Study on the modification effect of copper on Al-15Mg2Si composite

The effect of different concentrations of Cu (0, 1, 3, and 5 wt %) on the microstructure and mechanical properties of in-situ Al-15Mg(2)Si composites was studied. The thermal analysis approach was employed to better understand the effect of Cu on the solidification behavior and microstructure evolution. The results showed that adding Cu, narrows the time interval between liquidus and eutectic lines within which the melt is being solidified that can reduce the average size of the primary Mg2Si (Mg2SiP) particles. Adding Cu also modifies the hopper-like morphology of Mg2SiP particles and leads to the formation of hard Cu-rich compounds (theta-Al2Cu and Q-Al5Mg8Si6Cu2) in the microstructure. According to the tensile tests results, the maximum tensile strength and fracture strain belong to the composites containing 3.0 and 1.0 wt % Cu, respectively. However, the maximum quality index (290 MPa) was obtained in the composite containing 3.0 wt % Cu which was about 25% higher than that of the unmodified composite. Increasing the Cu content over 3 wt % increases the volume fraction of brittle Cu-rich compounds and microporosities in the microstructure that adversely affects the composite quality.