SMALL ANGLE NEUTRON SCATTERING MICROSTRUCTURAL INVESTIGATION OF TWO MARTENSITIC STEELS FOR NUCLEAR APPLICATIONS. R. Coppola(1), F. Fiori(2), E.A. Little(3), M. Magnani(4), (1) ENEA-Casaccia, C.P. 2400, 00100 Roma, (2) Istituto Nazionale di Fisica della Materia - Ist. Scienze Fisiche, Università di Ancona, 60131 Ancona, (3) University of Wales, U.K., (4) ENEA-Clementel - Bologna
This contribution presents the results of an investigation carried out using small-angle neutron scattering (SANS) to study the microstructure of two martensitic steels of interest for nuclear applications, namely: a) modified martensitic steel DIN 1.4914 (MANET - type) developed for fusion reactor applications (composition: C 0.17 Cr 10.5 Mo 0.50 Ni 0.85 Mn 0.60 Nb 0.20 V 0.25 Si 0.32 Fe to balance wt%). b) AISI 410 steel (C 0.15 Cr 13.00 Mn 0.45 Ni 0.47 Si 0.30 Fe to balance wt%). The present investigation is mainly focused on microstructural effects arising from the different Cr content, namely on the occurrence of C-Cr elementary aggregates, of very small size produced during tempering at 700deg.C. Evidence of this phenomenon is provided by previous work carried out on MANET both by SANS and by other microstructural techniques (1, 2).
The present investigation shows that, increasing the Cr content for an identical thermal treatment (20 h at 700deg.C after fast quenching from 1075deg.C) gives a higher SANS intensity for the AISI 410 samples which is interpreted as a higher volume fraction of C-Cr aggregates. No significant variation in average radius (~ 10 Å) is observed from one material to another. The compared analysis of nuclear and magnetic SANS components shows that there is also a SANS contribution of inhomogeneities having different composition from the one of those aggregates and much larger sizes (~100 Å): this is attributed to the presence of M23C6 carbide precipitates.
REFERENCES
(1) G. Albertini, M. Ceretti, R. Coppola, F. Fiori, P. Gondi, R. Montanari, Physica B 213-214 (1995) 812.
(2) G. Albertini, F. Carsughi, R. Coppola, F. Fiori, M. Stefanon, in print on J. N. Mat.