A Molecular Dynamics Simulation Study of the Cavitation Pressure in Liquid Al

To understand the formation mechanism of hot tearing defects generated during casting, a knowledge of the pressure at which cavities form spontaneously in the liquid metal is required. In this work, molecular dynamics (MD) simulations were used to compute the cavitation pressure Pc in liquid Al, where atomic interactions were described by an embedded atom method potential. The cavitation pressure was computed for various initial conditions and system sizes, and using classic nucleation theory, Pc was extrapolated from MD length and time scales to those appropriate for casting. A value of Pc ≈ −670 MPa was obtained, which is several orders of magnitude less than that predicted from hot tearing models. To investigate the possible role of heterogeneous nucleation sites, the Pc simulations were repeated on solid–liquid systems that were simultaneously solidifying. In addition, the influence of a trace impurity Mg on the cavitation pressure was also investigated. Neither the impure Mg atoms nor the solid–liquid interfaces act as heterogeneous sites.