Biomedical Porous Ni-Free Ti-Based Alloys with Superior Superelasticity and Mechanical Properties

Porous NiTi shape memory alloys (SMAs) exhibit excellent biocompatibility due to their pore structure, and superior mechanical properties because of their superelasticity, such as good fatigue and wear resistance. Thus, they are considered to have great potentials in hard-tissue replacement applications. However, excessive Ni ion released from porous NiTi SMAs after implantation become one of greatest worries in most of biomedical applications. The development of Ni-free Ti-based SMAs becomes an essential method to solve this problem. Because of the addition of the elements with high melting point, it is hard to obtain porous Ni-free SMAs with homogeneous microstructure and satisfied superelasticity using previous methods.

In this study, porous Ti-22Nb-6Zr (at.%) alloys were successfully fabricated by sintering pre-alloy powders obtained by high energy ball-milling. These porous Ti-22Nb-6Zr alloys showed high porosity (about 45%). The microstructure, mechanical properties and superelasticity of the porous Ti-22Nb-6Zr alloys were investigated. It has been found that the porous Ti-22Nb-6Zr alloys exhibit relatively homogeneous microstructure and high compressive strength (220MPa), as well as good superelsticity (2.4%) and cycle stability in comparison with that by sintering of elemental powders. It meets the requirement for bone replacement materials.