剪切力下半固态Sn-52Bi合金组织演变与塑性的研究

Influence of Shear Force on Microstructure Evolution and Plasticity of Semi-solid Sn-52Bi Alloy

采用机械搅拌的半固态铸造技术制备Sn-52Bi合金,探索了不同固相率下剪切力和作用时间对半固态Sn-Bi合金组织和塑性的影响。结果表明,在近液相线的146℃(固相率为4%),搅拌速度为320 r/min和搅拌6 min的工艺条件下,制备出分布均匀、直径约10μm球状初生相的半固态Sn-52Bi合金,其伸长率为31.3%,与在180℃下的合金金属熔液直接水冷凝固而成的相比提高了74.8%。随着剪切力作用时间的延长和半固态合金浆料中固相率的增加,半固态浆料的初生相易发生团聚,所制备的半固态Sn-Bi合金初生相为分布不均的蔷薇形或椭圆形,合金伸长率下降。

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.