A Phase-Field Model Study of Microstructural Effects on the Corrosion of Mg Alloys

Abstract

Understanding how alloy composition and thermal history determine the corrosion behavior is crucial to designing alloys with lower corrosion rates. We employ a model that combines the phase-field and smoothed boundary methods [1] to investigate the effect of second phases and particles on the corrosion behavior of Mg alloys. In this model, the dissolution rate at the metal/electrolyte interface is determined by the coupling of mass transport within the electrolyte and the Butler-Volmer electrochemical kinetics at the interface. The model is implemented in the PRISMS-PF framework [2,3], an open-source framework for phase-field modeling that employs a matrix-free finite element method. Simulations of corrosion are conducted with varying microstructure and compositions with associated corrosion parameters representative of Mg alloys. Specifically, we show how our approach can describe the experimentally observed microgalvanic effects due to the presence of impurities and second phases. Finally, we show the results of a parametric study of the dependence of the rate for various combination of the corrosion parameters for each phase.This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering as part of the Center for PRedictive Integrated Structural Materials Science (PRISMS Center) at University of Michigan.[1] A.F. Chadwick, J.A. Stewart, R.A. Enrique, S. Du, K. Thornton, Numerical Modeling of Localized Corrosion Using Phase-Field and Smoothed Boundary Methods, J. Electrochem. Soc. 165 (2018) C633–C646.[2] S. DeWitt, S. Rudraraju, D. Montiel, W. B. Andrews, K. Thornton, PRISMS-PF: A General Framework for Phase-Field Modeling with a Matrix-Free Finite Element Method. Submitted to npj Comput. Mater.[3] http://prisms-center.github.io/phaseField/