Improvement of mechanical, biological, and electrochemical properties of Ti6Al4V alloy modified with Nb and Ag for biomedical applications

This study aims to evaluate the mechanical and biological properties of a spark plasma-sintered (SPS) Ti6Al4V alloy modified with 5 and 10 wt% niobium (Nb) together with 2 wt% Ag. Five batches of Ti6Al4V, Ti6Al4V-5 Nb, Ti6Al4V-10 Nb, Ti6Al4V-5 Nb-2Ag, and Ti6Al4V-10 Nb-2Ag were sintered using SPS at 1400 degrees C for 5 min. X-ray diffraction (XRD) analysis was used to identify the phases of the specimens. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray mapping analyses were also utilized to study the powder morphology, microstructure, and fractured surfaces of the samples. Three-point flexural strength and Vickers microhardness tests were performed and the fracture toughness (K1 C) was calculated subsequently. The bulk parts showed a very high building density, which means that the plasma sintering parameters were optimal. Xray diffraction (XRD) analysis confirmed the existence of alpha and beta phases by adding niobium and silver. Potentiodynamic, electrochemical impedance spectroscopy, MTT assay, and antibacterial tests were also conducted to evaluate the biological properties of the sintered samples. The maximum values of flexural strength and K1 C were obtained for Ti6Al4V-5 Nb samples up to 1943 +/- 12 MPa and 63 +/- 1.1 MPa.m0.5, respectively. The hardness values of samples showed no significant difference by adding Nb and Ag. The samples containing Nb exhibit a lower passive current density compared to the pure Ti6Al4V alloy, suggesting that the addition of Nb positively influences corrosion resistance. According to the results of the antibacterial test, Nb slightly deteriorated the antibacterial properties, while after adding Ag, this property improved. The results of the MTT assay revealed that adding niobium and silver had no toxic effect on the samples.