Plasticity improvement of ZrCu-based bulk metallic glass by ex situ dispersed Ta particles

Effect of the volume fraction of the ex-situ reinforced Ta additions on the microstructure and properties of laser-welded Zr-based bulk metallic glass composites

“…The base alloy was prepared from pure elemental Zr, Cu, Al, Ag and Si of 99.9 wt% purity by arc melting under a Ti-gettered argon atmosphere. To form the homogeneous alloy ingots, the base alloy was produced through a two-step arc melting and casting process, as described in the literature [19]. The base alloy ingots were then re-melted with various contents (0, 2, 4 and 6 vol%) of Ta particles (with an average particle size of 20 ± 8 mm) to obtain the target composite compositions.…”

“…The similarity in the T x , T m and T l values of the different BMGCs may have resulted because the ex-situ Ta particles in the BMGCs were only physically mixed with the (Zr 48 Cu 36 Al 8 Ag 8 )Si 0.75 amorphous matrix during the fabrication. The extremely high melting temperature of the Ta particles (about 3017 C) and their low solubility [13,19] in this alloy system kept them as a separate phase in the ex-situ BMGC alloys. Therefore, the T x , T m and T l values of the BMGCs were more likely related to the thermal properties of the (Zr 48 Cu 36 Al 8 Ag 8 )Si 0.75 amorphous matrix, which were not significantly affected by the Ta additions.…”

“…Both approaches have their advantages and limitations [1,2,13]. Insitu composites usually have a good crystal-amorphous matrix interface and a finer crystalline reinforced phase, but this approach can limit the compositional range [13,19]. In contrast, the features of the reinforced phase, such as distribution and volume fraction, of ex-situ composites can be easily adjusted.…”

“…Recently, (Zr 48 Cu 36 Al 8 Ag 8 ) 99. 25 Si 0.75 -based BMG composites (BMGCs), ex-situ dispersed with various contents of Ta reinforced phase, were fabricated by J. S. C. Jang et al [19]. Although few studies [1,10] have reported that exsitu BMGCs exhibit problematic adhesion of the interface between the reinforced crystalline phase and the glassy matrix, their study found that, for a given Ta particle size, higher volume-fraction particles tended to result in the presenting of greater compression plasticity.…”

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

“…In such Ta-added BMGCs, the Ta-rich particles appear to act as obstacles in the amorphous matrix, arresting and diverting the propagating shear bands, and thus enhancing plasticity drastically. In our previous reports [24,26,27], the microsized Ta-rich particles can be observed directly from the surface of plastically deformed sample, absorbing the dynamic energy of shear banding and branching the principal shear bands into multiple shear bands. Since the thickness of typical shear bands was widely reported to be about 20 nm, thus the minimum obstacle size is generally postulated to be around or somewhat larger than this fine range about 20 nm.…”