STRUCTURAL AND MECHANICAL SPECTROSCOPY STUDY OF THE BETA(1)' MARTENSITE DECOMPOSITION IN CU-12-PERCENT-AL-3-PERCENT-NI(WT-PERCENT) ALLOY

In this work, the effect of annealing on the martensitic structure of a water quenched Cu-12%Al-3%Ni alloy is studied, Elastic moduli, elect rical resistivity, X-ray diffraction and internal friction experiments have been performed for temperatures and/or after annealings between 300 K and 790 K. Several stages of structural evolution have been evid enced. First, for annealing below 573 K, the beta(1)' martensitic stru cture is not changed but a reorientation effect in the (110) plane is evidenced while the freezing of the martensitic interface motion has b een observed by internal friction. Further annealings lead to the begi nning of the gamma(2), precipitation immediately followed by the irrev ersible decomposition of the beta(1)' martensite in two stable phases gamma(2)+alpha(2). Moreover, internal friction experiments have eviden ced a thermally activated peak. This peak is amplified when the marten site is decomposed so it cannot be linked to the presence of martensit e but rather, referring previous works, to reversible dislocation segm ent motions. (C) 1998 Elsevier Science S.A.