TIME EVOLUTION IN STATIC BETA-PHASE AND DYNAMIC BETA-MARTENSITE COEXISTENCE (CU-ZN-AL SMA)

The application of a SMA implies an accurate knowledge about the event ual time - behavior of the alloys. The effects of quenching and micro- heatings were studied by calorimetric and resistance measurements and the beta-martensite coexistence by stress - strain - temperature - tim e observations. Experimental analysis was performed using copper based single crystals (Cu-Zn-Al, e/a approximate to 1.48 e/a with Ms below room temperature). The phenomenological behavior establishes several t ime constants for each evolution. A change Delta T of temperature of t he parent phase near 300 K induces an asymptotic time evolution on M(s ) near 11 per cent. The parent to martensite coexistence produces an e volution of the equilibrium temperature (near 0.5 K) linked to the exi stence of an interface.