Compressive mechanical compatibility of anisotropic porous Ti6Al4V alloys in the range of physiological strain rate for cortical bone implant applications.

Porous titanium and its alloys are believed to be promising materials for bone implant applications, since they can reduce the "stress shielding" effect by tailoring porosity and improve fixation of implant through bone ingrowth. In the present work, porous Ti6Al4V alloys for biomedical application were fabricated by diffusion bonding of alloy meshes. Compressive mechanical behavior and compatibility in the range of physiological strain rate were studied under quasi-static and dynamic conditions. The results show that porous Ti6Al4V alloys possess anisotropic structure with elongated pores in the out-of-plane direction. For porous Ti6Al4V alloys with 60-70 % porosity, more than 40 % pores are in the range of 200-500 μm which is the optimum pore size suited for bone ingrowth. Quasi-static Young's modulus and yield stress of porous Ti6Al4V alloys with 30-70 % relative density are in the range of 6-40 GPa and 100-500 MPa, respectively. Quasi-static compressive properties can be quantitatively tailored by porosity to match those of cortical bone. Strain rate sensitivity of porous Ti6Al4V alloys is related to porosity. Porous Ti6Al4V alloys with porosity higher than 50 % show enhanced strain rate sensitivity, which is originated from that of base materials and micro-inertia effect. Porous Ti6Al4V alloys with 60-70 % porosity show superior compressive mechanical compatibility in the range of physiological strain rate for cortical bone implant applications.