Effects of high-pressure rheo-squeeze casting on the Fe-rich phases and mechanical properties of Al-17Si-(1,1.5)Fe alloys

The effects of high pressure rheo-squeeze casting (HPRC) on the Fe-rich phases (FRPs) and mechanical properties of Al-17Si-(1,1.5)Fe alloys were investigated. The alloy melts were first treated by ultrasonic vibration (UV) and then formed by high-pressure squeeze casting (HPSC). The FRPs in the as-cast HPSC Al-17Si-1Fe alloys only contained a long, needle-shaped β-Al₅FeSi phase at 0 MPa. In addition to the β-Al₅FeSi phase, the HPSC Al-17Si-1.5Fe alloy also contained the plate-shaped δ-Al₄FeSi₂ phase. A fine, block-shaped δ-Al₄FeSi₂ phase was formed in the Al-17Si-1Fe alloy treated by UV. The size of FRPs decreased with increasing pressure. After UV treatment, solidification under pressure led to further refinement of the FRPs. Considering alloy samples of the same composition, the ultimate tensile strength (UTS) of the HPRC samples was higher than that of the HPSC samples, and the UTS increased with increasing pressure. The UTS of the Al-17Si-1Fe alloy formed by HPSC exceeded that of the Al-17Si-1.5Fe alloy formed in the same manner under the same pressure. Conversely, the UTS of the Al-17Si-1Fe alloy formed by HPRC decreased to a value lower than that of the Al-17Si-1.5Fe alloy formed in the same manner.