CHARACTERISTICS OF THE MARTENSITIC-TRANSFORMATION AND THE INDUCED 2-WAY SHAPE-MEMORY EFFECT AFTER TRAINING BY COMPRESSIVE PSEUDOELASTIC CYCLING IN CU-ZN-AL SINGLE-CRYSTALS

Training effects on the characteristics of the transformation when using pseudoelastic compressive cycling are studied from sigma-epsilon curves and calorimetric measurements. Several characteristics produced by tensile cycling and observed in thermally induced martensitic transformations also appear in this case. For a fixed number of training cycles, the efficiency of the two-way shape memory effect (TWSME) obtained after compressive tests is higher than that measured when tensile experiments are done. In a certain range, the efficiency of the resulting TWSME after compressive training increases with the magnitude of the applied stress. Values of the stress (threshold stress) which trained samples with an induced TWSME are able to overcome when going to martensite are presented for two sets of samples. These opposing stresses are related to different degrees of the TWSME inhibition. These values increase with the number of compressive cycles and show a saturation behavior.