Volume 2, Issue 9 (October 2005)
Beta Titanium Alloy Processed for High Strength Orthopedic Applications
The general material requirements for Ti-15Mo have been standardized for surgical implant applications in ASTM F 2066 . This particular standard is currently limited to one microstructural condition that is produced by beta solution treating and rapidly quenching the material to avoid the formation of alpha phase. When the alloy is processed in this way, it maintains a very high level of ductility but relatively low tensile and bending fatigue strengths. Since beta titanium alloys can be strengthened substantially by thermal processes that introduce alpha phase, it may be possible to adjust the microstructure to achieve a balance of properties that will meet the requirements for more highly stressed applications. Tensile and rotating beam fatigue data for several dual phase material conditions of Ti-15Mo indicate that the alloy can be strengthened substantially without introducing tensile notch sensitivity. However, it was necessary to use an alpha/beta annealing process and avoid beta solution treatment prior to aging at 480 °C to achieve this balance of properties. The potential benefits of alpha/beta processing appear to warrant expansion of ASTM F 2066 beyond the current beta solution treated and quenched condition.