Critical obstacle size to deflect shear banding in Zr-based bulk metallic glass composites

• Published in: Intermetallics Vol. 64; pp. 102 - 105
• Main Authors: Jang, J.S.C., Li, T.H., Tsai, P.H., Huang, J.C., Nieh, T.G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2015
• Subjects: A. Metallic glass; B. Mechanical properties; B. Shear band; C. Casting; Deflection; Metallic glasses; Nanostructure; Obstacles; Particulate composites; Slip bands; Tantalum; Zirconium; C. Casting; B. Mechanical properties; B. Shear band; A. Metallic glass
• ISSN: 0966-9795
• DOI: 10.1016/j.intermet.2015.05.001

The Zr53Cu22Ni9Al8Ta8 bulk metallic glass composite (BMGC) rods have been reported to present superior plastic strain up to 30% at room temperature. The remarkable plasticity is demonstrated to be contributed by the in-situ Ta-rich precipitates in micro-sized (10–20 micro-meter) plus nano-sized (5–15 nm) scales, homogeneously distributed in the amorphous matrix. These Ta-rich particles act as discrete obstacles, separating and restricting the highly localized shear-banding, avoiding catastrophic shear-through of the whole sample and dramatically enhancing plasticity, as compared with the ZrCuNiAl monolithic BMG. To explore the critical particle size that can effectively deflect the shear banding, the Zr-based BMGC rods were plastically deformed to different strain levels (3%–25%) before fracture for investigating the interaction between the Ta-rich particles (micro- and nano-sized) and shear banding. The results suggest that the critical size of single particle or particle cluster for deflecting the shear band is greater than 20 nm and less than 100 nm. The best estimation suggests about 80 ± 20 nm. (a) Stress-strain curves of the Zr53Cu22Ni9Al8Ta8 BMGC samples, plastically strained to various strain levels before fracture. The insert shows the deformed specimens to different plastic strain levels. (b) A representative TEM micrograph shows the deflection of shear band in the deformed specimens subject to plastic strain of 15%. The insert images at upper right side is the associated electron diffraction pattern and at lower right side is the enlarged image at the area indicated by arrow. [Display omitted] •Zr53Cu22Ni9Al8Ta8 BMGC presents superior plastic strain up to 30%.•Nano- and micro-scale Ta-rich particles co-exist in the glassy matrix.•Micro-sized Ta-rich particles effectively restrict the shear-banding.•Shear bands can be blocked by particle clusters with a size of 80± 20 nm.