Microstructural Design for Improved Mechanical Behaviour of Advanced Materials
J. Phys. IV France 10 (2000) Pr6-59-Pr6-63
Martensitic transition of Cu-13.2Al-3Ni (wt.%) shape memory alloy studied by isothermal mechanical spectrometryV. Pelosin, G. Covarel and A. Rivière
Laboratoire de Mécanique et de Physique des Matériaux, UMR 6617, ENSMA, 1 avenue Clément Ader, BP. 40109, 86961 Futuroscope Chasseneuil cedex, France
Anelastic and elastic properties of polycristalline Cu-13.2Al-3Ni (wt.%) samples have been studied both during the transition and in the martensitic state. In order to eliminate any transient effect, the measurements have been performed in isothermal conditions over a large frequency range (10-3 Hz to 40 Hz) for temperatures between 293 K and 473 K. The damping determined at low frequency exhibits peculiar behaviour. First, an high damping level has been measured in the as quenched state. Then, ageing in the martensitic phase leads to the irreversible diminishing of the internal friction. This effect has been ascribed to the pinning of the variant interfaces by quenched vacancies. A second important result indicates that the direct transition (austenite → martensite) manifests by a sharp increase of the damping while the reverse transition (martensite → austenite) does not affect the internal friction all along the heating. These effects, compared to those previously observed on NiTi alloys, have been attributed to the freeze of the interface mobility by interactions with structural defects. Complementary MET study has pointed out a likely role of the dislocations and/or NiAl precipitates in the freezing process.
© EDP Sciences 2000