石墨球对系列冲击温度下球墨铸铁断口作用机制

 为了明确低温用球墨铸铁材料断裂微观机理，针对石墨球对系列温度球墨铸铁冲击断口演变过程的作用机制进行研究。采用SEM、激光共聚焦显微镜等手段系统分析了不同温度下石墨球对球墨铸铁冲击断裂过程的影响。定量断口分析结果表明，与冲击功随温度的变化一致，断口表面粗糙度Sa和空穴扩张比Rc/R0(韧窝与石墨球半径之比)均随温度的下降呈明显降低趋势。随着冲击试验温度的降低，由韧性断裂逐渐过渡到脆性断裂，这种断裂机制的变化导致断面粗糙度指数剧烈下降，空穴扩张比值趋近于1。冲击过程中裂纹总是在石墨 基体界面处发生开裂并沿着石墨 基体界面不断扩展，因此实际生产过程中应该注重改善石墨球与基体界面处组织状态。

Effect of graphite nodules on fracture of ductile cast iron #br#under low temperature impact loading

 In order to clarify the microscopic fracture mechanism of ductile cast iron used under low temperatures，the effect of graphite nodules on fracture evolution process under low temperature impact loading was studied，which was proposed to provide further development of low temperature ductile iron material and failure assessment. The impact fracture morphology was analysised by using SEM and confocal laser scanning microscope. The results of quantitative fractography indicate that both Sa and Rc/R0are decreased with temperature during the impact fracture process. The cracks initiate from the interface between nodular graphite and the matrix. Therefore，in the spheroidization process，attention should be paid to improving the microstructure of the interface between the graphite and the matrix.