic glass, an improvement which is assigned to an intrinsic mechanism, i.e., composite toughening by the network of hollow ductile iron spheres. [ABSTRACT FROM AUTHOR]

Published
2007
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26. Mechanics and structure of dislocations induced by thermal mismatch in composite material

Author

Andreas Mortensen., Massachusetts Institute of Technology. Dept. of Materials Science and Engineering, Dunand, D. C. (David C.), Andreas Mortensen., Massachusetts Institute of Technology. Dept. of Materials Science and Engineering, and Dunand, D. C. (David C.)

Abstract

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1991., Includes bibliographical references (leaves 231-235)., by David Christophe Dunand., Ph.D.

Published
2005

29. Processing of Bulk Metallic Glass Foams by Melt Infiltration Techniques

Author

NORTHWESTERN UNIV EVANSTON IL DEPT OF MATERIALS SCIENCE AND ENGINEERING, San Marchi, C., Brothers, A, Dunand, D. C., NORTHWESTERN UNIV EVANSTON IL DEPT OF MATERIALS SCIENCE AND ENGINEERING, San Marchi, C., Brothers, A, and Dunand, D. C.

Abstract

Processing of bulk metallic glass (BMG) foams, using melt infiltration techniques, is reported for the first time. Foaming methods based on infiltration of two types of pattern materials are described: investment of a continuous refractory yielding very low relative density structures (5% dense relative to the BMG), and investment of a discontinuous refractory pellet bed yielding higher relative density (50-60% dense relative to the BMG). Both methods are capable of producing foam structures; however high surface area and diminished thermal conductivity, especially in lower density structures, make vitrification of the alloy difficult.

Published
2002

35. Editorial

Author

Lefebvre, L.-P., primary, Banhart, J., additional, and Dunand, D. C., additional

Published
2008
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50. An in situneutron diffraction mechanical study of superelastic NiTi and NiTi-TiC composites

Author

Vaidyanathan, R., Bourke, M. A.M., Dunand, D. C., Vaidyanathan, R., Bourke, M. A.M., and Dunand, D. C.

Abstract

Superelastic NiTi and NiTi-TiC composites were subjected to static uniaxial compressive loading while neutron diffraction spectra were simultaneously acquired. A methodology was established to obtain quantitative strain, texture and phase volume fraction information during the forward and reverse stress-induced martensitic transformation. Despite the presence of 10 vol. % of stiff TiC particles, a macroscopic compressive strain of 3% was obtained in the composite on loading and was fully recovered on unloading. The observed behavior suggests that the martensite accommodates the mismatch with the transforming austenite (while they co-exist) and the TiC particles (in the case of the composite). Superelastic NiTi was also subjected to simultaneous neutron diffraction and uniaxial compressive cycling. The average phase strain in the mechanically-loaded austenite (at a given stress) remained unaltered during the load-unload cycles. However, differences in both volume fraction and texture of austenite and martensite were noted as cycling progressed, suggesting that these factors are responsible for the changes in the macroscopic stress-strain response of NiTi with mechanical cycling.

Published
2003
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