Estudo das transformações de fases ocorridas em ligas de Ti-Nb-Si submetidas a tratamentos termomecânicos

Abstract

Ti-Nb-Si alloys have a combination of properties that make them excellent alternatives for use in orthopedic implants. The application of thermomechanical treatments in these materials allows the modification of these properties. This thesis presents a study of the phase transformations occurring in Ti-Nb-Si alloys submitted to thermomechanical treatments. Ti-Nb-Si alloys were produced with three different compositions: Ti-35Nb-XSi (where X = 0.15, 0.25 and 0.35 wt%). After melting, the ingots were homogenized at 1000 ° C for six hours and then deformed by forging at four different levels with the aid of a matrix. Forged alloys were heated at temperatures of 400, 800 and 900 ° C. The alloy with composition of 0.35% Si was also submitted to the deformation process by ECAP. The changes caused by each process were evaluated using optical and scanning electron microscopy, Vickers hardness and X-ray diffraction techniques. The results showed that the cold deformation processes caused the increase of hardness in all the compositions, with the formation of the α-phase. The heating at the different temperatures promoted changes in the microstructura and in the alloys hardness.