Effect of thermal and mechanical cycling on the elastic and dissipative energy in CuAl(11.5wt%)Ni(5.0wt%) shape memory alloy

Effect of thermal and mechanical cycling on beta/beta', phase transformation in CuAl(11.5 wt%)Ni(5.0 wt%) single crystalline shape memory alloy was studied. The epsilon-sigma and xi-T hysteretic loops were investigated after different numbers of thermal and mechanical cycles (epsilon and xi are the relative deformation and martensite fraction respectively, sigma and T denote the stress and temperature). The epsilon-sigma loops were determined at fixed temperature (373 K). The xi-T loops under zero stress were calculated from the DSC curves measured. The elastic and the dissipative energy contributions, following the procedure given in [1,2], were calculated as the function of the transformed fraction for both types of the hysteretic loops. Finally the dependence of the total elastic, E, and dissipative energy, D, (per one cycle) on the cycling number was calculated. In thermal cycling E increased by about 12 J/mol, and D decreased by about 6 J/mol. On the other hand for mechanical cycling E decreased by about 6 J/mol and D increased by about 0.2 J/mol. (C) 2012 Elsevier B.V. All rights reserved.