How does spallation microdamage nucleate in bulk amorphous alloys under shock loading?

Abstract

Transmission electron microscopy of the amorphization of copper indium diselenide by in situ ion irradiation J. Appl. Phys. 111, 053510 (2012) Diffusion-controlled formation mechanism of dual-phase structure during Al induced crystallization of SiGe Appl. Phys. Lett. 100, 071908 (2012) Local structure of nitrogen in N-doped amorphous and crystalline GeTe Appl. Phys. Lett. 100, 061910 (2012) Facile creation of bio-inspired superhydrophobic Ce-based metallic glass surfaces Appl. Phys. Lett. 99, 261905 (2011) Unexpected short-and medium-range atomic structure of sputtered amorphous silicon upon thermal annealing J. Appl. Phys. 110, 096104 (2011) Additional information on J. Appl. Phys. Specially designed plate-impact experiments have been conducted on a Zr-based amorphous alloy using a single-stage light gas gun. To understand the microdamage nucleation process in the material, the samples are subjected to dynamic tensile loadings of identical amplitude ($ 3.18 GPa) but with different durations (83-201 ns). A cellular pattern with an equiaxed shape is observed on the spallation surface, which shows that spallation in the tested amorphous alloy is a typical ductile fracture and that microvoids have been nucleated during the process. Based on the observed fracture morphologies of the spallation surface and free-volume theory, we propose a microvoid nucleation model of bulk amorphous alloys. It is found that nucleation of microvoids at the early stage of spallation in amorphous alloys results from diffusion and coalescence of free volume, and that high mean tensile stress plays a dominant role in microvoid nucleation.

Intrinsic structural defects on medium range in metallic glasses

“…Just before void nucleation, the density begins to decrease a lot at the nucleation site. As free volume is believed to play an important role during the void nucleation process [46,49], this phenomenon is beyond our expectation. It implies that not only the free volume content but also the atomic packing has significant influence.…”

Cryogenic-temperature-induced transition from shear to dilatational failure in metallic glasses

“…This results in the emergence of 10-nm-scaled shear bands, which macroscopically leads to shear-dominated failure [14,15]. However, recent experiments [14,[16][17][18] and simulations [1,3] have revealed that the dilatation itself, whether induced by shear or hydrostatic tension, can dominate the brittle failure of metallic glasses. In this case, the crack tip propagates via cavitation events that involve a series of nanoscale void nucleation and coalescence processes with very limited plastic growth.…”

Cavitation instability in bulk metallic glasses

“…To understand the void nucleation mechanism, we proposed a we propose a void nucleation model of amorphous alloys developed from traditional stress temperature-driven models widely used in polycrystalline materials [6]. We also consider free-volume theory to understand and characterize microvoid nucleation in BMGs.…”