Cavitation in a metallic liquid: Homogeneous nucleation and growth of nanovoids

Abstract

Large-scale molecular dynamics (MD) simulations are performed to investigate homogeneous nucleation and growth of nanovoids during cavitation in liquid Cu. We characterize in detail the atomistic cavitation processes by following the temporal evolution of cavities or voids, analyze the nucleation behavior with the mean first-passage time (MFPT) and survival probability (SP) methods, and discuss the results against classical nucleation theory (CNT), the Tolman equation for surface energy, independent calculation of surface tension via integrating the stress profiles, the Johnson-Mehl-Avrami (JMA) growth law, and the power law for nucleus size distributions. Cavitation in this representative metallic liquid is a high energy barrier Poisson processes, and the steady-state nucleation rates obtained from statistical runs with the MFPT and SP methods are in agreement. The MFPT method also yields the critical nucleus size and the Zeldovich factor. Fitting with the Tolman's equation to the MD simulations yields the surface energy of a planar interface (~0.9 J m⁻²) and the Tolman length (0.4-0.5 Å), and those values are in accord with those from integrating the stress profiles of a planar interface. Independent CNT predictions of the nucleation rate (10(33 - 34) s(-1) m(-3)) and critical size (3-4 Å in radius) are in agreement with the MFPT and SP results. The JMA law can reasonably describe the nucleation and growth process. The size distribution of subcritical nuclei appears to follow a power law with an exponent decreasing with increasing tension owing to coupled nucleation and growth, and that of the supercritical nuclei becomes flattened during further stress relaxation due to void coalescence.

Cavitation in crosslinked polymers: Molecular dynamics simulations of network formation

“…polymer cavitation and crazing during deformation of thermoplastic polymers [6,8,[18][19][20][21][22]7]. However, we find that pores appear even in a highly connected network of strong covalent (FENE) bonds in addition to Lennard-Jones forces between all the beads.…”

“…However, traditional approaches to understanding crosslinked network formation focus on the overall crosslinked network, not on the possibility of void formation or other local variations [2][3][4][5]. Our interest in possible pore formation in crosslinked polymers that are formed from liquids is supported by simulations that show pores can arise by cavitation in amorphous liquids [6,7], even metals [8].…”

Time-dependent cavitation in a viscous fluid

“…(B12) (with r replaced by r 0 ) via increasing t i (r 0 ) by the growth time r r 0 dr/ṙ, as in Eq. (14). Since the growth integral has a singularity − ln (r 0 − 1) as r 0 → 1, the result will be r 0 independent, indicating asymptotically smooth matching of the nucleation and the growth regions.…”

“…While often destructive [2], cavitation also offers a remarkable glimpse into the world of elementary particles via the bubble chamber [3,4] and has a direct link to such puzzling phenomena as sonoluminescence [5] and, more generally, to sonochemistry [6]. Recent advances in molecular dynamics (MD) studies of cavitation in nonmetallic [7][8][9][10][11][12] and metallic [13,14] fluids can clarify the elusive properties of the smallest subnano bubbles which provide a key boundary condition for the classical-type nucleation-growth equations and alternatively can reveal situations where the classical approach has to be reassessed.…”

A phase-field-crystal alloy model for late-stage solidification studies involving the interaction of solid, liquid and gas phases

“…Rappaz, Drezet and Gremaud (RDG) developed a two-phase theory that takes into account both elastic and plastic deformation of the solid confining the narrow liquid channels that form hot tears [32]. The nucleation of the gas phase (or cavitation) in these continuum-based models is typically determined by setting up a pressure threshold which can be obtained from atomic-level models [33,34].…”