Ultrahigh damping in R-phase state of Ti-Ni-Fe alloy

Developing high damping materials with high strength is of significant technological importance, and Ti-Ni-based alloys are attracting much attention in this respect. The high damping peak in martensite state has been shown to be related to the interaction between twin boundary and hydrogen according to recent studies. In this letter the authors studied damping capacity of R phase in Ti50Ni48Fe2 alloy, which has the lowest twinning shear among known martensites (R, B19, and B19') in Ti-Ni-based alloys. They obtained a very high internal friction Q(-1)=0.2 for the relaxation-type peak in R phase, much higher than that for B19 martensite or B19' martensite. Their results suggest that choosing martensite with smallest twinning shear (thus with the highest mobility) is an important guideline for developing very high damping materials. Furthermore, avoiding introducing precipitates and dislocations is also essential for obtaining high damping. (c) 2006 American Institute of Physics.