Mechanics of the Interactions Between Elasticity, Phase Transformation, and Plasticity in NiTi

It is widely accepted that understanding the role of plasticity in phase transforming metals is critical to both existing and new technologies. Still, the interplay between plasticity and phase transformation is largely unquantified. Recently, new methodologies were established to couple micro and macro scale models of phase transforming crystalline materials with in-situ diffraction experiments.  These methods were applied in studying large quasi-static deformations of shape-memory and superelastic Nickel-Titanium alloys (up to 18% strain, 2GPa stress). The resulting analyses have allowed for empirical, micro-mechanical quantification of the individual roles of deformation mechanisms (elasticity, transformation twinning, deformation twinning, and slip) in the macroscopic shape memory behaviors. This body of work will be reviewed in the seminar. The results will motivate the concluding remarks on an advanced constitutive model that has been developed using coupled plasticity-transformation-strength physics elucidated via in-situ characterization.