Topological variations in aluminum-silicon alloys through inoculation with alkali earth elements: A first-principles study

Abstract

Aluminum-silicon is a simple binary eutectic system with limited solid solubility of aluminum in silicon. Hypoeutectic compositions of Al-Si are the basis of several alloys for aerospace and automotive industries. The eutectic phase mixture contains coarse plate-like silicon. Typically, alkaline earth elements such as strontium, calcium, and barium are added in minute quantities that produce a fibrous network of silicon to improve the fracture toughness. Here, we use first-principles calculations to understand the origin of these morphological variations and explain these through interatomic interactions between aluminum, silicon, and inoculant atoms. Our results show that silicon atoms cluster together and arrange themselves in a planar (100) configuration within the aluminum matrix. When strontium, calcium, or barium atoms are added to the system, these atoms prefer to be near the silicon clusters and change the planar morphology to a three-dimensional configuration with facets on (111) planes.