Elastic constants of bcc austenite and 2H orthorhombic martensite in CuAlNi shape memory alloy

Elastic constants of cubic austenite and orthorhombic 2H martensite phases in the Cu-Al-Ni shape memory alloy were determined by ultrasonic pulse-echo technique using multiple single crystal specimens and a novel optimization based evaluation method that minimizes the uncertainty stemming from experimental errors as well as experimental effort. Multiple martensitic single crystals were prepared from the austenite crystal by a dedicated deformation technique. Taking advantage of the fact that the elastic constants of the austenite and 2H martensite phase were evaluated on the same piece of material, soft acoustic modes and elastic properties of both phases were compared taking into account the lattice correspondence. It is found that the 2H martensite crystal partially inherits the soft acoustic modes of the austenite and hence its elastic properties.