Influence of Shear Force on Microstructure Evolution and Plasticity of Semi-solid Sn-52Bi Alloy
Hypoeutectic Sn-52 Bi alloy was obtained by semi-solid mechanical stirring casting technology. The influences of shear force and stirring time on the microstructure and plasticity of semi-solid alloy under different solid phase ratio were investigated. The results indicate that the semi-solid Sn-Bi alloy with uniformly distribute and nearly round primary β-Sn phase was obtained. The diameters of round primary β-Sn phase is about 10 μm. The elongation of semi-solid Sn-Bi alloy prepared under agitating rate with 320 r/min, the temperature of 146 ℃ and the stirring time of 6 min is 31.3%, which is improved by 74.8% compared to that of Sn-Bi alloy prepared from the molten alloy at 180 ℃ and solidified in water. With stirring time and solid phase ratio of semi-solid alloy slurry increase, the formed round primary β-Sn phase gathers easily under shear force. Rosette-like and oval primary β-Sn phase develops after the slurry solidified in water, and then the elongation of semi-solid Sn-Bi alloy decreases.