Thermal and deformation-induced phase transformation behavior of Fe-15Cr-3Mn-3Ni-0.1N-(0.05-0.25)C austenitic and austenitic-martensitic cast stainless steels

The austenite-stabilizing effect of carbon on the martensitic transformation behavior and the temperature dependent tensile properties of five Fe-15Cr-3Mn-3Ni-0.1N-(0.05-0.25C) cast stainless steels with austenitic and austenitic-martensitic microstructures was studied. As the carbon concentration increased in 500 ppm increments from 0.05 mass-% to 0.25 mass-%, the as-quenched martensite fraction as well as Ms, As, and Af phase transformation temperatures decreased. Increased carbon content was also found to increase the austenite stability against the deformation-induced αʼ-martensite formation. During tensile tests in the temperature range of −40-200 °C, stress- and strain-induced martensite formation occurred in the investigated steels. Due to the low room temperature stability of austenite in the examined steels, more favorable combinations of tensile properties were obtained at high tensile test temperatures where the deformation-induced martensite transformation of the austenite phase was postponed to high strains or completely suppressed.