Estudo e caracterização da liga nitinol

Abstract

The Nitinol alloy has a wide application due to superelasticity properties, shape memory, biocompatibility and high corrosion resistance. These features are present due the combination of nickel and titanium in equiatomic compositions. The shape memory effect, one of the most interesting effects associated with this alloys can be explained by austenitic to martensitic transformations. These transformations can also provide the phenomenon of superelasticity. These changes can occur through mechanical, electrical and thermal stimuli that induce reorientation of the structure by twining mechanisms. Another important feature of this alloy is its biocompatibility, which determines most of its application in the biomedical field, the production of stents, catheters, implants, among others. The characterization of the phase transformations, with its transition temperature, and stress levels, is an important step to define the component or device to be manufactured. Brazil currently imports the end products and also some ingots must undergo further conformations due to small amount of information available about this alloy. The high value of imports, and the added value to the final product, motivates the development of these alloys in the country. This work was performed a literature review to the state of art of the Nitinol alloy, comprising many properties like shape memory, superelasticity, mechanical properties, biocompatibility, characterization methods, processing and applications. This led to the characterization of an imported Nitinol wire, subjected to mechanical testing as a tensile and hardness; DSC tests; metallographic analysis and density determination, compared to commercial standards and values found in the literature.