Grain size refinement and magnetostriction of ferromagnetic shape memory Fe–Pd–Rh alloys

Abstract

This paper reports the forging of bulk ferromagnetic shape memory (FSM) Fe–30Pd–2Rh (at%) alloys to a ∼40% reduction in thickness, followed by thermal annealing at 950–1100 °C for various times and quenching in ice brine to induce recrystallization (i.e. grain size refinement). Investigation with the Vickers microhardness test reveals that the process of recrystallization results in increased ductility of the fine grains. TEM and magnetostriction investigations reveal two kinds of twins contained in the strain-forged sample annealed at 950 °C for 3 h, i.e. deformation and transformation twins, and these twins also improved a higher magnetostriction as well as ductility in the alloys that may be useful in magneto-mechanical applications (such as microactuator or spring).