Fig. 1. The true stress-strain curves at room temperature of the unfluxed and fluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG samples with an aspect ratio of H/D = 2:1. The inset is the enlarged regions pointed by black rectangle.

Fig. 2. A statistic results of stress drop (△σ) for (a) Unfluxed and (b) fluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG samples, the increasing rate of serration size (△σmax/△ε) is the slop of the red line.

Fig. 3. SEM images of the lateral of deformed samples of (a) unfluxed and (b) fluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMGs, which were unloaded before failure in compression. (c) and (d) are the enlarged SEM images of region A in (a) and region B in (b), respectively. (e) and (f) are the enlarged fracture features of fluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG sample after failure showing well-developed vein patterns and finger-like patterns, respectively.

Fig. 4. (a) The true stress-strain curve of fluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG samples with an aspect ratio of H/D = 1.5:1. The inset shows the sample after deformation (up to 30 % strain). (b) and (c) are SEM images of high magnification of the compressed sample in the inset of (a), showing multiple SBs. The true stress-strain curve of unfluxed sample was also shown for comparison.

Fig. 5. The relationship between compression strength (σc) and plastic strain (εp) of the typical Fe-based BMGs at room temperature.

Fig. 6. APT analysis on the unfluxed and fluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG samples. (a) The atom map for corresponding Fe, Ni, B, Si, Nb, P elements distribution of unfluxed and fluxed samples. Frequency distribution analysis of the composition of (b) unfluxed and (c) fluxed samples, obtained from experimental results and the binomial simulation, respectively. Several parameters employed to assess the quality of the fit of the experimental results to the binomial simulation and the corresponding atomic percentage are listed in the inserted tables of (b) and (c).

Fig. 7. The synchrotron XRD results of unfluxed and fluxed Fe39Ni39B12.82Si2.75P4.13Nb2.3 BMG samples. (a) Total structure factor S(Q), (b) enlarged region on the first peaks of S(Q) shown in (a) with the dashed lines denoting the peak positions, (c) reduced pair distribution function G(r), (d) enlarged region on the G(r) function shown in (c) at r ≤ 2.0 ? with dashed lines denoting the slope of the curve in this low-r region, (e) enlarged region on the first nearest neighbor peaks of G(r) function shown in (c), (f) enlarged region from q2 to q8 peaks of G(r) function shown in (c).

Fig. 8. The HRTEM images with the corresponding FFT pattern in the inset of (a) unfluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG sample and (b) fluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG sample, respectively, (c) and (d) are the enlarged images with the FFT patterns in the insets of the white square areas in (a) and (b), respectively, (e) the enlarged image of region A in (d), (f) the segmentation of the (e) for auto-correlation analysis.

Fig. 9. The segmentation of HRTEM images of the unfluxed (a) and fluxed (b) Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG samples for auto-correlation analysis. The dimension of each segment or cell is 1.915 × 1.915 nm2.

Fig. 10. (a) HRTEM image of fluxed Fe39Ni39B12.82Si2.75Nb2.3P4.13 BMG sample compressed uniaxial to a thin-disc shape (～30 % plastic strain), showing several SBs (red and green lines) and obvious phase separation, (b) the HRTEM image of compressed sample showing coarsening and disappearing of nanospheres in different regions of SBs, (c) the HRTEM image of SBs showing a sandwich-like heterogeneous structure, (d) the HRTEM image of high magnification of the white square area in (b) with green circles denoting the nanospheres and white squares showing the gathering of icosahedral-like clusters (white circles).

Fig. 11. (a) HRTEM image of SB at the initial stage of forming sandwich-like structure; (b) Enlarged region A in (a), yellow circle represent the icosahedral-like clusters.