Microstructure of austenitic stainless steels of various phase stabilities after cyclic and tensile deformation

The microstructures of two metastable high-alloyed CrMnNi cast TRIP steels and a stable AISI 316L austenitic stainless steel were studied in detail after tensile and cyclic deformation. Electron backscattered diffraction was employed to localize the martensitic phase transformation and electron channelling contrast imaging to describe the typical dislocation arrangements. These were complemented by transmission electron microscopy and by scanning transmission electron microscopy performed in a scanning electron microscope. The TRIP steel with the lowest austenite stability shows a more pronounced martensitic phase transformation realized from the austenite via the intermediate formation of epsilon-martensite. Martensitic phase transformation also occurred in the stable 316L austenitic stainless steel with a small volume fraction of alpha'-martensite, but only with cyclic deformation at low temperatures and/or at very high plastic strain amplitudes.