Produção, caracterização microestrutural e avaliação das propriedades mecânicas de ligas de Ti-Si-B com adição de Zr para o desenvolvimento de implantes ortopédicos

Abstract

Joint orthopedic components should present high hardness values, compressive strength, wear resistance, and good biocompatibility characteristics. Conventional titanium alloys are based on substitutional solid solutions. 85Ti-10Si-5B alloy implants with Ti+Ti6Si2B microstructures and produced by arc melting and subsequent heat treatment indicated superior characteristics of biocompatibility and bone integration than pure titanium. Oxidation and corrosion resistances of Ti+Ti5Si3 alloys are improved with the zirconium addition. In this context, the present study aimed to evaluate the effect of chemical composition and processing route on microstructure and their compression mechanical properties of potentially alloys for applications in joint orthopedic components. Thus, the 95Ti-2Si-1B, 89Ti-6Si-3B, 83Ti-10Si-5B, 93Ti-2Si-1B, 87Ti-6Si-3B e 81Ti-10Si-5B (%-at.) alloys containing the addition of Zr (2 and 4 %-at.) were produced by high energy milling and subsequent spark plasma sintering. To minimize the occurrence of excessive cold welding during milling, 5%-weight vegetable paraffine was added. The elemental powder were processed in planetary ball mill for 180 min, using hardened steel balls, 300 rpm and a 10:1 ball-to-powder mass ratio. Following, the Ti-Si-Zr-B were consolidated by SPS, using a graphite matrix, 1200 ºC and pressure of 20 MPa for 15 min. As-milled materials and sintered products were characterized by X-ray diffraction, scanning electron microscopy, dispersive energy spectrometry, compression tests and Vickers microhard tests. Regardless of the mixture of as-milled powders, intense -Ti peaks were identified in addition to other minorities of Si and vegetable paraffine, indicating that an atomic level homogenization was not achieved after milling for 180 min. Sintered Ti-Zr-Si-B alloys evaluated in this study presented metallic matrix (-Ti) and intermetallic precipitates (silicides and TiB). The Ti6Si2B was formed in microstructures of 95Ti-2Zr-2Si-1B, 89Ti-2Zr-6Si-3B, 83Ti-2Zr-10Si-5B, 93Ti-4Zr-2Si-1B, 87Ti-4Zr-6Si-3B e 81Ti-4Zr-10Si-5B. alloys. The sintered Ti-Zr-Si-B alloys presented values of yield stress, elastic modulus, ultimate compression stress and total normal deformation of 980-1165 MPa, 194,9 – 249,1 GPa, 1241-1523 MPa and 0.11-0.18 mm/mm, respectively. Also, there was a trend of increased mechanical resistance with the increased Si and B amounts in the nominal alloy, due to the greater amounts of intermetallic precipitates in microstructures. Similarly, the sintered Ti-Zr-Si-B alloys presented the Vickers microhardness values from 338 HV (95Ti-2Zr-2Si-1B) to 436 HV (81Ti-4Zr-10Si-5B).