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Fatigue-Characterization of Ti-Stabilized Austenitic Steel

: Lang, M.A.


Nondestructive Testing and Evaluation 15 (1999), Nr.3-4, S.171-190
ISSN: 0278-0895
ISSN: 1058-9759
Fraunhofer IZFP ()
fatigue; Magnetic Measurements; Metastable austenitic steel; Ultrasonic Measurements

The assessment of the actual fatigue damage and thus the remaining lifetime of materials is a subject of enormous scientific and economical relevance. This paper describes investigations for the nondestructive characterization of microstructural changes of the metastable austenitic steel X6 CrNiTi 18 10 (AISI 321). Due to its good mechanical and technological properties, i.e. high thoughness and corrosion resistance, AISI 321 is widely used in the chemical industry and power pland constructions. Experiments were carried out on sample batches fatigued at room temperature and T=300 deg C. The nondestructive investigations and the interpretation of their results base on the knowledge of the cyclic deformation behaivour of the material. That is characterized by cyclic hardening and softeting effects, wich are strongly influenced by placticity-induced martensite formation. Mafnetic measurements with highly sensitive magnetometers on basis of HTC-SQUIDs yield good correlation with the actual fat igue state. The creation of martensite was found to be more significant as damage parameter than the dislocation density.