Caracterização microestrutural da transformação martensítica induzida por deformação em uma liga NiTi superelástica

Abstract

In the present work, the influence of phase transformations induced by deformation of a superelastic NiTi alloy with approximately equiatomic chemical composition was studied. In a 1 mm diameter Nitinol wire, the phases present in the analyzed material were identified by microstructural characterization techniques, as received and submitted to different radius of curvature. The samples were analyzed by MO and later by SEM, according to the images, with the gradual reduction in the radius of curvature an increase in the volume of mechanically induced transformations was observed, as well as a refinement of the microstructure, being able to be quantified and measured by quantitative stereology. Microhardness tests were performed in order to verify variations in the mechanical properties, demonstrating that, according to the increase in the level of deformation, a greater induction of martensitic transformation occurs. It can be stated that the instability of the superelastic NiTi LMF in response to voltage, particularly the derivative of transformation and accumulation of residual voltage.