Low-frequency internal friction of hydrogen-free and hydrogen-doped NiTi alloys

✍ Scribed by F.M. Mazzolai; A. Biscarini; B. Coluzzi; G. Mazzolai; E. Villa; A. Tuissi

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 431 KB
• Volume: 55
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2007.03.020

✦ Synopsis

The internal friction (IF) and Young's modulus of the Ni 50.8 Ti 49.2 shape memory alloy have been measured as a function of temperature (130 K < T < 335 K) by a dynamic mechanical analyser at various strain amplitudes and frequencies. Besides the one associated with the austenite/martensite transformation, several other IF peaks have been observed both in the hydrogen-free and in the hydrogen-doped states of the material. Some of these peaks are non-thermally activated processes caused by stress-assisted hysteretic motions of twin boundaries and dislocations; some others represent thermally activated relaxations caused by reorientation of hydrogen elastic dipoles or by stress-induced motions of twin boundaries interacting with hydrogen. The present low-frequency measurements provide new information concerning the amplitude and frequency dependences of the damping processes, thus throwing new light on their structural mechanisms.