STRUCTURAL INTERNAL-FRICTION IN CUALNI CRYSTALS

Amplitude-dependent and amplitude-independent internal friction has be en studied in martensite and during temperature induced martensitic tr ansformation in CuAlNi single crystals after different heat treatments . The measurements of intrinsic damping were performed in ultrasonic a nd infrasonic frequency ranges. Low frequency measurements were combin ed with the direct observations of the stress-anelastic strain hystere tic loops. Observed regularities do not correspond to the breakaway mo del of amplitude-dependent internal friction both for quenched and age d samples. The conclusion is drawn, that during ageing in beta-phase t he behaviour of the pinning obstacles changes from highly mobile at ro om temperature and forming atmospheres around the mobile defects, pres umably dislocations, to rather immobile and homogeneously distributed in the bulk of the crystal. Amplitude dependent and amplitude independ ent internal friction components, measured at ultrasonic frequencies, exhibit different temperature dependences during direct martensitic tr ansformation. A maximum of the non-linear anelasticity was observed ne ar the M(s) temperature, implying a significant contribution of the pr emartensitic phenomena to the amplitude-dependent internal friction du e to phase transition.