On ECRS-6 [1], we have presented first results of the researches of fatigue degradation
and martensitic transformation of austenitic stainless steel AISI 321 by neutron diffraction stress
analysis. A series of samples preliminary ex-situ cyclically fatigued at the frequency of 5 and 0.5 Hz
was in-situ tested on the stress rig of the ENGIN instrument. In the high cycle fatigued (HCF)
samples, the applied stress-elastic strain responses of austenite and martensite phases were find out
to be strongly different as compared to the low cycle fatigued (LCF) samples, in which they are
close. Moreover, the martensite Poisson ratio in the HCF-samples is almost twice to that of
observed 0.28-0.30 in austenite and in both phases of the LCF-samples. With the purpose to search
the reason of such unusual behavior of the martensite phase, one of the HCF-samples has been
anew in-situ tested on the stress rig of the ENGIN-X in: 1) a LCF-mode at the frequency of 0.1 Hz
to increase the fatigue level, and 2) a quasistatic mode to measure the applied stress-elastic strain
responses of both phases. Also, two of the LCF-samples have been subjected to the ex-situ
secondary HCF-testing at the frequency of 5 Hz and again in-situ measured on the ENGIN-X stress
rig. Results of the mechanical characterization of phases in the twice fatigued austenitic stainless
steel are presented and discussed.
In-Situ Investigation of Strain-Induced Martensitic Transformation Kinetics in an Austenitic Stainless Steel by Inductive Measurements