Experimental and theoretical study of mechanical stabilization of martensite in Cu–Al–Ni.pdf

Materials Science and Engineering A 438–440 (2006) 730–733 Experimental and theoretical study of mechanical stabilization of martensite in Cu–Al–Ni single crystals C. Picornell a,∗, V.A. L’vovb , J. Pons a , E. Cesari a a Department de F´ısica, Universitat de les Illes Balears, Cra. de Valldemossa km 7.5, E-07122 Palma de Mallorca, Spain b Taras Shevchenko University, Department of Radiophysics, Glushkov Str. 2, Build. 5, Kiev 03127, Ukraine Received 8 May 2005; received in revised form 31 October 2005; accepted 28 February 2006 Abstract A direct correlation between the hysteresis of the partial stress–strain (σ–ε) cycles corresponding to the → martensitic transformation of a 82.5%Cu–13.5%Al–4.0%Ni (wt.%) single crystal and the induced amount of mechanical stabilization (MS) determined by calorimetry has been established. The results show a good agreement with the coefficient dσ/dT typically obtained from stress-inducing the transformation at different temperatures. In addition, the experimental σ–ε curves have been quantitatively reproduced by a statistical model of superelasticity. In partial cycles, a unique probability distribution function (probabilities of martensite appearance/disappearance) can be used for a correct description of all the forward cycles while different distributions, which depend on the maximal strain values achieved during the loading branch, have to be considered for the reverse cycles. Conversely, no mechanical stabilization of martensite has been observed during the → transformation of 75.0%Cu–17.4%Zn–7.6%Al (wt.%) single crystal in tension mode and, in this case, the forward and reverse partial transformations have been successfully modelled using the same probability distribution function. T