Composition Profiles around Solute-Lean, Spherical Nanocrystalline Precipitates in an Amorphous Matrix: Implications for Corrosion Resistance

Abstract

Although precipitates and the uneven solute distributions surrounding them are generally detrimental to the corrosion resistance of metals, solute-depleted nanocrystalline precipitates in an amorphous metallic matrix are unexpectedly benign. This good corrosion resistance might result from the beneficial effects related to solute buildup in the remaining amorphous matrix. In this work, we examine theoretically the influence of transformation strain, compositional strain, surface stress, capillarity, and alloy composition on the composition profile surrounding a spherical nanocrystalline precipitate growing into a supersaturated amorphous matrix. The imposed radial symmetry, the assumption of linear elasticity, and a quasistationary approximation of the matrix composition field at low supersaturations permit analytical expressions for the interfacial compositions and composition fields to be obtained. The results are compared with the known bulk effects of solute in real glass systems, to suggest that solute composition fields may contribute to the good corrosion resistance of partially nanocrystalline alloys.