Cyclic response-electrochemical interaction in mono- and polycrystalline AISI 316L stainless steel

Yuanfeng Li, University of Pennsylvania


In order to understand the role of passive films in corrosion fatigue, the interaction between fatigue cycling and the electrochemical reactions of an AISI 316L stainless steel has been studied in 1N H$\sb2$SO$\sb4$ solution with constant potential control. Specimens, both in mono- and polycrystaline forms, have been cycled ($\varepsilon\sb{\rm p1}$ = 1 $\times$ 10$\sp{-3}$) in the active region, the active-passive transition region, the passive I region and the passive II region, which differ in the nature of the passive films. The current transient during corrosion fatigue contains two components, produced by the elastic and plastic strains. Strong interactions perceived as variations in the transient currents, between the cyclic loading and the aggressive environment, have been found in the active, transition, and passive I regions. These interactions increase the strain localization and thereby cause a reduction in fatigue life, as compared to that in air. In the passive II region, the strain localization is not as great, and the life is not reduced. Surface morphologies produced by the different reactions cause different mechanisms to operate when the applied voltage changes. In the active region, a rapid dissolution on slip lines nucleates cracks after a few cycles, but propagation is delayed by a "blunting effect" caused by general corrosion on the specimen surface. In the transition region, cracks nucleated by preferential dissolution on slip lines become "sharpened" by a lower corrosion rate which is found to be orientation dependent. In the passive I region, the passive film is destroyed at the slip lines, and a local galvanic effect enhances both crack nucleation and propagation. For a basis of comparison, fatigue tests were also performed in air. In the CSS curve for single crystals, a plateau was found from $\varepsilon\sb{\rm p1}$ = 5 $\times$ 10$\sp{-5}$ to $\varepsilon\sb{\rm p1}$ = 2 $\times$ 10$\sp{-3}$, with a saturation stress about 59 MPa. If single slip operated, there was no effect of either orientation or passive films on the hardening behavior or saturation. The slip character of monocrystalline stainless steel proved to be planar. For polycrystals, wavy slip was emphasized by multi-slip created by incompatible deformation.

Subject Area

Materials science|Mechanical engineering

Recommended Citation

Li, Yuanfeng, "Cyclic response-electrochemical interaction in mono- and polycrystalline AISI 316L stainless steel" (1991). Dissertations available from ProQuest. AAI9200364.