Lamellar structure/processing relationships and compressive properties of porous Ti6Al4V alloys fabricated by freeze casting

Lamellar pores have superior biocompatibility due to their similarity to the lamellar structure of natural bones. In the present work, porous Ti6Al4V alloys with lamellar pores were successfully fabricated by directionally freeze casting. The lamellar structure/processing relationships were systematically studied through analyzing the interaction between ice front and alloy powders. The structural feature of translamella bridges is observed in the lamellar structure. The volume shrinkage of porous Ti6Al4V alloys is in the range of 44-60%. This is much higher compared with that of the porous ceramics. The solid content in the slurry exerts a strong influence on the porosity, while the freezing ice front velocity affects the structural wavelength and pore width. With the increase in ice front velocity, the structural wavelength decreases by an exponential function. The lamella formation mechanism and porosity gradient along the freezing direction were discussed. Young's modulus and yield stress of porous Ti6Al4V alloys fall in the range of 2-12 GPa and 40-300 MPa, respectively. The dominant compressive deformation mode is lamella buckling and splitting. The fabricated porous Ti6Al4V alloys possess higher relative yield stress.