Influence of rheo-diecasting processing parameters on microstructure and mechanical properties of hypereutectic Al-30% Si alloy

The effects of pouring temperature, vibration frequency, and the number of curves in a serpentine channel, on the microstructure and mechanical properties of Al-30% Si alloy processed by rheo-diecasting (RDC) were investigated. The semisolid Al-30% Si alloy slurry was prepared by vibration serpentine channel pouring (VSCP) process in the RDC process. The results show that the pouring temperature, the vibration frequency, and the number of the curves strongly affect the microstructure and mechanical properties of Al-30% Si alloy. Under experimental conditions of a pouring temperature of 850 degrees C, a twelve-curve copper channel and a vibration frequency of 80 Hz, the primary Si grains are refined into fine compact grains with average grain size of about 24.6 mu m in the RDC samples assisted with VSCP. Moreover, the ultimate tensile strength (UTS), elongation and hardness of the RDC sample are 296 MPa, 0.87% and HB 155, respectively. It is concluded that the VSCP process can effectively refine the primary Si grains. The refinement of primary Si grains is the major cause for the improvement of the mechanical properties of the RDC sample.