微观缩松对蠕铁微观组织和力学性能的影响

微观缩松缺陷的位置分布、体积大小表现出随机性特点,会对材料微观组织和宏观力学性能产生影响. 通过微观组织观测,研究了微观缩松对蠕墨铸铁材料微观组织的影响. 同时,建立了含微观缩松缺陷的三维代表性体积元模型,通过施加周期性边界条件和拉伸位移载荷,研究了微观缩松对蠕墨铸铁材料宏观力学性能的影响. 结果表明,蠕铁材料微观缩松缺陷周围组织中含有Ce,Mg元素,表明稀土蠕化剂与所研究的蠕墨铸铁的微观缩松的形成有密切联系,增加了材料内部形成微观缩松的倾向. 随着材料内部微观缩松体积分数的增加,材料的宏观等效弹性模量呈线性降低;微观缩松还会造成材料内局部区域的应力集中,易于微小裂纹的萌生及扩展. 

Effects of Micro Porosity on Microstructure and Mechanical Properties of Compacted Graphite Cast Iron

The micro porosity, existing in a random distribution of location and volume, makes great effect on the microstructure and mechanical properties of materials. In the study, the effect of micro porosities on the microstructure of compacted graphite cast iron was analyzed by micro-structural observation. At the same time, the representative volume element model representing the micro porosity was built up. Then, applying the periodic boundary conditions and tensile displacement load, the effects of micro porosity on mechanical properties of compacted graphite cast iron were investigated. The results show that Ce and Mg elements exist in the border of micro porosities, which indicates that these elements have a close relation with the micro porosity formation. Besides, the numerical analysis indicates that equivalent Young's modulus decreases linearly with the volume fraction of micro porosity increases. Moreover, stress concentration is found to be obvious in the vicinity of micro porosities, which can prompt the initiation and propagation of micro-cracks.