Martensitic Phase Transformations in CuAlNi Shape Memory Alloys

The main deformation mechanism of shape memory alloys (SMA) is martensitic phase transformation (PT). To model martensitic phase transformations in such materials, several models have been developed. In the micromechanical model developed by Levitas and Ozsoy (2009), complete system of equations that describes evolution of stresses in phases and crystallographic parameters, as well as macroscopic stress strain response for martensitic phase transformations under complex multiaxial loadings have been formulated. However, the experimental verification is incomplete. The objective of this study is to compare the experimental results in the literature for CuAlNi SMA with the results obtained from this micromechanical model. In the experiment used for comparison (Shield, 1995), a single crystal CuAlNi specimen is subjected to uniaxial load in several directions at different temperatures. According to the results obtained by using the constitutive equations of the model, the model describes the stress induced phase transformations very well when compared with these experiments. The uniaxial loading-unloading hysteresis loop shows good agreement with the experiments.