Irradiation induced stress relaxation and high temperature deformation behavior of neutron irradiated Ti based shape memory alloys

Abstract

Several tools using Ti based shape memory alloys (SMA) such as SMA coupler, connector, jack system and in-vacuum gate valve, have been developed to promote the remote maintenance and the quick replacement technology for fusion core parts. Recently, irradiation induced stress relaxation (IISR) has become a concern for components of the fusion core. IISR may be a severe problem for SMAs as well as the structural materials in the fusion reactor. The IISR of TiNi SMA and TiPd high temperature shape memory alloys (HTSMA), which have both transformation temperatures and working temperatures 400 K higher than those of TiNi alloys, may be controlled by the migration of vacancies rather than interstitials. This mechanism facilitates restoration of the damaged state to normal state under irradiation. TiPd HTSMAs may be used to fabricate irradiation-resistant shape memory devices for temperatures up to 800 K if proper heat treatments can be developed.