  Direct experimental characterization of indentation-induced martensitic
microstructures in pseudoelastic shape memory alloys (SMAs) is not possible,
and thus there is a lack of evidence and understanding regarding the
microstructure pattern and related features. To fill this gap, in this work we
employ the phase-field method to provide a detailed and systematic analysis of
martensitic phase transformation during nanoindentation. A recently-developed
finite-element-based computational model is used for this purpose, and a
campaign of large-scale 3D simulations is carried out. First, the
orientation-dependent indentation response in CuAlNi (a widely studied SMA) is
examined. A detailed investigation of the predicted microstructures reveals
several interesting features, some of them are consistent with theoretical
predictions and some can be (to some extent) justified by experiments other
than micro/nanoindentation. The results also highlight the key role of
finite-deformation effects and elastic anisotropy of the phases on the model
predictions. Next, a detailed study of indentation-induced martensitic
transformation in NiTiPd (a potential low-hysteresis SMA) with varying Pd
content is carried out. In terms of hysteresis, the results demonstrate the
prevailing effect of the transformation volume change over phase compatibility
in the conditions imposed by nanoindentation and emphasize on the dominant role
of the interfacial energy at small scales. Results of such scope have not been
reported so far.
