Energetic evaluation for inducing the thermoelastic martensitic transformation by mechanical stress in Cu-Zn-Al single crystals

The ease with which the thermoelastic martensitic transformation is induced by mechanical stress in four Cu-Zn-Al single crystals with pseudoelasticit y effect has been studied. Mechanical tests have been carried out at differ ent temperatures, and show an increase in the slope of the stress-strain cu rve corresponding to the beta --> stress-induced martensite (SIM) transform ation with an increase the test temperature. The relationship between the s lope and the temperature follows a power law equation, depending on the che mical composition, transformation temperature and defect density as the mos t important factors. The stored energy has been calculated from the stress- strain curves as the area under the curve when SIM transformation is finish ed, and the friction energy as the area of the mechanical hysteresis, for f our single crystals of Cu-Zn-Al alloys. The results indicate that when the M-s of the alloy increases, a decrease in stored energy can be observed. Al so, the increase of the test temperature produces an increase in the stored energy. (C) 1999 Elsevier Science Ltd. All rights reserved.