Preparation of hybrid particulates SiCnp and Mg2Si reinforced Al-Cu matrix composites

In this study, a new type of external added nano-sized SiC particles (SiCnp for short) and in-situ Mg2Si particles reinforced composites, i.e. (1.5 wt% Mg2Si + 1 wt% SiCnp)/Al-Cu composites, has been successfully prepared for the first time, and the microstructure and mechanical properties of the composites are studied. The eutectic Mg2Si phase in the Mg2Si/AI-Cu composites is refined from short strip with length of about 10 mu m to dot shape with diameter of about 2 mu m in (Mg2Si + SiCnp)/Al-Cu composites, which is uniformly distributed inside Al2Cu phases precipitated at the grain boundary. The alpha-Al grains are also significantly refined. It is also first discovered that SiCnp can act as nucleus of Mg2Si, or be captured by the Mg2Si phase during solidification, which promotes the heterogeneous nucleation of the eutectic Mg2Si phase to reduce the size of Mg2Si phase. The ultimate tensile strength (UTS) and yield strength of (Mg2Si + SiCnp)/Al-Cu composites are 325 MPa and 210 MPa, which are 3.2% and 28.8% higher than those of Mg2Si/AI-Cu composites, respectively. These properties are also improved by 20.4% and 21.4% respectively compared with SiCnp/Al-Cu composites, while (Mg2Si + SiCnp)/Al-Cu composites maintain good ductility.