Fracture Mechanisms in Bulk Metallic Glassy Materials

Abstract

We find that the failure of bulk metallic glassy (BMG) materials follows three modes, i.e., shear fracture with a fracture plane significantly deviating from 45 degrees to the loading direction, normal tensile fracture with a fracture plane perpendicular to the loading direction, or distensile fracture in a break or splitting mode with a fracture plane parallel to the loading direction. The actually occurring type of failure strongly depends on the applied loading mode and the microstructure of the material. Extensive evidence indicates that the Tresca fracture criterion is invalid, and for the first time, three fracture criteria are developed for isotropic materials with high strength, such as advanced BMGs or the newly developed bulk nanostructural materials.

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

“…1b presents the macroscopic failure modes at different temperatures. It can be seen that, at temperatures of 300, 221, 152 and 77 K, the fracture angles are about 56°, 59°, 60°and 61°, respectively, falling in the common range for metallic glasses under uniaxial tensions [29,38,39]. This means that the failure in these cases is dominated by shear stress, but is also affected by normal stress.…”

Serrated plastic flow during nanoindentation in Nd-based bulk metallic glasses

“…Serrated flow phenomenon during nanoindentation was already found at low strain rates [7 -10]. In this work, the plastic deformation in Nd 60 Al 10 Ni 10 Cu 202x Fe x (x ¼ 0; 5,7,10,15,20) was studied by using nanoindentation experiments and atomic force microscopy. The effect of the microstructure on the serrated flow behavior is studied in this alloy system.…”

Structural aspects of elasto-plastic deformation of a Zr-based bulk metallic glass under uniaxial compression

“…6(a) beginning of softening (indicated by an arrow in Fig. 6(a) uniaxial compression, which occurs at about 42° [47]. It is also 385 worth to note that, the calculated h cmax increases also after the 386 beginning of softening up to the fracture.…”

“…Due to the amorphous structure and lack of long-range order, 45 bulk metallic glasses (BMGs) do not experience any of the plastic 46 deformation mechanisms of their crystalline counterparts, such 47 as dislocation gliding or twinning [1]. Alternatively, the formation 48 and propagation of localized shear bands nucleated from shear 49 transformation zones (STZs) is the most accepted mechanism of 50 room temperature plastic deformation in BMGs [1].…”