一种镍基高温合金黑斑缺陷的组织分析及形成机理研究

研究一种镍基高温合金饼坯出现的宏观偏析＂黑斑＂区域相变行为及析出相的形成特点,并采用热力学相计算手段对合金黑斑区的相变规律和元素的热力学平衡分配进行计算。结果表明,合金中黑斑主要是富Ti的碳化物严重偏析造成。从黑斑的组织特点分析及热力学相计算可以得出,Ti在凝固过程中发生了强烈的枝晶间液态偏聚,同时C也有一定程度的偏聚,这些元素不同程度的液态偏聚行为是造成黑斑相富集的主要原因。

The microstructure analysis and formation mechanism research for freckle defect of a Ni-based superalloy

In order to analyze the formation mechanism of the freckle of a Ni-based superalloy,some research have been done to study the phase transition behavior and characteristics of phase precipitates of the freckle region.The freckle formation and their phase characterization in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method.These results show that,for freckle characterization,a large number of carbide phase precipitate in freckle area which is enriched of element Ti.From the microstructure characteristics analysis and the thermodynamic calculation,it can be concluded that element Ti segregate strongly to dendritic liquid during the solidification,while a weak segregation exist in C.The different extent of segregation of the elements was the main cause for freckle.