The Role of Cavitation in Glass Fracturing

Wang Wei Hua’s group at the Institute of Physics of the Chinese Academy of Sciences investigated the role of cavitation in the fracture behavior of different types of glass in a study that could prove useful in developing stronger versions of the material.

Cavitation has long been assumed to be the underlying mechanism involved in the fracture of metallic glasses, as well as other glassy systems. However, research efforts to observe the cavitation behavior of fractures has thus far been unsuccessful in delivering conclusive information of the effect.

The researchers first performed Vickers indentation (done with a pyramidal diamond, and a procedure that determines a material’s hardness) on a sample attached to an inclined substrate. The inclination, together with the pyramid indenter, was introduced to induce opening-mode loading that results in a cleavage emanating from the indent corner. This was observed with a scanning electron microscope.

The experiment showed that crack propagation is dominated by the self-organized nucleation, growth, and coalescence of nanocavities in metallic glasses.

The work further showed the evolutionary process of crack morphologies from separated nanocavities to wave-like nanocorrugations and confirmed that cavitation is the origin of periodic fracture surface patterns.

The researchers also found that cavitation-induced nanopatterns are additionally prevalent in typical polymer glass and silicate glass, which suggests that the cavitation mechanism is prevalent in the fracture of glasses. Plastic flow exhibited by the cavitation process therefore proves that nanoscale ductility is involved in the breakage of nominally brittle glasses.

Proving cavitation behavior in the fracture of glasses challenges the traditional understanding of how glasses break. The researchers’ findings have significant implications for the understanding of the fundamental process of failure in disordered systems and provides insight for engineering better glasses.

The research was published in Science Advances (www.doi.org/10.1126/sciadv.abf7293).