Deformation-induced martensite transformation in AISI 321 stainless steel under dry sliding friction

Austenitic stainless steels are some of the most popular structural materials. This is explained by their chemical and mechanical properties among which one may particularly note their high ductility. Due this reason they are successfully subjected to cold working. One of the interesting phenomena of mechanical impact on the structure of austenitic stainless steels is a strain-induced martensitic transformation. The formation of martensite (alpha'-phase) is due to the metastable state of austenite (gamma-phase) near the room temperatures. Such structural transformation can lead to both positive and negative effects. For instance, the increase in the fraction of alpha' leads to decrease in corrosion resistance. Therefore, consideration of the mechanism of deformation-induced transformation requires additional attention. In this paper, the first results of the analysis of AISI 321 stainless steel subjected to friction are presented. Operando studies using synchrotron radiation were carried out to identify the features of structural transformations. It was established that friction interaction leads to complete gamma -> alpha' transformation. Strain hardening and fracture of subsurface layers were revealed with metallographic analysis. It was evaluated that a hardness of strain-induced phase more than twice higher than the hardness of austenite. (C) 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the III All-Russian Conference (with International Participation) "Hot Topics of Solid State Chemistry: From New Ideas to New Materials".