Low-temperature internal friction of modified Ti50Ni42Co8 alloy

In this work we have investigated the internal friction of the alloy Ti₅₀Ni₄₂Co₈ with Hf (0.5–0.8 at. %) and Y (0.1 at. %) additives in the temperature range 4.2–293 K at frequencies of 200–600 Hz. We see two peaks on the temperature dependence of the internal friction for the alloy oxidized in an air atmosphere at 1100 K: the first peak at T=40 K is connected with movement of interphase boundaries during the thermoelastic phase transformation occurring according to the scheme B2 R B19'; and the second peak at 220–240 K is mainly connected with diffusion under the pressure of hydrogen adsorbed on the oxide particles. The hydrogen penetrates the alloy during sample preparation upon etching and electropolishing in acid solution. Support for the latter hypothesis comes from internal friction vs temperature data for the alloy hydrogen-charged at 1073 K in a gaseous atmosphere and then subjected to vacuum annealing at the same temperature, as well as the results of x-ray diffraction analysis.Voronezh Polytechnical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 14–20, December, 1992.