INTERNAL-FRICTION AND PRECIPITATION IN TI-RICH NITI ALLOYS

The internal friction (Q-1), electric resistance (R), frequency (f), and zero position shift (epsilon) as functions of temperature are measured on Ti-rich NiTi alloys. A new internal friction (IF) peak beside the lower side of the original IF peak of the martensitic phase transition appearing in quenched specimens is observed in the aged specimen. Further study by SEM and X-ray diffraction indicates that the Ti-rich precipitation appears in the aged specimen. It is suggested that the new IF peak is also associated with the martensitic phase transition, but with a lower M(s) point in the region near the Ti-rich precipitation.