Variation of microstructure and mechanical properties with nano-SiCp levels in the nano-SiCp/AlCuMnTi composites

Nano-sized SiC particles (SiCnp for short) reinforced Al-5Cu-0.5Mn-0.15Ti composites have been successfully fabricated by a process consisting of high energy ball milling, mechanical stirring and ultrasonic treatment for composite slurry and squeeze casting. The variation of microstructure and mechanical properties with SiCnp levels in xSiCnp/AlCuMnTi (x = 0.5, 1, 1.5, 2 wt%) composites is investigated for the first time. The SiCnp are uniformly distributed in the SiCnp/Al-5Cu composites made with the process. With the increase of SiCnp content from 0.5 to 2.0 wt%, the primary α-Al and Al2Cu phases are refined significantly up to 1.5 wt% but then become coarser at 2.0 wt%. The optimal mechanical properties are obtained in 1.5 wt% SiCnp/AlCuMnTi composites, which exhibit 298 MPa in ultimate tensile strength (UTS), 178 MPa in yield strength (YS) and 12.9% in elongation. These properties are increased by 18.7%, 11.3% and 25.3%, respectively, compared with the AlCuMnTi matrix alloy. The enhancement of strength is attributed to four strengthening mechanisms, among which the ΔσCTE and ΔσOrowan are the most important contributors. It is noteworthy that with more SiCnp in the present composites, the strength increases while elongation increases as well.