Cyclic deformation behaviour of AISI 321 austenitic steel and its characterization by means of HTC-SQUID

AISI 321 austenitic steel forms martensite due to quasi-static and cyclic l oading. This presupposes the exceeding of the threshold value of cumulated plastic strain. The main aim is to determine the fatigue damage of austenit ic steel by characterizing the martensitic structure with the help of the S QUID measuring technique. Several specimen batches were evaluated and there by the load amplitudes and the test temperatures were varied (room temperat ure and 300 degrees C). The experiments result in characteristic curves of the SQUID signals according to the fatigue damage which could be confirmed with comparative measurements with different methods, such as, e.g. ultraso nic absorption measurements. The extremely sensitive SQUID measuring techni que allows also detection of information in specimens fatigued at a tempera ture of 300 degrees C in which the phase fractions of strain-induced marten site are extraordinarily low. (C) 2000 Elsevier Science S.A. Ail rights res erved.