Molecular dynamics simulation of Ga penetration along Σ5 symmetric tilt grain boundaries in an Al bicrystal

Ho-Seok Nam and David J. Srolovitz
Phys. Rev. B 76, 184114 – Published 21 November 2007

Abstract

Liquid metal embrittlement (LME) is a common feature of systems in which a low melting point liquid metal is in contact with another, higher melting point, polycrystalline metal. While different systems exhibit different LME fracture characteristics, the penetration of nanometer-thick liquid metal films along the grain boundary is one of the hallmarks of the process. We employ EAM potentials optimized for Al-Ga binary alloys in a series of molecular dynamics simulations of an Al bicrystal (with a Σ5 36.9°(301)/[010] symmetric tilt boundary) in contact with liquid Ga with and without an applied stress. Our simulations clarify the mechanism of LME and how it is affected by applied stresses. The interplay of stress and penetrating Ga atoms leads to the nucleation of a train of dislocations on the grain boundary below the liquid groove root which climbs down the grain boundary at a nearly constant rate. The dislocation climb mechanism and the Ga penetration are coupled. While the dislocations do relax part of the applied stress, the residual stresses keep the grain boundary open, thereby allowing more, fast Ga transport to the penetration front (i.e., Ga layer thickening process). The coupled Ga transport and “dislocation climb” is the key to the anomalously fast, time-independent penetration of Ga along grain boundaries in Al. The simulations explain a wide range of experimental observations of LME in the Al-Ga literature.

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  • Received 10 March 2007

DOI:https://doi.org/10.1103/PhysRevB.76.184114

©2007 American Physical Society

Authors & Affiliations

Ho-Seok Nam1,* and David J. Srolovitz1,2

  • 1Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
  • 2Department of Physics, Yeshiva University, New York, New York 10033, USA

  • *Present address: School of Advanced Materials Engineering, Kookmin University, Seoul 136-702, Korea. hsnam@kookmin.ac.kr

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Vol. 76, Iss. 18 — 1 November 2007

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