The Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 (at.%) bulk metallic glass composites with various crystallization fractions were prepared by pretreating the bulk metallic glassy samples with pulsing current, and then by isothermal annealing at near initial crystallization temperature for different periods of time. The precipitations and crystallization fractions were studied by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), and their effects on mechanical properties of the composite were studied by microhardness, uniaxial compression test and scanning electron microscopy (SEM). The experimental results show that the primary precipitate is quasicrystalline phase and other metastable phases including Be 2 Zr, Zr 2 Cu and FCC would precipitate subsequently. In the initial crystallization process, in which the crystallization fraction increases from 0 to 8.2%, both fracture strength and plastic strain increase, with the maximum plastic strain up to 6.4%. When the crystallization fraction is larger than 8.2%, the fracture strength and the plastic strain decrease sharply. Furthermore, the alloy with low crystallization fraction is fractured by shearing, while for high crystallization fraction it is fractured by splitting and cleavage. The results show that the mechanical properties of the glassy alloy could be optimized by controlling the processing parameters. bulk metallic glass, pulsing current, crystallization fraction, plasticity, shear band PACS: 64.70.Pf, 81.40.Lm, 81.30.Mh, 61.50.KsBulk metallic glasses (BMGs) possess extraordinary properties, such as high strength and strong corrosion resistance, which has attracted much attention from scientists in the area of materials and physics [1][2][3]. Usually the strengths of BMGs come up to theoretical values, much higher than those of the crystalline alloys with the same chemical compositions [1-4]. But BMGs exhibit very limited global plasticity since they deform by shearing through the formation of shear bands that tend to form highly localized shear bands, resulting in crack formation and premature fracture [1][2][3][4][5]. Recently, however, investigations have reported that some BMGs exhibit large plastic strains in compression due to the generation of multiple shear bands [6][7][8][9][10][11]. This implies possibility to enhance the plasticity of BMGs through effectively hindering the highly localized shear along the primary shear bands and promoting the activation of shear bands. The reported results show that one way for improving the ductility of BMGs is to introduce second phases to BMGs by in-situ formation [6] or by isothermal annealing [7], which might benefit the generation of shear bands. For instance, Sun et al. [10] reported that 12% compressive plastic strain could be achieved by in-situ forming spherical crystals within the glassy matrix, while Hofmann et al. [11] reported that Zr-Ti-based bulk metallic glass matrix composites (BMGCs) display tensile plasticity of 8.6%-13.1%. However, effects of different second phases and their cryst...
