Effects Of Fe On Microstructures And Mechanical Properties Of Ti-15nb-25zr-(0,2,4,8)Fe Alloys Prepared By Spark Plasma Sintering

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 20mm and thicknesses of 3mm are obtained by sintering at 1000 degrees C for 10 min followed by cooling in the furnace. Some of the specimens are then heat-treated at 900 degrees 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 beta and alpha '' phases are observed in the as-sintered and heat-treated specimens owing to the insufficient diffusion of the alloying elements. Fe stabilizes the beta 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-15Nb-25Zr-( 0, 2, 4)Fe alloys and slightly decreased in Ti-15Nb-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-25Zr-( 0, 2, 4)Fe. Moreover, the heat-treated Ti-15Nb-25Zr-8Fe exhibits a high strength of approximately 1780MPa 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 beta-Ti alloys prepared by SPS and subsequent optional short heat treatment.