Abstract:
Martensitic transformation, either athermal or strain-induced, in metastable AISI 301
austenitic steel is of high technical interest as this facilitates manipulation of mechanical
properties. This work is part of a project aimed at identifying the influence of variables that
determine the athermal α′-martensitic transformation in this steel in order to ensure consistent
martensite formation and optimized mechanical properties. The influences of initial austenitic
grain size and surface concentrations of interstitial elements (C, N) on martensite start
temperature were investigated. The surface concentrations of both carbon and nitrogen were
decreased through decarburisation and the formation of martensite upon cooling from ambient
temperatures was directly observed using a cryogenic Scanning Electron Microscope (cryo-
SEM). It was found that martensite formed on the heat-treated surfaces at much higher
temperatures than that expected for AISI 301 steel. The observations were confirmed using
electron backscatter diffraction (EBSD). Other analytical techniques including glow-discharge
optical emission spectroscopy (GDOES), and Neutron Diffraction were carried out to explain
the observations.
