灰铸铁中TiN形态及其形成热力学与生长机理

发布时间：2018-04-01 06:28

  本文选题：灰铸铁　切入点：氮化钛颗粒　出处：《材料热处理学报》2015年12期

【摘要】：为了研究灰铸铁中TiN颗粒形成与长大规律及其组织特征,采用显微组织及热力学计算研究某汽车发动机缸体铸件中TiN颗粒形态、尺寸及分布,并对TiN形成与长大机理进行了分析讨论。结果表明,因回炉料中TiN的遗传性形成的TiN颗粒尺寸相对较大,超过20μm;从铸铁熔体中结晶的TiN颗粒尺寸为4~8μm;从过冷奥氏体中析出的TiN颗粒尺寸相对较小为1~2μm。热力学计算表明,TiN结晶取决于铸铁熔体中[%Ti]·[%N]的溶度积,当铸铁熔体中[Ti]在0.045%附近([%Ti]·[%N]=2.47×10~(-4))时,铸铁熔体过冷到1368℃,即开始结晶TiN。由于TiN与MnS晶体结构相同,点阵常数相近,过冷铸铁熔体中TiN多以MnS为基底非自发成核长大。
[Abstract]:In order to study the formation, growth and microstructure of TiN particles in gray cast iron, the morphology, size and distribution of TiN particles in an automobile engine cylinder block casting were studied by means of microstructure and thermodynamics calculation. The mechanism of formation and growth of TiN was analyzed and discussed. The results showed that the size of TiN particles was relatively large due to the heredity of TiN in recirculating charge. The size of TiN particles crystallized from cast iron melts is 4 ~ 8 渭 m, and that of TiN particles precipitated from undercooled austenite is relatively small to 1 ~ 2 渭 m. Thermodynamic calculations show that the crystallization of tin depends on the solubility product of [Ti] [N] in cast iron melts. When [Ti] in cast iron melts is near 0.045% ([Ti] [N] = 2.47 脳 10 ~ (-4) C), the supercooled cast iron melts begin to crystallize at 1368 鈩，

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