Desenvolvimento de malhas flexíveis de ligas com memória de forma níquel-titânio (Ni-Ti) para aplicações biomédicas.

Abstract

Shape Memory Alloys (SMA) are functional materials that have the ability to recover large deformations, when compared to conventional metals, after being subjected to a change in temperature or mechanical loading. Among them, the SMA of the binary system Nickel-Titanium (Ni-Ti) have stood out for biomedical applications because they present the combination of biocompatibility, mechanical strength, ductility and damping capacity. Due to the difficulties related to the workability of these materials, new manufacturing alternatives have been studied for the manufacture of complex shapes, as welding techniques. In this context, the objective of this work was to manufacture and characterize thermo-mechanically prototypes of superelastic (SE) and shape-memory effect (SME) Ni-Ti meshes from laminated superelastic commercial wires and subjected to GTAW (Gas Tungsten Arc Welding) spot welding. Initially, Ni-Ti wires with a diameter of 0.67 mm were cold rolled to obtain thin and flexible ribbons (0.15 mm thick) to be welded using a controlled GTAW pulse process. After preliminary tests to determine the best welding parameters (power and pulse time) prototypes of SMA Ni-Ti meshes were fabricated. The obtained laminated ribbons presented mechanical resistance 37% higher than the Ni-Ti SMA wire. The welding promoted changes in the welding temperatures as well as on the mechanical resistance of the ribbons, with a reduction of around 59% in relation to the SME ribbon without welded joint. The obtained meshes presented the shape memory effect and the superelasticity. It is concluded that it is possible to make meshes with functional characteristics from cold rolling and GTAW spot welding.