Neutron diffraction studies and multivariant simulations of shape memory alloys: Empirical texture development-mechanical response relations of martensitic nickel-titanium

摘要

Mechanical responses and texture developments were observed in situ during the creation of multiaxial stress states in polycrystalline NiTi parallelepiped specimens, achieved via sequential compression along unique principal axes. For all of the compression stages, regardless of initial texture, the two major texture components behaved similarly: (10 0) poles aligned with, while (011) poles oriented perpendicular to, the loading direction. The effective critical resolved shear stress needed to induce significant reorientation, however, was reduced through prior loading. In the macroscopic responses, prior transverse direction loading resulted in widemng of the reorientation plateau, a reduction of the effective Young's modulus, and substantial alteration of effective Poisson's ratios during axial direction straining. Additionally, these empirical results are presented in a manner conducive to the verification of shape memory alloy micromechanics and continuum mechanics constitutive models.