Microstructures and magnetostriction of two-phase Fe66-Pd30-Ni4 high-temperature ferromagnetic shape memory alloys

The microstructures and magnetostrictive strains of ferromagnetic shape memory Fe-Pd30 alloy systems with additions of Ni elements (4 at.%) have been investigated by a magnetostriction meter, scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The research results show that the magnetostrictive strains of the Fe66-Pd30-Ni4 alloys after homogenization treatment (λ‖s=79×10-6) are higher than those of the as received materials (λ‖s=55×10-6). The lower magnetostriction of the as received metal is due to segregation-impeded parts of the L10 twin boundary motion in realistic magnetic fields. In addition, an important discovery in this study is that doping the Fe-Pd30 alloy system with Ni substitution for Fe seems to prevent the decomposition of L10 + L1m twin phase into stoichiometric L10 + L1m + αbct structures when the strain-forged alloys are solution treated and recrystallization annealed, and then aged at 400 °C for 100 hours. The magnetostrictive strain...