Plastic deformation mechanisms that explain hot-rolling textures in Nickel–Titanium

Abstract

Plastic deformation of B2 Nickel Titanium is usually attributed to {110}〈001〉 slip and {114}〈221〉 deformation twinning. The most commonly observed hot-worked texture of these alloys, is defined by a {111}〈uvw〉 gamma fiber and {hkl}〈110〉 partial alpha fiber. A Visco-Plastic Self Consistent (VPSC) model was used to establish relationships between microscopic slip and twin activity with the observed macroscopic hot-rolling texture. This knowledge will better aid in modeling NiTi austenite plasticity. Since the primary slip modes in NiTi do not have five independent slip systems, and deformation that can be accommodated by twinning is limited, multiple deformation modes must contribute to NiTi ductility. It is shown that {110}〈001〉 slip, {100}〈001〉 slip and, {114}〈221〉 twin deformation modes need to be active simultaneously to explain the observed textures. The relative CRSS ratios and hardening parameters were varied to study the effect of the deformation modes on the various texture components. Textures observed below 723 K and at less than 80% rolling reduction were simulated with deformation primarily accommodated on the {110}〈001〉 slip mode and {114}〈221〉 twinning mode. Textures observed at temperatures greater than 903 K and greater than 80% rolling reductions were captured in the simulations that included all three deformation modes. Activity on the {100}〈001〉 slip mode strongly correlated with the {110}〈110〉 texture component observed at high temperatures.