中文摘要：

利用脉冲电解抛光的方法制备了含有晶界的三维原子探针（3DAP）针尖样品,用原子探针层析方法（APT）研究了杂质原子在690合金晶界附近的偏聚情况。结果表明：样品经过固溶处理并在500℃～0.5 h时效后,碳化物仅在部分有利于形核的晶界位错纠结处析出,大小为5～10 nm。用三维原子探针可观察到晶界处杂质原子的偏聚现象,C主要偏聚在晶界附近1个原子层内,Si和P偏聚在晶界附近约2个原子层的厚度内。根据这些元素的偏聚数据,讨论了它们发生偏聚时的规律。

英文摘要：

Needle-like specimens of three dimensional atom probes（3DAP） were prepared by pulse electro-polishing.The segregation of impurity atoms at grain boundaries in Alloy 690 was studied by atom probe tomography（APT）.The results show that the carbide only initiated at some grain boundary dislocations after solid solution treatment at 1100℃ and then by aging at 500℃ for 0.5 h.At the grain boundary segment where carbide does not precipitate,the segregation of carbon atoms can be detected.The width of carbon atoms segregate at grain boundary is only 1 atomic layer.The widths of silicon and phosphorus atoms segregate at grain boundary are about 2 atomic layers.It can be concluded that the segregation tendency of the impurity atoms depends on their atomic radius.