NEUTRON SMALL-ANGLE SCATTERING STUDY OF UNMIXING IN FE-CR ALLOYS

Unmixing kinetics has been studied in Fe-Cr alloys containing 20, 35 and 50 at.% Cr, at 500-degrees-C, up to 500 h after efficient and controlled quenching. The nuclear neutron small angle scattering evolution is explained using non linear approximations. No abrupt differences are found between alloys, one of them being in the nucleation-growth regime, and the other two being probably in the spinodal range. In all of them, a first transient regime is evidenced, and is attributed to local rearrangements. The reduction of intensities into absolute units allows the progress of the unmixing reaction to be followed. In the present case, unmixing does not reach completion, and two lengths are necessary to describe the system.