Produção e caracterização microestrutural de ligas Ti-Zr e Ti-Ta-Zr produzidas por moagem de alta energia e subsequente tratamento térmico

Abstract

Titanium and its alloys are widely used as biomaterial for fabrication of implantable orthopedic devices such as scaffolds used for bone reconstruction. However, the titanium and the Ti-6Al-4V alloy present limited mechanical strength and biocompatibility, respectively. To enhance to these features, various new titanium alloys containing the addition of Zr, Mo, Nb and Ta have been evaluated such as the Ti-35Nb-5Ta-7Zr (wt.-%) alloy. High-energy milling techniques have has been contributing for obtaining homogeneous materials under the chemical and microstructural characteristics. In this way, the present study aims to perform the microstructural characterization and evaluation of Vickers hardness of the Ti-7Zr and Ti-5Ta-7Zr (wt.-%) alloys produced by high-energy ball milling and subsequent heat treatment. The powder mixtures were processed for different milling times: 20, 60, 120, 240, and 640 min. Following, the cylinder samples with diameter of 10 mm were prepared by axial pressure (~120MPa) from the milled powders for 640 minutes, and heat treatment at (1100oC for 4 h). The as-milled powder mixtures and the sintered samples were characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and hardness tests. The results indicated that the particle sizes were increased with the milling evolution up to 600 minutes, indicating that the cold welding mechanisms were more pronounced than the fracture mechanisms, especially in the Ti-5Ta-7Zr powder mixture. The lattice parameters of α-Ti were changed with the increase of milling time, due to the dissolution of Zr and/or Ta atoms in their crystalline structure. Peaks of β-Ti were more intense in XRD pattern of the Ti-5Ta-7Zr alloy with the increase of milling time. The sintered Ti-7Zr and Ti-5Ta-7Zr alloys indicated the presence of homogeneous microstructures of α-Ti and α-Ti+β-Ti grains, respectively, beside the significant presence of pores from the route and sintering parameters adopted, which are suitable to get scaffolds for bone reconstruction.