Description
Deformation-induced martensitic transformation as the basis of a hardening process is dependent, among others, on the stress state. In applications such as cryogenic cutting, where a hardened martensitic subsurface can be produced in metastable austenitic steels, different stress states exist. Furthermore, cutting typically occurs at high strain rates greater than 103 s −1 . In order to gain a deeper insight into the behavior of a metastable austenitic steel (AISI 304) upon cryogenic cutting, the influence of high strain rates under different loading conditions was analyzed. It was observed that higher strain rates lead to a decrease in the α 0 -martensite content if exposed to tensile loads due to generated adiabatic heat. Furthermore, a lath-like α 0 -martensite was induced. Under shear stress, no suppression of α 0 -martensite formation by higher strain rates was found. A lath α 0 - martensite was formed, too. In the specimens that were subjected exclusively to compressive loading, almost no α 0 -martensite was present. The martensitic surface generated by cutting experiments showed deformation lines in which α 0 -martensite was formed in a wave-like shape. As for the shear specimens, more α 0 -martensite was formed with increasing strain rate, i.e., force. Additionally, magnetic etching proved to be an effective method to verify the transformation of ferromagnetic α 0 -martensite.
