凝固条件和应变速率对Sn-58Bi钎料拉伸性能和断裂行为的影响

研究了熔炼制备的Sn-58Bi无铅钎料于水冷、空冷、炉冷三种方式冷却后在应变速率0.001，0.002，0.004 s−1下的拉伸性能和断裂行为. 结果表明，水冷和空冷钎料共晶组织细小，尤其是空冷钎料共晶组织更为均匀，而炉冷钎料共晶组织粗大且偏析严重. 随着应变速率增大，三种钎料抗拉强度均提高而断后伸长率均变小. 炉冷钎料组织偏析导致硬脆富Bi相聚集，抗拉强度最大，但断后伸长率极低，为典型的脆性断裂；水冷和空冷钎料的均细共晶组织显著提高了钎料断后伸长率，具有更均匀共晶组织的空冷钎料断后伸长率最大，呈现韧性或韧脆性混合断裂.

Effect of solidification condition and strain rate on tensile properties and fracture behavior of Sn-58Bi solder

The tensile property and fracture behavior of the Sn-58Bi lead free solder solidified in water, air and furnace, respectively, are studied at different strain rate of 0.001, 0.002, 0.004 s^–1. Results shown the eutectic structure of water cooling and air cooling Sn-58Bi solders is finer, in particular, the eutectic structure of air cooling solder is more uniform, while the eutectic structure of furnace cooling solder is coarse with serious microstructural segregation. The tensile strength of the solder becomes larger and the percentage elongation after fracture is smaller with increase of strain rate. Because of the accumulation of hard and brittle rich Bi which becomes from microstructural segregation in the Sn-58Bi solders, the tensile strength of furnace cooling solder is the maximum, however, its percentage elongation after fracture is the minimum, the fracture surface appears to be a typical brittle mode. The uniform eutectic structure can significantly improve the percentage elongation after fracture of the water cooling and air cooling Sn-58Bi solders, especially the percentage elongation after fracture of air cooling solder is maximum due to the best homogeneous eutectic organization, the fracture surface of air cooling solder is a brittle-ductility mixed fracture mode.