Observation of a relaxation phenomenon during ageing of Fe-Ni-C martensite by means of small angle neutron scattering

The technique of small angle scattering of neutrons was used to obtain information about the phenomena occurring at the early stage of aging of a Fe--25Ni--0.7C martensite formed during cooling to liquid nitrogen temperature. The scattering of polarized neutrons was measured at room temperature. A relaxation caused by the change of the magnetic structure was observed. It was assumed that diffusion of carbon atoms changes the nearest neighborhood of Fe and Ni atoms at an early stage of aging and leads to changes in the inhomogeneous magnetic structure of the solid solution. It also indicated that the application of the small angle neutron scattering techniques can provide information about the scales of the inhomogeneous distribution of C atoms in martensite and about some thermodynamical parameters of C atom migration.