H. Ishikawa, Y. Sutou, T. Omori, R. Y. Umetsu, K. Oikawa, R. Kainuma, K. Ishida, Tohoku University, Sendai, Japan
Shape memory alloys (SMAs) with superelasticity (SE) are widely used for core materials of medical devices. Especially, Ti-Ni-based SMAs are very attractive for such medical devices because of their excellent SE. Recently, it is increasingly required to use the medical devices in minimal lesioned potion e.g. intracranial and peripheral vascular. In those conventional alloys, however, the low X-ray contrast resulting from their low specific gravity is one of the serious problems. Pd-In based alloys are suggested to show high specific gravity and corrosion resistance. Recently, the present authors have studied the effect of third elements on the phase stability in Pd-In binary alloy, and found that martensitic transformation occurs in Pd-In-Fe alloys. Furthermore, some alloys show transformation from the paramagnetic parent phase to the ferromagnetic martensite phase. In this study, the martensitic transformations, magnetic properties and crystal structures of the austenite and martensite phases in Pd-In-Fe alloys were investigated. It was confirmed that Pd57In25Fe18 alloy shows martensitic transformation from a Heusler-type (L21) ordered bcc phase to a 2M-type (D022) structure at 323 K and that an almost perfect pseudoelastic effect can be obtained at above the reverse transformation temperature. Pd56.2In26.3Fe17.5 alloy shows that the coercivity of the martensite phase at 4.2 K is much larger than that in other ferromagnetic SMAs such as Ni-Mn-Ga, Fe-Ni-Ga, etc.. Since high corrosion resistance and specific gravity are expected in these Pd-based SMAs, the present alloys are potentially applicable not only as magnetic SMAs, but also as materials for medical devices.
Summary: The martensitic transformations, magnetic properties and crystal structures of the austenite and martensite phases in Pd-In-Fe alloys were investigated. It was confirmed that Pd
57In
25Fe
18 alloy shows martensitic transformation from a Heusler-type (L2
1) ordered bcc phase to a 2M-type (D0
22) structure at 323 K and that an almost perfect pseudoelastic effect can be obtained at above the reverse transformation temperature. Pd
56.2In
26.3Fe
17.5 alloy shows magnetic transformation from the paramagnetic parent phase to the ferromagnetic martensite phase below 150 K. It is also confirmed that the coercivity of the martensite phase at 4.2 K is much larger than that in other ferromagnetic SMAs such as Ni-Mn-Ga, Fe-Ni-Ga, etc..
