Fracture through cavitation in a metallic glass

Abstract

-The fracture surfaces of a Zr-based bulk metallic glass exhibit exotic multi-affine isotropic scaling properties. The study of the mismatch between the two facing fracture surfaces as a function of their distance shows that fracture occurs mostly through the growth and coalescence of damage cavities. The fractal nature of these damage cavities is shown to control the roughness of the fracture surfaces. [17,18] have shown to be self-affine, with a roughness exponent ζ ≈ 3/4 in spite of huge differences in the fracture mechanisms. It was therefore suggested [5,19] that ζ might have a universal value, i.e., independent of the fracture mode and of the material.More recently, it has been shown [11,13] that fracture surfaces are anisotropic, i.e. when profiles along the direction of crack propagation are considered, the roughness exponent is equal to β 0.6. Bonamy et al. [12] have shown that the set of exponents {ζ 0.75, β 0.6} define a universality class corresponding to length scales smaller than the process zone size, where non linear elastic processes take place. Above this process zone size, another university class is observed [12,20,21] characterized by a set of exponents {ζ 0.4, β 0.5} that can be understood theoretically within the Linear Elastic Fracture Mechanics framework.A third regime arises at very small length scales, characterized by a roughness index close to ζ ≈ 0.5, observed in a metallic alloy and in a soda-lime silicate glass [8][9][10] along a direction perpendicular to the direction of crack propagation. This regime was suggested [22] to be

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.…”

“…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. The cavitation-mediated brittle failure is strongly suggested by the resulting fracture surface morphologies [14,[16][17]19]: very fine dimples that are approximately equiaxed in shape and nanoscale periodic corrugations.…”

Cavitation in Amorphous Solids

“…While the shear response of amorphous solids has received a significant amount of attention in the theoretical physics and molecular simulation literature over the past decade [1-8], significantly less attention has been devoted to hydrostatic loading in such systems [9,10]. This omission appears significant since experimental studies in metallic glass (MG) and other amorphous solids reveal nanocavities [11,12] that form during or subsequent to deformation and strongly implicate cavitation in the physics of the fracture process zone, even when the fracture behavior is relatively brittle [13][14][15]. The importance of cavitation in fracture is supported by recent molecular dynamics (MD) simulations in glassy Cu 50 Zr 50 and Fe 80 P 20 [16].…”

Structural inhomogeneities in glasses via cavitation

“…Such structures can be associated with shear banding or (micro-)cavity formation and may lead to the initiation of crack formation or a strong brittleness [3][4][5][6][7][8]. Cavities are naturally formed when a liquid is expanded such that the two-phase region of gas-liquid coexistence is entered [9][10][11][12][13][14].…”