2004 年 45 巻 8 号 p. 2752-2756
We have found a large magnetostriction of 1 × 10−3 for FSMA (ferromagnetic shape memory alloy) Fe-29.6 at%Pd ribbon of 70 μm thickness prepared by rapidly solidified melt-spinning. The ribbon contains FCT martensite twins at room temperature. The magnetic field induces a strain caused by conversion of variants in the FCT martensitic phase. This strain and shape recovery ratio increase with temperature and the former reaches a maximum value at 380—400 K, though FCT-FCC transformation temperature of the single crystal is 293—307 K. In order to confirm of this phenomenon, we investigated the phase transformation behavior of the ribbons by DSC, magnetization measurement and an acoustic elastometer method. During heating and cooling, the modulus defect ΔM/M and damping Q−1 of the as-spun ribbon sample exhibit tow-step (330—350 K and 400—420 K) phase transformation. From these results, it is found that the low-temperature FCT-FCC transformation is consistent with the value obtained from a single crystal of Fe-29.6 at%Pd. On the other hand, the high-temperature transformation, which is due to local residual strains, is peculiar to rapidly solidified ribbon.
