Spinodal decomposition in Fe-25 at%Co-9 at%Mo

Abstract

The ternary alloy Fe-25 at%Co-9 at% Mo has been investigated with regard to its decomposition behavior employing in-situ small-angle neutron scattering (SANS) and 3D atom probe (3DAP) investigations. Similar alloys have been reported in literature to exhibit spinodal decomposition when aged in a homogenized state. Close to the spinodal line, however, an exact differentiation of the modes of decomposition in this alloy is difficult. In order to establish fundamental knowledge on the decomposition behavior, the alloy has been aged from a homogenized state at various temperatures. The resulting decomposition mode has been analyzed by an evaluation of nuclear and magnetic SANS curves with respect to the emerging interference maximum. The development of the peak height and peak position with time was interpreted by power laws predicted by generalized nucleation theories. Additionally, the evolution of the ratio of magnetic to nuclear scattering intensities with time yields information on the chemistry of the emerging microstructure during aging. The results obtained from SANS were combined with concentration profiles generated from 3DAP data of exemplary samples. The results show that at low aging temperatures spinodal decomposition prevails, whereas with increasing temperatures other decomposition mechanisms become dominant.