In order to solve the problem of where, why, and how to start pitting, it is necessary to study the influence of different dissolution activity of the internal heterogeneous structures of the complex inclusions. In this paper, mechanism of internal activity difference of two typical Yttrium composite inclusions on pitting corrosion is revealed from atomic scale by using immersion test, FE-SEM/EDS analysis and first-principles calculations. The results show that, for Mg-Y-S composite inclusions, pitting potential is lower than that of the matrix, therefore, The matrix around the composite inclusions dissolves preferentially; for Y-S-O composite inclusions with core-shell structure, Y-O inclusions in the shell are deformed and cracked due to the internal stress of the matrix and Y-S during the immersion process, resulting in the simultaneous dissolution of inclusions and steel matrix.

为了解决在何处，为什么以及如何开始蚀坑的问题，有必要研究复杂包裹体内部异质结构的不同溶解活性的影响。本文通过浸没试验，FE-SEM / EDS分析和第一性原理计算，从原子尺度揭示了两种典型的钇复合夹杂物对点蚀的内部活度差异的机理。结果表明，Mg-YS复合夹杂物的点蚀电位低于基体，因此，复合夹杂物周围的基体优先溶解。对于具有核-壳结构的YSO复合夹杂物，由于浸入过程中基体和YS的内应力，壳中的YO夹杂物会变形和破裂，