Large reversible magnetic-field-induced strain in a trained Ni49.5Mn28Ga22.5 polycrystalline alloy

The magnetic-field-induced strain (MFIS) is investigated in a directionally solidified Ni-Mn-Ga polycrystalline alloy. A 0.2% reversible MFIS is achieved after superelastic training, which is a large value as reported in polycrystalline samples without any external stress. Such prominent behavior is attributed to the oriented internal stress induced by superelastic training. On the basis of the phase-field simulation combined with experimental studies, the field induced strain behavior and the underlying microstructure evolution of Ni-Mn-Ga polycrystalline alloy are studied. The results show that the preferential orientation of martensite variants formed by the oriented internal stress is responsible for the large reversible MFIS. It is demonstrated that superelastic training would be an effective processing way to improve the MFIS in polycrystalline Ni-Mn-Ga alloys. • Polycrystalline Ni 49.5 Mn 28 Ga 22.5 (at. %) alloy prepared by directional solidification was used. • Superelastic training was applied on the directionally solidified Ni-Mn-Ga polycrystalline alloy. • A 0.2% reversible MFIS was achieved after superelastic training. • The phase-field simulation was employed to illustrate the experimental results.