Nanoscale Periodic Morphologies on the Fracture Surface of Brittle Metallic Glasses

Abstract

Out-of-plane, nanoscale periodic corrugations are observed in the dynamic fracture surface of brittle bulk metallic glasses with fracture toughness approaching that of silica glasses. A model based on the meniscus instability and plastic zone theory is used to explain such dynamic crack instability. The results indicate that the local softening mechanism in the fracture is an essential ingredient for controlling the formation of the unique corrugations, and might provide a new insight into the origin of fracture surface roughening in brittle materials.

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

“…This implies that the temperature decrease from 300 to 4.2 K leads to a significant drop in fracture toughness of Vitreloy 1 of at least one order of magnitude. The estimated fracture toughness of the as-cast Vitreloy 1 at 4.2 K is comparable to the room-temperature value of the heavily annealed Vitreloy 1 [47] or brittle metallic glass systems (Mg-or Fe-based) [14,16,19]. Such low toughness guarantees the brittle propagation of cracks via the cavitation mechanism, which is verified by the dimples and nanoscale periodic corrugations observed in the propagation region (Fig.…”

“…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.…”

Shear transformation zone volume determining ductile–brittle transition of bulk metallic glasses

“…7f. Similar nano-scale periodic corrugations have also been found on the fracture surfaces of high-velocity plate impact tests of Vit1 [17], the brittle Mg-based BMGs [31,32] and the impact test samples of relaxed Zr-based BMG [9,10,16,33]. The fracture toughness K c of this 653 K annealed sample at 77 K was calculated to be $1.3 MPa ffiffiffiffi m p through Eq.…”

Damage and dissipation mechanisms in the dynamic fracture of brittle materials: Velocity driven transition from nominally brittle to quasi-brittle

“…However, a number of puzzling observations remain at smaller velocities. In particular, even for velocities much lower than v b , (i) the measured dynamic fracture energy is generally much higher than that at crack initiation [10,[23][24][25][26] and (ii) fracture surfaces roughen over length scales much larger than the microstructure scale ("mist" patterns) [27], the origin of which remains debated [28][29][30][31][32][33][34][35][36][37].…”