Influence of pore characteristics on microstructure, mechanical properties and corrosion resistance of selective laser sintered porous Ti-Mo alloys for biomedical applications

After preforming by selective laser sintering and subsequently post-heating at 1000 °C and 1200 °C, porous Ti-Mo alloys with 4, 6 and 8 wt.% Mo contents display two characteristic porous structures that include three-dimensionally interconnected pores and mutually isolated pores, respectively. The cell walls exhibit a lamellar microstructure that comprises dominant α and minimal β phases at room temperature. The porous alloys experience a linear elastic deformation followed by a long plastic yield up to a peak stress and then fracture eventually under compressive loading. The mechanical properties are improved with the decrease of porosity. During potentiodynamic polarization, the high porous samples undergo several active-passive transitions prior to passivation, while the low porous samples convert directly from Tafel to passive region. The impedance data show that the passive film formed on surface of porous alloys possesses a duplex structure that consists of a barrier inner layer and a porous out layer, and the corrosion protective performance is mainly provided by the barrier layer. The electrochemical results indicate that a more porous sample is more liable to corrosion attack than a less porous one. Both mechanical properties and corrosion resistance show strong dependence on porous characteristics.