title: Influence of Si addition on the microstructure and mechanical properties of Ti-35Nb alloy for applications in orthopedic implants.
abstract: In the development of new materials for orthopedic implants, special attention has been given to Ti alloys that show biocompatible alloy elements and that are capable of reducing the elastic modulus. Accordingly, Ti-Nb-Si alloys show great potential for application. Thus, this is a study on the microstructures and properties of Ti-35Nb-xSi alloys (x=0, 0.15, 0.35 and 0.55) (wt%) which were thermally treated and cooled under the following conditions: furnace cooling (FC), air cooling (AC), and water quenching (WQ). The results showed that Si addition is effective to reduce the density of omega precipitates making beta more stable, and to produce grain refinement. Silicides, referred as (Ti,Nb)3Si, were formed for alloys containing 0.55% Si, and its formation presumably occurred during the heating at 1000°C. In all cooling conditions, the hardness values increased with the increasing of Si content, as a result from the strong Si solid solution strengthening effect, while the elastic modulus underwent a continuous reduction due to the reduction of omega precipitates in beta matrix. Lower elastic moduli were observed in water-quenched alloys, which concentration of 0.15% Si was more effective in their reduction, with value around 65 GPa. Regarding Ti-35Nb-xSi alloys (x=0, 0.15 and 0.35), the "double yield point" phenomenon, which is typical of alloys with shape memory effect, was observed. The increase in Si concentration also produced an increase from 382 MPa to 540 MPa in the alloys' mechanical strength. Ti-35Nb-0.55Si alloy, however, showed brittle mechanical behavior which was related to the presence of silicides at the grain boundary.
authors.affiliation: Department of Materials Science and Engineering, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: A M G
authors.initials: AM
authors.lastname: Tavares
authors.affiliation: Department of Materials Science and Engineering, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: W S
authors.initials: WS
authors.lastname: Ramos
authors.affiliation: Metallurgical Engineering Program-PEMM/COPPE, Federal University of Rio de Janeiro, C.P.68505, 21945970 Rio de Janeiro, RJ, Brazil.
authors.forename: J C G
authors.initials: JC
authors.lastname: de Blas
authors.affiliation: Department of Materials Engineering, Faculty of Mechanical Engineering, State University of Campinas, 13083-860 Campinas, SP, Brazil.
authors.forename: E S N
authors.initials: ES
authors.lastname: Lopes
authors.affiliation: Department of Materials Engineering, Faculty of Mechanical Engineering, State University of Campinas, 13083-860 Campinas, SP, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Caram
authors.affiliation: Department of Materials Science and Engineering, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil.
authors.forename: W W
authors.initials: WW
authors.lastname: Batista
authors.affiliation: Department of Materials Science and Engineering, Federal University of Sergipe, 49100-000 São Cristóvão, SE, Brazil. Electronic address: sasouza.sandra@gmail.com.
authors.forename: S A
authors.initials: SA
authors.lastname: Souza
mesh_terms: D000497:Alloys / Q000737:chemistry*; D008422:Materials Testing; D055595:Mechanical Phenomena; D009556:Niobium / Q000737:chemistry*; D009985:Orthopedics; D019736:Prostheses and Implants; D012825:Silicon / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000497:Alloys; D009556:Niobium; D014867:Water; D014025:Titanium; D012825:Silicon
keywords: Mechanical properties; Microstructure; Titanium alloys