A significant elastocaloric effect was detected in a Fe-31.2Pd (at. %) single crystal when a compressive stress was applied in the [001]P direction of the parent phase at temperatures of 240-290 K. The temperature decrease caused by the removal of adiabatic stress was approximately 2 K and the refrigeration capacity was calculated to be 2 MJ/m3 under a stress of 100 MPa. This significant elastocaloric effect over a wide temperature range was caused by the remarkable temperature dependence of the Young's modulus in the [001]P direction.

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Precursor phenomena of displacive transformation have been studied by optical and transmission electron microscope observation and X-ray diffraction of Ti-(50 À x)Ni-xFe (x ¼ 2, 4, 6, 8 in at.%) alloys. We found that a Ti-44Ni-6Fe alloy exhibits a second-order-like incommensurate-commensurate transition without latent heat and discontinuity in lattice parameters. In other words, diffuse scatterings appear in an electron diffraction pattern at an incommensurate position on cooling; they move gradually towards 1/3h110i as the temperature decreases and lock into the commensurate position at 180 K. The commensurate phase is not expanded along one of the h111i directions, unlike the R-phase formed by a first-order transformation in Ti-48Ni-2Fe and Ti-46Ni-4Fe alloys. In addition, the commensurate phase shows a nanoscale domain-like structure, which is inherited from the incommensurate state of the parent phase. Thus, the anomalies in physical properties observed in the incommensurate state are most likely the precursor phenomena of the commensurate phase in the Ti-44Ni-6Fe alloy. In the case of a Ti-42Ni-8Fe alloy, the incommensurate state remains even at 19 K.