Strain-induced martensite formation in metastable austenitic steels with varying carbon content

Abstract Fatigue tests are performed on cylindrical, sheet and foil specimens to investigate the strain-induced martensitic transformation of austenatic steels. The tests set a variety of strain amplitudes and temperatures as well as various carbon concentrations for the investigated materaals in order to broaden the scope of the martensitic transformation and thereby its characterization. It is confirmed that there is a threshold value of plastic strain amplitude for the investigated materials above which the incremental increase in martensite volume fraction in the specimen under continued cyclic loading is of significance. Block-loading tests indicate that cycles at amplitudes below this threshold do not contribute to the austenite transformation. Thermodynamic calculations are applied in order to provide information on the stability of the material with regard to carbon content. It is shown that carbon concentration can be established by gas charging of the materials so that the driving force for tran...