Effects of aging treatments on the fatigue resistance of superelastic NiTi wires

摘要

Thermomechanical and aging treatments can be powerful tools to improve the fatigue life of NiTi wires submitted to severe conditions of cyclic deformation. In this work, aging treatments were performed in an initially superelastic NiTi wire in temperatures ranging from 300 degrees C until 600 degrees C for 30 min. The as-received and heat treated wires' microstructures were characterized by XRD, the transformation temperatures were obtained by DSC and the mechanical characterization was performed in tensile tests. The wires were then submitted to lo w-cycle fatigue tests in a rotating-bending machine at a maximum strain of 4%. The heat treatments were effective on improving the fatigue resistance, especially when the R-phase was formed. The highest number of cycles to failure was obtained in the samples heat treated at 400 degrees C and 450 degrees C.