Near β-type Zr-Nb-Ti biomedical alloys with high strength and low modulus

The as-cast Zr-12Nb-xTi (x = 0, 2, 4, 8, 16 at.%) alloys were synthesized in a nonconsumable vacuum arc melting furnace. The aim is to explore biomedical materials with excellent mechanical properties for hard tissue replacements. The microstructures were characterized by using optical microscopy (OM) and X-ray diffractometry (XRD), and the mechanical properties were measured by compression tests. The results show that the phase composition of the all samples is composed of β and ω. The presence of ω phase may be due to the athermal β→ω transformation. In the Zr-12Nb-(2-16)Ti alloys, besides of the needle-like structures, a lenticular structure was observed. The grain size decreases firstly and then increases with increasing Ti content. When the Ti concentration is 8%, the grain size reach a minimum about 180-320 μm. The Zr-12Nb-xTi (x≧4) alloys exhibit relatively higher mechanical properties, especially the Zr-12Nb-8Ti alloy. Its compression strength reaches 1940 MPa and the value of plastic strain is 45.8%. Additionally, the Young's modulus of the Zr-12Nb-xTi alloys ranges from 23 to 27 GPa, which is in range of that of the human skeleton.