Evaluation of the strain-induced martensitic transformation by acoustic emission monitoring in 304L austenitic stainless steel: Identification of the AE signature of the martensitic transformation and power-law statistics

The aim of the present investigation is to characterize plasticity-induced martensite formation of metastable austenitic stainless steel at room temperature. Acoustic Emission (AE) monitoring is performed on a 304L austenitic stainless steel during fatigue tests. This work aims at identifying the acoustic emission signals associated with the formation of the strain-induced martensite. The present work includes the study of the influence of the specimen geometry. The use of statistical pattern recognition allowed the identification of the acoustic emission signatures for three mechanisms: dislocation motion, mechanical damage and martensitic transformation (MT). Moreover statistics on the energies of the AE signals were found to obey power laws (P(E) ∼ E−α) with exponent α = 1.75 ± 0.15 for the cluster associated with martensite formation.