Metallic and composite systems

Investigation of steels

measured by the SANS

Duplex steel is contains two different phases and is of high industrial interest. Duplex steel samples subjected to various ageing processes were investigated by small angle neutron scattering (SANS). Assuming that the scattering objects in steels have cuboid or rombohedral form, in case of monodisperse size distribution, the scattering law yields known formulae and characteristic size of these particles. The form factor and the contrast factor of the objects relative to the material's average provides information on the angle of orientation of the diagonal of the rhombes relatively to the principal axes of investigation. We have observed the growth of cuboids with sizes changing from a ≈ 17 nm to a ≈ 20.5 ± 6.6 nm due to thermal treatment. Further thermal treatment led to polydispersity of the scattering particles, the average particle size estimated to be ≈ 17 nm.

Figure 1. SANS analysis of steel samples (a) S1  as received,  (b) S2 aged at low temperature, (c)  S3 aged at high  temperature. This yields the characteristic thermal treatment to evaluate the aging process.