Friction-induced phase transformations and evolution of microstructure of austenitic stainless steel observed by operando synchrotron X-ray diffraction

A materials’ structure and its evolution due to friction play a crucial role in understanding wear related processes. So far, structural changes caused by are mostly studied using ex situ destructive characterization techniques, such as microscopy of post-mortem the prepared specimen polishing etching techniques. In this paper, AISI 321 austenitic stainless steel (ASS) during frictional loading were observed nondestructive operando method based on synchrotron X-ray diffraction (XRD). Although martensitic transformation starts at ca. -187 °C, induces γ-(ε, α′) alloy room or even higher temperatures. The ε-martensite formation is only for relatively short time. Subsequently, mechanically-mixed layer (MML), composed mainly α′ phase, forms sample’s surface. Using XRD peak profile analysis, we accumulation dislocations, their ordering, and/or stress field shielding before after phase transformations. steady-state conditions reached 69 cycles manifested reaching threshold values size coherent scattering regions (CSRs) dislocation density γ phases. For better evolution, microstructure sample was scanning electron (SEM) experiment. MML, delamination, vortices, carbide crushing discussed.