Significant plasticity enhancement of ZrCu-based bulk metallic glass composite dispersed by in situ and ex situ Ta particles

Using two-step arc melting process and suction casting, the Zr47.3Cu32Al8Ag8Ta4Si0.7-based bulk metallic glass composites (BMGCs) rods with ex situ added micro-sized Ta particles have been successfully fabricated. The structure and thermal properties of these BMGCs samples were examined by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). It was found that these BMGCs with ex situ added Ta exhibit similar thermal properties in comparison with their base alloy counterpart, with relatively high glass forming ability (GFA). For the mechanical study, the results of compression test show that more than 25% compressive plastic strain and 1800 MPa fracture strength at room temperature can be obtained for the 2 mm diameter rod of the ZrCu-based BMGC ex situ added 6 and 9 vol.% Ta particles, respectively. Images from SEM on the fractured surfaces show that the homogeneously distributed Ta particles (20 ± 8 μm) would form semi-uniform confinement zones to restrict the shear band propagation. In other words, the inter-particle free space and the size of confinement zone (mean free path of shear bands) is apparently the controlling factor in affecting the plasticity of BMGCs.

Confinement zone of Ta particles provide a plastic shielding to obstruct shear banding and so as to significantly increase the plasticity of Zr-based BMGC. Evidence of remarkable plasticity improvement of Zr-based BMGC dispersed by the combination of in situ and ex situ Ta particles can be seen from the stress–strain curve (a) as well as the fractured samples of monolithic BMG ((b): brittle fracture) and BMGC ((c): severe plastic deformation).Figure optionsDownload as PowerPoint slideHighlights
► Shear bands are arrested by the interface of glassy matrix/Ta in the Zr-based BMGCs.
► Ta particles of BMGC distributed as a semi-uniform confinement zone.
► Confinement zone exhibits smaller size than plastic zone of crack-tip in the BMGC.
► Confinement zone of Ta provide a plastic shielding to obstruct shear banding.
► Plasticity can be improved from 0% (monolithic BMG) to 44% plastic strain (BMGC).