Mechanism analysis of pitting induced by Al2O3 inclusions: insight from simulation calculation

Abstract

The micro-area characterization experiments like scanning Kelvin probe force microscope (SKPFM) and Kernel average misorientation have the defects of complex sample preparation and occasional errors in test results, which makes it impossible to accurately and quickly analyze the pitting behavior induced by inclusions in some cases, prompting attempts to turn to simulation calculation research. The method of calculating band structure and work function can be used to replace current-sensing atomic force microscopy and SKPFM to detect the potential and conductivity of the sample. The band structure results show that Al₂O₃ inclusion is an insulator and non-conductive, and it will not form galvanic corrosion with the matrix. Al₂O₃ inclusion does not dissolve because its work function is higher than that of the matrix. Moreover, the stress concentration of the matrix around the inclusion can be characterized by first-principles calculation coupled with finite element simulation. The results show that the stress concentration degree of the matrix around Al₂O₃ inclusion is serious, and the galvanic corrosion is formed between the high and the low stress concentration areas, which can be used to explain the reason of the pitting induced by Al₂O₃ inclusions.