Abstract
Al ion implantation was carried out with the aim of suppressing the absorption of hydrogen from the environment into the Ti-Ni shape memory alloy. A 100nm thick, high-density Al layer was formed at the surface by ion implantation. The initial stress of martensite phase accommodation did not change by ion implantation and hydrogen absorption. On the contrary, the deformation stress corresponding to a strain of 4% in the martensite phase and shape recovery stress changed by both ion implantation and hydrogen absorption. A low dose of implantation revealed that hydrogen absorbed near the surface diffused further into the specimen. The specimen with a high dose of ion implantation lost its shape memory properties due to the compositional change indicated by the shift of transformiation temperature. In all cases, ion implantation affected the shape memory properties irrespective of the presence or absence of hydrogen, although the ion-implanted layer was limited in the vicinity of the surface.
