INFLUENCE OF THE MICROSTRUCTURE EVOLUTION ON FERRITIC/MARTENSITIC STEELS DURING FATIGUE TESTS

M.F. GIORDANA; I. ALVAREZ-ARMAS; A.F. ARMAS

Rosario

Congreso; 11º Congreso Internacional de Metalurgia y Materiales SAM-CONAMET 2011; 2011

SAM-CONAMET

Reduced activation ferritic/martensitic (RAFM) steels are leading candidates for blanket/firstwall structures of future fusion reactors. It is evident from previous results that continuous cycling produces changes in the microstructure and a marked cyclic softening. This effect could become a significant engineering problem affecting creep, swelling and segregation phenomena during irradiation. Although the origin of the effect and the kinetics of the softening behaviour are not well understood, it was, principally, attributed to the gradual elimination of obstacles, such as dislocation segments, precipitates and grain or lath boundaries, to the motion of dislocations. Particularly in RAFM steels, a more pronounced cyclic softening rate and independence of this softening rate with the strain amplitude were also reported. In the literature some authors have rationalized such behavior as a consequence of the higher martensite start temperature of this type of steels. In this work the cyclic behaviour of three ferritic/martensitic steels, the European RAFM steel EUROFER 97 and the commercials AISI 410 (similar amount of carbon as EUROFER 97) and AISI 420 (with 0.28% C) have been studied and compared.