中文摘要：

为了揭示高合金化难变形GH742合金在等温凝固过程中元素的偏析规律，利用SEM和EDAX及密度计算研究了该合金的显微组织和元素的偏析情况，并分析了相变对偏析元素及液体密度的影响。结果表明，在凝固过程中，GH742合金中的主要偏析元素是Nb和Ti，液体密度随凝固温度的下降而上升，在1330℃以下，一次碳化物的析出，使剩余液体中的合金元素发生重新分配，并由此导致局部液体密度的不均匀。

英文摘要：

To investigate the segregation behaviour of GH742 alloy during the isothermal solidification, the microstructure of GH742 alloy and the distributions of alloying elements during the isothermal solidification have been studied by SEM and EDAX, accompanied by liquid density calculation. Meanwhile, the influence of phase transformation on the Nb, Ti distributions and the liquid density are also researched. The results show that the main segregated alloy elements are Nb and Ti, and the liquid density increases with the temperature decreasing. The elements in residual liquid are redistributed due to the precipitation of carbonization below 1330 ℃, as a result, the local liquid density is inhomogeneous.