PREDICTING THE ORIENTATION-DEPENDENT STRESS-INDUCED TRANSFORMATION AND DETWINNING RESPONSE OF SHAPE-MEMORY ALLOY SINGLE-CRYSTALS

The present investigation examines three models that predict the orien tation dependence of the stress-induced transformation strain in shape memory alloys (SMAs). The merits of each model are considered in ligh t of experimental results for three SMAs: NiTi, Cu-Ni-Al, and Ni-Al. P ublished experimental results fit model predictions well in most cases ; the few exceptions can be accounted for by factors not included in t he present models. As part of the comparison of model results with exp erimental observations, Ni-Al stress-strain curves generated by one of the models are found to closely match experimental stress-strain curv es for the [001], [011], and [111] stress axis orientations. Finally, the predicted transformation stress anisotropy is analyzed in detail t o examine the effect of detwinning of the stress-induced martensite.