Structural Internal Friction in CuAlNi Crystals
Department MTM, Katholieke Universiteit Leuven, De Croylaan 2, 3001 Heverlee, Belgium
2 A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, Politekhnicheskaja 26, 194021 St. Petersburg, Russia
3 Institute of Material Science, University of Antwerpen (RUCA), Middelheimlaan 1, 2020 Antwerp, Belgium
Amplitude-dependent and amplitude-independent internal friction has been studied in martensite and during temperature induced martensitic transformation in CuAINi single crystals after different heat treatments. The measurements of intrinsic damping were performed in ultrasonic and infrasonic frequency ranges. Low frequency measurements were combined with the direct observations of the stress-anelastic strain hysteretic loops. Observed regularities do not correspond to the breakaway model of amplitude-dependent internal friction both for quenched and aged samples. The conclusion is drawn, that during ageing in β-phase the behaviour of the pinning obstacles changes from highly mobile at room temperature and forming atmospheres around the mobile defects, presumably dislocations, to rather immobile and homogeneously distributed in the bulk of the crystal. Amplitude dependent and amplitude independent internal friction components, measured at ultrasonic frequencies, exhibit different temperature dependences during direct martensitic transformation. A maximum of the non-linear anelasticity was observed near the Ms temperature, implying a significant contribution of the premartensitic phenomena to the amplitude-dependent internal friction due to phase transition.
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