Preparation Of High Ductility Sn-62Bi Alloy And The Research Of Its Extrusion Processing Technology

In this paper, hypereutectic Sn-62Bi alloy was obtained by semisolid casting technology, and the Sn-62Bi alloy wire was prepared by extrusion forming process. The microstructure and mechanical properties of hypereutectic Sn-62Bi alloy which produced by the semisolid process and the the Sn-62Bi alloy wire which prepared by extrusion forming process were investigated by tensile strength test, metallographic analysis. The result indicated that semisolid casting process not only improve dramatically the ductility of Sn-62Bi alloys with relatively high Bi content, but also optimize the property of Sn-62Bi alloys wire which prepared by extrusion forming process.Hypereutectic Sn-62Bi alloy was obtained by semisolid mechanical stirring casting technology. The influence of shear force and stirring time on the microstructure and plasticity of semisolid alloy under different solid phase ratio was investigated. The results indicated that the semisolid Sn-62Bi alloy with uniformly distributed and fine quadrate primary Bi phase was obtained. The size of quadrate primary Bi phase was about 30 μ m. The elongation of semisolid Sn-62Bi alloy prepared under agitating rate with 500 r · min-1, the temperature of 145 ℃ and the stirring time of 15 min was 39.9%, which was improved by 283.3%, compared to that of Sn-62Bi alloy prepared from the molten alloy at 180℃ and solidified in water. When the agitating temperature was 150℃, friction and collision of quadrate primary Bi phase particles increased with stirring time increase, which led to were broken further and nucleation rate increased. Semi-solid Sn-62Bi alloy with smaller and more uniformly distributed quadrate primary Bi phase particles was obtained and its elongation was improved.A new direct ultrasonic treatment (DUT) setup with the ultrasonic horn placed in the horizontal direction was developed and used in the preparation of semisolid Sn-62Bi slurry. The influence of DUT temperature on microstructure and properties of Sn-62Bi alloy were studied. Compared to the conventional liquid casting Sn-62Bi alloy without DUT, it is discovered that the primary Bi blocks of semisolid Sn-62Bi alloy prepared with the DUT process distribute more homogeneously and are smaller. With the treatment by ultrasonic vibration in the semisolid state for 120 s, the higher the primary Bi phase fraction in the slurry, the smaller the size of primary semisolid Bi blocks formed after solidification. The average side length of the primary Bi blocks was from 30 μm to 80 μm. The elongation of Sn-62Bi alloy treated by DUT for 120 s at 145 ° C is 43.21%, as compared to the conventional liquid casting Sn-62Bi alloy without DUT. This indicates that DUT process could improve dramatically the ductility of Sn-62Bi alloys with relatively high Bi content.The Sn-62Bi alloys wire property which obtained by extrusion process and the property of Sn-62Bi alloys before extrusion with good correlation. The finer and uniform of the average side length of the primary Bi blocks before extrusion, the better of the property of Sn-62Bi alloys wires after extrusion.