Prediction of fatigue life of metastable austenitic steel by a combination of acoustic and eddy current data

•Monitoring the lifetime, using changes in the elastic anisotropy and the increase of the α′-phase.•High-accuracy acoustic monitoring, based on monitoring wave velocity ratios and α′-phase.•Extraction of information on the past loading history (strain range and the number of cycles N). Low-cycle fatigue of metastable austenitic steel is studied experimentally, by combining high-accuracy acoustic monitoring of elastic anisotropy and eddy current monitoring of volume fraction of the martensite. This combined approach allows estimation of fatigue life as well as the information on the past loading history. At the microstructural level, the data allow one to identify the end of the incubation stage and the onset of active growth of the martensitic α′ phase. Changes of elastic anisotropy and their dependence on the strain range, as well as their linkage to underlying micromechanics, are discussed.