Internal friction of Ti-Ni alloys

The low-frequency internal friction and the modulus have been measured on Ti-Ni alloys of varying compositions, from Ni 49.89 to 51.0 at. %, in a wide range of temperatures covering the martensitic and the reverse transformations. The effect of heat treatment on the internal friction has also been investigated. The internal friction shows a sharp peak around the martensitic transformation and/or the formation of pre-martensitic state `R-phaseʹ. The height and temperature of the peak depend strongly on the composition and on the heat treatment. Corresponding to the internal friction peak a remarkable depression of the modulus has been observed. At temperatures lower than 250 K two types of temperature dependences were observed; one is a step-type that changes slowly with temperature, and the other is a peak-type around 200 K. An annealing at 873 K has enhanced the low-temperature internal friction, while the solution heat treatment at 1273 K has appreciably decreased it. In all cases the damping of the parent phase is very low; the internal friction is lower than 10·10-4. The electrical resistivity and the thermoelectric power have been measured.