Abstract: Amorphous alloys have attracted much attention in the field of cavitation erosion (CE) due to their good comprehensive properties. However, due to the special amorphous structures that are difficult to characterize, their micro-response behaviors and damage mechanisms during the CE process have not been well elucidated. In this paper, advanced techniques including focused ion beam (FIB) and transmission electron microscope (TEM) were used to comparatively study the microstructure evolution and volume loss rules of Cu_47.5Zr_45.1Al_7.4 and Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 bulk metallic glasses (BMG) under the action of cavitation load and cavitation heat to reveal their CE mechanisms. The results showed that the absence of small atoms in Cu_47.5Zr_45.1Al_7.4 led to a large free volume, thereby compromising its hardness, modulus, and yield strength. However, this also made it more susceptible to shear banding, which in turn enhanced its energy absorption capabilities. Although Cu_47.5Zr_45.1Al_7.4 had a higher glass transition temperature (T_g) and onset temperature of crystallization (T_x), as well as a wider supercooled liquid phase region (ΔT_x), its exothermic peak was obviously pronounced and the transformation temperature range was significantly narrower. Therefore, it is more likely to adaptively form Cu-rich nanocrystals under the action of cavitation heat. Additionally, the larger free volume in the shear band was conducive to the diffusion of atoms and the occurrence of adaptive nanocrystallization behaviors in Cu_47.5Zr_45.1Al_7.4. These nanocrystals were able to effectively force crack deflection, thereby dissipating impact energy and delaying the fatigue spallation of the material. Consequently, Cu_47.5Zr_45.1Al_7.4 exhibited a far longer incubation period and a noticeably lower cumulative volume loss.

Key words: Amorphous alloy, Cavitation erosion, Cavitation heat, Nanocrystallization, Shear band