Investigation of Cavitation in Glass- Forming Liquids

In an effort to better understand the source of toughness in metallic glass, we have investigated cavitation in glass-forming liquids. When subjected to negative hydrostatic pressure, a liquid will reduce its energy through the formation of a cavity. This phenomenon is the competing process to shear band growth and the development of a large plastic zone, which we have identified as the crucial parameter for the wider adoption of metallic glass as an engineering material. We report the homogeneous and heterogeneous nucleation of cavities in Zr41.2Cu12.5Ti13.8Be22.5Ni10 (Vitreloy 1) liquid by the application of a critical negative pressure. For homogeneous nucleation, we estimate a critical negative pressure of less than 500 MPa at a temperature of roughly 1000 oC and a timescale of ~7 s. The heterogeneous nucleation of cavities is observed and is estimated to take place at much smaller negative pressures, thus an important finding as this easy pathway to cavitation represents a limiting factor for plastic zone development in metallic glass. When liquid Vitreloy 1 is subjected to a negative pressure less than the critical pressure for homogeneous nucleation on a laboratory timescale of 1 to 7 s and is free of heterogeneous nucleation sites, no cavities are formed. The liquid is thus “metastable” on laboratory timescales with respect to cavitation at these temperatures and estimated negative pressures.