Abstract:A preparation technology of semi-solid metal slurry introducing grain process (IGP) was developed. The effects of processing parameters on the microstructures of the semi-solid A356 Al-alloy slurries were investigated, and the formation mechanism and morphology controlling of the spherical primary α(Al) grains were discussed. The results show that when the preparing slurry is 4 kg, IG size is 10 mm, dosage is 3.5% and dumping temperature (DT) is 611-617 °C, the mean diameter of the primary α(Al) grains in the semi-solid slurries can reach 40-75 μm and the shape factor can reach 0.82-0.89. When the IG size is  10 mm, DT is 613 °C and dosage is 2%-4%, the mean diameter can reach 45-82 μm and the shape factors can reach 0.78-0.88. With decreasing DT or increasing dosage properly, the primary α(Al) grain morphology is better. When Q_R=Q_A and R_h=R_c, as long as the DT is suitable, excellent semi-solid slurry can be produced. As a result of the IG melting, a large amount of dendritic fragments can become the direct source of the primary α(Al) grains. Meanwhile, many undercooled areas are formed, where abundant primary α(Al) grains are multiplied by heterogeneous nucleation.

Key words: A356 Al alloy; semi-solid; introducing grain; primary α(Al)