Atom probe analysis of Sr distribution in alsi foundry alloys

Abstract

The addition of traces of Sr to AlSi foundry alloys induces a flake-to-fibrous transition of the eutectic phase which enhances tensile, impact and thermal shock properties. Since this modification is not always completely homogenous, the underlying mechanisms have to be reviewed. In this work the three dimensional Sr distribution in eutectic Si was analyzed by Laser Pulsed Atom Probe Tomography. Well modified fibers revealed nanometric segregations rich in Al and Sr. These features presented cluster-, planar- and rod-like morphologies which can be related to mechanisms involved in Si growth restriction. This finding reinforces the fact that Sr has a direct influence on the growth mechanism of eutectic Si.