Wetting of L10 twin and antiphase boundaries by nanometer-scale L12 in Fe-Pd alloys

This paper reports microstructure associated with the L10 and L12 two-phase coexistence region in magnetic Fe-Pd alloys and analyzes the observed complex nanometer scale wetting layer structures. Fe - 61.8 at% Pd samples were continuously cooled from the disordered A1 phase through the eutectoid isotherm and aged at 650 °C for various times. X-ray diffraction reveals that the samples first order to L12 then transform to L10-dominant L10 + L12 two-phase mixture. It is shown that L10 forms {110} polytwin microstructure with straight {11¯0} antiphase boundaries (APBs), where L12 exists as nanometer-scale wetting layers along the twin boundaries and APBs. The variant selection for L12/L10 wetting layers is discussed, and evidence of closed/open APB structures is shown with high-resolution transmission electron microscopy.