Compression-compression fatigue of selective electron beam melted cellular titanium (Ti-6Al-4V)

Regular 3D periodic porous Ti-6Al-4V structures intended to reduce the effects of stress shielding in load-bearing bone replacement implants (e. g., hip stems) were fabricated over a range of relative densities (0.17-0.40) and pore sizes (similar to 500-1500 mu m) using selective electron beam melting (EBM). Compression-compression fatigue testing (15 Hz, R = 0.1) resulted in normalized fatigue strengths at 10(6) cycles ranging from 0.15 to 0.25, which is lower than the expected value of 0.4 for solid material of the same acicular alpha microstructure. The three possible reasons for this reduced fatigue lifetime are stress concentrations from closed porosity observed within struts, stress concentrations from observed strut surface features (sintered particles and texture lines), and microstructure (either acicular alpha or martensite) with less than optimal high-cycle fatigue resistance. (C) 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 99B: 313-320, 2011.