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Variation in mechanical properties with crystallinity of a La-based bulk metallic glass

Ramamurty, U and Nagendra, N and Li, Y (2001) Variation in mechanical properties with crystallinity of a La-based bulk metallic glass. In: Metastable, Mechanically Alloyed and Nanocrystalline Materials ISMANAM - 2000. International Symposium, 9-14 July 2000, Oxford, UK, pp. 61-66.

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Abstract

The influence of crystallinity on the mechanical properties of a bulk La-based metallic glass was investigated. The degree of crystallization in the metallic glass was systematically altered by varying the annealing time above the glass transition temperature, $T_g$. The elastic modulus, E, of the nanocrystalline amorphous matrix composite was observed to increase abruptly at ~40% crystallinity, χ. The hardness, H, however increases only linearly with the increase in χ. Instrumented impact test results show a significant decrease, by ~90%, in impact toughness, γ with the introduction of a small percentage of crystallinity. This decrease in toughness was also associated with a distinct change in fracture morphology, from a ductile vein type fracture in the bulk glass to intergranular cleavage fracture in the crystalline material. Microscopic mechanisms responsible for the observed transitions in mechanical properties are discussed

Item Type: Conference Paper
Additional Information: Copyright of this article belongs to Trans Tech Publications
Keywords: annealing;brittle fracture;crystallisation;crystallites;ductile fracture;ductile brittle transition;elastic moduli;fracture toughness;glass structure;glass transition;lanthanum alloys;metallic glasses;nanostructured materials;Vickers hardness
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 17 Aug 2007
Last Modified: 27 Aug 2008 12:45
URI: http://eprints.iisc.ernet.in/id/eprint/10533

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