INVITED: Mechanistic Study of Passivation Film Evolution Under Tensile Loading in a Metastable Compositionally Complex Alloy

Stress corrosion cracking (SCC) is one of several degradation mechanisms by which a material can eventually fracture if not properly addressed. The mechanistic study of the SCC phenomenon has revealed that the nature of dislocation and passivation film interaction plays a vital role in the degradation of materials by SCC. Hence, in addition to studying dislocation dynamics, it is crucial to understand passivation film evolution during SCC conditions. To that end, this study involved understanding passivation film evolution in a metastable compositionally complex alloy (variously referred to as high entropy alloy, multi-principal element alloy, and complex concentrated alloy). First, a dog bone shaped tensile test specimen was subjected to a constant uniaxial tensile load in a neutral salt solution at room temperature for 24 h. For comparison, an identical tensile test specimen was put in a salt solution under a similar condition without applying any load. It was followed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) to characterize the passivation film. Both EIS and XPS results revealed that the properties and chemical make-up of passivation film evolved under SCC conditions differed from that developed under no load conditions. This finding suggests that studying the nature of passivation film under SCC conditions is essential to mitigate the issue of materials degradation and fracture caused by SCC, which will eventually lead to the development of advanced materials with better resistance to SCC for industrial applications.