共晶转变过程中施加机械搅拌及再加热对Sn-58Bi合金组织与力学性能的影响

Influence of Mechanical Agitation and Reheating on Microstructure and Mechanical Properties of Sn-58Bi Alloy During Eutectic Transformation Process

在测试Sn-58Bi共晶合金凝固完成时间的基础上,在共晶转变过程中对已析出的共晶固相和液相混合物进行机械搅拌和再加热,研究了再加热温度对共晶合金组织与力学性能的影响。结果表明,在180℃熔融状态无机械搅拌低压吸铸水冷却条件下所获得的Sn-58Bi合金中共晶组织由蔷薇状的Sn相和粒状Bi相所组成,其伸长率为19.5%;在共晶温度139℃下机械搅拌10 min,直接加热到140℃并保温5 min后低压吸铸水冷所制备的Sn-58Bi合金由直径约为5μm球状Sn相和层状共晶组织构成,其伸长率提高至37.5%,与180℃下合金熔液不经过机械搅拌直接水冷相比提高了97%。随着再加热温度升高至液相线以上,所获得的合金组织中的Sn相为短棒状,呈现出树枝晶析出的趋势,合金的塑性下降。

On the basis of the test of Sn-58 Bi eutectic alloy solidification completion time, mechanical stirring and reheating of the mixture with precipitated eutectic solid and liquid during eutectic transformation were carried out. The effects of reheating temperature on mechanical properties and microstructure of the eutectic alloy process were investigated. The results indicate that eutectic microstructure of the Sn-58 Bi alloy obtained at 180℃ molten state without mechanical mixing under low-pressure suction casting and then water cooling conditions is composed of rosette Sn phase and granular Bi phase,and the elongation of the alloy is 19.5%. The Sn-58 Bi alloy obtained at the eutectic temperature of 139 ℃ with mechanical mixing for 10 min and then direct heating to 140 ℃ for 5 min, next under low-pressure suction casting and then water cooling conditions is composed of spherical Sn phase with the diameter of about 5 μm and the lamellar eutectic microstructure, and the elongation of the alloy increases to 37.5%. Compared to the molten alloy at 180 ℃ without mechanical agitation and water cooling,its elongation is improved by 97%. With the reheating temperature increases to above liquidus, Sn phase in microstructure is short rod shape, which presents the precipitation trend of dendritic grain and the elongation of the alloy is decreased signally.