Alpha plus beta annealed and aged Ti-15 Mo alloy for high strength implant applications

Management of femur fractures requires titanium alloy implants that provide a good combination of static strength and ductility plus sufficient high cycle fatigue strength to resist repetitive loading. A research program was initiated to determine whether aging treatments could increase the strength of alpha + beta Ti-15Mo while maintaining acceptable tensile ductility. A pilot heat treating study indicated the best combination of strength and ductility was obtained using an α + β annealing temperature of 705°C ± 10°C followed by an aging treatment of 482°C ± 10°C. EBSD data for four suppliers revealed that the alpha phase ratios ranged from 16.3% to 18.6% and the beta phase ratios ranged from 81.4% to 83.7%. Mean beta grain size diameters ranged between 1.42 and 1.78 µm. Tensile testing qualification data from four suppliers was statistically analyzed and reviewed. Minimum reproducible tensile values were established and incorporated into ASTM F2066-13 implant material standard. Cantilever fatigue testing was performed with proximal femoral nail implants that were fabricated into fully finished implant constructs. Fatigue results for 125°, 130°, and 135° implant constructs met the acceptance criteria regarding the fatigue runout load limits and failure modes that were identified. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2010-2018, 2017.