Effect of Bi on graphite morphology and mechanical properties of heavy section ductile cast iron
Effect of Bi on graphite morphology and mechanical properties of heavy section ductile cast iron
复制标题
Bi对大断面球墨铸铁石墨形态和力学性能的影响
作者：
Song Liang;Guo Erjun;Tan Changlong
为改善大断面球墨铸铁的力学性能，在球墨铸铁中加入了铋。制备了5种铋含量为0 ~ 0.014 wt.%的铸件；从铸件边缘到中心选取不同凝固冷却速度的四个位置进行组织观察和力学性能测试。研究了铋含量对大断面球墨铸铁石墨形貌和力学性能的影响。结果表明：随着冷却速度的降低，5种铸件不同部位的抗拉强度、伸长率和冲击韧性均降低；随着Bi含量的增加，同一位置的石墨形貌和力学性能均得到改善，其中Bi含量不高于0.011wt.%时，力学性能的改善较为明显。但当Bi含量进一步增加到0.014wt时。%时，由于块状石墨数量的增加和块状石墨的聚集，其力学性能的改善并不明显。随着Bi含量的增加，拉伸断裂机制由脆性断裂转变为韧脆混合断裂。
To improve the mechanical properties of heavy section ductile cast iron, bismuth(Bi) was introduced into the iron. Five castings with different Bi content from 0 to 0.014 wt.% were prepared; and four positions in the casting from the edge to the center, with different solidifi cation cooling rates, were chosen for microstructure observation and mechanical properties test. The effect of the Bi content on the graphite morphology and mechanical properties of heavy section ductile cast iron were investigated. Results show that the tensile strength, elongation and impact toughness at different positions in the fi ve castings decrease with a decrease in cooling rate. With an increase in Bi content, the graphite morphology and the mechanical properties at the same position are improved, and the improvement of mechanical properties is obvious when the Bi content is no higher than 0.011wt.%. But when the Bi content is further increased to 0.014wt.%, the improvement of mechanical properties is not obvious due to the increase of chunky graphite number and the aggregation of chunky graphite. With an increase in Bi content, the tensile fracture mechanism is changed from brittle to mixture ductile-brittle fracture.