Modeling the transformation stress of constrained shape memory alloy single crystals

Abstract

Shape memory alloys (SMA) are a unique class of engineering materials that can be further exploited with accurate polycrystal constitutive models. Previous investigators have modeled stress-induced martensite formation in unconstrained single crystals. Understanding stress-induced martensite formation in constrained single crystals is the next step towards the development of a constitutive model for textured polycrystalline SMA. Such models have been previously developed for imposition of axisymmetric strain on a polycrystal with random crystal orientation; the present paper expands the constrained single crystal SMA model to encompass arbitrary imposed strains. To evaluate the model, axisymmetric tension and compression strains and pure shear strain are imposed on three SMA: NiTi, CuAlNi (β1→γ′1) and NiAl. Model results are then used to understand the anisotropy and asymmetry of transformation stress in the three SMA considered. Finally, the impact of the present results on polycrystal behavior is addressed.