ACOUSTIC EMISSION BEHAVIOR OF MARTENSITIC TRANSFORMATION DURING DEFORMATION OF Cu-Al-Ni SHAPE-MEMORY ALLOY SINGLE CRYSTALS

摘要

Cu-Al-Ni shape memory alloy exhibits a super-elasticity that shows perfect recovery of plastic deformation. The super-elasticity used in this study results from a perfect reversible marten-sitic transformation. AE behavior during the stress-induced martensitic transformation has been investigated using two types of specimens of Cu-Al-Ni shape-memory alloy single crystal, each of which have different stress concentration factor. The rise time of martensitic transformation in the early stage during tensile deformation was evaluated using a wavelet transform analysis instead of the frequency-domain slope method of whole waveform. Shorter rise time of AE waveform was found in the early stage and associated with the nucleation of the martensite regardless of the specimen shape.