Plasticity improvement of an Fe-based bulk metallic glass by geometric confinement

Deformation behaviour of amorphous Fe-Ni-W/Ni bilayer-confined bulk metallic glasses

“…17 The enlargement of the confined stress arrests the propagation of the shear bands, preventing the catastrophic failure from the avalanches and resulting in a stable plastic flow before the failure. 16,25 Recently, many studies have reported that the interface can induce the initiation of more smaller shear bands and the corresponding increased interactions (branching and arresting) between the shear bands that, in turn, increase the plasticity of a coated specimen. 16,19 Besides the confining effect, the outside nickel layer is also found to be effective at hindering the propagation of the shear bands, dissipating the stored elastic energy in the core BMG.…”

“…16,25 Recently, many studies have reported that the interface can induce the initiation of more smaller shear bands and the corresponding increased interactions (branching and arresting) between the shear bands that, in turn, increase the plasticity of a coated specimen. 16,19 Besides the confining effect, the outside nickel layer is also found to be effective at hindering the propagation of the shear bands, dissipating the stored elastic energy in the core BMG. 16 Moreover, since the hardness of the Fe-Ni-W coatings (measured as 647 HV) is much larger than the hardness of the BMG specimen (about 442 HV), the inner Zr-BMG layer may act as the softer phase, initiating the shear bands, and the outer amorphous Fe-Ni-W layer may act as the harder phase, inhibiting the propagation of the shear bands.…”

“…16,19 Besides the confining effect, the outside nickel layer is also found to be effective at hindering the propagation of the shear bands, dissipating the stored elastic energy in the core BMG. 16 Moreover, since the hardness of the Fe-Ni-W coatings (measured as 647 HV) is much larger than the hardness of the BMG specimen (about 442 HV), the inner Zr-BMG layer may act as the softer phase, initiating the shear bands, and the outer amorphous Fe-Ni-W layer may act as the harder phase, inhibiting the propagation of the shear bands. 29,30 The complicated mechanisms for the initiation and propagation of the shear bands (intermittent sliding) in the bilayer-confined BMGs may need further verification; however, the corresponding serrated flow shown in the stress-strain curves, without much decrease in the loads, distinctly illustrates the stable plastic flow in the bilayer-confined BMGs.…”

“…[14][15][16][17][18] For example, by electroplating a single coating layer of Ni, the plasticity of a nominally "brittle" Fe-based BMG was increased from 0.5 % to 5 %. 16 In 2012, Chen et al 17 reported an improvement in the plasticity of a Zr-based BMG using a Cu/Ni bilayer coating, in which the soft Cu coating absorbs the loading stress while the hard Ni layer imposes a confining effect. The bilayer coating successfully increased the plasticity of the as-cast Zr-based BMG from 1.3 % to 11.2 %.…”

Plasticity enhancement in Ni–P amorphous alloy/Ni/Zr-based metallic glass composites with a sandwich structure

“…Numerous methods have been developed to improve the ductility of BMGs in order to inhibit the occurrence of the catastrophic failure under action of compressive stress [7][8][9][10][11][12][13]. Liu et al [9] demonstrated that a Zr-based amorphous alloy, composed of hard regions surrounded by soft regions, experienced superplastic deformation at room temperature and suggested that the exceptional deformability is ascribed to the homogeneous and concurrent nucleation and evolution of high-density shear bands throughout the materials.…”