Enhanced combination of strength and ductility in the semi-solid rheocast hypereutectic Al Si alloy with the effect of in-situ TiB2 particles

This study aims to address the issues of low strength and high brittleness associated with common industrial hypereutectic aluminum alloys. We report here that the addition of TiB2 particles (TiB2p) not only enhances the strength of the rheocast hypereutectic Al17Si alloy, but also exerts a positive effect on its ductility. As the content of TiB2p reaches 6 wt%, the strength and ductility of composites are increased by 63.4% and 62%, respectively (UTS = 283.3 MPa, and EL = 1.62% in this study). The EBSD results show that the densities of low-angle and high-angle grain boundaries increase with the content of TiB2p. The interfaces of TiB2p/Si and TiB2p/Al are investigated by TEM, HRTEM, and an atomic structure model simulation. A model addressing dislocation multiplication, and crack initiation and propagation is developed to elaborate the strength-ductility synergy mechanisms of the TiB2p/Al-17Si composite.