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The deformation behavior of Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass was studied by in situ scanning electron microscopy (SEM) quasi-static uniaxial compression tests at room temperature. Multiple shear bands were observed with a large plasticity. Microscopic examination demonstrates that slipping, branching and intersecting of multiple shear bands are the main mechanisms for enhancing the plasticity of this metallic glass. Additionally, nano/micro-scale voids and cracks at the intersecting sites of shear bands and preferential etching of shear bands were observed as well. These observations demonstrated that the formation of shear bands in bulk metallic glasses is resulted mainly from local free volume coalescence. © 2005 Elsevier B.V. All rights reserved. Recently, bulk metallic glasses (BMGs) have attracted large interest due to their unique physical, mechanical and chemical properties [1][2][3][4][5][6]. However, BMGs loaded under unconstrained conditions usually fail catastrophically with little global plasticity. This deformation behavior has limited the application of BMGs as engineering material so far. At low temperatures (well below the glass transition), plastic deformation of BMGs is usually localized into thin shear bands [7]. Many macroscopic mechanical properties (e.g. plasticity and ductility) are, thus, controlled by the individual and collective behavior of the shear bands. Therefore, the initiation and propagation of localized shear bands in metallic glasses has been the subject of both theoretical and experimental investigation for number of years [8][9][10][11][12][13][14][15][16][17][18]. However, the precise nature of initiation and propagation of shear bands as well as the possible mechanisms for enhancing the plasticity of BMGs still remain uncertain.In the present letter, the plastic deformation behavior of Zr 41 gated by in situ scanning electron microscopy (SEM) quasistatic uniaxial compression experiments at room temperature. The mechanisms for enhancing the plasticity in this alloy are elucidated. The observed nano/micro-scale voids and cracks at the intersecting sites of shear bands as well as the preferential etching of shear bands provide some evidences to support the free volume theory of the formation of shear bands in metallic glasses [12,13]. Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass was produced by arc melting the pure elements together under a purified Ar atmosphere in ingots of the desired composition, each ingot was then re-melted twice to ensure a homogeneous composition. From these ingots 8 mm diameter rods of metallic glass were prepared by suction casting the molten alloy into a copper mold. The cylinders, thus obtained were confirmed to be non-crystalline by conventional X-ray diffraction.The samples were machined into dog bone-like shape to ensure that the deformation occurs in the middle constraint region of the specimen. The dimensions of the deformation region are 2.0 mm × 2.0 mm × 1.0 mm. For microscopic observations, the...

Compressive deformation behavior of the Nd 60 Fe 20 Co 10 Al 10 bulk metallic glass was characterized over a wide strain rate range (6.0!10 K4 to 1.0!10 3 s K1 ) at room temperature. Fracture stress was found to increase and fracture strain decrease with increasing applied strain rate. Serrated flow and a large number of shear bands were observed at the quasi-static strain rate (6.0!10 K4 s K1 ). The results suggest that the appearance of a large number of shear bands is probably associated with flow serration observed during compression; and both shear banding and flow serration are a strain accommodation and stress relaxation process. At dynamic strain rates (1.0!10 3 s K1 ), the rate of shear band nucleation is not sufficient to accommodate the applied strain rate and thus causes an early fracture of the test sample. The fracture behavior of the Nd 60 Fe 20 Co 10 Al 10 bulk metallic glass is sensitive to strain rate. q

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