Effect of Hydrogen on the Elastic and Anelastic Properties of the R Phase in Ti50Ni46.1Fe3.9 Alloy

The linear and non-linear internal friction, effective Young's modulus, and amplitude-dependent modulus defect of a Ti50Ni46.1Fe3.9 alloy have been studied after different heat treatments, affecting hydrogen content, at temperatures of 13-300 K, and frequencies near 90 kHz. It has been shown that the contamination of the alloy by hydrogen gives rise to an internal friction maximum in the R martensitic phase and a complicated pinning stage in the temperature dependence of the effective Young's modulus at temperatures corresponding to the high-temperature side of the maximum. Dehydrogenation of the H-contaminated alloy transforms the internal friction maximum into a plateau and minimizes the pinning stage. The internal friction maximum is associated with a competition of two different temperature-dependent processes affecting the hydrogen concentration in the core regions of twin boundaries. The amplitude-dependent anelasticity of the R phase is also very sensitive to hydrogen content, its temperature dependence reflects the evolution of extended hydrogen atmospheres near twin boundaries.