Effects of Fe on microstructures and mechanical properties of Ti-15Nb-25Zr-(0, 2, 4, 8)Fe alloys prepared by spark plasma sintering

Li Q., Yuan X., Li J., et al. Effects of Fe on microstructures and mechanical properties of Ti-15Nb-25Zr-(0, 2, 4, 8)Fe alloys prepared by spark plasma sintering. Materials Transactions 60, 1763 (2019); https://doi.org/10.2320/matertrans.ME201913.
Biomedical Ti-15Nb-25Zr-(0, 2, 4, 8)Fe (mol%) alloys are prepared by mixing pure element powders and spark plasma sintering (SPS). Specimens with diameters of 20 mm and thicknesses of 3 mm are obtained by sintering at 1000°C for 10 min followed by cooling in the furnace. Some of the specimens are then heat-treated at 900°C for 1 h followed by water quenching. Zr and Fe are dissolved in Ti; however, segregation of Nb is observed in all of the alloys. The β and α′′ phases are observed in the as-sintered and heat-treated specimens owing to the insufficient diffusion of the alloying elements. Fe stabilizes the β phase and provides a solution-strengthening effect. With the increase in the Fe content in the as-sintered specimen, the compressive strength and micro-Vickers hardness are improved in the Ti-15-Nb-25Zr-(0, 2, 4)Fe alloys and slightly decreased in Ti-15-Nb-25Zr-8Fe. The as-sintered Ti-15Nb-25Zr-4Fe alloy exhibits the maximum compressive strength of 1740 MPa. Although the plasticity is decreased by the Fe addition, a fracture strain of approximately 17% is obtained for Ti-15Nb-25Zr-4Fe, indicating a good plasticity. The heat treatment cannot eliminate the segregation of Nb, but can improve the plasticity and slightly increase the strengths of Ti-15Nb-25-Zr(0, 2, 4)Fe. Moreover, the heat-treated Ti-15Nb-25Zr-8Fe exhibits a high strength of approximately 1780 MPa and fracture strain of approximately 19%. Therefore, good comprehensive mechanical properties, including high strengths, high hardnesses, and good plasticities, can be obtained in Fe-added β-Ti alloys prepared by SPS and subsequent optional short heat treatment.