Abstract
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.
Highlights
Ti-Ni-based shape memory alloys are quite attractive functional materials [1]
The effect of hydrogen on elastic and anelastic properties of Ti-Ni-based alloys have attracted considerable attention, especially after Fan et al [4,5] have shown that hydrogen is unintentionally introduced during conventional heat treatment
Fan et al [4,5] have shown that the relaxation internal friction (IF) peak observed by many researchers at low frequencies is due to an interaction of twin boundaries with hydrogen
Summary
Ti-Ni-based shape memory alloys are quite attractive functional materials [1]. Anelastic properties of Ti-Ni-based alloys are widely explored, both for microstructural characterization of the alloys and for their application as high-damping materials [2]. The effect of hydrogen on elastic and anelastic properties of Ti-Ni-based alloys have attracted considerable attention (see [3] for a review), especially after Fan et al [4,5] have shown that hydrogen is unintentionally introduced during conventional heat treatment Fan et al [4,5] have shown that the relaxation internal friction (IF) peak observed by many researchers at low frequencies (about 200 K at 1 Hz) is due to an interaction of twin boundaries with hydrogen. We have studied the effect of hydrogen contamination during heat treatments on the low-temperature elastic and anelastic properties of a Ni50.8 Ti49.2 alloy at ultrasonic frequencies, for which the ‘200 K’ relaxation IF peak cannot be observed [6].
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