Study of residual stress and vacancy defects in oxide dispersion strengthened steels

Abstract

This study was focused on commercial oxide-dispersion strengthened (ODS) steels - MA 956 (20%Cr), ODM 751 (16%Cr) and ODS Eurofer (9%Cr), developed for fuel cladding of GEN IV reactors. The ODS steels are described in order to comparison their microstructure features. Vacancy defects were observed by Doppler Broadening Spectroscopy (DBS) and Positron Annihilation Lifetime Spectroscopy (PALS). Residual stress proportional to all kinds of defects was investigated by Magnetic Barkhausen Noise (MBN) measurement. The positron techniques demonstrated the highest defect concentration for ODS Eurofer followed by MA 956. The lowest defect density belongs to ODM 751; although these defects are the largest (three or four vacancy clusters). MA 956 and ODS Eurofer have di-vacancies in predominance. MBN results are in a good accordance with positron techniques. The highest residual stress is for ODS Eurofer, followed by MA 956. Finally, the lowest residual stress proportional to hardness is found for ODM 751. (c) 2012 TheAuthors Published by Elsevier B.V. Selection and/or peer-review under responsibility of Organizing Committee.