Deformation field of CuA1Ni single crystal shape memory alloy : a study by using high sensitive Moiré interferometry

The deformation field of single crystal CuAlNi Shape Memory Alloy (SMA) during stress-induced martensitic transformation was first studied by using high sensitivity Moire Interferometry. Uniaxial tensile tests were conducted in the temperature and deformation regime in which the alloy exhibited the Shape Memory Effect (SME) and Superelasticity (SE). Two kinds of austenite-martensite (A-M) interfaces with different deformation features were first identified. The experimental discovery questioned the invariant plane hypothesis used in crystallographic theory of martensitic transformation. 4-point-bending tests were conducted on the specimen which exhibited Shape Memory Effect (SME). The displacement field of wedge-like martensite and its evolution during the transformation was recorded. During the growth of wedge-like martensite, it was found that one boundary of the martensite moved and rotated continuously. Key words: shape memory alloy, shape memory effect, superelasticity, thermoelastic martensitic transformation, stress-induced martensitic transformation, uniaxial tension, 4-point-bending test, Moire interferometry, deformation fiel