S. Williamson, M. Roach, L. Zardiackas, University of Mississippi Medical Center, Jackson, MS; V. R. Jablokov, H. Freese, ATI Allvac, Monroe, NC
The interest in the development of α, β, and α + β titanium alloys in several different conditions for possible use as biomaterials have increased in recent years. One of the major titanium alloys of interest is Ti-15Mo in the beta annealed condition due to its lower modulus of elasticity which can be used to mimic the stiffness of bone. This study focused on the comparison of smooth and notched fatigue characteristics of four titanium materials: annealed Ti-6Al-4V ELI (ASTM F136), annealed CP Ti Grade 4 (ASTM F67), annealed β-Ti-15Mo (ASTM F2066), and annealed and aged α/β Ti-15Mo. Base line data was established by testing for compositional analysis, microstructural evaluation, Vicker’s microhardness, and smooth and notched tensile properties. Corrosion fatigue testing was performed in tension-tension on smooth and notched samples in both aerated distilled/de-ionized and Ringer’s solution at 37º C using the guidelines of ASTM F1801 with the given R (σmin/σmax) of 0.053. In the smooth condition, α/β Ti-15Mo had a fatigue run-out limit of 800 MPa compared to 700 MPa for Ti-6Al-4V ELI, 550 MPa for CP Ti Grade 4, and 500 MPa for β-Ti-15Mo. Notch fatigue samples, tested in Ringer’s solution, run-out limits were 275 MPa for α/β Ti-15Mo, 200 MPa for both CP Ti Grade 4 and β-Ti-15Mo, and 150 MPa for Ti-6Al-4V ELI. The α/β Ti-15Mo showed greater smooth and notched mechanical properties as compared to the other titanium alloys. All alloys tested showed no notch sensitivity under single cycle testing but all showed a depression of the S/N curve under cyclic testing. Ti-6Al-4V ELI exhibited the greatest amount of notch fatigue sensitivity while β-Ti-15Mo exhibited the least amount. Fatigue properties of α/β Ti-15Mo were greater at all levels on the S/N curves compared to the other titanium alloys evaluated for both smooth and notched conditions.
Summary: This study focused on the comparison of smooth and notched fatigue characteristics of four titanium materials: annealed Ti-6Al-4V ELI (ASTM F136), annealed CP Ti Grade 4 (ASTM F67), annealed
b-Ti-15Mo (ASTM F2066), and annealed and aged
a/
b Ti-15Mo. Corrosion fatigue testing was performed in tension-tension on smooth and notched samples in both aerated distilled/de-ionized and Ringer’s solution at 37°C using the guidelines of ASTM F1801 with the given R (
smin/
smax) of 0.053.
