Mechanical properties of bulk metallic glass matrix composites

Citation

Conner, Robert Dale (1998) Mechanical properties of bulk metallic glass matrix composites. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/xvhx-px15. https://resolver.caltech.edu/CaltechETD:etd-02282006-161438

Abstract

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This report discusses two aspects of research on bulk metallic glasses. The first is an effort to increase their toughness by combining them with reinforcement to form a composite. The second is the first direct measurement of plane strain fracture toughness of bulk metallic glass.

Particulate and continuous fiber reinforced composite materials were fabricated using bulk metallic glass as the matrix. The particulate composites combined W, WC, SiC and Ta reinforcements in a matrix with the composition Zr57Nb5Al10Cu15.4Ni12.6. Continuous fiber composites were fabricated using W and 1080 carbon steel (music) wire reinforcement in a Zr41.25Ti13.75Cu12.5Ni10Be22.5 matrix. In both cases the metallic glass remained amorphous during processing.

Compressive strain to failure was greatly enhanced in both particulate and continuous fiber composites by the formation of multiple shear bands. Tungsten reinforcement provided the greatest improvement. The tungsten is wet well by the metallic glass, and forms a strong interface.

Both particulate and fiber reinforced composite showed improved tensile properties. Energy (per unit volume) to break increased 52% for 5% Vf, 150 [...] W reinforced Zr57Nb5Al10Cu15.4Ni12.6 and 18% for 60% Vf music wire reinforced Zr41.25Ti13.75Cu12.5Ni10Be22.5. Tightly bonded ductile particles and weakly bonded continuous fibers proved best for enhancing the tensile properties of bulk metallic glass.

Fracture toughness of the unreinforced Zr41.25Ti13.75Cu12.5Ni10Be22.5 bulk metallic glass was determined using 3-point bend measurements and coherent gradient sensing (CGS). The measured fracture toughness is nominally 55 [...]. Once initiated, cracks in the unreinforced metallic glass propagated in an unstable manner. Continuous fiber reinforcement was demonstrated to arrest crack propagation in 3-point bend fracture tests of bulk metallic glass matrix composites.

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