Mechanical Properties of Fe-Pd Ferromagnetic Shape Memory Alloy Thin Films Prepared by Dual Source DC Sputtering
The purpose of this work is to quantitatively clarify the shape memory behavior of Fe-Pd films containing ~30at%Pd by thermal cycling testing under various constant stresses. Fe-Pd films (4 $m thick) were deposited onto Si wafers with thermally formed 1$m-thick SiO2 layer using a dual-source dc magnetron sputtering apparatus. The deposited films were all annealed at 900°C for 60 min followed by iced water quenching. Perfect shape recovery was observed for Fe-30.0at%Pd film when the applied stress was lower than 300 MPa. The maximum recoverable strain was ~0.6%. Fe-29.2at%Pd film, on the other hand, showed unrecovered strain after thermal cycling even if the applied stress was 40 MPa. XRD measurements of the Fe-29.2at% Pd film before and after thermal cycling revealed irreversible fcc-bct martensitic transformation that occurred during cooling process at a temperature around -80°C. The critical stress of Fe-Pd films, at which plastic deformation commences to occur, is higher for films with 30 at% Pd than for films with 29.2 at% Pd, which is practically advantageous. The Ms temperature of these films is lower than room temperature when no bias stress is applied, while it becomes higher than room temperature when appropriate bias stress is applied, obeying Clapeyron-Clausius law.
T. Chandra, K. Tsuzaki, M. Militzer , C. Ravindran
S. Inoue et al., "Mechanical Properties of Fe-Pd Ferromagnetic Shape Memory Alloy Thin Films Prepared by Dual Source DC Sputtering", Materials Science Forum, Vols. 539-543, pp. 3173-3178, 2007