CHARACTERIZATION, THERMOMECHANICAL BEHAVIOR AND MICROMECHANICAL-BASEDCONSTITUTIVE MODEL OF SHAPE-MEMORY CU-ZN-AL SINGLE-CRYSTALS

Cu-Zn-Al shape memory alloys are grown as single crystals by the Bridg man technique with a final shape directly suitable for thermomechanica l tests (cylinders with tapered heads: 25 mm gauge length, 4 mm in dia meter). The four classical transformation temperatures are checked by Differential Scanning Calorimetry and resistivity. The orientation of crystal structure is investigated by X-ray diffraction. Isothermal pse udoelastic tensile tests show that the width of the hysteresis loops a nd the slope of the stress-strain curves during phase transformation i ncrease as the applied stress rate increases. A micromechanical-based constitutive model allows us to describe this single crystal behaviour . Copyright (C) 1996 Acta Metallurgica Inc.