Microstructures and Properties of Metal Reinforced Zr 57 Nb 5 Al 10 Cu 15.4 Ni 12.6 Bulk Metallic Glass Composites
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Microstructures and Properties of Metal Reinforced Zr57Nb5Al10Cu15.4Ni12.6Bulk Metallic Glass Composites Haein Choi-Yim, Robert D. Conner, and William L. Johnson W.M. Keck Laboratory of Engineering Materials, Mail Code 138-78, California Institute of Technology, Pasadena, California 91125 ABSTRACT To increase toughness of a metallic glass with the nominal composition Zr57Nb5Al10Cu15.4Ni12.6, it was used as the matrix in the composites reinforced with W fiber, W particles, and W/Re particles. Microstructures of the composites are studied by scanning electron microscopy and electron microprobe. Compression results are presented. Dynamic deformation behavior of the composites is studied in ballistic tests. The tests were performed firing composite rods into 6061 T651 aluminum target and 4130 steel targets. The composite rods failed by localized adiabatic shear banding and exhibited self-sharpening behavior. INTRODUCTION Recent studies of composites with a bulk metallic glass matrix have been proven that a variety of reinforcement materials have been introduced into the metallic glass matrix without inducing crystallization (1-2). This was made possible by use of multicomponent deep eutectic metallic systems that exhibit an extremely high glass forming ability. Zr57Nb5Al10Cu15.4Ni12.6 glass forming alloy is known as the one of the best glass forming system (3). This metallic glass former is very robust against heterogeneous nucleation at the surface or at interfaces. The range of plastic deformation of the composites was improved drastically (300%) under compression in the case of WC, W, and Ta particles even with 5 to 10% volume fraction particles (4-5). This is attributed to the formation of multiple shear bands in the presence of particles. In tension no significant improvement of plasticity was observed. However, the energy to break the material increased substantially. The investigation of the fracture surfaces after failure under tension reveals an increasing tendency to ductile failure with increasing volume fraction and decreasing size of the particulate. This paper describes microstructures, quasistatic and dynamic deformation behavior of Zr57Nb5Al10Cu15.4Ni12.6 metallic glass matrix composite with 80 vol% tungsten fiber, 50 vol% tungsten particle, and 50 vol% tungsten and rhenium particle (5 to 1 size ratio with 6.25% by Mass rhenium). Tungsten reinforcement increased compressive strain to failure by over 800% compared to the unreinforced Zr57Nb5Al10Cu15.4Ni12.6. The increase in compressive toughness comes from the fiber restricting shear band propagation, promoting the generation of multiple shear bands and additional fracture surface area. The high strain rate deformation behaviors of tungsten fibers or particles reinforced Zr57Nb5Al10Cu15.4Ni12.6 metallic glass composites are studied in ballistic penetration experiments. Ballistic penetration tests were performed firing metallic glass composite rods into 6061 T651 aluminum and 4130 steel targets. Localized shear banding failure of these composites results i
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