Deformation-induced martensite formation during cyclic deformation of metastable austenitic steel: Influence of temperature and carbon content

To study the influence of the parameters carbon content, temperature and total strain amplitude on the deformation-induced martensite formation in metastable 301 austenitic steel, hollow cylindrical fatigue specimens were carburized and decarburized in methane-hydrogen gas mixtures. Fatigue experiments were carried out in a temperature range between RT and T= -100 degrees C while monitoring the fraction of deformation-induced martensite versus the number of cycles by means of a magneto-inductive ferrite sensor. The results show that deformation-induced martensite formation leads to pronounced cyclic hardening. A certain amount of accumulated plastic strain is necessary and a threshold value of the plastic strain amplitude must be exceeded to trigger martensitic transformation. The effect of the carbon content and/or the temperature on the formation of alpha' martensite is very strong in such a way that high carbon concentrations and elevated temperatures stabilize the austenite phase. (c) 2007 Elsevier B.V. All rights reserved.