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 P _c 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, P _c was extrapolated from MD length and time scales to those appropriate for casting. A value of P _c ≈ −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 P _c 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.